<br>

Recent Submissions

  • Species Diversity and Relative Abundance of Fisheries Resources Found in Beach Seine along the Central Coast of Ghana

    Aggrey-Fynn, J.; Sackey-Mensah, R. (2012)
    The diversity and relative species abundance of fisheries resources were studied from Winneba to Cape Coast on the central coast of Ghana during December 2007 to May 2009. Samples of organisms were collected at random from beach seine landings during the study period. The fishes were counted and identified to the family and species levels. Ecological indices such as Shannon-Wiener diversity index, equitability and Sørenson’s similarity index were used to analyse the data. Specimens from Winneba, Saltpond and Cape Coast comprise 56 species belonging to 30 families. Carangidae, Haemulidae, Clupeidae and Sciaenidae were some of the families, where key species occurred during the study. The relative abundance of key organisms in the beach seine landings include Chloroscombrus chrysurus (26.0%) in 2007, Brachydeuterus auritus (22.8%) in 2008, Ilisha africana (14.7%) in 2008, Sardinella aurita (13.1%) in 2009 and Selene dorsalis (11.2%) in 2007. The organisms that were in low relative abundance were Acanthurus monroviae, Penaeus notialis, Galeoides decadactylus and Trichiurus lepturus. Shannon-Wiener diversity index, estimated in the study, ranged from 2.54 to 2.83. Species equitability range was 0.67–0.77, and the Sørenson’s similarity estimated ranged was 0.66–0.69. The estimations of fish species diversity and equitability were higher (H’ = 2.83; J’ = 0.77) during the 2009 study in the central coast of Ghana. The similarity indicators in the various paired periods during the study showed considerable similarity in the organisms that were exploited by the beach seine in the area. The study explains the linkage between the diversity and relative species abundance of the coastal fisheries resources and offshore marine resources in Ghana, and the need to regulate beach seine operations in order not to over exploit the juvenile stocks.
  • Marine magnetic data processing in equatorial regions off Ghana

    Buchanan, S.K; Scrutton, R,A; Edwards, R,A; Whitmarsh, R,B (RAS, 1996)
    Total field magnetic values recorded during a survey be RRS Charles Darwin off Ghana yielded large track-crossover errors of up to 120 nT (RMS value of 58.7 nT), which masked the weak magnetic anomalies in this equatorial region. The heading effect of the ship's magnetic field and strong diurnal variation in the Earth's field are likely causes of the errors. A heading effect experiment shows differences of up to 30 nT for Charles Darwin on different headings, which have been corrected for. The diurnal variation has been calculated by using the magnetic field observations themselves, because observatories are either too distant or were inoperative at the time of the survey. A method that uses the anomalies corrected for heading effect and differences at track crossovers was found to produce an acceptable curve, with an amplitude of 120 nT and a shape similar to that of equatorial observatories. Fully corrected anomalies have crossover errors of up to only 40 nT with an RMS value of 17.5 nT. These anomalies reveal a linear magnetic anomaly low along the continental slope off Ghana.
  • Structure and Dynamics of demersal assemblages on the continental shelf and upper slope off Ghana, West Africa

    Koranteng, K.A (Inter-Research, 2001)
    Using two-way indicator species and detrended correspondence analysis, species on the continental shelf and upper slope of Ghana were classified into 6assemblages. The structure of the assemblages is determined primarily by depth and type of sediment on the seabed. There are clear faunal discontinuities around 30-40, 100, and 200m depth. The dynamics of the assemblages are influenced by physico-chemical parameters of the water masses, mainly temperature, salinity and dissolved oxygen, which are periodically modified by the seasonal coastal upwelling that occurs in the area. The observed changes in the composition and relative importance of species in the assemblages can be related to increased fishing activity and environmental forcing.
  • Earthworm and maggots meals as potential fishmeal replacement

    Yaqub, H.B. (1997)
    Three meals were formulated from the earthworm (Endrilus eugineae) and maggot (Musca domestica) and fish (Engraulis encrosicolus). These meals were evaluated as a potential replacement for fishmeal. This is because fishmeal could be very expensive at times. The three meals were used in feeding the catfish (Heterobranchus isopterus) fry for 30 days. The study was conducted in 1991 at the Institute of Renewable Natural Resources Farm, University of Science and Technology. Two replicates were done using four hapas in each replicate. Each hapa was stocked with 50 fry and fed. Those in the fourth hapa were not fed to ascertain the effect of supplementary feeding on the growth of the fish. Weight increment was found to be less in the fourth hapa than the other three hapas, though the difference was not significant at the 5% level. On the basis of weight increment, the best growth performance was produced by maggot meal. It was followed by earthworm and fish meals respectively. Based on food conversion ratio maggot meal was again the best, followed by earthworm and fish meals respectively. The importance of supplementary feeding was evidenced in the higher weight increment in fish that were fed than those that were not fed. Maggot and earthworm meals could therefore be a whole or partial replacement for fishmeal. The difficulty in the harvesting or rearing maggots and earthworms may however reduce this potential.
  • Obervations on the commercial light fishing operation in Ghana.

    Quartey, R.; Bannerman, P. (2005)
    Light fishing operations (LFO) in Ghana is concentrated in the three major coastal municipalities of Greater Accra (Tema), Central (Mumford & Elmina) and Western (Sekondi) Regions; these areas have the port facilities for landing of the catch by the larger inshore vessels that operate the purse seine fishery in Ghana and which predominantly operate the light attraction. Currently there are about 250 registered inshore vessels in the country whose sizes range between 39 – 60 feet , only a small fraction are actually working at the moment due to problems with spare parts and operations. Light attraction is the technique of aggregating fish by artificial light; and light fishing is the process of fishing the attracted fish by hooking, gill-netting or by any other gear (P.P. Dinglasan, 1972). The light source may be by means of a fire torch, pressure kerosene lamp, gas lit lamp and battery or generator assisted incandescent lamp (FAO Training Series, 1988). Currently the light fishing operations in Ghana use mainly the purse seine gear with a small size generator powering the incandescent lamp. They are minimally mechanized using fish finders, a two-way radio for communication and a diesel driven winch drum to facilitate the search and hauling of the catch.
  • Improvements in the Ghanaian tuna statistics system

    Quartey, R.; Bannerman, P. (2005)
    Light fishing operations (LFO) in Ghana is concentrated in the three major coastal municipalities of Greater Accra (Tema), Central (Mumford & Elmina) and Western (Sekondi) Regions; these areas have the port facilities for landing of the catch by the larger inshore vessels that operate the purse seine fishery in Ghana and which predominantly operate the light attraction. Currently there are about 250 registered inshore vessels in the country whose sizes range between 39 – 60 feet , only a small fraction are actually working at the moment due to problems with spare parts and operations. Light attraction is the technique of aggregating fish by artificial light; and light fishing is the process of fishing the attracted fish by hooking, gill-netting or by any other gear (P.P. Dinglasan, 1972). The light source may be by means of a fire torch, pressure kerosene lamp, gas lit lamp and battery or generator assisted incandescent lamp (FAO Training Series, 1988). Currently the light fishing operations in Ghana use mainly the purse seine gear with a small size generator powering the incandescent lamp. They are minimally mechanized using fish finders, a two-way radio for communication and a diesel driven winch drum to facilitate the search and hauling of the catch.
  • Diversity and stability of demersal species assemblages in the Gulf of Guinea

    Koranteng, K.A. (West African Journal of Applied Ecology, 2001)
    The structure of demersal fish assemblages on the continental shelf and upper continental slope of the Gulf of Guinea is described. Community structure is determined primarily by depth and type of sediment on the seabed. Changes in the composition of the identified species assemblages over a 25-year period are examined. The dynamics of the assemblages are influenced by physico-chemical parameters of the water masses, mainly temperature, salinity and dissolved oxygen, which are periodically modified by the seasonal coastal upwelling that occurs in the western Gulf of Guinea. Increased irresponsible fishing operations (like the use of explosives) that lead to habitat alteration and other anthropogenic activities like oil and gas exploration which have the potential to cause environmental changes pose a threat to biodiversity in continental shelf waters of the Gulf of Guinea. industrial trawling in coastal waters and environmental forcing conjointly influenced the changes in the composition and relative importance of species in the assemblages.
  • Seasonal and Long-Term Changes in the Distribution and Abundance of Demersal Fishery Resources in Continental Shelf Waters off Ghana, West Africa

    Koranteng, K.A. (2001)
    Between 1963 and 1990, the abundance of demersal fishery resources in Ghana’s shelf waters underwent significant changes whereby the relative importance of major species changed in every trawl survey conducted in the area. Triggerfish (Balistes capriscus) dominated this ecosystem for nearly twenty years (from early 1970s to late 1980s) displacing bigeye grunt (Brachydeuterus auritus) as the most abundant species.The density of all demersal species (excluding triggerfish) assessed in bottom trawl surveys decreased from 50 kg ha-1 in 1963-64 to 32.4 kg ha-1 in 1990. The lowest density of 22.5 kg ha-1 occurred between 1973 and 1977. Density of triggerfish was high between 1973 and 1982, reaching a value of 28 kg ha-1 between depths of 30 and 50 m. Its density subsequently declined and by 1990, the species had virtually disappeared from the study area. In the period of decline of triggerfish, the density of rays, soles and cuttlefish increased.The observed changes in relative importance and density of species is attributed in part to the proliferation of the triggerfish in this ecosystem and also to changes in the marine climate over the period in question.
  • Study of the structure and dynamics of demersal fish assemblages on the continental shelf and upper slop off Ghana, West Africa

    Koranteng, K.A. (1998-09-27)
    Using two-way indicator species analysis and detrended correspondence analysis, species on the continental shelf and upper slope of Ghana were classified into six assemblages. The structure of the assemblages is determined primarily by depth and type of sediment on the seabed. There are clear faunal discontinuities around 30-40 m, 100 m and 200 m depth. The dynamics of the assemblages are influenced by physico-chemical parameters of the water masses, mainly temperature, salinity and dissolved oxygen which are periodically modified by the seasonal coastal upwelling that occurs in the area. The observed changes in the composition and relative importance of species in the assemblages can be related to increased fishing activity and environmental forcing.