An Experimental Trammel Net in the River Nile, Aswan, Egypt Influencing the Age and Growth of the Nile tilapia Oreochromis niloticus (Linnaeus, 1758)

Kassem Et Al., Mahmoud A. H.

doi:10.21608/ejabf.2023.291672

An Experimental Trammel Net in the River Nile, Aswan, Egypt Influencing the Age and Growth of the Nile tilapia Oreochromis niloticus (Linnaeus, 1758)

Document Type : Original Article

Author

Mahmoud A. H. Kassem et al.

10.21608/ejabf.2023.291672

Abstract

Oreochromis niloticus, a widely distributed and commercial fish in Egypt, needs continuous updating and studying. The current work aimed to study the length-weight relationship, condition factors, age and growth of O. niloticus, and the effect of fishing gear on fish stocks. A total of 608 O. niloticus specimens were collected by three modified trammel nets with different mesh sizes (56, 64 and 76 mm) in percentages of about 49.8%, 47.4% and 2.8%, respectively. Total length (TL) ranged from 12 to 24.3cm, and total weight ranged from 42.8 to 253g for all samples. The exponent "b" of the length-weight relationships was "3" for females (b = 2.79), males (b = 2.69) and all samples (b = 2.66), reflecting the negative allometric mode of growth. The highest condition factors were found in February for females and January for males and combined sexes, and all values were >1.0. The age of O. niloticus was determined to be 4 years old. Von Bertalanfi's growth constants are L = 28cm; K = 0.28 y-1, and to = -1.9. Regarding the age differences with variation in mesh sizes, it has been pointed out that the use of median and large mesh sizes is important to avoid small fish in a lower age group, which is considered for fisheries management and conservation.

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