Occurrence of macro-algae in the by-catch of Beach Seine Fisheries at Sakumono, Ghana

Dense growths of macro-algae contribute to primary productivity in nearshore marine environments and their abundance has been correlated with fish catch. Though the two resources are captured together in beach seine nets, macro-algae are usually regarded as a nuisance by fishermen and discarded (as by-catch). The species composition, abundance and seasonality of macro-algal species in fisheries by-catch of beach seine nets at Sakumono, Ghana were determined between November 1999 and September 2001. Data was analysed using a combination of both univariate and multivariate procedures. The species richness of macro-algae in the catch was high and appeared to vary monthly. Biomass of macro-algae in the catch was found to be low (range 0–6.7%) and formed only 7.7% of the by-catch. The significance of macro-algae in by-catch is discussed

Influence of Tourist Pressure on Beach Litter and Microbial Quality - Case Study of Two Beach Resorts in Ghana

Beach litter accumulation and reduced water quality are important aspects of beach degradation which have adverse effects on the users of the beach and marine life. The study aims at determining how the degree of human pressure at the La and Korle Beach resorts in Accra, Ghana, which serve different social communities, contributes to beach degradation. A weekly collection of fresh and accumulated litter from a belt transect of 500 m2 and samples of seawater from each beach were obtained during a 3-week festive period (Dec. 26, 2005–Jan. 9, 2006) and a 3-week non-festive period (Jan. 23, 2006–Feb. 6, 2006). Thirty-two types of litter were identified and the total number and weight of litter collected from La were 2261 and 72695 g, and that of Korle were 2691 and 43239 g, respectively. Plastic material dominated the total litter at 66% for Korle and 53% for La, respectively. The numbers of litter increased with increasing visitor pressure during the festive season for Korle, although the type and diversity of the beach litter was location specific irrespective of the season for both sites. Microbial values for coliforms were higher for Korle than La, with significant increase in Korle during the festive season. The implications for leisure activity like swimming at both sites has minimalhealth risks since the mean levels of the indicators are within the WHO international permissible range

Food preferences of the common tern, sterna hirundo (Linnaeus, 1758) at the Densu floodplains, Accra

Seabirds are important in the dynamics of marine ecosystems because they recycle important biomass of lower trophic level organisms. Their faeces and carcasses provide important food sources for terrestrial and benthic scavengers. As a result of the abundance of food resources along the coast of Ghana, common terns (Sterna hirundo) are found in large numbers in productive brackish or saltwater wetlands, and are notable for indicating location of rich fish stocks at sea and in lagoons. The study aimed to determine the variety of food available, and any food preferences exhibited by S. hirundo at the Densu floodplains near Accra. While earlier studies of food habits of seabirds worldwide used examination of regurgitates and telescopic observations, the study quantitatively analyzed guts of common tern for their food content using standardized methods. The utilization by common terns of the Panbros lagoon fish resource during roosting in the night was quantified. Results showed that food available to the birds included marine and fresh or brackish water fish, crustaceans and worms. During caging, only one bird fed on 15 individuals of Hemichromis fasciatus. Prey items such as exoskeleton of crab zoea larvae, capitellid worms, fish otolith, pieces of fish bones and vertebrae, detrital materials and sand grains were found in the guts. The presence of capitellid worms in the guts, a known indicator of excess nutrient enrichment, showed that S. hirundo utilized the Panbros lagoon fish resource in feeding, and the roosting ground was under much stress. The study stressed the importance of complementing conservation efforts for common terns with attempts to manage the fish resources in the Densu floodplains

Acute toxic effects of deltamethrin on tilapia, Oreochromis niloticus (Linnaeus, 1758)

The effect of toxic compounds are variable among living organisms in different habitats. Toxicity tests are conducted to measure the effects of different pollutants on one or more species of organisms and in the form of LC50s, assist in the development and application of water quality criteria for the protection of the aquatic environment. Active tilapia, Oreochromis niloticus, samples with size ranging between 4 and 6 cm standard length were exposed to different concentrations (between 0 and 30 ìg/l) of Deltamethrin for 96 h in 50 l glass aquaria. This was to assess the dose-response of O. niloticus to different concentrations of the pesticide, and to estimate the LC50 using Probit analysis. The very low LC50 value of 15.47 ìg/l obtained indicates that Deltamethrin is highly toxic to O. niloticus. This LC50 value should serve as a guide for the application of Deltamethrin in agriculture. Further study into the processes and mechanism by which Deltamethrin adversely affects the physiology of fishes have been recommended

A simple model for the simultaneous management of seabird populations and discards at sea

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Exploitation Rates and Management Implications for the Fisheries of Bontanga Reservoir in the Northern Region of Ghana

The exploitation rates of eight major component fishery species, Auchenoglanis occidentalis, Brycinus nurse, Clarias gariepinus, Hemichromis fasciatus, Marcusenius senegalensis, Oreochromis niloticus, Sarotherodon galilaeus and Tilapia zillii, of gill net fishery of Bontanga reservoir, were studied from March 2004 to March 2006 based on length-based models. The exploitation rates (E) of A. occidentalis and H. fasciatus were 0.7 and 0.6, which exceeded the optimization (Eopt) criterion of 0.5 for sustainable exploitation of fisheries, indicating that these species were over exploited. For B. nurse and S. galilaeus, E . 0.5, indicating that these species were at their maximum rates of exploitation. For C. gariepinus, M. senegalensis, O. niloticus and T. zillii, E < 0.5, indicating that these species were not over exploited. Based on the selection factor of the legal minimum gill net mesh size of 5 cm of Ghana Fisheries Act 625, the estimated mesh size for catching the eight species ranged from 9.9.19.3 cm, calling for an upward review of the legal minimum mesh size of gill nets from 5 to 10 cm for sustainable exploitation of reservoir fisheries. The adoption of minimum mesh size of gill nets of 10 cm, restriction of further entry into the fishery, control rights and community based co-management system are some management options suggested to enhance sustainable exploitation and management of the fisheries

Abundance, biomass and species composition of nearshore fish assemblages in Ghana, West Africa

Many of the world's fish populations are overexploited, including Ghana's fish resources. This study examines spatio-temporal trends in fish species composition in relation to biotic, abiotic and anthropogenic factors, towards achieving better-informed management of the beach-seine fisheries. Fishery-dependent data were collected between November 1999 and October 2001 from 94 beach-seine hauls fished at two stations along the Ghanaian coast. The catch consisted of fish, crustaceans, other invertebrates, and macroalgae. Generally, juveniles of species that are exploited by offshore fisheries were found in the catches. Species abundance and their occurrence generally peaked between November and January. Duration of solar radiation and tide level appeared to be important predictors of fish biomass. It is important to exploit the nearshore fish assemblage sustainably because of its nursery role. A co-managed (fishers and government) three-month ban on beach-seining (between May and July) is recommended as the most appropriate control measure towards the sustainability of Ghanaian fish stocks. Keywords: artisanal, beach-seine, fisheries, Ghana, nearshore, surf zone, West AfricaAfrican Journal of Marine Science 2006, 28(3&4): 689–69