engleski

The Reproductive Traits of Scomber japonicus (Houttuyn, 1782) in the Eastern Adriatic Sea

The aim of the present study was to investigate the fisheries biology of Scomber japonicus (Houttuyn, 1782) in the Adriatic Sea, in order to enable implementation of appropriate regulatory measures for fisheries. The reproductive biology and sexual patterns of S. japonicus (chub mackerel) were examined from monthly random samples of commercial catches from the purse seine net (10 mm stretched mesh size) in the eastern Adriatic Sea. The annual mean chub mackerel fork length (FL) was examined from 1998-2007. Average fork lengths were approximately 25 cm between 1998 and 2002, and decreased to 22 cm between 2003 and 2007. In addition, sex ratios fluctuated as a function of size and month: females were more abundant in the smaller length classes, and before and after spawning ; while males were more abundant in the larger length classes and during spawning. The overall sex ratio was 0.68 ; females were significantly predominant. 50% of the chub mackerel population was sexually mature at a FL of 18.3 cm, and both males and females reached sexual maturity at FLs of 20.4 cm and 16.8 cm, respectively. Based on gonad maturity stages, gonad weight and gonadosomatic index, chub mackerel spawned from May to August, with peak spawning in June for both sexes. The mean absolute fecundity was 181, 277±62, 090 oocytes per ovary. A positive exponential correlation was found between fecundity and fork length, gonad weight, and total chub mackerel weight (r2=0.640 ; r2=0.686 and r2=0.607, respectively).

sex ratio; size at maturity; spawning season; fecudity; S. japonicus; Adriatic Sea

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