Phycology and fisheries development - a review.

Algae are the chief primary producers in the aquatic environment. Thus, they supply proteins, carbohydrates and mineral salts to the primary consumers and consequently sustain many fishes of commercial interest. Despite algae being a good source of food for some fishes, some cyanobacteria are of low nutritional value and with dinoflagellates may secrete toxins that kill fish. Algae population varies according to seasons and this affects algae - dependent organisms. Optimal algal population is favoured by eutrophication but when there is rapid eutrophication, algal blooms may result. This may lead to the death of zooplankton, game fish and even man. The realization of fish as a major source of protein in Nigeria spurred various workers to investigate the natural food for such fishes as clupeids, Synodontis spp., Chrysichthys spp., Schilbe spp., Tilapia, Alestes, Lates sp. Hydrocynus sp., Siluranodon sp., Eutropus, Bagrus docmac, B. bayad, Heterobranchus sp. Cymnarchus sp., Clarias spp, Hemicynodontus sp. and Brachysynodontis sp. Important fish species cultured in Nigeria include Tilapia nilotica, Tilapia melanopleura, Tilapia galilea, Cyprinus carpio (Common carp), Heterotis niloticus, Lates niloticus (Niger perch), Chrysichtys nigrodigitatus (Catfish) C. gariepinus (Catfish) and others. Aquaculture has not advanced as much in Nigeria as in developed countries where algae could be cultured as feed for fish, shrimps, prawns and other crustaceans in commercial quantities. The economic importance of algae in fisheries cannot be overstressed. Their absence could cause disruption of equilibrium, while excess of them could result to mortality of aquatic fauna.