Growth, Fishing Mortality, and Exploitation Rates of Oreochromis niloticus and Oreochromis aureus Caught by Trammel Nets from El-Salam Canal, Egypt

Badr El-Bokhty, El-Azab E.; Fetouh, Mohamed A.

doi:10.21608/ejabf.2023.322918

Growth, Fishing Mortality, and Exploitation Rates of Oreochromis niloticus and Oreochromis aureus Caught by Trammel Nets from El-Salam Canal, Egypt

Document Type : Original Article

Authors

10.21608/ejabf.2023.322918

Abstract

This preliminary study is the first concerning the age, growth, fishing, mortality, and exploitation rates of two tilapia fish (Oreochromis niloticus and Oreochromis aureus) caught by trammel nets from El-Salam Canal. Analysis of the length-frequency data of collected fish using the FiSAT program revealed von Bertalanffy's growth curve indicators as L_∞ = 24.86 cm, k = 1.3 year^-1 for O. niloticus and L∞ = 19.14 cm, k = 1.9 year^-1 for O. aureus. The longevity (maximum age) reached by O. niloticus was 4 years and for O. aureus was 3 years as revealed by Bhattacharya analysis. The lengths at first capture (L_c) of O. niloticus and O. aureus were 9.94 and 10.82cm, respectively. The total, natural and fishing mortality rates for O. niloticus were Z= 4.92 y^-1, M=2.02 y^-1 and F= 2.9 y^-1, and those for O. aureus were Z= 5.99 y^-1, M=2.78 y^-1 and F= 3.21 y^-1. The estimated values of exploitation ratios (E) were 0.59 and 0.54 for O. niloticus and O. aureus, respectively. Based on the optimal exploitation value (0.5), the results indicate that both species are considered to be over-exploited at El-Salam Canal, and the illegal fishing gear should be banned. In addition, more investigations should be carried out on other fishing gear to understand the real situation of tilapia stock in the canal.

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