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Study of Age, Growth and Some Population Dynamics Aspects of the Nile Cyprinidae Fish, Labeo niloticus, From the River Nile at El-Kanater El-Khyria, Egypt

By walaa on June 15,2008

 

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

Abstract

      In the present work, certain biological characteristics of Labeo niloticus (Forsskål, 1775) of the maincourse of the River Nile at EL-Kanater EL-Khyria, Egypt were investigated during the period fromAugust 2003 to August 2005. The length-weight relationship was found to be: log W (gm) = -2.27765 +3.18395 log L (cm) and the condition coefficient (K) was 1.03. Age determination using annual rings offish scales indicated that the longevity of this species reaches 6 years. The maximum increase in lengthwas noted in the first age group. The von Bertalanffy growth equation was computed as: Lt = 72.99 {1 –e – 0.355(t + 0.1789)} where the asymptotic length (L) = 72.99 cm. Growth in length and weight were studied.Reproductive cycle including gonadosomatic index and the size and age at first sexual maturity wereinvestigated. The body lengths at first sexual maturity (Lm50) and first capture (Lc) were equal to 32 cm.Thus, it is recommended to prevent catching fish sizes less than 30 cm T.L. or 266.3 gm T.W. This is togive at least one time for the mature fish to spawn and to recruit the fish stock. The total mortality rate was73% yearly, whereas, the estimated values for natural and fishing mortality coefficients were 0.64 and0.66, respectively. The exploitation rate of the fish stock was 0.51. For proper management, the presentlevel of exploitation rate should be reduced to maintain a sufficient spawning biomass. The length andage at first capture as well as that at recruitment were found to be Lc = 32.0 cm, tc = 1.44 yr and Lr = 14.0cm, tr = 0.42 yr, respectively. The growth performance of Labeo niloticus (φ = 3.28) was the highest incomparison with other localities.Key words: Age and growth, Egypt, EL-Kanater EL-Khyria, Labeo niloticus, mortality, population

dynamics, reproduction, River Nile.


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