Food and feeding habits of grey mullets (Mugilidae) in the River Volta and River Pra estuaries in Ghana were studied between February 1997 and July 1998 as part of efforts to encourage their culture. Stomach contents of fish samples, obtained with a cast net and a drag net, were analysed using the 'points' and frequency of occurrence method. Diatoms, detrital material and sand particles were the major items in the stomachs of all the species from the two estuaries. Their diet did not show any substantial seasonality, neither did it change with size. The various species ingested sand particles of selected range with Liza dumerilii ingesting the widest range in both estuaries, 41.2-1195.8 µm in the Volta estuary, and 33.0-1649.0 µm in the Pra estuary. Species that ingested the same modal size of sand particles showed preferences for different food items. The shortest mean relative gut length (gut length to body length ratio) of 1.82 and 1.72 were calculated for L. dumerilii in the Volta and Pra estuaries, respectively, while the longest mean relative gut length of 4.56 was calculated for Mugil cephalus in the Volta estuary and 4.33 for Liza grandisquamis in the Pra estuary. All the species showed a diurnal feeding habit, with the main feeding period occurring between 08.00 and 12.00 h. The peak feeding time, however, differed among the species.

This aper examines the status of the tilapia fishery in Fosu Lagoon at Cape Coast, in the Central Region of GLana (5'07' N, l"16' W). The blackchin tila ia, Sarotherodon melanotheron (Ruppel), constitutes about 90% by weight of the total fish catch, and t ! e annual yield of 452-664 kg/ha is ap reciably higher than those reported for other tropical lagoons. Variations in the CPUE (0.30-0.96 &g/man-h) were related to fluctuations in the water level of the lagoon. Using the ELEFAN method, estimates of the growth and mortality parameters, based on length-frequency data were: Loo = 16.1 cm TL, K = 0.82/ yr, Z = 4.95/yr, M = 1.90/yr and F = 3.05/yr. The growth estimates and the maturity-length ratio suggest that the population is stunted. The mean length at first capture (Lcso) was estimated to be 6.2 cm TL. Although the present rate of exploitation (E = 0.62) appears high, an analysis of the relative yielder-recruit (Y'/R) and high recruitment shows that this exploitation rate can be maintained by the Egoon population. Recruitment occurs throughout the year with two peaks, and this probably ensures the sustenance of the high yield.

Mangrove wetlands are one of the most important ecosystems on earth, providing habitats for both marine and terrestrial organisms as well as supporting essential human services. However, high dependence of humans on these systems is leading to significant transformation of mangrove wetlands and reduction in their ecosystem services including fisheries. The objectives of this study were to estimate the biomass of two mangrove wetlands in Ghana within urban and rural contexts and determine the fish fauna assemblages as part of baseline setting. The study used the structural parameters of mangrove species and allometry to estimate the biomass of both forest systems. Fish community structure were determined based on ecological surveys. The findings show that the standing biomass of the mangrove forests were significantly higher (p < 0.01) in the rural wetland (394.49 t/ha) compared to the urban wetland (126.29 t/ ha). Fish fauna assemblages, referring to species richness and diversity were higher in the urban wetland at 4.21 and 2.64 respectively compared to the rural wetland at 3.46 and 2.09 respectively. This paper concludes that a well-developed mangrove system with high mangrove biomass may not necessarily imply high fish species richness and diversity.

This study described some aspects of the reproductive biology of Blackchin tilapia (Sarotherodon melanotheron, Cichlidae) from Brimsu reservoir. A total of 457 specimens were sampled using a monofilament gill net of mesh size 25 mm from September, 2009 to September, 2010. Standard length for the species ranged between 7.5 and 17.6 cm, with both males and females having a unimodal modal length of 10.0 to 10.9 cm. The length at sexual maturity (L 50) was 11.26 and 11.34 cm for males and females, respectively. The pattern of fluctuation in gonadosomatic index indicates that the species had an extended spawning season starting from February to August.

The monthly feeding activity and food habits of populations of Ethmalosa jimbriatu occurring in the sea and an estuary in Cape Coast, Ghana district were investigated during a 14-month period. The juvenile fish, whose total length (T.L.) ranged from 5-3 to 14.7 cm, occur in the estuary and appeared to be more active feeders than the marine samples which measured 15.0-30.4 cm. The peak feeding activity in the marine population coincided with the onset of ' upwelling ' in the sea, which period is characterized by high salinities, decreasing temperatures and high zooplankton production. The species is primarily a plankton feeder. The stomachs of the marine samples contained mainly protozoa, crustacea, molluscan larvae and a considerable amount of detritus while the stomachs of the estuarine fish contained mainly phytoplankton, protozoa, sand grains and organic detritus. These observations have been discussed in relation to other reports on populations occurring along the West African coast.

No abstract

Juvenile mugiiid fishes, Liza falcipinnis, L. dumerilii, Mugil hanunensis and M. curemu, which enter the Elmina Lagoon in the Cape Coast District of Ghana, have a similar diet comprising mainly bacteria, diatoms, blue-greenlgreen algae, protozoans, detritus and particulate organic matter. No seasonal changes in the diet and feeding activity were observed. The relative gut length (intestine to standard length ratio) and diet showed no significant changes with size of fish in all the species. All four species were diurnal feeders, but their peak feeding times differed. Interspecific competition for food was possibly limited by species preferences for substrate particles of particular size range and differences in feeding chronology.

The gonads of Ethmulosu fimhriuta have been classified according to five and four maturity stages in the male and female, respectively. The species appears to mature at 22.0 cm in Ghana waters. The fecundity and frequency distribution of oocytes have been determined.Monthly changes in the proportions of gonadal stages and gonadosomatic index indicate that the species spawns in the sea from October to March. The results have been compared with data on populations occurring in other West African countries.