Recent Submissions

  • Epibionts on Flexopecten felipponei (Dall, 1922), an uncommon scallop from Argentina

    Schejter, L.; Bremec, C. (2007)
    Flexopecten felipponei (Dall, 1922) is a non-commercial, seldom reported pectinid from the SW Atlantic Ocean. In this contribution we review its taxonomy, describe epifaunal species and their levels of encrustation, and discuss the composition of the macrobenthic assemblage where this scallop Iives. Eighteen epibiont taxa were observed to Iive on the valves of these scallops. The most frequent and abundant epibionts on F. felipponei were serpulids, barnacles, and oysters. Although both valves were encrusted, the left valves had higher percentages of coverage. The benthic community contained 69 invertebrate taxa that generally charaeterize other mid-shelf bottorns between 37°S and 39°S. Eight pea crabs of the species Tumidotheres maculatus (Say, 1818)were found inside eight individuals of F. felipponei. Two other scallops had burrows of Polydora websteri Hartman, 1943. These were the first observations of these infestations on F. felipponei.
  • Broodstock management and induced spawning of flounder Paralichthys orbignyanus (Valenciennes, 1839)under a closed recirculated system

    Bambill, G.A.; Oka, M.; Radonic, M.; López, A.V.; Müller, M.I.; Boccanfuso, J.; Bianca, F. (Universidad de Valparaiso. Instituto de Oceanografía, Valparaiso, 2006)
    The present study was conducted to determine the parameters regulating spawning performance of P. orbignyanus wild broodstock. The adaptation to captivity was successfully achieved with minimal stress levels. In three consecutive spawning seasons, the annual photothermal manipulation was not effective for the maturation and natural spawning of females although males were running. Females were HCG injected, releasing non fertilized eggs. Artificial fertilization was carried out after stripping the fish with a total production of 18,000 fertilized eggs in 2001 (egg diameter=800±10 µm), 55,300 in 2002 (egg diameter= 850±12 µm)and 1,635,000 fertilized eggs in 2003 (egg diameter 818.4 ±30.08 µm, oil drop 98.1 ±2.96 µm). For the study of the ovulationtime, females were hand-stripped every 48 h (female 1), 96 h (female 2)and 144 h (female 3), after being induced by hormones. No statistical differences were found for fertilization and hatching rates and SAI. This could be attributed to the small sample sizes, individual variation and/or stripping frequencies. Nevertheless, qualitative differences were evident. Although long-term studies are needed to confirm these observations, 96 h stripping frequency could be considered a good technique to obtain eggs and larvae experimentally. The estimated fecundity by this technique varied from 185,951 to 399,118 total eggs per kg of female
  • Presence of Palaemon Macrodactylus Rathbun 1902 (Crustacea: Decapoda: Caridea: Palaemonidae) in Mar del Plata harbor, Argentina: first record from Southwestern Atlantic Waters

    Boschi, E.E.; Spivak, E.; Martorelli, S.R. (2006)
    Adults of the palaemonid prawn Palaemon macrodactylus Rathbun, 1902 were reported for the first time from the southwestern Atlantic waters. Males and ovigerous females were collected in Mar del Plata harbor (38 degree 03' S; 57 degree 31' W), Argentina; larvae obtained from one of the collected females were reared in the laboratory until the juvenile stage. The geographical range of P. macrodactylus was previously restricted to the Pacific Ocean: it was originally described in Japan and has been reported as an invasive species in the western coast of USA in the 1950's and in Australia in the 1970's. Recently, this prawn has been also reported from European waters.
  • The Invasive Rapa Whelk Rapana venosa (Valenciennes 1846): Status and potential ecological impacts in the Rio de la Plata estuary, Argentina-Uruguay

    Giberto, D.A.; Bremec, C.; Schejter, L.; Schiariti, A.; Mianzan, H.W.; Acha, E.M. (2006)
    Recent range extensions of the invasive rapa whelk Rapana venosa, biological data of the population and possible ecological impacts on the food webs of the Rio de la Plata estuary are presented. A total of 41 rapa whelks and 21 egg capsules were collected between February 2004 and March 2006. Specimens were found all over the mixohaline waters of the estuary, with records off Montevideo, Samborombon Bay and off Punta Rasa. Specimens ranged between 28 and 120 mm shell length. Almost all R. venosa presented epibionts all over the shell, suggesting an exposed lifestyle. Egg-masses were attached to specimens of R. venosa, debris and plastic garbage. The spatial distribution of R. venosa within the estuary was coupled with the spatial distribution of Mactra isabelleana, a typical subtidal bivalve of mixohaline waters. The implications for the food webs of the estuary, including possible predators, are discussed. The presence of R. venosa in muddy sediments together with the finding of egg-capsules over the specimens, and the low salinity values at which it is found in the Rio de la Plata estuary, confirmed the high plasticity of R. venosa and the potential capability of successfully invading novel environments.
  • Ecological boundaries in estuaries: macrobenthic ß-diversity in the Rio de la Plata system (34-36°S)

    Giberto, D.A.; Bremec, C.; Cortelezzi, A.; Rodrigues Capitulo, A.; Brazeiro, A. (2007)
    In this study, we analyse spatial patterns of macrobenthic communities of the Río de la Plata system, and assess the species turnover or beta diversity and its relationship with environmental gradients. Macrobenthic samples and physico-chemical parameters were collected from 20 sampling sites along a transect of 560 km, including the freshwater (FW), estuarine (ES)and marine (MA)sectors. Three main assemblages corresponding to the above mentioned sectors were defined with multivariate analysis (cluster, MDS). In total 134 taxa were recorded, 81 in MA, 33 in FW and 38 in ES, represented mainly by polychaete, mollusc and crustacean species. Depth, salinity and clay showed the strongest correlation with the observed faunal patterns (pw=0.62; BIO-ENV analysis). Beta diversity varied between dominant taxonomic groups and was positively correlated with changes in salinity. The high variability in the composition of assemblages was reflected in beta diversity, reaching its highest values at the boundaries between the defined sectors. This study suggests that beta diversity represents a useful tool to define ecological boundaries for benthic communities in the Río de la Plata.
  • Crecimiento y rendimiento en carne del Lenguado Paralichthys orbignyanus (Valenciennes, 1839) cultivado en Argentina

    Müller, M.I.; Radonic, M.; López, A.V.; Bambill, G.A. (CIVACIVA, 2006)
    The results of the final on-growing (500 g to 1 kg)of flounder Paralichthys orbignyanus under closed recirculated water systems and controlled conditions are presented. 22.5 percent of fish reached 1 kg alter 2.1 months of starting the on-growing trial. Sex ratio was 20.6 percent females and 79.4 percent males. Average length for females and males was 38.53 ± 4.58 cm TL and 32.52 ± 5.25 cm TL, respectively. Average body weight for females and males was 710.58 ± 262.95 g and 427.59 ± 203.01 g, respectively. Statistically significant differences were found for average length for sex (p0.01)and for average body weight for sex (0.01 0.05). Flesh yield was 43.1percent fillets without skin and 57percent fillets with skin. Flesh of cultivated flounder had a higher proportion of lipids and humidity than flesh of wild flounder. The present study shows the aquaculture potential of flounder Paralichthys orbignyanus and the higher growth of females suggests the convenience of monosex culture
  • Consumo de oxígeno, crecimiento y utilización del alimento durante el desarrollo larval del besugo Pagrus pagrus (Linné, 1758)(Pisces:Sparidae).

    Aristizabal, E.O. (Universidad de Valparaiso. Instituto de Oceanología, 2006)
    Knowledge of the life history of fish larvae is of practical importance to understand variations in the survival rate not only for cultivated fish but also for fishery biology studies. With the aim of recognizing critical changes during the first days of life of red porgy larvae, the oxygen consumption, growth, and food utilization were studied. After hatching, the larvae were transferred to two 400 L fiberglass tanks with microalgae (Nannochloropsis oculata)and enriched rotifers (Brachionus plicatilis)as initial food. During the incubation and larval rearing, water temperature was kept at 18.0 ± 0.5ºC and salinity ranged from 33.0 to 34.0 psu. Results indicate a decrease in larval growth between day 3 and 4 after hatching, when larvae opened their mouths, began exogenous feeding and have almost exhausted their yolk sac and oil globule. At the end of this period, variations in the carbon and nitrogen content were also detected. Oxygen consumption showed an isometric mass-specific change with an inflexion at day 6 after hatching, which was coincident with the inflation of the gas bladder and the development of gills. The nitrogen coefficient (NQ)revealed a sudden change in the utilization of amino acids and lipids from endogenous reserves between the embryo and the newly hatched larvae. Hatching and first feeding time are two critical changing moments for the larval survival of this species.
  • Efficiency of co-feeding red porgy (Pagrus pagrus L.)larvae with live and compound diet

    Aristizabal, E.O.; Suárez, J. (Universidad de Valparaiso. Instituto de Oceanología, 2006)
    The red porgy (Pagrus pagrus)is an important commercial and recreational species with very good prospect for aquaculture. Because significant mortalities, the mass production of this species is limited. This paper describes three weaning strategies to investigate their effects on the survival and growth of red porgy larvae reared in laboratory: A)traditional three-step weaning (rotifers - Artemia - diet)(control); B)one-step early weaning by co-feeding (rotifers - Artemia + diet), and C)one-step direct early weaning (rotifers - diet). Sigificative differences were recorded among treatments (P0.05). Best survival rate (45.6 ± 7.6 percent)and growth (7.4 ± 0.5 mm)were found in treatment B. Results indicate that co-feeding red porgy larvae with inert and live diets from day 20 after hatching is a promising weaning strategy in the hatchery of this species.
  • Effect of the incubation temperature on the embryonic development and hatching time of eggs of the red porgy Pagrus pagrus (Linne, 1758)(Pisces: Sparidae)

    Radonic, M.; López, A.V.; Oka, M.; Aristizabal, E.O. (2005)
    Assessment of egg quality at early embryonic stages may be useful predictive criterion to evaluate the potential mass juvenile production in red porgy Pagrus pagrus. The objective of the present study is to describe in detail the embryonic developmental stages in the red porgy and the time taken by larvae to hatch at three incubation temperatures. Fertilized eggs obtained from natural spawnings were incubated at 15, 20 and 25°C. Photomicrographs of all the embryonic stages were taken at the three temperatures. Cell divisions after fertilization and organ appearance during the embryonic development were identified. The sequence in cellular divisions and appearance of sensory and motor organs were the same for the three temperatures, although the higher the temperature, the faster the stages of development. Hatching time was also determined by the incubation temperature. At 25°C the completely-formed embryo hatched at approximately 25 h 26 min after fertilization whereas at 20°C and 15°C hatching occurred 37 and 60 h post fertilization. Knowledge of the normal embryonic stages, the sequence of cleavages, the egg diameter, the number of oil drops, the timing of organ formation and the hatching rate is a basic requirement for assessing the eggs batches quality during seed mass production.