Biology and management of fish stocks in Bahir Dar Gulf, Lake Tana, Ethiopia

Resúmen

The biology of the fish stocks of the major species in the Bahir Dar Gulf of Lake Tana, the largest lake in Ethiopia, has been studied based on data collected during August 1990 to September 1993. The distribution, reproduction patterns, growth and mortality dynamics and gillnet selectivity of these stocks are described.

The major fish categories, Barbus spp., Clarias gariepinus, and Oreochromis niloticus contribute equally to the catches. O. niloticus is most abundant in the shallow littoral zone, while C. gariepinus and the larger piscivorous Barbus species are found mainly in the deeper open water area of the lake. These larger species are mainly exploited by the motorized boat fishery. The catch from the reed boat fishery, confined to the littoral zone, consists mainly of O. niloticus and Barbus tsanensis.

The breeding activity of all major species is associated with the rainy period and increase in lake water level. C. gariepinus has a short breeding period in July whereas O. niloticus and B. tsanensis show extended activity with peak breeding during July and September-October respectively. They are fully recruited to the fishery at 2 - 4 years of age well beyond the age of maturity. During the breeding period a higher catch rate is observed for Barbus species.

The sustainable potential yield of 32 kg.ha. ^-1.yr. ^-1estimated for the Bahir Dar Gulf area, indicates that there is scope for some expansion of the fishery. The shortage in fish storage, distribution and marketing facilities, the limited local market and lack of fishing tradition are major constraints to the development of the fishery.