Biological Aspects and Fisheries Management of Tilapia Fish Oreochromis niloticus (Linnaeus, 1758) in El-Bahr El-Faraouny Canal, Al-Minufiya Province, Egypt

摘要

In the present investigation, age, growth, mortality, exploitation, yield and biomass and reproduction of Nile tilapia ( Oreochromis niloticus ) from El-Bahr El-Faraouny Canal, Al-Minufiya Province, Egypt, were determined. The regression parameter ?n? of dependence of total weight upon total length was found to be negative allometric growth. The coefficients of condition were computed. The annual rings on fish scales were used for age determination. The longevity of this species was found to be 6 years. The maximum increase in length was noted during the first year of life and showing a gradual decrease in growth as the fish got older. The O. niloticus population had a sex ratio of 1:1.08 (M:F) which did not deviates ( X2 = 1.997, p>0.05) from the hypothetical distribution of 1:1. The maturity stages were classified macroscopically into five stages. Higher values of Gonadosomatic Index (GSI) for males and females occurred nearly throughout the year with peak from May to August indicating prolonged spawning season. There is a selective mortality towards smaller fish sizes. Therefore, for management purposes it is recommended that the local authorities must be set a regulation to control the illegal fishing activity and larger mesh sizes of fishing nets should be used to increase the mean lengths at first capture and their marketable sizes leading to more economic returns and also to conserve the spawning stock part of O. niloticus population. A comparison of the various parameters of O. niloticus in the present study with those of other authors in different localities and times in Egypt revealed year-to-year and geographically differences. These differences were discussed and were found to be attributed to the effect of increased pollution of the canal. Finally, the present study recommended that El-Bahr El-Faraouny Canal must be in protection against pollution.