SOME BIOLOGICAL ASPECTS OF SHRIMP SCAD, ALEPES DJEDABA (FORSSKAL, 1775) LANDING AT NORTH COAST SINAI, MEDITERRANEAN SEA, EGYPT

Document Type : Researches

Authors

1 Dept. Fish Resou. and Aquac., Fac. Environ. Agric. Sci., Arish Univ., Egypt.

2 Fac. Aquacul. and Marine Fisheries, Arish Univ., Egypt.

3 National Inst. Oceanography and Fisheries, Egypt.

Abstract

This paper concentrates on measuring some biological parameters of Shrimp scad, Alepes djedaba such as age, growth rate, length at the first capture, and length at first sexual maturity. For that purpose, a total of 2591 fish individuals were collected from eastern Mediterranean Sea (North Sinai Coast) in the period from January to December 2019. Aging was estimated by reading the rings on otolith. Lengths of samples ranged from 9.7 to 26.9 cm and the corresponding weight were 6.5 to 206.7 g. All fishes aged from 0 to 5 years, with age 1st, 2nd, 3th year being the most dominant age groups, while the fishes older than 5th years were disappeared. The length-weight relationship indicated negative isometric growth (b =2.9903). Back – calculation lengths were 13, 15.67, 18.4, 20.18 and 21.77 cm to for ages 1st, 2nd, 3th, 4th and 5th years, respectively. Von-Bertalanffy growth parameters (VBGP) were L∞=29.26, K=0.1895yr-1, t0= -1.9956yr-1. The growth performance (φ) was 2.22. The sex ratio of males to females (M: F) of Alepes djedaba was ≈ 1:1.17. Reproductive activity period was expressed by GSI. The maximum values of Gonado-Somatic index (GSI) were recorded in the period from May to October (ranged from 4.3- 4.8). The length at first capture (Lc) was estimated at 17 cm for combined sexes and the length at first maturity (Lm) was estimated at 18.4, 19.1 and 18.8 cm for males, females and combined sexes respectively. Length at first maturity (Lm) must be increased by widening the net mesh size to catch Alepes djedaba at lengths greater than 19.1cm.

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