Reproductive biology of Blackchin tilapia, Sarotherodon melanotheron (Pisces: Cichlidae) from Brimsu Reservoir, Cape Coast, Ghana

Feeding Ecology and Reproductive Biology of some Economically Important Fish Species in the Tono Reservoir, Ghana

The study of feeding ecology and reproductive biology ensures that the right management measures are applied for best output of fish stocks. Selection of good fish species for culture is also made possible through feeding and reproductive studies. Ghana over-relies on the culture of Nile tilapia and African catfish because there is no reliable scientific information on potential fish species that can be included for fish farming. The current study sought to investigate food habits and reproductive characteristics of economically important fish species in the Tono Reservoir of Northern Ghana. Monthly sampling was carried out from January, 2015 to December, 2016 (24 months). Specimens were obtained using cast net and gillnets of varying mesh sizes. Specimens were immediately transported to the laboratory in a chilled iced chest of temperature 4 for morphometric measurements and microscopic analysis of gut content and gonads. Thirty-three (33) individual food items were identified from all the fish species. Phytoplankton was the most important diet (Index of Relative Importance, IRI = 1923) whereas zooplankton was the least important diet (IRI = 35) out of the five major categories of food items identified from all the fish species. The major peaks of gonadosomatic index (GSI) of females were noted in February – March and June – July. Over 80 % variation of fecundity was explained by the predictors (standard length, fish weight and gonad weight) for Clarias gariepinus and Auchenoglanis occidentalis. All the fish species were classified as omnivores and they spawned more than once in a year making all of them good candidates for aquaculture. Management measures should focus on regulating agricultural activities close to the reservoir and fishing activities in the reservoir for sustainable fish production and exploitation.

Annual Pattern on Abundance and Sex Ratio Distribution of Selected Fish Fauna of Ikere Gorge Reservoir, Oyo State, Nigeria

Sex ratio affects the growth of wild population, thus, with the declining wild fish population, the study was designed to determine the effect of seasons on the sex ratio of fish population from Ikere Gorge, Nigeria for 18 months. Fish composition, diversity, distribution and abundance were determined according to standard methods. Sexes were determined and sex ratio was calculated using a standard method. A total of 5,823 fish specimens were caught during the period. The captured fish species were identified and classified into 34 species belonging to 13 families. The species richness was higher in the dry months than in the wet months. Fish diversity indices and evenness revealed a better diverse and even ecosystem in the wet season than the dry season. A marked significant difference (p < 0.05) was observed between the species in the dry months than the wet season. Chrysichthyes nigrodigitatus (35.07±7.59a) was significantly (p < 0.05) more abundant than the other species in the dry season. The sex ratio was skewed in favour of the female populations for C. nigrodigitatus, Tilapia melanopleura and Sarotherodon galilaeus but the reverse was the case for L. niloticus population. No monthly variation was observed in sex ratio of the species. The fish fauna from Ikere Gorge showed marked variations in the catch composition between the dry and wet months. C. nigrodigitatus and the Cichlids (Hemichromis fasciatus, S. galilaeus, Tilapia macrocephla and T. melanopleura) were present all year.