Growth, Mortality, and Reproduction of Poor Cod (Trisopterus minutus Linn., 1758) in the Central Aegean Sea

Authors: GÜLNUR METİN, AKIN TÜRKER İLKYAZ, HASAN TUNCAY KINACIGİL

Abstract: A total of 1527 of poor cod (Trisopterus minutus Linn., 1758) were collected by trawl hauls between April 2001 and March 2002 from İzmir Bay (central Aegean Sea). The size of the fish (total length) ranged from 10.6 cm (minimum, September) and 24.8 cm (April). The population was composed of 53% males, 41% females, and 6% immature individuals, with a female to male ratio of 1:1.3. The age composition of the samples was from I to V. The von Bertalanffy growth parameters were L_{\infinity} = 28.1 cm, W_{\infinity} = 254.0 g, K = 0.26 y^{-1}, and t_{o} = -1.52 y. The length at first sexual maturity was 13.3 cm in females and 12.5 cm in males. Spawning season begins in December and reaches its maximum level in January while continuing April. Fecundity ranged from 1236 to 21,463 eggs/female and showed significant correlation with fish length and weight. The total (Z), natural (M), and fishing mortality (F) rates, and the exploitation ratio (E) for all individuals were estimated respectively as Z = 0.82, M = 0.38, F = 0.44, and E = 0.57 y^{-1}. This shows that the poor cod smaller than 14 cm must not be harvested and fishing should be prohibited from January to April and that the poor cod stock in the central Aegan Sea is being exploited at a slightly higher than the optimal level.

Keywords: Trisopterus minutus, age, growth, mortality, reproduction, sexual maturity length, central Aegean Sea

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