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Journal of Fisheries and Aquatic Science
  Year: 2012 | Volume: 7 | Issue: 2 | Page No.: 104-133
DOI: 10.3923/jfas.2012.104.133
 
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Environmental Studies on Synodontis schall (Bloch and Schneider, 1801) (Pisces: Siluriformes: Mochokidae) in The River Nile at Gizza Sector, Egypt: Biological Aspects and Population Dynamics

Midhat A. El-Kasheif, Mohammad M.N. Authman and Seham A. Ibrahim

Abstract:
Age, growth, mortality, exploitation, yield and biomass have been investigated for Synodontis schall populations to provide quantitative information about one of the important fishes, inhabiting River Nile, Egypt, in order to improve their fishery management. The length-weight relationships and coefficients of condition were computed. The annual rings on fish vertebrae 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 von Bertalanffy growth equation was computed. The population parameters were estimated. The instantaneous annual rates of total, natural and fishing mortality were calculated as 0.59, 0.35 and 0.25, respectively. The rate of Exploitation (E) amounted to 41%. Peak values of gonadosomatic index (GSI) for males and females occurred from May to August, indicating one season of spawning. The body length at first sexual maturity (Lm50) and mean selection length (Lc) were equal to 31 and 28 cm, respectively. There is a selective mortality towards smaller fish sizes. Therefore, for management purposes it is recommended to increase the length at first capture to maintain a sufficient spawning biomass for recruitment. Various parameters of fishes of present study when compared with those from other localities showed significant differences. These differences were discussed and found to be attributed to the different ecological conditions in the studied regions.
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How to cite this article:

Midhat A. El-Kasheif, Mohammad M.N. Authman and Seham A. Ibrahim, 2012. Environmental Studies on Synodontis schall (Bloch and Schneider, 1801) (Pisces: Siluriformes: Mochokidae) in The River Nile at Gizza Sector, Egypt: Biological Aspects and Population Dynamics. Journal of Fisheries and Aquatic Science, 7: 104-133.

DOI: 10.3923/jfas.2012.104.133

URL: https://scialert.net/abstract/?doi=jfas.2012.104.133

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