AACL Bioflux, vol: 9,4 (2016)
Biometrics of bigeye scad, Selar crumenophthalmus and shrimp scad, Alepes djedaba from Semarang waters, Indonesia
Siwat V., Ambariyanto A., Widowati I.
Abstract
Fish species Selar crumenophthalmus (bigeye scad) and Alepes djedaba (shrimp scad) are some of the continuously exploited fish species by small-scale artisanal fishery in Semarang waters, Indonesia. The aim of this study was to determine the biological characteristics of their stocks through measuring of their lengths and weights, condition factors, sex-ratios and gonadosomatic index (GSI). Twice each month (fortnightly) 50 specimens each for both fish species were randomly collected from the fish lot at Tambak Lorok Auction Hall, Semarang, during the period from middle of April to middle of June the same year 2015. A total of 250 specimens each for each fish species were collected altogether and examined in the study. Length at first maturity (Lm) for S. crumenophthalmus and A. djedaba were 12.5 cm and 10.3 cm respectively, while their asymptotic lengths (L∞) were 23.8 cm and 23.0 cm, respectively. Regression equation for S. crumenophthalmus was Log W = -1.470 + 2.857 * Log SL (r2 = 0.955) while for A. djedaba was Log W = -1.565 + 2.939 * Log SL (r2 = 0.961). The average condition factor of males of S. crumenophthalmus was 2.318, females 2.300, while for A. djedaba the males was 2.422 and females 2.432. The sex-ratios of both fish species did not significantly deviate from the normal Mendelian ratio of 1:1. The lowest and highest values for the gonadosomatic index of S. crumenophthalmus was 2.83 and 5.57, respectively while for A. djedaba was 2.92 and 5.70, respectively. © 2016 BIOFLUX SRL. All rights reserved.
Keyword: Alepes djedaba; Biometrics; Fishery; Selar crumenophthalmus