Abstract/Summary

Interannual variation in yield per species from a freshwater reservoir in Bangladesh was analysed by using long-term landing data. Each species was categorized according to characteristics in interannual yield variation. The characteristics were defined with respect to size of the interannual variation in terms of absolute and relative variation around the mean yield and long-term trends in catch levels. Annual variation was directly (t18 = 7.84; P < 0.01) related to the yield and can serve as a good indication of the status of the fishery when catches are low. The target fish, Indian major carps (IMC) Labeo rohita, Labeo calbasu, Catla catla and Cirrhinus mrigala, showed large variation in annual yield. This might have occurred because of variation in annual recruitment. Illegal use of gears is mostly related to variation in year class strength, and is assumed to be the most important source of change of stock variation. An increase in catch rate was recorded for Corica soborna. Such a stable combination may only be possible for a certain period without a long-term trend. Trends in the yield rate of the major fish category for three decades reveal a sharp decline in the catch of IMC. In contrast, small clupeid-like C. soborna have the highest yield rate. Fishing gears can play a crucial role in this fishery. Fisheries managers must always be alert when issuing fishing licenses and on the control on gears. The conclusion is that the IMC fishery of Kaptai Reservoir is an overexploited fish stock. In this fishery, the same gears are usually employed indiscriminately for different species and size classes. To stabilize the fishery, the existing policy needs to be strengthened and more effectively implemented. Also, some fishing gears and traps need to be restricted. An effective stock protection policy is suggested. Further study on catch size of individual species is essential prior to the development and implementation of any management scheme.