FEEDING ECOLOGY OF HUMPBACK WHALES 

IN CONTINENTAL SHELF WATERS NEAR 

CORDELL BANK, CALIFORNIA 

A Thesis 

Presented to 

The Faculty of the Department of Moss Landing Marine Laboratories 

San Jose State University 

In Partial Fulfillment 

of the Requirements for the Degree 

Master of Science 

By 

Thomas R. Kieckhefer 

May 1992 

APPROVED FOR THE DEPARTMENT OF 
MOSS LANDING MARINE LABORATORIES 
~I~r 
APPROVED FOR THE UNIVERSITY 

/ 
iii 
ABSTRACT 

Daytime feeding behavior of humpback whales (Megaptera 
novaeangliae) in Gulf of the Farallones, California, and adjacent waters was 
observed during autumn of 1988 to 1990. Bodega Canyon, Cordell Bank, and 
the Farallon Islands were the primary sites of feeding activity. Fecal samples of 
whales and zooplankton tows contained euphausiids exclusively, dominated by 
Thysanoessa spinifera (79%), with lesser amounts of Euphausia pacifica (14%), 
Nyctiphanes simp/ex (4%), and Nematoscelis diffici/is (3%). In 1988 and 1990, 
whales also were infrequently observed feeding on small schooling fish, 
presumably Pacific herring (C/upea pal/asH), northern anchovy (Engraulis 
mordax) , and juvenile rockfish (Sebastes spp.). 
Feeding was the most common behavior observed (52%), and less 
frequently traveling (23%), milling (21 %), and resting (4%). Whales used 
different methods to consume euphausiid prey at the surface (0·10 m), in 
shallow water (11-60 m), and deep water (61·140 m). Humpback whales fed at 
the surface 56% of time in 1988 and 32% of time in 1990, using primarily lateral 
lunges to capture swarms of euphausiids. In 1989, no surface feeding was 
observed; however, deep, long·duration dives were followed by extended 
surface intervals with many respirations. These 1989 observations coincided 
with increased prey depth as indicated by depth sounder records of diving 
whales and prey scattering layers. 
In 1989, increased prey depth and associated feeding behaviors were 
strongly associated with unusually high surface temperatures, calm seas, and 
changes in water circulation. Environmental conditions in 1989 triggered the 
most intense and wide-spread occurrence of red tide in this region since 1980. 
Red tide samples collected throughout this period contained Alexandrium 
(=Gonyau/ax) catenella and Noctiluca scintillans. Surface feeding was 
observed only in 1988 and 1990, when surface prey were available and red 
tides were very limited in extent, duration, and intenSity. Annual variations in 
humpback whale feeding behavior were related to prey availability which is 
affected by corresponding environmental conditions. 
iv 
ACKNOWLEDGM ENTS 

This study was made possible thanks to the help of many people and 
organizations. First, the study could not have been completed without the valuable 
research assistance of Chris Tanner, Peter Rudolph, Daniel E. Shapiro, Thea Jenssen, 
Chris Rado, and Birgit Liskey. Thanks to Dr. Bernd WGrsig for the use of his Mark III 
Zodiac in 1988. and his help and support in getting funds for a more seaworthy vessel. 
the RN Ridgway (a 6.7 m Boston Whaler/Guardian equipped with a LORAN. radar, 
depth sounder, VHF radio, and appropriate safety gear). which was used in 1989 and 
1990. Tracy Thomas, Chuck Cheaney, and Mike Prince assisted me in properly 
outfitting the RN Ridgway. Thanks to John Calambokidis and Gretchen Steiger 
(Cascadia Research Collective); Gary Ranos (captain of the SN laorana); Dan Bockus 
and Marc Webber (Oceanic Society Expeditions); Dave French and Rick Powers 
(captains of the FNs' New Sea Angler and Jaws); Deke Nelson (captain of the RN 
Susan Kay); Ron Blodgett (captain FN Happy Jack); as well as Bob LaMar (Northern 
Airventures) for their support out at sea in providing locations of whales, prey and fecal 
samples, and safety throughout the study. Jo Guerrero, Jill Schoenherr, Janet Stein, 
Nancy Black, Sheila and Alan Baldridge, Carol Keiper, and Thomas A. Jefferson all 
gave me inspiration to undertake this project and provided never-ending 
encouragement. I would like to give a special thanks to William A. Archibald and his 
family for their unending support and assistance with the computer design of this 
project, as well as filling my head with all the future possibilities of computer 
technology. Jim Oakden, Lynn McMasters, and Eric Dorfman provided consultation and 
assistance with the graphics. I thank Sheila Baldridge (Moss Landing Marine 
Laboratories) and Eleanor Uhlinger (Bodega Marine Laboratories) for their great 
assistance in finding valuable references. I thank Susan Smith (Southwest Fisheries 
Center) for her help identifying euphausiid mandibles. and Gregg Langlios 
(Department of Health Services, Shellfish Program) for providing the red tide data. 
Historic humpback whale stomach samples were provided by Dale Rice and Alan 
Wolman (National Marine Mammal Laboratory). Oceanographic data were provided by 
David Husby (Pacific Fisheries Environmental Group), and satellite images by Newell 
Garfield (Naval Postgraduate School). Drs. Bernd WOrsig, James Harvey, John Oliver, 
Peter Klimley, and Gregor Cailliet gave me continual support and guidance. James 
Harvey. Jo Guerrero, Bernd WOrsig, Gregor Cailliet, John Calambokidis, Nancy Black, 
and Tom Jefferson improved the manuscript with suggestions in their reviews. I would 
also like to thank the entire staff at Bodega Marine Laboratories and Moss Landing 
Marine Laboratories for their gracious assistance and encouragement throughout the 
study. Finally, I would like to thank Mrs. Viola Otis, my family, and relatives, who always 
believed in me. 
Several funding agencies supported this study, including the Gulf of the 
Farallones National Marine Sanctuary (contract no. CX 8140-0-009); Southwest 
Fisheries Center (order no. 43NABNF002718 under a subcontract from Cascadia 
Research Collective); Dr. Earl H. Myers and Ethel M. Myers/Oceanographic and Marine 
Biology Trust; Lerner-Gray Fund for Marine Research; Sigma Xi, Grants-in-Aid of 
Research; Packard Foundation; International Research Expeditions; and the 
Environmental Studies Internship Program at University of California, Santa Cruz. 
The RN Ridgway was funded by: J.W. Kieckhefer Foundation; Margaret T. 
Morris Foundation; San Jose State Foundation/Moss Landing Marine Laboratories; 
and a donation from my father, James F. Kieckhefer, for safety equipment. 
v 
TABLE OF CONTENTS 

ABSTRACT ....................................................................................................................iii 

METHODS 

RESULTS 

DISCUSSION 

Correlations between Whale Behavior, Prey Occurrence, and 

APPENDICES 

ACKNOWLEDGMENTS ............................................................................................. .iv 

LIST OF TABLES ..........................................................................................................vi 

LIST OF FIGURES ........................................................................................................vii 

INTRODUC-nON ............................................................................................................1 

Surveys................................................................................................................5 

Whale Observations ..........................................................................................7 

Prey Collections and Documentation ...........................................................11 

Laboratory Analyses ........................................................................................12 

Environmental Data .......................................................................................... 1 3 

Whale Sightings ................................................................................................15 

Whale Behavior ................................................................................................. 1 7 

Prey Occurrence ...............................................................................................31 

Environmental Data and Red Tide ................................................................38 

Foraging Behavior and Energetics ................................................................50 

Prey Distribution and Relative Abundance ..................................................55 

Oceanographic Conditions and Productivity ...............................................60 

Environmental Conditions ...............................................................................64 

LITERATURE CITED ....................................................................................................68 

A: Defined Behavior Categories ....................................................................80 

B: Behavioral Ethogram ...................................................................................81 

C: Defined Respiration Variables ..................................................................82 

D: Calculated Respiration Variablesl Standard Approach .......................83 

E: Standard Body Length and Mandible Measurements ..........................84 

F: Euphausiid Right Mandible Identification ................................................85 

G: Sky and Sea Condition Codes .................................................................86 

VI 
LIST OF TABLES 
Table 1. 	Mean humpback whale respiration variables by behavioral 

categories of feeding, milling, and traveling during the autumn 

of 1988-1990 .................................................................................................20 

Table 2. 	Opportunistic recordings of humpback whale sounds in the 

study area during the autumn of 1988-1990 ...........................................30 

Table 3. 	 Humpback whale fecal samples collected in the study area 

during the autumn of 1987-1990 ...............................................................34 

Table 4. 	 Percentage of euphausiids caught in plankton tows in 1990 at 

the surface (0-10 m), shallow (11-60 m), and deep (61-140 m) ......... .40 

Table 5. 	Location and capture dates of humpback whale stomach 

contents collected during commercial whaling off Central 

California from 1960-64 ..............................................................................57 

vii 
LIST OF FIGURES 

Figure 1. Study area off central California, 1988-1990 ...................................... 6 

Figure 2. Track lines of vessel surveys and range of red tides ........................ 8 

Figure 3. Locations of humpback whales and prey ............................................16 

Figure 4. Percent frequency of humpback whale behaviors ........................... 18 

Figure 5. Percent frequency of surface, shallow, and deep feeding .............. 19 

Figure 6. Mean blow rate of feeding, milling, and traveling humpback 

whales........................................................................................................21 

Figure 7. Surface duration, number of blows per surface duration, 

and dive duration for feeding at all depths (0-140 m) .......................23 

Figure 8. Surface duration, number of blows per surface duration, 

and dive duration of surface (0-10 m), shallow (11-60 m), 
and deep (61-140 m) feeding ................................................................24 

Figure 9. Surface duration, number of blows per surface duration, 

and dive duration for 1990 feeding depths .........................................25 

Figure 10. Photographs of humpback whale bubble-cloud formation ..............26 

Figure 11. Percentage of fluke-down, fluke-up, and high fluke-up dives 

for surface, shallow, deep feeding depths ..........................................28 

Figure 12. Depth sounder records of whales diving at different descent 

angles ........................................................................................................29 

Figure 13. Depth sounder records documenting a deep and shallow 

scattering layer during 1989 ..................................................................33 

Figure 14. Length 'frequency ~Iistogram of 1990 tow samples, 

comparing the lengths of Thysanoessa spinifera to 
Euphausia pacifica ..................................................................................35 

Figure 15. Length frequency of Thysanoessa spinifera caught in tows 

for 1988, 1989, and 1990 .......................................................................36 

Figure 16. Linear regressions of standard body length versus right 

mandible length of Thysanoessa spinifera and Euphausia 
pacifica......... ............................................................................................ , .37 

Figure 17. Calculated standard body length frequencies for 

Thysanoessa spinifera and Euphausia pacifica from right 
mandibles collected in humpback whale fecal samples ..................39 

viii 
CONT. LIST OF FIGURES 
Figure 18. 	 Percent frequency of occurrence of Cassin's Auklet, Red 

Phalarope, and Red-necked Phalarope observed relative to 

mean prey depth ......................................................................................41 

Figure 19. 	 Fitted curves comparing mean daily prey depth, surface 

temperature, Secchi depth, Beaufort state, and bottom 

depth for the months of September, October, and November 

in 1989 and 1990 .....................................................................................42 

Figure 20. 	 Linear regressions of prey depth versus surface 

temperature for 1989 and 1990 ........................................................... .44 

Figure 21. 	 Fitted curves comparing mean daily surface light and 

underwater (10m) light to scattering layer depths for the 

months of September, October, and November in 1990................. .46 

Figure 22. 	 Monthly mean Paralytic Shellfish Poison (PSP) toxin levels 

for Marin County, California. and mean prey depth for the 

months of September, October, and November in 1988-90........... .4 7 

Figure 23. 	 Estimated red tide ranges and durations in 1988-90....................... .48 

Figure 24. 	 Satellite images of sea surface temperature (SST) for the 

most cloud-free days found in 1989 and 1990 ...................................62 

Figure 25. 	 Monthly coastal upwelling indices and sea surface 

temperature for July-December 1988-90 ............................................63 

1 
INTRODUCTION 
Most humpback whales (Megaptera novaeangliae) in the northeast 
Pacific feed in Alaskan waters in summer and breed in waters surrounding 
Hawaii and Mexico during winter. Each autumn, 100 to 200 individuals, 
primarily adults from the Mexican group, migrate to the Gulf of the Farallones, 
California, and adjacent waters to feed (Dohl et al. 1983; Webber and Cooper 
1983; Calambokidis et al. 1989a, 1990, 1991a). This central California 
assemblage of humpback whales was severely depleted during commercial 
whaling from 1956 to 1965 (Rice 1963, 1971, 1978). Gulf of the Farallones 
surveys from 1980 to 1982 indicated that numbers of humpback whales were 
increasing (Dohl 1983; Dohl et al. 1983). However, recent surveys conducted 
by Cascadia Research Collective from 1986 to 1988 found that the numbers of 
humpback whales were less than reported in 1982, and no current evidence 
suggests their recovery (Calambokidis et al. 1989a, 1990, 1991 a,b; Steiger et 
al. 1989). Annual variations in their numbers and distribution were great, which 
possibly related to the distribution and availability of prey (Calambokidis et al. 
1990, 1991 b). 
Aside from observations of humpback whales feeding in and around the 
Gulf of the Farallones, little is known about their behavior in these waters. 
Several studies have qu.antitatively linked feeding behavior of whales to 
availability and type of prey (WOrsig et al. 1984, 1986; Dolphin 1987a,b,c,d; 
Hamner et al. 1988; Guerrero 1989). WOrsig et al. (1984) found that blow rates 
of bowhead whales (Balaena mysticetus) feeding in the Arctic decreased when 
they fed in the water column versus when they were skim feeding at the surface. 
2 
Likewise, Hamner et al. (1988) reported southern right whales (B. australis) 
slowly moving at the surface and hyperventilating before long dives to feed on 
sub-surface Antarctic krill (Euphausia superba). Guerrero (1989) found that 
surface behaviors of gray whales (Eschrichtius robustus) were different when 
they were feeding on mysid swarms compared with feeding on infaunal 
amphipods. Dolphin (1987a,b,c,d) found that respiration rates of humpback 
whales in southeast Alaska were positively correlated with depth of feeding. 
Observations of humpback whale surface feeding have confirmed that 
they have a diverse repertoire of behaviors, such as lunge feeding and "bubble­
netting" (Ingebrigsten 1929; Jurasz and Jurasz 1979; Watkins and Schevill 
1979; Hain et al. 1982; Baker 1985; D'Vincent et al. 1985). Various prey species 
or densities may affect these different feeding methods (Jurasz and Jurasz 
1979; Watkins and Schevill 1979; Hain et al. 1982; Baker 1985). In lunge 
feeding, whales display several different behaviors, with variations occurring in 
their body postures and angles of trajectory from the water's surface. Jurasz and 
Jurasz (1979) reported lunge angles of 30° and 90°, which described a lateral 
and vertical lunge. In addition, diagonal (45°) lunges, with bodies upright and 
oblique to the water's surface, were used when whales fed on fast, schooling 
prey (Kieckhefer pers. obs. S.E. Alaska 1982). During bubble-net feeding, a 
whale forms a circular or cylindrical-shaped screen of bubbles by a series of 
underwater exhalations. apparently to herd and concentrate prey at the surface 
(Jurasz and Jurasz 1979). Following the completion of a bubble-net, a vertical 
lunge is often executed in the center. 
In southeast Alaska, apparent cooperative feeding of humpback whales 
(e.g. 8-11 whales synchronously lunging at the surface capturing herring) have 
3 
been described, and vocalizations may have assisted in corralling fish prey or 
coordinating whale efforts (Baker 1985; D'Vincent et al. 1985). In the same 
area, two to four whales eschelon feeding or surface lunge-feeding in 
staggered formation has been observed (Jurasz and Jurasz 1979; Baker 1985). 
Eschelon formations have also been reported in skim-feeding bowhead whales 
(8. mysticetus; WOrsig et al. 1984; WOrsig 1988). 
Prey of humpback whales in the North Pacific were identified in samples 
obtained during whale feeding (Jurasz and Jurasz 1979; Wing and Krieger 
1983; Krieger and Wing 1984; D'Vincent et al. 1985; Baker 1984; Dolphin 
1987a,b; Krieger 1988) and in stomach contents of stranded animals and 
carcasses examined at whaling stations (Mathews 1937; Rice 1963, 1977; 
Nemoto 1970; Calambokidis et al. 1989a). Humpback whales, in southeast 
Alaska, fed mainly on euphausiids, especially Thysanoessa rashii, and less on 
Euphausia pacifica, Thysanoessa /ongipes, and Thysanoessa spinifera (Wing 
and Krieger 1983; Krieger and Wing 1984; Dolphin 1987a,b). Their diet also 
includes schooling fishes, such as Pacific herring (C/upea pallash), capelin 
(Mallotus villosus), and walleye pollock (Theragra chalcogramma; Wing and 
Krieger 1983; Krieger and Wing 1984). During 1956-65, commercially killed 
whales from the Cordell Bank/Gulf of the Farallones area contained anchovies 
and euphausiids . Stomach contents contained roughly 60% northern anchovy 
(Engraulis mordax) and 40% Euphausia pacifica, with only trace amounts 
« 0.5%) of Pacific herring, Thysanoessa spinifera , shrimp, and rockfish 
(Sebastes spp.; Rice 1977; Calambokidis et al. 1989a). Distribution and 
abundance of prey changed annually. 
Seasonally, there is an abundant supply of juvenile schooling rockfish, 
especially shortbelly (Sebastes jordam), chilipepper (5. goodel) , bocaccio 
(5. paucispinis), and yellowtail rockfish (5. f/avidus) in the Cordell Bank/Gulf of 
the Farallones area, which are potential prey items for humpback whales 
(Larson 1987; D. Pearson pers. comm. 1988; Hobson and Howard 1989). In 
addition, Smith and Adams (1988) found abundant surface swarms of T. 
spinifera off the Farallon Islands. 
Combined with concurrent studies of whale distribution, movements, and 
population size, this study proposes to accurately describe the importance of 
this region as a food resource to this remnant group of humpback whales. To 
investigate the feeding ecology of humpback whales near Cordell Bank/ Gulf of 
the Farallones, five objectives were pursued: (1) assess percentage of time 
spent feeding compared with other behavioral states of rest, slow travel, fast 
travel, and mill/search; (2) quantify respirations and surface behaviors 
associated with feeding (surface and sub-surface) and non-feeding; (3) 
characterize feeding behavior for different types of prey (e.g. euphausiids vs. 
fish, shallow vs. deep prey); (4) identify prey species and determine their depth 
in the water column; and (5) relate the distribution of prey to topographic 
features and annual variations of environmental factors. 
5 
METHODS 

Surveys 
From 21 August to 5 November 1988, 26 August to 3 December 1989, 
and 29 August to 12 December 1990, data were collected in and around 
Cordell Bank and the Gulf of the Farallones (Fig. 1). In 1988, a 4.9-m Mark III 
Zodiac with a 25 HP outboard motor was used, and in 1989 and 1990 a 6.7 m 
Boston Whaler with a main 175 HP outboard engine and a 30 HP auxiliary 
engine was used. Both vessels were docked in Bodega Bay, and equipped with 
a VHF radio, LORAN, and Lowrance X-16 depth sounder (192 kHz, 20° cone 
angle). Mean scattering layer depths were visually estimated from the thickness 
of the echo traces and measured to the nearest meter in the water column. A 
portable time/event recorder (Tandy 102-32K) was interlaced with the vessel's 
LORAN and an external portable hard drive. During surveys, the vessels' 
speed, direction, and location were automatically recorded every 10 min into 
the time/event recorder and the external portable disk drive provided unlimited 
storage space. Other information consistently recorded during surveys included: 
number and species of birds present within 300 m; scattering layer depth 
(±1.0 m); and bottom depth (±1.0 m); and environmental data {discussed later}. 
Aerial surveys of the study area were conducted opportunistically to 
document whale distribution, abundance, and movement patterns 
(Calambokidis et al. 1989a, 1991 a). In addition, Oceanic Society Expeditions 
reported whale sightings near the Farallon Islands, and local commercial 
fishermen and party-boat skippers reported sightings around Cordell Bank and 
along the coast. 
6 
380 20' N 
Depth in Meters 1230 20' W 123' 00' W 
Figure 1. Humpback whale study area off central California (outlined) and 
geographical regions, Bodega Canyon, Cordell Bank, and the Farallon Islands 
referred to throughout the text as the primary sites of feeding activity. The study 
area was approximately 2600 km2, which included Cordell Bank and the Gulf of 
the Farallones National Marine Sanctuaries. 
Sampling effort usually occurred in areas of greatest whale 
concentrations, most frequently along Bodega Canyon, Cordell Bank, and the 
Farallon Islands (Fig. 2). Daily reports of the locations of whales determined our 
vessel course each day. Individual whales were tracked for approximately 30 
minutes, during which time their location and behavioral states were recorded. 
To minimize disturbance of whales during behavioral observations, the boat 
remained> 100 m from whales, which is a National Marine Fisheries Service 
guideline (Federal Register 1979). In addition, the smaller engine was used 
approximately 20 min before and during the observation period. The motor was 
run at a constant speed to avoid noise associated with throttle shift, which 
causes a ratchet-like sound underwater and changes in pitch (Baker et al. 1983; 
Kieckhefer pers. obs. 1985; Bauer 1986; Watkins 1986; Dolphin 1987a,b,c,d; 
Whitehead and Carlson 1988). Work was conducted under permits obtained by 
National Marine Fisheries Service (no. 579, 1988 and 1989 and no. 703, 1990) 
and the Department of Fish and Game (no. 2253, 2153, and 7022, respective 
years). 
Whale Observations 
Two to four boat crew described individual whale behaviors and 
respiration patterns, and entered behavioral codes and comments into the 
time/event recorder. At the start and end of each whale observation the 
following data were recorded: time, date, position, sighting number for the day, 
group size, number of calves, number of boats and ships present within 2 km, 
number and species of birds present within 300 m, mean scattering layer depth, 
bottom depth, and environmental and sea conditions. 
31"00 
Figure 2. Track lines of vessel surveys from September to November in 1988, and from September to December 
1989 and 1990. 
<Xl 
9 
A group was defined as whales within five body lengths of each other (WOrsig et 
al. 1986). Whale behaviors were categorized into 7 different states: rest, slow 
travel, fast travel, mill/search, surface feed, shallow feed, and deep feed 
(Appendix A). Behavioral categories were recorded throughout the observation 
period. Surface (0-10 m depth) feeding was the most obvious with behaviors 
such as, lateral, diagonal, and vertical lunging. Shallow (11-60 m) and deep 
(61-140 m) feeding depths of whales were indirectly determined from the 
occurrence of the scattering layer and echo traces of swimming whales. 
Unique whales (ones with distinctive dorsal fin shapes or pigmentation) 
of groups were identified and tracked with 7 x 50 binoculars (Fujinon). All 
surfacings, respirations, dives, and aerial behaviors were systematically 
entered into the portable time/event recorder (Baker et al. 1983; WOrsig et al. 
1984,1986; Bauer 1986; Appendix B). Five respiratory variables were 
recorded: blow interval, number of respirations (blows) per surface duration, 
duration at surface, dive duration, and blow rate (WOrsig et al. 1984, 1986; 
Dolphin 1987a; Appendix C). Duration at the surface included whales near the 
surface and blow intervals less than 90 seconds. Duration of dive was the 
period of time spent diving below the near-surface waters (approx. 5 m depth) 
and was distinguished by blow intervals greater than 90 sec or by posturing of 
tail stock (arched peduncle or raised flukes). All feeding behaviors (i.e. lateral 
lunging, diagonal lunging, and shallow vs. deep dives) were quantitatively 
documented. 
Opportunistic recordings of whale vocalizations were made on Marantz 
PMD-430 tape recording with a sonobuoy hydrophone and preamplifier. 
Sounds were categorized as feeding (uniform; D'Vincent et al. 1985), social 
10 
(unpatterned; Silber 1986), and songs (patterned; Payne and McVay 1971). All 
recording levels were constant throughout the study. Whale distance was 
estimated by volume level of recordings. After behavioral observations were 
concluded, all whales were approached slowly from behind, within 100 m when 
possible, photographed and identified by differences in dorsal fin shapes and 
pigmentation patterns on the ventral surface of their flukes (Katona et al. 1979). 
Various feeding behaviors also were photographically documented at this time. 
After photographs were taken, a new group of humpback whales would be 
located for observation. 
Because successive respiration variables of whales were not 
independent data points, this "standard" approach (e.g. Dolphin 1987b,c ; 
Guerrero 1989; Harvey and Mate, 1984; Wursig et al. 1984,1986) was not used 
in the statistical analyses. For comparative purposes to other studies using the 
standardized approach see Appendix D. 
To statistically test data correctly with observations independent of the 
mean, the mean of each individual whale was calculated and analyzed (Zar 
1984; Hoeskstra and Jansen 1986). Nonparametric statistics were used on all 
respiration variables analyzed due to their skewed distributions. Comparisons 
among years of mean surface duration, number of blows per surfacing, dive 
duration, and blow rate within each behavior category were tested using a 
Kruskal-Wallis test (3 group) and Mann-Whitney U-test (2 group) at the P ~0.05 
significance level. Means of respiration variables were calculated for each 
behavior category except for rest, which was rarely observed. A nonparametric 
TUkey-type multiple comparison test (with unequal sample sizes) was used to 
determine between year differences. All behavioral observations were of 
11 
unique adults and whales older than two years under "undisturbed" conditions 
(other vessels> 2 km away). Statistical methods followed Zar (1984). 
Prey Collections and Documentation 
Prey information (samples, depth records) was collected only after 
observing a focal whale for at least 30 min. Presence (or absence) of scattering 
layers, and their mean depth in the water column, were continuously recorded 
while passing through areas where whales were feeding. Prey were captured 
with a dip net, horizontal tows with a plankton net (0.75 m diameter, 505 !J,m 
mesh), or jigging with hook and line. 
For surface (0-10 m) plankton tows, the net was towed horizontally at the 
corresponding prey depth obtained from the depth sounder for 10 to 20 min at 
an average boat speed of 4-6 km/h. Indirect methods of identifying deep prey 
layers were used in 1988 and 1989 (e.g. stomach content analysis of local 
salmon and rockfish caught in areas where whales were feeding). Shallow 
(11-60 m) and deep (61-140 m) zooplankton net tows in 1990 were used to 
quantify the relative percentage of euphausiids and other zooplankton in areas 
where whales were feeding. Once mean depth of prey was determined on the 
depth sounder, a 12 kg lead ball was attached to the net's stainless steel hoop 
and the appropriate amount of line released. A wire angle was used to 
determine the amount of line required (hypotenuse) to sample within the 
targeted scattering layer. The net was towed at a constant speed (approx. 
4-6 km/h) and course for 10 to 20 min. 
12 
Laboratory Analyses 
Plankton samples were fixed in 10% formalin within 8 hrs of collection, 
and later transferred to 40% ethanol before analyses. Samples were split into 
approximately 50 ml volumes with a Folsom plankton splitter. Using an Olympus 
dissecting microscope (10x to 40x), euphausiids were sorted, identified to 
species (Kathman et al. 1986), and counted. 
Standard body length (tip of rostrum to tip of telson) was measured to the 
nearest millimeter for all Thysanoessa spinifera and Euphausia pacifica 
(Appendix E). Length comparisons of T. spinifera and E. pacifica were 
completed for 1990 only, because the previous years' towing gear did not 
provide adequate means of sampling deep-dwelling E. pacifica. Fertilized 
females of T. spinifera were distinguished by the presence of brownish, barbell­
shaped spermatophores. Size-frequency distributions were generated for 
pooled data for each year. Distributions of T. spinifera and E. pacifica for 1990 
and distributions of T. spinifera for 1988, 1989, and 1990 were statistically 
compared using Kolmogorov-Smirnov tests for difference in relative cumulative 
frequency distributions. 
Humpback whale fecal samples were collected opportunistically using a 
1 mm mesh net, bailing bucket, plastic bag, or nylon stocking. Samples were 
divided and preserved in 10% formalin and 40% ethanol (the latter was used 
due to a concern that 10% formalin might dissolve fish otoliths). All fish otoliths, 
and euphausiid right mandibles (Appendix F) and spermatophores were 
identified to species and counted from 5-ml aliquots of each sample. 
Total body length of T. spinifera and E. pacifica were estimated from a 
regression equation applied to lengths of mandibles found in fecal samples. 
13 
Total body length classes of 10 mm, 15 mm, and 20 mm for T. spinifera 
(n = 169) and E. pacifica (n = 144) taken from plankton samples were equally 
selected and measured to the nearest millimeter. Right mandibles were 
removed and measured (tip of incisors to tip of mandibular insertion) to ±0.1 mm 
with an Olympus Image Analyzer (Appendix E, F). Regression functions of total 
body length and total mandible length were calculated for both T. spinifera and 
E. pacifica. 
Environmental Data 
Environmental data were entered into the time/event recorder every 
survey hour or new whale sighting, and were updated as necessary every 10 
min. Data included: sky condition and sea state (Appendix G), swell height 
(±0.5 m), secchi depth (±0.1 m), sea surface temperature (±0.2°C). along with 
bottom depth and mean scattering layer depth. Secchi depths were collected 
with a circular white-vinyl disk of 27-cm diameter and measured as described in 
Preisendorfer (1986). Sea surface temperature data were collected with a 
calibrated Micronta digital thermometer 
Throughout each survey, a separate computer (LI-COR DataLogger) was 
programmed to continually record average surface light levels every 10 min 
from a fixed directional light meter (Quantum 2700). Light levels were measured 
in JlE m-2 s-1, where 2000 JlE m-2 s-1 was equivalent to a clear and sunny sky at 
12 noon. Total light energy was restricted to the wavelengths between 300 and 
720 nm or photosynthetically available radiation (PAR). Average light levels 
were measured instead of instantaneous levels due to rough sea conditions 
and continual pitch and roll of the research vessel. Light penetrating the water 
14 
to a depth of 10m was calculated from secchi depth using the vertical extinction 
coefficient as described in Parsons et al. (1984). 
Other indicators of changing environmental conditions such as 
occurrence of red tide blooms, sea birds, fish, and turtles in the study area were 
noted and their positions recorded. Red tide samples were collected (via 303 
Ilm mesh net or wide-mouth sample jar) and brought to the laboratory for 
identification. 
Polynomial curves (2-degree) were fitted to daily mean scattering layer 
depth, sea surface temperature, Secchi depth, Beaufort state, and bottom depth 
for all whale sightings collected in 1989 and 1990. To determine if an 
environmental variable{s) had a significant effect on the vertical distribution of 
the scattering layer during 1989 and 1990, a stepwise regression at the P ~0.05 
significance level was applied. Daily mean light measurements and 
corresponding scattering layer depths were analyzed separately. 
Monthly coastal upwelling indices at 39°N, 125°W and sea surface 
temperature at NOAA buoy 46013 (38.2°N, 123.3°W) were compared from July 
through December 1989-90. In addition, archived satellite images of sea surface 
temperature (SST) were studied and images that clearly show the oceanographic 
conditions in the study area from July through December 1989-90, were processed 
at the Naval Postgraduate School in Monterey, California. 
15 
RESULTS 

Whale Sightings 
Humpback whale groups were observed for 232 hours during autumn of 
1988, 1989 and 1990. Whale behavior was recorded on 26 groups (27 h) 
during 31 days at sea in 1988, 99 groups (96 h) during 53 days in 1989, and 
146 groups (109 h) during 56 days in 1990. During these periods, mean group 
size was 2.1 to 3.0 individuals (1988: 2.5 ±1.38 SO, range = 1-6; 1989: 3.0 
±1.73 SO, range =1-12; 1990: 2.1 ±1.29 SO, range = 1-12). Detailed 
observations of respiration patterns and other surface activity were made on 
138 different individuals: 23 in 1988 (12.5 total hours), 51 in 1989 (25.8 hours), 
and 64 in 1990 (25.0 hours). 
Locations of humpback whale observations varied among years. In 1988, 
humpback whales and prey were dispersed and did not feed for long periods of 
time at one location. In 1989, concentrations of whales were located west of the 
Farallon Islands in September and near Cordell Bank and Bodega Canyon in 
mid-October and November. In mid-September 1990, whales were found in 
shallow waters near Fort Ross, whereas in October and November 
concentrations of whales occurred around Bodega Canyon and Cordell Bank 
(Fig. 3). 
Mother-calf pairs were observed infrequently in all 3 years. In 1988, two 
sightings were made near North Farallon Island. Two sightings occurred near 
southeast Farallon Island in 1989, and eight sightings near Bodega Canyon 
and Cordell Bank were recorded in 1990. 
38"20' 
3a~ 00' 
:)7040' 
Figure 3. Locations of humpback whales and prey, humpbacks without prey, prey without humpbacks, and no 
humpbacks and no prey from vessel surveys during the fall of 1988, 1989, and 1990. The presence or absence 
of prey was primarily based on depth sounder recordings. 
...... 
0> 
17 
Whale Behavior 
Feeding was the most prevalent activity observed in all three years, 
comprising about half the total percent frequency of occurrence (mean =51.4% 
±4.94 SO; Fig. 4). Mill/search behavior a.nd slow travel occurred less often than 
feeding, and were seen with comparable frequency throughout the study (mean 
= 21.5 ±2.04 SO and 16.4 ±1.07 SO, respectively). Fast travel and rest occurred 
infrequently (mean =6.5 ±1.87 SO and 4.2 ±4.08 SO, respectively) in all three 
years (Fig. 4). 
Feeding depth varied significantly among years according to changes in 
depth of prey (X2 = 115.5, df = 4, P < 0.001 ; Fig. 5). Surface feeding (0-10 m 
prey depth) was observed in 1988 and 1990, but was not seen in 1989. Oeep 
sub-surface feeding (61-140 m prey depth) occurred mainly in 1989, less 
frequently in 1990, and was not observed in 1988. Shallow sub-surface feeding 
(11-60 m prey dept h) occu rred in all years. 
Respiration variables were recorded for each behavior category except 
for rest, which was rarely observed (Table 1). Among-year differences in mean 
blow rate were significant only for feeding and milling behaviors (H = 7.95, 
P < 0.01 and H = 6.53, P < 0.05; df =2; Fig. 6). When feeding, blow rate was 
less in 1989 than either 1988 or 1990; however, mean blow rates were 
statistically different only when 1988 and 1989 were compared (1.7 vs. 1.1; 
Q=2.80, df = 3, P < 0.01). There was no difference in mean blow rate among 
years when whales were engaged in slow travel and fast travel. 
60 
1988 0 
1989 II 
() 
c 
CD 5°1~ 1990 II 
Feed Mill/Search Fast Travel Slow Travel Rest 
Figure 4. Percent frequency of humpback whale behaviors observed in 1988-1990. Sample sizes are above bars. 
CD
...
... 
40:::s () 
() 
0
-0 30
>­() 
c 
CD
:::s 
20C" CD
... 
La. 
tft 
10 
0 
..... 
0:> 
1989 II 
1 1990 II 
I 011 • 0 Surface (0-10 m) Shallow (11-60 m) Deep (61-140 m) 
4360, 11988 D I 

CD 50 i 

u 
c 
CD 
a-
a­
::J 40u 
u 
0
-o 30
>­u 
c 
CD 
::J 
C" 20CD 
a-
U. 
~ 0 
10 
J I i 
Figure 5. Percent frequency of surface, shallow, and deep feeding. Sample sizes are above bars. 
..... 
(.0 
Table 1. Respiration variables by behavioral categories of feeding, milling, and traveling humpback whales. 
Independent sampled means were calculated from the mean of individual whales (bold) for each year. Total number 
of sampled means are shown in parentheses. Among years significance levels from Kruskal-Wallis test are coded 
as follows: ***P<O.001, ** P<O.01 , *P<O.05, ns =not significant. 
RESPIRATION 
VARIABLE 
BEHAVIOR CATEGORY 
88 
Feeding 
89 90 
Mill/Search 
88 89 90 
Fast Travel 
88 89 90 
Slow Travel 
88 89 90 
Duration at Surface 
mean (min) 
SO 
95%Cl 
n 
(n) 
0.9 
0.52 
0.37 
10 
(132) 
••• 
3.4 
1.54 
0.53 
35 
(120) 
1.7 
0.88 
0.27 
42 
(299) 
••• 
0.9 3.0 2.0 
0.51 1.29 1.33 
0.53 0.78 0.56 
6 13 24 
(27) (36) (59) 
ns 
1.0 1.8 1.1 
0.38 1.66 0.36 
0.29 2.06 0.37 
9 5 6 
(55) (32) (23) 
ns 
1.3 1.8 1.3 
0.72 1.17 1.01 
0.67 0.68 0.47 
7 14 20 
(21) (46) (53) 
No. Blows/Surface Duration 
mean 
SO 
95% Cl 
n 
(n) 
3.3 
1.79 
1.28 
10 
(132) 
••• 
11.8 
4.62 
1.59 
35 
(120) 
5.8 
3.11 
0.97 
42 
(299) 
••• 
3.1 10.3 6.7 
0.70 4.57 4.00 
0.73 2.76 1.69 
6 13 24 
(27) (36) (59) 
ns 
3.8 5.6 3.5 
1.14 4.32 1.16 
0.88 5.37 1.21 
9 5 6 
(55) (32) (23) 
ns 
4.7 6.3 4.3 
1.26 3.97 2.47 
1.17 2.29 1.15 
7 14 20 
(21) (46) (53) 
Duration of Dive 
mean (min) 
SO 
95%Cl 
n 
(n) 
1.4 
0.91 
0.65 
10 
(125) 
••• 
6.7 
2.67 
1.06 
27 
(105) 
3.4 
2.80 
0.95 
36 
(290) 
•• 
0.7 5.5 4.9 
0.40 2.12 3.04 
0.50 1.51 1.35 
5 10 22 
(19) (32) (58) 
ns 
1.8 4.1 1.6 
1.28 2.12 1.08 
1.19 2.64 1.13 
7 5 6 
(48) (33) (22) 
ns 
2.5 4.4 2.6 
0.84 2.37 1.76 
0.89 1.43 0.90 
6 13 17 
(18) (46) (48) 
Blow Interval 
mean (sec) 
SO 
95%Cl 
n 
(n) 
19.5 
7.64 
5.47 
10 
(197) 
ns 
18.2 
3.23 
1.06 
38 
(1279) 
21.0 
8.86 
2.73 
43 
(954) 
ns 
20.2 19.1 20.5 
7.94 2.76 8.39 
8.33 1.60 3.46 
6 14 25 
(54) (251) (331) 
ns 
19.2 20.4 22.8 
3.65 2.21 8.16 
2.46 2.32 6.82 
11 6 8 
(162) (118) (72) 
ns 
18.7 18.9 21.4 
6.34 3.74 8.85 
5.87 2.16 4.03 
7 14 21 
(70) (223) (147) 
Blow Rate 
mean (no. blows/min) 
SO 
95%Cl 
n 
(n) 
1.7 
0.92 
0.68 
10 
(123) 
•• 
1.1 
0.19 
0.08 
24 
(84) 
1.3 
0.47 
0.17 
34 
(254) 
• 
2.1 1.2 1.2 
0.57 0.57 0.65 
0.71 0.40 0.30 
5 10 20 
(18) (26) (46) 
ns 
2.0 1.2 1.3 
0.76 0.87 0.35 
0.70 1.08 0.37 
7 5 6 
(46) (31) (20) 
ns 
1.2 1.2 1.3 
0.17 0.70 0.66 
0.18 0.42 0.37 
6 13 15 
(18) (40) (42) I 
N 
o 
53.0 7(18)10 (46) 
(123) 
5C 2.5 
(31 )'E 
... 
10 20 13 15 
(40) (42)1\1 (26) (46)34~ 2.0 
(254)~ ~:is 6 
(18)g 1.5 N IIII *
** ns 11111kt" ns 
-~ a:: 1.0 
~ 
iii 0.5 
O.O~I--~--.--r----~--~~~----~~--~-----r--~~---
88 89 90 88 89 90 88 89 90 88 89 90 
Feeding Mill/Search Fast Travel Slow Travel 
Figure 6. Mean blow rate of feeding, milling, and traveling humpback whales in 1988, 1989, and 1990. 
Mean (horizontal bar),±1 standard deviation (vertical line), ±95%confidence limits (box), numberofwhales 
(bold). and successive sample size (in parentheses) are shown. Between year significance levels from 
Kruskal-Wallis test are coded as follows: *** P<0.001, **P<0.01, * P<0.05, ns =not significant. 
I\.) 
..... 
22 
Respiratory patterns of feeding whales differed dramatically among 
years. The surface duration, number of blows per surface duration, and dive 
duration were significantly greater in 1989 than 1988 or 1990 (H 2! 12.73, df =2, 
P < 0.001; Fig. 7). These same three respiration variables were greater in 1989 
than 1988 and 1990 for shallow dives (Fig. 8). but there was no difference in 
these variables in 1988 and 1990. Surface duration and number of blows per 
surface duration during deep feeding were significantly greater in 1989 than 
1990 (2 =2.81 and 2.74, df =00, P < 0.01). Mean dive duration, however, was 
not significantly different between 1989 (6.3 min ± 2.91 SO) and 1990 (5.9 min 
± 2.31 SO). Within each year, increasing prey depth was strongly associated 
with increasing feeding dive duration, surface duration, and number of blows 
per surface duration. This relationship was best documented in 1990, the only 
year when feeding was recorded in all 3 depth categories (H = 12.73, H = 
25.57, H =24.85, respectively; df =2; all P < 0.001 ; Fig. 9). 
Surface feeding whales typically lunged to capture prey (92% total 
surfacings). They consistently performed lateral lunges (84% of surfacings) to 
capture prey more than other types of lunges (diagonal lunges 7%; vertical 
lunges 1 %). Bubble-clouds were observed just before an executed diagonal 
and lateral lunge (Fig. 10). Due to variable sea conditions and observation 
distances exceeding 100 m most of the time, counts of bubble-clouds were not 
made consistently. 
23 
(120) 
a. 
5.5 35 
5.0 
'2 4.5 

'E 4.0 

6 3.5 
:;:: 
42 
::I 
~ 3.0 
(299)
o 2.5 
CII 
u ~ 2.0 10 *** (132)~ 1.5 
1.0 
0.5 
0.0 +------r---------r-------~---
1988 1989 1990 
b. 
3518 (120)c:: 

.,g 16 

~ 

~ 14 

~ 12 

~ 
 42 ~ 10 (299) 
i 8 

10 

6 
 ***(132) 
4 
o 2 
z 
o +------r---------r-------~---
1988 1989 1990 
c. 10.5 27 
(105) 
9.0 
"2 7.5 36'E (290)6 6.0 
:;:: 
~ 

~ 4.5 

CII *** 10>is 3.0 (125) 
1.5 
O.O+------r-------,-------,---­
1988 1989 1990 
Year 
Figure 7. Surface duration, number of blows per surface duration, and dive 
duration in 1988, 1989, and 1990 for feeding at all depths (0-140 m). Presentation 
as in Figure 6. 
24 
a. 
6 

8 
 26
(36) (84) 
b. 

18 
 26
8
c (84)(36)
.g 16 

III
B14 

CD 17 

i! '" 12 

~ 10 

!. 8 
 ~... 
!II 
~ 6 5 15 
 *** (203)~ 4 ill. 
·ens ~ 2 ill 
o+-~__~O__~____~-'__~____~O~~__r-__ 
~ $ 00 ~ ~ 00 ~ $ 00 
c. 

10 
 7 20 

(34) (71) 13 

9 
 (35) 
8 

'E" 7 
 12
g (55) 
ns§ 6 

.~ 5 

d 4 
 ......... 

5GI 3 

5 15
2 
 (75) (200) 

tll"~"$ns 0 

O+-~--T--.-----.--~~----~~~--r--
~ ~ 00 ~ ~ 00 ~ ~ 00 
Surface (0-10 m) Shallow (11-60 m) Oeep (61-140 m) 
Depth of Dive 
Figure 8. Surface duration, number of blows per surface duration, and dive 

duration of surface (0-10 m), shallow (11-60 m), deep (61-140 m) feeding, 1988­
1990. Between year significance levels are from Kruskal-Wallis test (3 groups) 

and Mann-Whitney U-test (2 groups). Presentation as in Figure 6. 

25 
a. 
3.5 

17 

(41)3.0 
14C (55)!. 2.5 
c *** o 15 
(203)! 2.0 
:::I Q 
III 1.5 
~ 
~ 1.0 
0.5 
0.0+----.---------...------..---­
b. 1712 (41) 

.S! 

i! 10 

c 
:::I 14 
i
Q (55) *** 
8 
~ i 6 
1/1 
~ 4 
iii 
'0 2 
~ 
o+-----.--------~------------~---
c. 139 
(35) 
8 
127 
(55) 
***!.c 6 
! 
c 
o 
:::I 
Q 
III
.=: 
Q 
o+i----~------------~----------~------
Surface (0-10 m) Shallow (11-60 m) Deep (61-140 m) 
Depth of Dive 
Figure 9. Surface duration, number of blows per surface duration, and dive 
duration of surface (0-10 m). shallow (11-60 m), deep (61-140 m) feeding for 
1990. Between year significance levels are from Kruskal-Wallis test (3 groups). 
Presentation as in Figure 6. 
26 
8. 

b. 
c. 
Figure 10. Humpback whale bubble-cloud formation: a) bubbles seen underwater 
coming out of a whale's mouth in Hawaii,1982, b) bubbles breaking-down into fine 
mist (photos by author, courtesy of Kewalo Basin Marine Mammal Lab), and c) whale 
blowing a bubble-cloud just before a lateral lunge near Cordell Bank, California, 1990 
(photo by Daniel E. Shapiro). 
27 
Fluke-down, fluke-up, and high tluke-up behaviors preceding feeding 
dives were strongly correlated to prey depth (X2 = 117.13, df = 4, P < 0.001 ; 
Fig. 11). Fluke-down dives occurred most often during surface feeding (44% of 
total surface feeding dives). Fluke-up dives occurred most often during shallow 
feeding (67%); high fluke-up dives were seen most often during deep feeding 
(60%). Deep feeding dives were also typically preceded by a distinctive flex 
posture (i.e. a rolling concave stretch of the entire tail stock just before a high 
fluke-up dive). This flex posture preceded 77% of deep-feeding dives, and was 
never observed during surface or shallow feeding. 
No attempt was made to record whale depth on the depth sounder. 
However, on seven occasions depth sounder records incidentally documented 
a fluke-down (30°), fluke-up (50°), and high fluke-up (80°) dive. On one 
occasion the entire descent (75° angle from surface) and ascent (60° angle to 
surface) of a whale travelling through a scattering layer at a mean depth of 100 
m was recorded (Fig. 12). The duration of the dive was 4.2 min. 
In 1988-90, 32 opportunistic hydrophone recordings were made of 
humpback whales engaged in feeding, mill/search, and traveling (Table 2). 
Recordings were 15 min to 45 min in duration, totaling 12.8 h of recording time 
for the 3-year period. Feeding sounds, social sounds, and songs were 
qualitatively distinguished for each behavior using characteristics identified by 
D'Vincent et al. (1985), Silber (1986), and Payne and McVay (1971). No 
feeding vocalizations were recorded. Whales were quiet during all modes of 
feeding, except for singers recorded during deep feeding on 24 September and 
8 October, 1989. 
a. b. c. 
ij-
Surface Feed 

(0-10 m) 

n", 305 

Shallow Feed 

(11-61 m) 

n:. 166 

Deep Feed 

(61-140 m) 

n =160 

31 
'f~ 
r-­
r-­
o 10 20 30 40 50 60 70 

% Auke-down Dives 

o 10 20 30 40 50 60 70 

% Auke-up Dives 

o 10 20 30 40 50 60 70 

% High Fluke-up Dives 

Figure 11. Percentage of fluke-down, fluke-up, and high fluke-up dives for surface (0-1 0 m). shallow (11-60 m), deep 
(61-140 m) feeding depths. Sample sizes (n) are shown. 
N 
co 
- -
- - - - - - - -
29 
a. 30° Descent b. 50° Descent c. 80° Descent 
0.0­
_~p?ir_ 
40.0­
Fluke-down 
- - Dive- - - - ­
80.0­
- - -
. 
- - - ­
120.0­
. 
-
. . 
-
. . . 
-
160.0­
. 
200.0 M 
t----O.O 
. . 
-
. . 
- -
. 
­
120.0 
. 
-
. .
- -
. 
- ­
160.0 
-
. . 
-
. . . . . 
200.0 Mnom 
t----o.o 
High Fluke-up . 
Dive 
d. 75° Descent and 60° Ascent 
......--0.0-----------1 
High Fluke-up 

- Dive 

Figure 12. Depth sounder records of whales diving at (a) 30° fluke-down, (b) 
50° fluke-up, and (c) 80° high fluke-up_ Bottom chart recording (d) documents 
an entire descent (75° angle from surface) and ascent (60° angle to surface) 
of a whale swimming through a deep scattering layer. Duration of dive was 4 
min and 30 seconds. 
Table 2. Opportunistic recordings of humpback whale sounds in the Cordell Bank! Farallon Basin area during the 
fall of 1988to 1990. Feeding depth categories of surface (0-10 m), shallow (11-60 m), and deep (61-140 m) in bold. 
Vocalizations are scored either yes (Y) or no (N) and described as feeding, social, and/or songs (after O'Vincent 
et al 1985; Silber 1986; Payne and McVay 1971) 
Desciptlon1Distant Vocal VocalYear I Date I Location I TIme I Behavior TGroup1Calve (m-d) (lat. & long.) (h:m) Category Size (V or N) (V or N) 
.:.:.:.:.:.:.:.:.:.;.;.:.:.:.:.:.; :.:.:-:.:.:.:.:.:.:.:.:.:.:.:.::-:.:.:.:-;...........................;.:.:.:.:-:.:...:.:.:-:.:-:.:-:.:.:.:.:.:.:.: :.:-:.:.:.:.:-:.:.:-:.:.:-:........ .............................................:.. -: .....:.:.:.:.:.:.:.:...;...;.:-:.:-:.:.::-:.:.:.:.:.:-:.;......... 
1988 ISep-O1 37° 51 'N, 123° OS'W 15:45 surface feed 4 0 N N 
Sep-02 37° 51 'N, 123° OS'W 10:35 surface feed 4 0 N N 
Sep-21 37° 57'N, 123° 12'W 14:51 slow travel 3 1 Y singing Y 
Oct-12 38° 02'N, 123° 13'W 17:14 surface feed 2 0 N N 
Oct-12 38° oo'N, 123° 25'W 18:36 slow travel 2 0 Y social Y 
Oct-29 38° 20'N, 123° 28'W 14:43 mill/search 2 0 N N 
Oct-30 38° 04'N, 123° 21'W 11:25 mill/search 4 0 Y singing Y 
Oct-30 38° 04'N, 123° 22'W 12:19 slow travel 2 0 Y singing Y 
:.:.:.:.:.:.:.:-:.:.:.:.:.:...................... :.:.;.:.......................................................................:...:.:.:.:.: :.:.:- ..:.:.:.:.:.:.:.:.:-:.:.:-:.:-:.:-:-:.;.:-:-:......................................;.....;.;.:.:.:-:.:.:.:.:.:.:-:.:-:.:.:.:.:.:.:.:.:........ 
1989 ISep-07 37° 41 'N, 123° 04'W 15:00 slow travel 4 0 Y social N 
Sep-08 37° 45'N, 123° 10'W 15:47 mill/search 4 0 N N 
Sep-12 38° 09'N, 123° 18'W 12:45 deep feed 2 0 N N 
Sep-13 37° 55'N, 123° 26'W 15:15 deep feed 3 0 N N 
Sep-14 37° 45'N, 123° 04'W 16:15 mill/search 1 0 N Y 
Sep-24 37° 46'N, 123° 13'W 11:30 deep feed 2 0 V singing Y 
Oct-08 38° 17'N, 123° 25'W 14:45 deep feed 5 0 V singing Y 
Oct-09 38° 14'N, 123° 25'W 13:00 deep feed 3 0 N N 
Oct-09 38° 16'N, 123° 29'W 17:45 deep feed 2 0 N N 
Oct-31 38° 10'N, 123° 27'W 14:13 shallow feed 2 0 N Y 
Oct-31 38° 10'N, 123° 23'W 18:15 shallow feed 2 0 N N 
Nov-09 38° OS'N, 123° 23'W 15:35 shallow feed 2 0 N Y 
1990 I Sep-20 
.....:.:.:::::::::::::::::::::::: 
38° 24'N, 123° 12'W 16:03 
':':"':':':':"':"':"':';';"':':::::::::::'::.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.'. 
shallow feed 12 N N 
Sep-21 38° 30'N, 123° 17'W 18:15 surface feed 1 0 N N 
Sep-25 38° 28'N, 123° 20'W 16:30 surface feed 1 0 N N 
Oct-25 38° 04'N, 123° 28'W 16:19 mill/search 3 0 N Y 
Oct-26 38° OS'N, 123° 28'W 15:59 mill/search 2 0 Y 
Oct-27 38°OS'N, 123° 31'W 18:01 slow travel lOY 
Nov-l0 37° 58'N, 123° 26'W 13:00 deep feed 2 0 I 
Nov-ll 38° oo'N, 123° 27'W 17:30 deep feed 2 0 
Nov-13 37° 56'N, 123° 28'W 11 :51 mill/search 3 1 
Nov-17 37° 58'N, 123° 19'W 14:16 surface feed 2 0 
Nov-18 37° 58'N, 123° 21'W 12:15 surface feed 1 0 
Nov-18 37° 59'N, 123° 21'W 13:09 surface feed 2 0 
..........:...:...:.:.:.:.. '.:.:.:.:.:.' 
w 
o 
31 
Songs of seven humpback whales were recorded: one near Point Reyes 
(9/21/88) and the Farallon Islands (9/24/89), two near Cordell Bank (10/30/88), 
and three near Bodega Canyon (10/8/89, 10/26/90, 10/27/90). Distant 
vocalizations (social) comprised over half (56%) the recordings made in 1988­
90. Songs of humpback whales were recorded earlier in 1988 (9/21) and 1989 
(9/24) than in 1990 (10/26). 
Prey Occurrence 
In 1988 and 1990, humpback whales fed on euphausiids (primarily T. 
spinifera) and occasionally schooling fishes (primarily C. pal/asil) , whereas in 
1989, whales were only observed feeding on euphausiids (primarily T. spinifera 
and E. pacifica ). Prey of surface-feeding whales were occasionally visible from 
the observation boat. In 1988 and 1990, euphausiid swarms were repeatedly 
(n=17) seen near lunge-feeding whales. On five occasions, surface-feeding 
whales were observed feeding on schooling fish. These fish were tentatively 
identified as Pacific herring,Clupea pal/asii in four feeding events and juvenile 
rockfish, Sebastes spp. during one feeding period. In Half Moon Bay, 40 km 
south of the study area, humpbacks were frequently reported feeding on 
northern anchovy (E. mordax) throughout this 3-year study (pers. comm. R. 
LaMar 1990). 
Depth of scattering layers during September and October varied 
significantly among years. Prey were consistently shallower in September­
October 1988 (13.9 m ± 10.97 SO, n = 31) and 1990 (27.5 m ± 29.63 SO, 
n = 38) than in 1989 (115.2 m ± 41.10 SO, n = 87). A deep (61-140 m) 
scattering layer was never recorded in 1988, and only rarely (14%, n = 12) in 
32 
1990. In contrast, 82% of scattering layers recorded in 1989 (n=31) occurred 
below 60 m depth (Fig. 13). 
Eleven fecal samples of humpback whales were opportunistically 
collected in 1987 (n=1 ; collected by Cascadia Research Collective), 1988 (n=2), 
1989 (n=2), and 1990 (n=6). Fecal samples contained only euphausiid hard 
parts. Based on right mandible counts, samples were composed of 80.6% 
Thysanoessa spinifera (±15.21 SO, n = 1848) and 8.3% Euphausia pacifica 
(±16.41 SO, n = 291; Table 3). No evidence of fish prey (e.g. otoliths, vertebrae) 
were found in fecal material. 
Plankton tows were consistently dominated by a single euphausiid 
species. In 1990, when vessel equipment allowed sampling of all three prey 
depths, T. spinifera comprised 98.1 % of surface tows (0-10 m) and 87.6% of 
shallow tows (11-60 m). Euphausia pacifica comprised 99.6% of deep 
(61-140 m) tows. Small numbers of Nyctiphanes simplex (1.7% and 0.4%) and 
Nematoscelis difficilis (1.5%) were caught in surface and shallow tows, 
respectively. In 1990, T. spinifera were significantly larger (12.3 mm ± 2.54 SO) 
than E. pacifica (11.4 mm ± 2.05 SO; 0 = 27.94, P < 0.001; Fig. 14). 
Mean lengths of T. spinifera decreased significantly from 1988 to 1990 
(0 ~ 24.84, P < 0.001). Individuals were largest in 1988 (15.9 mm ± 2.52 SO), 
smaller in 1989 (12.8 mm ± 1.34 SO) and smallest in 1990 (12.3 mm ± 2.54 SO; 
Fig. 15). 
Calculated standard body lengths of T. spinifera and E. pacifica in fecal 
samples were longer than those caught in tow samples. Calculations were 
based on linear regressions of body length to mandible length from tow 
samples (Fig. 16). 
33 
a. 1----------------0.0__--I 
1----------------40.0-----I 
1----------------80.0----I 
b. 1--------------0.0------I 
1-------'----------8.0-------I 
-- ­
,.r~: 
1-----...........------32.0 ----'-'~----..I 

1-----LOWRANCE----40.0 M-------j 
Figure 13. Depth sounder records documenting (a) deep scattering layer with 
a mean depth of 124 m on September 8, 1989 and (b) shallow scattering layer 
with a mean depth of 19 m on October 31,1989, which only occurred later in the 
1989 season. 
34 
Table 3. Humpback whale fecal samples (n = 11) collected in the study area 
during the fall of 1987 to 1990. Right mandibles and spermatophores were 
identified for each species and counted from a 10 ml aliquot. Sample sizes (in 
parentheses) and ±1 standard deviations of the grand mean are shown. 
No. of Sperma" ...Date Percentage of Right Mandibles 
T. splnifera E. pacifica Unknown? T. spinlfera E. pacifica 
1987 
Oct 7* 0 086% 0% 14% 
(63) (0) (10) 
1988 
Oct 16* 2 089% 0% 11% 
(41 ) (0) (5) 

Oct 16* 
 85% 0% 15% 11 0 
(79) (0) (14) 
1989 
Sep 24 75% 11% 14% 98 0 
(162) (22) (31 ) 

Dec 2 
 44% 48% 8% 0 0 
(86) (93) (15) 
1990 
Aug 30 1 060% 32% 8% 
(326) (176) (43) 

Oct 9 
 130 088% 0% 12% 
(144) (0) (20) 

Oct 27* 
 89% 0% 11% a a 
(176) (0) (22) 

Nov 12 
 89% 0% 11% 2 0 
(276) (0) (33) 

Nov12 
 87% 0% 13% 5 a 
(193) (0) (30) 

Nov 13* 
 94% 0% 6% 2 a 
(302) (0) (19) 

Grand 
 80.6% 8.3% 11.1% 23 0 

Mean 
 ± 15.21 SO ±16.41S0 ± 3.00 SO ± 45.8 SO 
(1848) (291 ) (242) (251) 
Other Prey Remains: 
Trace findings of copepods, fish eggs, ctenophores, and polychaetes. 
*Note: samples collected by Cascadia Research Collective. 
30 
~ T.~p;n;fera 
x = 12.3 mm 

CD 25 ~ I SO = 2.52, n =2674 
() 
c: III E':"'p8Cifica20 
x = 11.4 mm 
SO = 2.05, n = 10661 1 III 
'0 15 

>. 
()
c: 
~ 10 
0­
e 
u. 
'ifl. 5 
o ~5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 :::::25 
Body Length (mm) 
Figure 14. Length frequency histogram of 1990 tow samples, comparing the lengths of 
Thysanoessa spinifera to Euphausia pacifica (22 tows and 13 tows, respectively). 
w (J1 
36 
25 
20 
15 
10 
5 
9 10 11 12 13 14 15 16 17 18 1 9 20 21 22 23 24 ;,25 
1989 
T. spinifera 
X=12.7 mm 
SD - 1.34 
(n = 403) 
~ Undetm. Sex 
• Fer!. Female 
S5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 ;,25 

1990 

T. spinifera 
X= 12.3 mm 

SD·2.52 

(n.2674) 

S5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 ;,25 

Body Length (mm) 

Figure 15. Length frequency of Thysanoessa spinifera caught in tows for 1988, 

1989, and 1990 (4, 3, and 22 tows, respectively). Fertilized females (black) were 

distinguished by the presence of transferred spermatophore packets. 

30 

25 

20 

15 

10 

5 

0 

30 

III 

u 
I:: 
III

...
... 
:::l 

U 

U 

-
0 
0 
>­
u 
I:: 
III 

:::l 

CT 
III

... 
u.. 
~ 0 
30 

25 

20 

15 

10 

5 

1988 
T. splnlfera 
x=15.9 mm 
SD - 2.52 
(n .156) 
S5 6 7 8 

37 
a. Thysanoessa spinifera 

30t.=~t=~==~==~==~======~~--~--~--~ 
28 
26
-E 24 
.§. 22 
J:0, 20 01 ........ """" .. ""+" 
C ~ 18 
>. 16 
"C 
o 14 
CD 
12 
10 
8+-~~~~r-T-,-~~~~~~-r~--r-~~--~--~~ 
.4 .6 .8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 
b. Euphausia pacifica 
30+---~~~~~~~-+~~~--~~--~~~~~----+ 
28 ·1 y =12.95x + 2.84, r-squared =0.928 *** 
- 26'EE 24
-J: 22
-Dl 20 -I."""""""""C 
~ 18 
~ 16 
o 
m 14 
12 "' ........."" ..,..... 
10 
8~~-r~~r-~;-~~~~~---r~--r-T-~---;--~~ 
.4 .6 .8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 
Mandible Length (mm) 
Figure 16. Linear regressions of standard body length versus right mandible 
length of Thysanoessa spinifera and Euphausia pacifica. Equations, 95% 
confidence limits for the slope of regression line, and significant levels of*** 
P<O.001 are shown. 
38 
Mean body lengths (± SO) of T. spinifera in fecal samples were 16.0 mm (±1.81) 
in 1988, 16.7 mm (±2.19) in 1989, and 16.2 mm (±1.88) in 1990. Euphausia 
pacifica had a mean body length of 16.1 mm (±2.16) in 1989 and 16.0 mm 
(±2.58) in 1990 (Fig. 17). 
There was a greater percentage of fertilized female euphausiids in the 
plankton tows for 1988 (34.5%) than 1989 (0%) and 1990 (1.1%; Fig. 15). 
Thysanoessa spinifera spermatophores were identified in fecal samples each 
year; the highest number occurred in 1989 (96 on 24 Sep) and 1990 (130 on 9 
Oct; Table 3). 
In 1990, T. spinifera were most of the biomass collected in surface and 
shallow plankton tows (grand mean = 92.8% ±7.35 SO), whereas E. pacifica 
accounted for 99.6% ±0.64 SO of the biomass in deep tows (Table 4). 
Nyctiphanes simp/ex and N. difficilis occurred rarely and only in surface and 
shallow tows (grand mean = 1.1 % ±0.92 SO and 0.8% ±1 .06 SO, respectively). 
The occurrence of 3 species of planktivores, Cassin's auklet (Ptychoramphus 
a/euticus) , Red Phalaropes (Pha/aropus fulicaria), and Red-necked Phalaropes 
(P. /obatus), were closely correlated with the presence of surface and near­
surface scattering layers (Fig. 18). 
Environmental Data & Red Tide 
Daily mean scattering layer depths and corresponding environmental 
factors when whales were present were measured less frequently in 1989 than 
1990 (18 and 32 days, respectively). For 1989 and 1990, the daily surface 
temperature, Secchi depth, Beaufort state, and bottom depth were highly 
variable compared to the distribution of scattering layer depths (Fig. 19). 
39 
"" a. October 16(1) 
12l16.2. 1.64 SO. n .381 b. October 16(2) 
c. September 24 
16.5.2.70 so, n. 911 
17.8 ± 2.(0 SO, n - 16 
"" d. December 2 
.. 
"" e. August 30 
15.7.1.57 SO,". 127, 
16.0±2.58S0,".97 : 
$,10 11 til 13 1. 15 16 17 18 19 20 21 2'2' 23 ~2. 
g.October27 
t?i18.0' 1.61 SO, n .115: 
"10 11 12 13 ,. 15 16 17 18 19 20 21 22 23 ~24 
30 I. November 12(2) fgl6.6' 1.8350,".1561 
os , 
,. 
,s 
'0 
S10 11 12 13 H 1$ ,. 17 18 13' 20' 21 22 23 ~2. 
Body Lengll> (frml 
30 f. October 9 !g15.3. 2.35 SO, n· 821 
.. 
J 
r 
t , • 
..
., 
$10 11 12 13 1. 15 16 17 HI 19 ttl ::n 22 23 ~2. 
20 
15 
"" h, November 12(1) 
,0 
30 j, November 13 
12l16.1 ±2.01 50,".1741 
os 
2. 
,. 
,s 
$10 11 12 13 ,. 1$ ,. 17 18 19 20 21 21 23 ~24 
Body Lengll> (rrml 
Figure 17. Calculated standard body length frequencies for Thysanoessa spinifera 
and Euphausia pacifica from right mandibles collected in humpback whale fecal 
samples, 1988-90. Mean, ±1 standard deviation, and sample size (n) for each 
species and sample are shown. 
Table 4. Percentage of euphausiid prey species caught in plankton tows in 1990 at the surface (0-10 m), shallow 
(11-60 m), and deep (61-140 m). Sample sizes (n), ±1 standard deviations, and pooled sample sizes 
parentheses) are shown. 
PLANKTON 
TOW 
DEPTHS T. spinifera :~~, 
% EUPHAUSIID PREY SPECIES 
E. pacifica N. simplex II N. difficilis 
Surface (0-10 m) 
n=9 
Shallow (11-60 m) 
n =12 
98.0% 
± 1.74 SO 
(1246) 
87.6% 
±22.39 SO 
(1424) 
I 
Ii,i, 
0.7% 
± 1.17 SO 
(4) 
10.5% 
± 17.86 SO 
(131 ) I 
1.7% 
± 1.85 SO 
(12) 
0.4% 
± 0.85 SO 
(7) 
0.0% 
± 0.00 SO 
(0) 
1.5% 
± 5.25 SO 
(14) 
Deep (61-140 m) 
n=3 
0.4% 
±0.64 SO 
(4) 
99.6% 
± 0.64 SO 
(931 ) I
,~~~ 
0.0% 
± 0.00 SO 
(0) 
0.0% 
± 0.00 SO 
(0) 
.t:>­
o 
41 
50 
45 
8 40c 
!
... 35:::s (,) 
(,) 300 
a 25>­(,) 
c (I) 20 
:::s 
tr 15! 
LI. 
~ 10 0 
5 
0 
- 10E
-
.c
-
20 
a. 
~ 30 
... (I) 
>- 40 ~ 
C) 50 
C 
'i: 60
.! 
as -(,) 70 
UJ 
c 
as 80 (I) 
:IE 90 
100 
l1li Cassin's Auklet 
~ Red/Red-neck Phalaropes 
II Scattering Layer Depth 
13 
75 
1988 1989 1990 

Figure 18. Percent frequency of occurrence of Cassin's auklet and Phalarope 
observed relative to mean prey depth for 1988, 1989, and 1990. Standard errors 
(lines below bars) and sample sizes are shown. 
a. SCA TTERING LA YER 
o 
v!~ ~\"'~f'·&."·'9'r,,\lv-:.. ~ 
ro t v "~ 
'" 
j ~ 80 
100 

120 •• 

140 

160 
 • 
180 
2OO~1~~~~~~~--~~~~-r-
b. SURFACE TEMPERATURE 	 C. SECCHI DEPTH 
16·°1 Vv V. 	 t t8.0 
15.0 1~~ ~+. V ,. f 
• 11:0 ,,, ..... 'T V .. ,.I.. I ti• 14.0 
v 
v 	
•
~ 12.0 'II • V 	 ••If • ~ I: 130 	 ::I 13.0 v" t . 
14.0 V V
!a. 12.0 15.0 

16.011.0 
17.0 
1801 I I I10.0 September Oc1ober November 	 September Oc1ober •• 
d.BEAUFORTSTATE e. BOTTOM DEPTH 

o 

100 • VSOl 
S' ~ 150 ~t~.~}'..... Ft 	 .. 200 'L-ll 11· P' ..... V; 
i 
s.o 
4.S 
4.0 
3.5 
3.0 
2.S 	
• i 250 'ii" 
300~ 	 'vwt··· y. 
350. V 
•V 	 400 
450 V 
September Octob"r November 
Figure 19. Fitted curves comparing mean daily prey depth, temperature, Secchi depth, Beaufort state, and bottom 
depth, for September, October, and November in 1989 and 1990. Standard errors (vertical lines) are shown. 
~ 
F\) 
• 
September Oc1ober November 
V 
sool I 	 I 
September Oc1ober November 
43 
In 1989, daily mean depth of the scattering layer was greater than in 
1990 during September and October. In 1989 and 1990, surface temperatures 
declined throughout the study period. Secchi depth increased in 1989, and 
visibility improved during the 3-month study period. However, in 1990, water 
visibility fluctuated from relatively clear to turbid waters by mid-October and 
back to clearer waters again by the end of November. Beaufort state increased 
during the study period in 1989, but remained the same in 1990. Daily mean 
bottom depths where humpback whales fed were highly variable for both years, 
but fitted curves yielded equivalent depths throughout the study period 
(t =1.889, df =48, P < 0.01). 
The greatest difference in depth of scattering layer between 1989 and 
1990 occurred during September. During September, the mean surface 
temperature in 1989 (14.6 °C ± 0.39 SD) was greater than in 1990 (13.3 °C ± 
1.64 SD), whereas Beaufort state (1.5 ± 0.71 SD and 2.3 ± 1.21 SD, 
respectively) and secchi depth (11.7 m ± 1.12 SD and 12.5 m ± 3.83 SD, 
respectively) were less. 
In 1989, only surface temperature was significantly related with scattering 
layer depth (stepwise regression, F =17.5, df = 17, P< 0.001), where greater 
surface temperatures corresponded closely to greater depths of the scattering 
layer (r2 = 0.52; Fig. 20). Other variables were not related to prey depth in 1989 
or 1990. However, in 1990, daily mean Beaufort states were greater and more 
variable than in 1989, resulting in more wind-induced mixing of subsurface 
waters. Lower mean surface temperature and secchi depths recorded during 
1990 were a reflection of periodic upwelling events. 
--
44 
a.1989 
o+-~~~~~~~~~~~~~~+-~~~~~-+~~~--+ 
E 
a.. 

CD 

>­as 
...J 
C) 
c 
.~
-
o 
en 
180 
200 . I . : : , . . : I "lo.. 
1010.511 11.5 1212.5 1313.51414.5 1515.5 16 
b.1990 
20 
40 
100 ................. 
120 
m 140 
1 60 I.::'..: . I . 
. . . I . • ..... { 
·1 y =:29.21 x - 287.56" r-SqUared:= 0.5~2**~ I....·....·'.........>r""<~·...········· 
: 
-E
-a.. 
CD 
~ 
...J 
C) 
I 
c 
::~ttF3=[ET~TTi~~~T 
80 
100 
180 ..............: ... ............·:··....·
·· .. ····1 ....·,1 y = -1.35~ + 56~75, r~squared =~.OO~ nsf·· 
I :: I' • • : : :200 I :: ::::; 
10 10.5 11 11.5 12 12.5 13 13.5 14 14.5 15 15.5 16 
Surface Temperature (OC) 
Fjgure 20. Linear regressions of prey depth versus surface temperature for 1989 
and 1990. Equations, 95% con"fidence limits for the slope of regression line, and 
significance levels (*** P < 0.001 and ns = not significant) are shown. 
45 
Overall, irradiance (overcast vs sunny) was not significantly related to 
prey depth in 1989 or 1990. Mean irradiance was slightly greater in 1989 (1031 
IlE m-2 S-1 ±439.3 SO, n =40) than 1990 (988 IlE m-2 S-1 ±448.1 SO, n =158). 
However, during September, irradiance in 1989 was significantly greater than 
1990 (1567 ~LE m-2 s-1 ±154.6 SO vS.1243 JlE m-2 s-1 ±469.9; Z =2.35, df =00, 
P< 0.05). Light avoidance by euphausiid prey was not apparent in 1989 or 
1990, but their orientation to daily fluctuations in light levels (phototaxis) was 
positive. In 1990, there was a the slight vertical movement of the scattering layer 
(approx. 20 m) to increasing and decreasing light levels during the study period 
(Fig. 21). 
In 1989, prey depth was positively correlated (r =0.96, P < 0.05) with the 
monthly magnitude of red tide as determined by the Department of Health (Fig. 
22). Red tide blooms varied in duration and extent during the three-year study 
period (Fig. 23). In late October 1988, a red tide bloom was observed around 
Bodega Bay. The red tide blooms in early October and late November 1990 
were comparable, extending 16 km off Bodega Bay. The 1989 bloom persisted 
much longer, from September to mid-October, and its range extended much 
further out, approximately 32 km out from Bodega Bay to the Farallon Islands 
and Cordell Bank (Fig. 23). 
Dinoflagellate species varied among years and locations. Red tide 
samples collected in the study area were composed of Noctiluca scintillans in 
all three years and were red/orange. In 1988 and 1990, brief outbreaks of 
brownish/red Ceratium tripos (red was Noctiluca scintillans intermixed) 
occurred in late October 1988, and were present in early October and late 
November in 1990. 
•••• 
46 
1600 
,... 
-U, 1400 
~ 
~ 	1200 
::i
-~ 1000 
c 
as 800 ~ 
... 
.!: 	 600 
a: 
~ 
c. 	 400 
200 
0 
20 
-E 	 40
-
60 

80 

100 

120 

140 

1800r------------------------------------------------, 
• 
ll. Surface Light 
IJ.IJ. T Underwater (10m) Light 
<t Scattering Layer Depth 
".1 •• ,11 1•1"'1. 6 
, ••• " 6 6.tlt'I'li 
I I I I IJ.' , I , 
"'I, IJ. IJ. " 
"" 	 IJ. I' I
"," 	 ,.,­
A'", A,,"A. 	 11••••••••••• '1.". 
IJ.IJ. •• T 
<t 

160 September October 	 November 
Figure 21. Fitted curves compari ng mean daily surface light and underwater 
(10m) light with scattering layer depths for the months of September. 
October, and November in 1990. Total light energy was restricted to the 
wavelengths between 300 and 720 nm or photosynthetically available 
radiation (PAR). 
____________________ _ 
47 
240 
-
220
.c 
en ;;: 
=a; 200 

.c 

en 180
en 
8

.,.. 160

-en 
::J
-
140 
'iij 
i: 120

..J 
(.)
.;< 100 
{:. 
c: 80 

1'0 
CI> 
:E 60 

42 

0 

20 

40 

en -.. 
CI> 
ai 60 

E
-
.c 
a 80 

CI> 

Q 

CI>
..
>- 100 
c. 
120 

140 

160 

71 

18 
D 1988 

III 1989 

.1990 

uDftj)~ 
!L,~W~!L, 
__________ J 
20 27 
 28
19 15
18 

26 

September OCtober November 
Figure 22. Monthly mean Paralytic Shellfish Poison (PSP) toxin levels for Marin 
County, California, and mean prey depth forthe months of September, October, 
and November in 1988-90. Micrograms of toxin per 100 grams of intertidal 
mussel and oyster shellfish were analyzed. Levels below 42 are below the limits 
of detection, and levels of 80 or above are alert levels (PSP data are from the 
Department of Health Services, CA, PSP Final Reports). Monthly sample sizes 
(above and below bars) and standard errors (length of t-bars) are shown. 
1988 1989 1990 
Late Oct Sep to Mid Oct Early Oct & Late Nov 
Red Tide Sample • 
Estimated Range EM 
Figure 23. Locations of collected red tide samples in late October 1988, September to mid-October 1989, and 
early October and late November 1990. The range of red tides were estimated by visual confirmation, collected 
samples on vessel surveys, and PSP reports from the Department of Health Services. 
~ 
co 
49 
In contrast, samples collected early during the extensive 1989 bloom contained 
the toxic dinoflagellate, Alexandrium catenella (previously named Gonyaulax 
catenella) and was succeeded in late September by a thick bloom of Noctiluca 
scintillans. 
50 
DISCUSSION 

Foraging Behavior and Energetics 
Humpback whale feeding behavior differed significantly in 1989 
compared with 1988 and 1990, corresponding closely to differences in prey 
depth. Surface feeding was typically lateral lunging preceded by a fine-misted 
bubble-cloud emitted underwater and observed at the surface. Though it is not 
known how whales create this cloud, it is possible that they emit bubbles from 
their mouth, allowing their baleen to sieve a mist of fine bubbles which rise to 
the surface (Reidenberg and Laitman 1991; J. Reidenberg, pers. comm., 1991; 
Fig 10). In an aquarium, bubbles emitted from an air stone disoriented 
T. spinifera. Fine bubbles adhered to their feeding appendages and under their 
carapaces; this disrupted free swimming and immediately drove them to the 
surface (Komaki 1966; Kieckhefer pers. obs. 1990). Bubble-clouds produced by 
feeding whales may similarly incapacitate swimming euphausiids and 
concentrate them at the water's surface (Jurasz and Jurasz 1979; Hain et al. 
1882; Baker 1985), making surface feeding more efficient. Other feeding 
behaviors using bubbles, like bubble-net feeding (Ingebrigsten 1929; Jurasz 
and Jurasz 1979; Hain et al. 1982), were not observed. Likewise, Dohl et al. 
(1983) from 1980 to 82 and Calambokidis et al. (1989a, 1991 a) from 1986 to 
1990 never observed humpback whales bubble-net feeding in the study area. 
There were a few unconfirmed reports of bubble-net feeding further south, off 
Pigeon Point and Half Moon Bay, possibly correlated with humpback whales 
feeding on northern anchovy (R. LaMar, pers. comm. 1990). 
Surface-feeding groups were observed on four occasions in 1988 and 
51 
on eleven occasions in 1990, where two or three whales appeared to combine 
their efforts in capturing prey. On eight occasions, pairs of whales were 
repeatedly observed lateral lunging in tandem (approximately 4 m between 
individuals), whereas on four occasions, one whale would execute a lateral 
lunge immediately followed by a second following whale executing a diagonal 
lunge. On three occasions, whale trios were observed apparently feeding 
cooperatively. The two outside whales lateral lunged, while the center whale 
performed either a vertical or diagonal lunge. This feeding method, known as 
"echelon" feeding, was used by humpback whales feeding in southeast Alaska 
(Baker 1985) and by skim feeding bowhead whales in the Arctic (WOrsig et al. 
1984; WOrsig 1988). It is possible that this configuration of whale feeding 
counteracts the classic escape response of schooling prey (e.g. fountaining or 
swimming around and behind the stimulus), because the trailing whale 
intercepts prey escaping from the lead whale (Pitcher and Wyche 1983; 
Hamner et al. 1983; Hamner 1984; Baker 1985; Hall et al. 1986; O'Brien 1987; 
Strand and Hamner 1990). 
Nevertheless, cooperative surface feeding was rarely seen, compared 
with southeast Alaska. In southeast Alaska, larger groups (8-11) have been 
observed feeding on faster, more mobile prey, such as Pacific herring (Jurasz 
and Jurasz 1979; Baker 1985; D'Vincent et al. 1985). It is possible that feeding 
on euphausiids does not require a cooperative effort, because euphausiids are 
slower swimmers than fish. 
Humpback whales feeding cooperatively on schooling fish vocalize 
before surface lunging in southeast Alaska (D'Vincent et al. 1985). In addition, it 
has been reported that humpback whales feeding in the same area, on 
52 
euphausiids and fish vocalize when they create bubble-nets (Payne 1979; 

Kieckhefer pers. obs. 1982). It has been suggested that the mechanical 

vibration created by humpback whale vocalizations may assist in corralling prey 

or coordinating group efforts (Baker 1985; D'Vincent et al. 1985). In contrast, 

humpback whales feeding near Cordell Bank were silent (n = 18, Table 2). 

Songs of humpback whales were recorded several times in the Cordell 
Bank area. Though songs are generally produced in the breeding grounds (e.g. 
Schevill 1964; Winn and Winn 1978; Thompson et al. 1979), humpback songs 
have been reported in the feeding areas in the North Atlantic (Stellwagen Bank, 
Massachusetts; Mattila et a11987) and North Pacific (Stephens 
Passage/Frederick Sound, Alaska; McSweeney et al. 1989). Mattila et al. 
(1987) suggested that singing in the feeding grounds may be related to (1) 
mixing of individuals from different regions or to (2) unknown factors that 
stimulate migration. Because humpback whales are often sighted in the study 
area from April through December with peak abundance in September (Dohl et 
al. 1983, Calambokidis et al. 1989a) and when songs were first recorded in this 
study (Table 2), it is more likely that the former theory, relating to mixing, would 
be true. In general, vocalizations of any nature produced in the feeding grounds 
could confer some feeding advantage. For example, they may inform other 
whales of a localized food source (Mobley et al. 1988). 
Surface feeding was characterized by fast, short-duration dives, and 
rapid surface swim speeds compared with deep diving, thus possibly incurring 
higher oxygen demand (Costa 1991). In 1989 and 1990, blow rates of surface 
feeding whales were significantly greater than deep feeding whales in 1988 
and 1990. It is likely that euphausiids at the surface avoided predators better in 
53 
deep than shallow water. Well illuminated, relatively warm surface water may 
enable them to detect shadows more easily, cooperate in more efficient evasive 
schooling responses, and move faster (O'Brien 1987; Strand and Hamner 
1990). Cooperative surface feeding among humpback whales in this setting 
may greatly increase feeding success. 
Costa (1991) asserted that the major factors influencing whether a 
predator will pursue prey at a specific depth are prey type, size and energy 
content, and behavior. At deeper depths, whales have no barriers, comparable 
to the air-water interface, against which to trap prey. Deeper prey depths require 
longer more demanding travel times. In 1989, whales made long-duration dives 
up to 17 min, and had extended durations of up to 9 min at the surface. At the 
surface, whales appeared to be hyperventilating, swimming slowly (0-1 kts) and 
breathing up to 23 times. In 1989, feeding humpback whales appeared 
extremely lethargic at the surface compared to the rapid, high-energy swimming 
of surface feeding whales in 1988 and 1990. Hamner et al. (1988) reported 
southern right whales (8. australis) slowly moving at the surface and 
hyperventilating before long dives to feed on sub-surface Antarctic krill 
(Euphausia superba). Because only deep-dwelling prey were available in 
1989, whales apparently reduced their oxygen consumption by slowing down 
their swimming speed at the surface. 
Time spent at the surface has been correlated positively with the duration 
of preceding dive of Weddell seals (Leptonychotes weddel/i; Kooyman et al. 
1980), bottlenose dolphin (Tursiops truncatus, Ridgway 1986, Ridgway et al. 
1969), gray whales (Eschrichtius robustus, Harvey and Mate 1984; WOrsig 
1984; WOrsig et al. 1986), southern right whales (Eubalaena australis, Hamner 
54 
et al 1988), sperm whales (Physeter macrocephalus, Lockyer 1977), and 
humpback whales (Baker 1985; Bauer 1986; Dolphin 1987a,b,c,d). The dive 
depth of humpback whales during feeding can be predicted with a high degree 
of confidence from their respirations and dive patterns (Dolphin 1987b). 
Transit time to prey during deep dives was shortened by increasing the 
angle of descent. Humpback whales raise their posterior and flukes high into 
the air by braking forward momentum with their pectoral fins rotated forward, 
thus providing the initial downward thrust needed for sub-surface dives (Edel 
and Winn 1978; Kieckhefer pers. obs. 1983; Fig. 12). The angle of the body 
during a dive (30°, 45°, or 90°) was dependent on their swim speed and angle 
of their pectoral fins. In this study, fluke~up and high fluke-up dives were seen 
mostly during shallow and deep feeding. On seven occasions, depth sounder 
traces indicated humpback whales diving to deep scattering layers at an angle 
>700 after high fluke-up dives. In addition, whales were consistently observed 
flexing their tail stock before deep dives (77%). This behavior may enhance 
body circulation from consecutive deep diving periods, or generate enough 
momentum to reach a steep angle to descend more quickly to desired depths. 
These whales may have been diving as deep as 180 meters, based on depth of 
scattering layer (Fig. 19a). More direct evidence, such as time-depth records, 
are needed to confirm the actual feeding depth of humpback whales. 
The maximum feeding depth of humpback whales is unknown; however, 
it is assumed that baleen whales do not exceed 300 meters in depth (Nemoto 
1963). In the North Atlantic, Whitehead (1983) obtained depth sounder traces of 
humpback whales traveling to depths of 195 m (n =104), whereas in southeast 
Alaska, Dolphin (1987a) found that humpback whales restricted their feeding to 
55 
the upper 120 m (n = 284) and only 8 dives (3%) exceeded 120 m. Dolphin 
(1987a) suggested that extended surface intervals and steady ventilations may 
be indications that these whales are exceeding their aerobic dive limit, 
revitalizing their oxygen debt after continuous deep dives. This suggestion was 
based primarily on anaerobic diving debts in seals, in which disproportionate 
increases in surface duration results (Kooyman et al. 1980). However, the 
slower swimming speed of humpback whales during deep, long duration dives 
may use oxygen more slowly, thus avoiding anaerobic diving (Kooyman 1989; 
Costa 1991). 
Prey Distribution and Relative Abundance 
Euphausiids represent a major fraction (5-10%) of the total biomass of 
plankton, and are a major food source for many marine birds, seals, and baleen 
whales (Mauchline 1980). However, it is not their numbers alone that make 
them so important in the food chain, but that they live in great concentrations. 
Thysanoessa spinifera are dominant in the neritic (coastal) environment, and 
E. pacifica is found further offshore along the northeast Pacific coast (Brinton 
1962a; Hebard 1966; Youngbluth 1976). Extensive surface shoals of T. 
spinifera form along the California coast from Fort Ross to the Channel Islands 
(Barham 1956; Brinton 1962a; Harvey 1979; Smith and Adams 1988; 
Schoenherr 1991). Hebarb (1966) found that T. spinifera was the most 
abundant species of euphausiid off Oregon from September through February. 
In the coastal areas of the Bering Sea, humpback whales fed largely on T. 
spinifera and its egg masses (Hollis 1939). During this study, humpback whale 
fecal samples and plankton tows confirmed that T. spinifera was the primary 
56 
euphausiid prey. 
Plankton tows obtained during this study support Brinton's findings 
(1962b) that T. spinifera remains in the upper 100 m, whereas E pacifica 
performs diurnal vertical migrations, with peak abundance at 200-400 m during 
daylight and at the surface at night. Thysanoessa spinifera was found 
predominantly in surface and shallow tows, whereas E pacifica was 99.6% of 
the biomass in deep tows. The occurrence of E pacifica in humpback whale 
fecal samples in 1989 may have been associated with whales feeding deep 
and further offshore along the continental shelf break. 
Rice (1978) reported that stomach contents of humpback whales killed 
from 1956 to 1965, in the vicinity of Cordell BankiFaralion Islands, contained 
roughly 60% northern anchovy and 40% Euphausia pacifica, with only trace 
amounts «0.5%) of Pacific herring and Thysanoessa spinifera. Catcher boats 
operated 230 km from the Golden Gate Bridge, off the continental slope/edge in 
water depths of 2,700 to 4,000 meters (Rice 1963,1971). Distance offshore may 
explain the high percentage of E pacifica compared with T. spinifera in those 
humpback whales (Rice 1977; D. W. Rice. pers. comm. 1991). Five sub-samples 
of humpback whale stomachs from whales taken during the 1956-65 
Cordell/Faralion whaling fishery (National Marine Mammal Laboratory, Seattle, 
WA) were examined. These samples contained mostly E pacifica (>98%), 
which correlated with whales captured beyond the continental shelf in water 
depths of 2,200 to 3,700 meters (Table 5). 
Table 5. Location and capture dates of humpback whales when stomach contents were collected during 
commercial whaling off Central California from 1960-64 (Sub-samples provided by D.W. Rice and A.A. Wolman, 
National Marine Mammal Laboratory, Seattle, WA). 
Capture Date 
(d-m-y) 
Location 
(Iat. & long.) 
Sex Length 
(m) 
Bottom Depth 
(m) 
Prey Type* Standard Body Length** 
(mean ± SO, n) 
30 Apr 60 370 47'N, 1230 32'W M 14.0 2561 E. pacifica 18.9 mm ± 1.57 SO, n =7 
20 Aug 61 380 OO'N, 1230 42'W F 11.0 2744 E. pacifica 19.3 mm ± 1.24 SO, n =19 
24 Apr 62 370 45'N, 1230 30'W F 15.9 2195 E. pacifica 19.9 mm ± 2.17 So, n =8 
28 Apr 63 370 50'N, 1240 02'W F 10.7 3658 E. pacifica 19.0 mm ± 1.07 So, n =15 
29 Apr 63 370 41 'N, 1240 03'W M 12.8 3567 E. pacifica 18.3 mm ± 0.89 SO, n =8 
* Oominant prey item found in all sub-samples was >99%. 
** Body lengths were derived from length measurements of right mandibles found in all sub-samples and calculated by 
appropriate standard body length/mandible length linear regression equation. 
(J1 
'-I 
58 
The formation of surface or subsurface swarms has been reported in 18 
species of euphausiids living predominantly in higher latitudes (Omori and 
Hamner 1982). Euphausiids feed mainly on phytoplankton and/or small 
zooplankton, such as copepods. Daytime surface swarming of euphausiids is of 
interest, because they differ from normal vertical migrators. The factors that 
bring about the formation of daytime surface swarms are not clear and may be 
different for each species. Theories proposed to account for daytime surface 
swarms are: (1) predators driving euphausiids to the surface (Bigelow and 
Schroeder 1953; Komaki 1967; Brown et al. 1979; Endo 1984), (2) euphausiids 
congregating at the surface to feed (Mauchline and Fisher 1969; Brown et al. 
1979; Hamner 1984), (3) maturation or reproduction occurring at surface (Endo 
1984; Nicol 1984; Smith and Adams 1988), (4) passive transportation to the 
surface by currents or tides (Brinton 1962b; Forsyth and Jones 1966; Brown et 
al. 1979; Schoenherr 1991), or (5) a breakdown of an environmental barrier, 
such as a thermocline, which enables them to vertically migrate to the surface 
(Komaki 1967; Endo 1984). 
Surface swarms of E. pacifica are rare along the California coast, 
whereas surface swarms of T. spinifera are common during summer (Brinton 
1962b). Because T. spinifera remains in the upper 100 m both day and night, in 
contrast to E. pacifica's diel vertical migrations, the California current's strong 
thermocline throughout most of the year may act as a barrier to E. pacifica 
occurrence at the surface. Endo (1984) found E. pacifica at the surface in 
spring off Sanriku, Japan. He suggested that the absence of a thermocline in 
early spring allowed E. pacifica to swarm at the surface. In the lower St. 
Lawrence estuary, Canada, Thysanoessa raschi and M. norvegica, however, 
59 
had no difficulty crossing the thermocline during their diel vertical migrations 
(Simard et al. 1986). 
Smaller euphausiids caught in plankton tows than found in fecal samples 
was likely caused by net avoidance, especially by larger and faster swimming 
euphausiids. It has been suggested that euphausiids detect nets visually by 
seeing shadows during the dayljght and bioluminescence at night (Wiebe et 
aI.1982), or acoustically by vibrational stimuli of the towing cable, harness, or 
approaching net (Fleminger and Clutter 1965; Hovekamp 1989). Although the 
fecal sample size was small (n = 11) for 1987-1990, the overall mean lengths of 
T. spinifera and E. pacifica in fecal samples were consistently larger than net 
samples, providing a more accurate estimate of size classes of euphausiids 
eaten by humpback whales. 
Higher percentages of fertilized T. spinifera were collected in 1988 and 
1990 than 1989. These undoubtedly comprise a richer food source for 
humpback whales, which may explain greater numbers of whales in 1988 and 
1990 (Calambokidis et al. 1989a). The occurrence of fertilized euphausiid 
females likely reflects favorable oceanographic conditions that created more 
productive, nutrient-rich upwelled waters (Brinton 1962b). 
Under-estimation of fish feeding was possible, because the digestive 
system of whales may completely dissolve fish otoliths and other calcium hard 
parts in its acidic solution before they are excreted (Jobling 1987). However, the 
coloration of all feces collected were red-brick, indicating euphausiid feeding; 
versus yellow-green, which indicate anchovy or saury feeding (Rice pers. 
comm. 1991). Yellow-green feces of humpback whales were frequently seen at 
the surface off Half Moon Bay and adjacent waters, during aerial surveys 
60 
(R. LaMar, pers. comm. 1990). This strongly suggested that humpback whales 
fed on fish south of the study area. 
Oceanographic Conditions & Productivity 
To understand fluctuations in prey availability in relationship to 
humpback whale distribution and abundance near Cordell BanklFaralion 
Islands, it is essential to know something about the environment they both 
inhabit. The annual pattern of currents in the study area are divided into three 
variable, overlapping periods: (1) upwelling, from February through August; (2) 
oceanic, from September through October; and (3) Davidson, from November 
through January (reviewed by Sverdrup et al. 1942). This study focused on the 
peak feeding period of humpback whales, from September through November 
(Calambokidis et al. 1989a). During this time, the end of an upwelling period, 
the entire oceanic period, and the beginning of the Davidson Current were 
observed. In late summer and fall, the northwest winds subside, causing a 
reduction in the strength of the offshore California Current and reduction in cold, 
nutrient-rich coastal waters from upwelling. As a result, warm oceanic water and 
warm, nutrient-deficient waters from the northward-flowing counter-current 
(Davidson Current) moves coastward. 
The interaction between wind stress and the California current appears 
to generate upwelling of cold, nutrient-rich water to the sea surface (e.g. Bakun 
and Parrish 1980; Parrish et al. 1981; Abbott and Barksdale 1991; Strub et al. 
1991 ; Washburn et al. 1991). These seasonal surface conditions probably 
produce the large zooplankton biomass, which occurs in fall off central 
California (Abbot and Barksdale 1991; Smith et al. 1986). Topographic features, 
61 
like banks, sea mounts, canyons, and a wide range of continental shelf and 
slope widths, may have a significant influence on water circulation (Schwing et 
al. 1991). In this study, Bodega Canyon, Cordell Bank, and the Farallon Islands 
were the primary sites of feeding activity (Fig. 3). During upwelling periods, 
these topographic features create eddies, gyres, and fronts which may act as 
"trophic traps" concentrating and/or attracting prey for whales and other 
predators (Kenney and Winn 1986; Smith et al. 1986; Piatt et al. 1989; Schwing 
et al. 1991). 
On 2 September 1990, a well-developed cyclonic gyre (Fig. 24 f), 
apparently generated in the south, deflected out of Bodega Canyon and around 
to the northeast of Cordell Bank (Ericksen 1991). Whale positions, 3 days 
before and after this image was taken, were consistently found along the north 
frontal edge of this gyre. However, if offshore flow is continuous or too strong. 
less motile organisms, such as phytoplankton and some zooplankton, will be 
dispersed rapidly offshore, creating relatively unproductive waters inshore (see 
Fig. 24 and 25, July and August 1989). On the other hand, if wind conditions are 
weak for long periods, it does not provide proper conditions to set-up of these 
boundaries between different water masses (Ramp et al. 1991). This was 
evident from September through December in 1989 (Fig. 24 and 25). Mean 
monthly upwelling indices for all three years indicated that 1989 had the most 
upwelling during the strong upwelling period of July and August, and upwelling 
dropped abruptly in the following months in conjunction with an increase in 
surface temperatures (Fig. 25). It is predicted that these environmental factors 
were instrumental in setting-up ideal conditions for red tide blooms (Franks et 
al. 1989). 
62 
1990 
d. November 18 h. November 1 
Figure 24. Satellite images (TIROS-N/NOAA) of sea surface temperature (SST) for 
the most cloud-free days found in 1989 and 1990. For all images the range of linear 
gray scale was set at 10-16° C. Lighter shades denote colder water. Plus symbols 
in b, c, f, g, and h denote whale positions 3 days before and after images were taken. 
The 200 and 1000 m depth contours are shown. (Images were provided by N. 
Garfield, Department of Oceanography/Naval Postgraduate School, Monterey, CA). 
63 
a. Coastal Upwelling Indices 
200 
180 

160 

~ 140 
E g 120 
.... 
~ 100in 
i 80 
60 

40 

20 

0 

• 1989 
•••• ';7•••• 1990 
y...... 
.... Y
'. ........ 
JUL AUG SEP OCT NOV DEC 
b. Sea Surface Temperature 
14.5 
14.0 
13.5 
13.0 
1/1

:l 
 12.5]i 
GI 
0 12.0 
GI 

GI 

C, 11.5 
GI 
Q 11.0 
10.5 
10.0 
9.5 
q..
" ...., . 
" ,' 
t"'" 
JUL AUG SEP OCT NOV DEC 
* Note: missing data for entire month of December 1990. 
Figure 25. (a) Monthly coastal upwelling indices (m3 * S-1 * 100 m length of 
coastline-1) at 39°N, 125°W and (b) sea surface temperature (CO) at NOAA buoy 
46013 (38.2°N, 123.3°W) for July-December 1989 and 1990. Note extremely 
high upwelling and low temperatures during July and August 1989 followed by a 
sharp decrease in upwelling and increase temperature in September. Study 
period (shaded area) and standard errors (vertical lines) are shown. (Data 
provided by D.M. Husby, Pacific Fisheries Environmental Group, Monterey, CA). 
64 
Correlations between Whale Behavior, Prey Occurrence, and 
Environmental Conditions 
Altered environmental conditions, such as an increase in water 
temperature by a strong "EI Nino," change prey availability for many sea bird 
populations near the Gulf of the Farallones (e.g. Ainley and Lewis 1974; Ainley 
et al. 1986; Kaza and Boekelheide 1984; Croll 1990), as well as around the 
world (review by Cairns 1987). More subtle changes in oceanographic 
conditions that trigger severe red tide (din01'lagellate) blooms, such as in 1989, 
may have physically displaced daytime surface swarming of T. spinifera, 
forcing them deeper in the water column (Boalch 1984, Potts and Edwards 
1987, Ogata et al. 1989) or possibly killed them with their fatal toxins (Jenkinson 
1989, White et al. 1989). Moreover, humpback whales may die from ingesting 
prey loaded with dinoflagellate toxins (Anderson 1988; Geraci 1989, Geraci et 
al. 1989). 
Increased light intensity in 1989 may have influenced deeper scattering 
layers compared with 1988 and 1990. However, direct response of light 
avoidance by euphausiid prey was not apparent. For example, in 1990, there 
was a slight vertical migration (approx. 20 m) of euphausiid prey to fluctuations 
of daily light over the study period; however, there was a positive phototaxis 
response (Fig. 21). In general, dinoflagellate blooms are primarily regulated by 
various environmental factors such as temperature, sea state (Beaufort ), day 
length, light intensity, and quality and quantity of nutrients (Franks et al. 1989; 
Imai 1989). The combined environmental conditions in 1989 before the study 
period (July to August) may have triggered the most intense, wide-spread 
occurrence of red tide in this area since 1980 (Figs 23, 24, 25). When winds are 
65 
calm and temperatures peak shortly after a strong upwelling period, dormant 
cysts of dinoflagellates germinate and flourish near the surface waters. The 
depth of maximum cell concentration appears dependent primarily on light 
intensity. Passow (1991) hypothesized that dinoflagellates migrated upwards 
toward higher light intensities until a certain level of irradiance was reached, 
after which migration was directed downwards to avoid light intensities greater 
than threshold. Diel vertical migrations of concentrated shoals of dinoflagellates 
can exceed 40 m in depth (Passow 1991). During periods of wind, 
dino'flagellates are mixed deeper, to depths exceeding 40 m, and move near 
the surface to their threshold light levels during calm periods (Boalch 1984; 
Passow 1991). 
In the Gulf of the Farallones and adjacent waters, seabirds, such as Red 
phalaropes (Phalaropus fulicaria) , Red-necked phalaropes (P. lobatus) , and 
Cassin's auklets (Ptychoramphus aleuticus) , feed on surface and shallow sub­
surface plankton. Phalaropes feed on copepods at the surface of fronts (Brown 
1980; Briggs et a!. 1984, Haney 1989). Cassin's auklets eat euphausiids 
primarily near the surface down to depths of 40 m (Burger and Powell 1990). 
The percentage decrease of observed Phalaropes (32% to 0%) in 1989 may 
have indicated the disappearance or displacement of copepods deeper in the 
water column (Fig. 18). Frequency of occurrence of Cassin's auklets also 
decreased in 1989 (42% to 24%), possibly because T. spinifera were less 
abundant (Mauchline 1967; Nemoto 1972). Mean depth of the scattering layer 
from September through November 1989, was 84.6 m ±46.30 SO, which 
exceeded the diving capabilities of Cassin's auklets (Burger and Powell 1990). 
In addition, large variation in Cassin's auklets' diet occurred in 1980, 
66 
T. spinifera was 68% of diet in 1979 and only 6% in 1980, whereas E. pacifica 
increased from 32% of diet to 75% (Ainley et al. 1990). This correlates with one 
of the largest red tide outbreaks in California, which began during the month of 
July 1980 (Price 1989; Price and Kizer 1990). 
Potts and Edwards (1987), working off Plymouth Breakwater, England, 
observed the physical and toxic effects of the dinoflagellate, Gyrodinium 
aure/um, on larval, post-larval, and juvenile fish. Juvenile fish were not widely 
distributed throughout the water column, but were concentrated in a band 50 cm 
over the sea floor. Following the bloom there was a dramatic reduction in 
numbers of larval and post-larval fish. Boalch (1984) and Jenkinson (1989) 
reported concentrations of more than five million G. aure/um per liter of water 
during warm and stable sea conditions, which adversely displaced certain 
species deeper in the water column. Other less mobile species died, due to 
viscous, anoxic conditions created in the sea water and/or direct contact with 
the toxin. Kvitek et al. (1991) suggested that sea otters (Enhydra /ufris) in 
southeast Alaska are displaced horizontally away from red tide blooms to the 
outer coast where toxic clams are rare. 
There appears to be a fine balance between the optimal conditions of 
humpback whale feeding on surface swarming prey versus adverse conditions 
when prey are deep in the water column and less aggregated. Information on 
the demographic structure of the two primary euphausiid stocks, Thysanoessa 
spinifera and Euphausia pacifica, is needed for the survey area. It is also 
necessary that whale and prey data be integrated with CTDs, remotely sensed 
SSTs, and bathymetric data to examine correlations between their distribution 
and oceanographic features (Fairfield et al. 1991). Underlying hydographic 
67 
processes occurring at this region were most likely missed by remotely sensed 
SSTs alone. More site-specific knowledge of hydrographic processes existing 
around the Farallon Islands, Cordell Bank, and Bodega Canyon may provide a 
better understanding of the physical and biological factors regulating the 
abundance and distribution of humpback whales and their prey. 
68 
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80 
APPENDIX A 

DEFINED BEHAVIOR CATEGORIES: 
Behavioral states were categorized as: 
1. 	Rest: indicated when a focal whale lies motionless near the surface for 
5 min or more. 
2. 	Slow Travel: consists of continuous, sustained swimming less than or 
equal to 6 km/h (3 knots). close to the surface with little 
change in direction. 
3. 	Fast Travel: consists of continuous. sustained swimming greater than 
6 km/h, close to the surface with little change in direction. 
4. 	Mill/Search: erratic, non-oriented (zig-zagging) diving with changes 
in speed and direction as if searching for prey. No 
visible prey layer detected on the depth sounder. 
5. 	Surface Feed: circling and diving over a localized area, often lunging 
with mouth open at the surface. Distinct prey layer 
visible within the upper 10m. 
6. 	Shallow Feed: circling and diving continually in the same area over a 
distinct prey layer detected between 10 and 60 m in 
the water column. 
7. 	Deep Feed: circling and diving continually in the same area over a 
distinct prey layer detected below 60 m in the water 
column. 
81 
APPENDIX B 

BEHAVIORAL ETHOGRAM: 
RESPIRATION: 
FS ;; First Surface (with no blow) 
F ;; First Surface Blow 
B = Blow 
M "" Missed BIow(s)? 
N =No Blow Rise 
A "" Arch Back 
D ;; Fluke-DOWN Dive 
U = Fluke-UP Dive 
H = High Fluke-UP Dive 
NF = Not First Surfacing 
BUBBLE & BLOW BEHAVIOR·. 

BH = Bubbles at Blow Hole 
BT = Bubble Trail 
BC ;; Bubble Cloud 
FB = Fountain Blow 
WB = Wheeze Blow 
TB = Trumpet Blow 
FEEDING BEHAVIOR: 

BN ;; Bubble Netting 
L L = Lateral Lunge 
D L = Diagonal Lunge 
VL = Vertical Lunge 
UL "" Unidentified Lunge? 
TAIL BEHAVIOR: 
LT = Lateral Tall Display 
TS = Tail Slap (belly-down) 
LS = Lateral Tall Slap 
rr = Inverted Tail Slap (belly-up) 
TC =Tail Clap (horizontal) 
SW = Tail Swish (side-to-side) 
FL = FLex (roll peduncle) 
PECTORAL FIN BEHAVIOR: 

P E 
P S 
VP 
RP 
PD 
BODY 
HG 
UN 
SS 
S T 
HEAD 
BR 
SH 
HL 
HS 
WC 
HO 
AD 
BE 
SP 
= Lateral Pec Extension 
= Lateral Pec Slap 
= Ventral Pec Slap (belly-up) 
;; Roll back & forth Pee Slap 
= Pec Display 
BEHAVIOR: 
= HanGing (horizontal at surface) 

= UNdulation (bob up & down) 

= S-Shaped posture 

"" Sharp Turn (erratic dir. change) 

AND LEAPING BEHAVIOR: 
= BReach 
= Spy Hop 
= Head Lunge (not assoc. wi feeding) 
= Head Slap 
;; Whale Contact 
;; Hits Object (other than whale) 
= Agonistic Display 
= BEached 
= Unidentified SPlash? 
VOCALIZATIONS: 
IVV = Vocalization cue for recordings. 
MISC. CODES: 
Q = QUESTION? (describe in comment) 
MD = Missed Data? 
X '" Delete previous entry. 
XX = Delete last sequence of entries. 
*Note: Common humpback whale behaviors observed in Cordell Bank/Gulf of 
the Farallones region are in bold print. 
82 
APPENDIX C 
DEFINED RESPIRATION VARIABLES: 
Surface-dive cycles were used as primary means of quantifying differences in 
behavioral states. The following five variables of respiration were measured: 
1. 	Blow Interval (BI) : time interval of 90 sec or less between 
exhalations at (or near) the surface. 
2. 	Number of Blows per Surface Duration (NBS): number of 
exhalations during a surface period. 
3. 	Duration at Surface(DS): period of time spent at (or near) the 
surface between successive dives. Surface duration was terminated 
by arching the peduncle or raising of the flukes above the water to 
initiate a dive, or by a submergence with blow interval exceeding 90 
seconds. 
4. 	Duration of Dive (DO) : period of time during a dive to first 
surfacing. First exhalation exceeding 90 sec in length usually marked 
the beginning of a surface duration. 
S. 	Blow Rate (BR) : total number of exhalations divided by surface 
duration and dive duration from each complete surface-dive cycles. 
SURFACE-DIVE CYCLE 

OS DO 
BR = NBS/(DS+ DO) 
RESPIRATION 
VARIABLE 
BEHAVIOR CATEGORY 
Feeding 
88 89 90 
Mill/Search 
88 89 90 
Fast Travel 
88 89 90 
Slow Travel 
88 89 90 
Duration at Surface 
mean (min) 0.7 3.1 1.3 0.8 2.3 1.8 1.0 1.2 0.9 1.1 1.7 1.1 
SO 0.69 1.69 1.30 0.93 1.54 1.70 0.88 0.91 0.68 0.78 1.10 0.92 
95%CL 0.12 0.31 0.15 0.37 0.52 0.44 0.24 0.33 0.29 0.35 0.33 0.25 
(n) (132) (120) (299) (27) (36) (59) (55) (32) (23) (21) (46) (53) 
No. Blows/Surface Duration 
mean 2.5 10.5 3.9 3.0 7.4 6.1 3.7 4.3 3.0 4.1 5.7 3.6 
SO 1.75 5.30 3.24 1.84 4.97 4.70 1.94 2.74 1.76 2.03 3.47 2.36 
95%CL 0.30 0.96 0.37 0.73 1.68 1.22 0.53 0.99 0.76 0.92 1.03 0.65 
(n) (132) (120) (299) (27) (36) (59) (55) (32) (23) (21) (46) (53) 
Duration of Dive 
mean (min) 1.3 6.2 1.8 0.9 5.4 4.5 1.9 3.7 1.6 2.5 4.3 2.5 
SO 1.12 3.30 2.26 0.60 2.91 3.33 1.34 2.88 1.15 1.14 3.27 1.84 
95%CL 0.20 0.64 0.26 0.29 1.05 0.87 0.39 1.02 0.51 0.57 0.97 0.53 
(n) (125) (105) (290) (19) (32) (58) (48) (33) (22) (18) (46) (48) 
Blow Interval 
mean (sec) 23.1 18.7 22.5 19.6 19.5 19.3 20.5 19.6 23.1 18.4 19.7 23.3 
SO 15.41 8.21 14.24 17.18 9.05 10.67 14.13 8.77 13.44 12.51 11 .11 14.11 
95%CL 2.17 0.45 0.91 4.69 1.13 1.15 2.19 1.60 3.16 1.50 1.47 2.30 
(n) (197) (1279) (954) (54) (251) (331) (162) (118) (72) (70) (223) (147) 
Blow Rate 
mean (no. blows/min) 1.5 1.1 1.4 2.0 0.9 1.2 1.7 1.2 1.3 1.1 1.1 1.1 
SO 0.74 0.45 0.65 0.92 0.53 0.75 1.21 1.07 0.41 0.50 0.59 0.58 
95%CL 0.13 0.10 0.08 0.45 0.22 0.22 0.36 0.39 0.19 0.25 0.19 0.18 
(n) (123) (84) (254) (18) (26) (46) (46) (31) (20) (18) (40) (42) 
:II 
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84 
APPENDIX E 

STANDARD BODY LENGTH & MANDIBLE MEASUREMENTS: 

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APPENDIX G 
SKY CONDITION: 
CODE NO. DESCRIPTION 
1 Clear 
2 Partly cloudy 
3 Cloudy 
4 Overcast 
5 Light rain or rain within 6 km 
6 Heavy rain 
7 Patchy fog or fog within 6 km 
8 Serious fog 
9 Rain and fog 
lot 
SEA CONDITION (BEAUFORT): 
BEAUF 
NO. 
DESCRIPTION WIND SPEED 
(km/h) 
WAVE 
(m) 
0 Smooth and mirror-like Calm (0-2 -­
1 Light ripple Light air (2-6 0.3 
2 Small wavelets, not breaking Light Breeze (7-11 0.6 
3 Scattered whitecaps Gentle B'ftleze 12-191 1.2 
4 Small waves, frequent whitecaps Mod. breeze (20-30 1.8 
5 Moderate waves, many whitecaps Fresh breeze 31-39 2.0 
6 All whitecaps, some spray Strong breeze 40-50 3.0 
7 Breaking waves, spindrift begins Near gale 51-61 4.3 
8 Medium high waves, foamy Gale 62-74 5.5 
*Note: Beaufort 6-8 not meaningful (time to go home!).