Culture performance of Oreochromis niloticus and Sarotherodon galilaeus using similar management strategies

Sarotherodon galilaeus and Oreochromis niloticus are 2 readily available fish species in Nigeria, often cultured interchangeably. The findings are presented of a comparative study conducted to provide information on their performance using similar nutrient loadings without supplemental feed. Results showed a better performance of O.niloticus over S.galilaeus, which may be partly explained by the dietary mechanisms of the fish. Further trials on gut content analyses are require

Ecophysiological perspectives of blue-green algal blooms

Blue-green algae (cyanobacteria) have had a profound and unparalled impact on the aquatic environment because of the phenomenon of bloom formation. In many countries, water management is threatened with extensive and persistent noxious blooms of blue-green algae in surface and near-surface mesotrophic and eutrophic waters. In view of this, ecological and physiological factors responsible for blue-green algal dominance are discussed. The implications of cyanobacterial blooms are highlighted and recommendations made to combat this menac

The cladoceran fauna of Nigeria : a checklist, review of literature and distribution

L'étude a porté sur 623 échantillons collectés entre 1971 et 1981 dans 145 stations en eau douce au Nigéria. On a dénombré 61 espèces et une sous-espèce pour 31 genres de Cladocères. Trente deux espèces sont nouvelles pour le Nigéria et 4 pour l'Afrique. Ce sont #Ilocryptus verrucosus, Chydorus reticulatus, Camptocercus lilljeborgi dadayi et #Leydigia leydigi. La présence des espèces dans les divers habitats est discutée. Il apparait par ailleurs des liens faunistiques étroits entre l'Afrique et l'Amérique du Sud. (Résumé d'auteur

An appraisal of the current status of the fisheries of Eleiyele Reservoir by its fisheries cooperatives

In a study undertaken to evaluate the status of the fisheries of Eleiyele Reservoir (Nigeria) between 1995 and 1997, thermal stratification was observed to breakdown between December and March. Of the physico-chemical variables, transparency was positively correlated (p<0.05) with primary productivity, conductivity and dissolved oxygen concentration. Primary productivity ranged between 0.38mgC/m super(2)/d and 3.OmgC/ m super(2)/d, being lowest in April. BOD values ranged between 1.3mg-2.2mgO/l indicative of clean unpolluted water. Nine fish species belonging to the families Cichlidae, Centropomidae and Mochokidae were identified. Cichlids were the most abundant with Hemichromis species being predominant. Fishing was only carried out in the reservoir during the dry season months of November to April. Fish landing data for the reservoir, obtained from the Fisheries Division of the Ministry of Agriculture and Natural resources, Oyo State, in conjunction with comparative data from the Cooperative fishermen was low. It demonstrated a decreasing trend from January to April and during the period between 1985 and 1996, when compared with data collected in 1985 and 1986 from a previous similar study. Reasons for the low fish yield from the reservoir are discussed and compared with other Nigerian reservoir

Cumulative impact of effluents on plankton dynamics in Awba Reservoir, Ibadan

The assessment of changes in the biological community of water is a very sensitive measure of its quality. The plankton community structure of Awba reservoir in the University of Ibadan, Nigeria was monitored between April and October 1989 to determine the impact of natural eutrophication and effluent discharge on its dynamics. Generally, the dissolved oxygen content, pH, conductivity and ammonia-nitrogen values indicated a deterioration in water quality at stations receiving organic or chemical effluents. The plankton structure was characterized by a blue-green algae - Protozoa dominated community. The Simpson's diversity index at all stations was less than one implying a heterogeneous community where a few species dominated. Tropical Freshwater Biology VOL. 8 1999, pp. 1-15 KEY WORDS: effluents - water quality - Simpson's diversity index - plankton community structur