Population structure of Sind sardinella Sardinella sindensis (Day, 1878) in northern Persian Gulf and Oman Sea, Iran

The population dynamics of Sardinella sindensis (Day, 1878) was studied from samples in the commercial fishery in the coastal waters of the Persian Gulf and Oman Sea. A total of 12,898 specimens were collected through monthly sampling of boat purse seine and beach seine catches. Total length of the sampled fishes ranged from 5.0 to 19.9 cm. The von Bertalanffy growth parameters determined using monthly length frequency distribution were asymptotic length (L∞ = 21 cm), growth coefficient (K = 1.2 year-1) and age at zero length (t0 = -0.14 year). The estimated value for longevity (tmax) was 2.5 years. The probability of capture was calculated as Lc25=10.2 cm, Lc50=10.9 cm and Lc75=11.8 cm total length. Four cohorts with mean lengths of 7.2, 11.7, 15.7 and 18.6 cm were discerned in a year, with two recruitment peaks. The calculated length-weight equation was W= 0.0078 L3.02. The instantaneous rates of mortality (Z) was estimated as 4.02, with natural mortality M=2.19 and fishing mortality F=1.83 year-1. The exploitation rate (E) was 0.46, which was found to be reasonable for current fishing effort. From the yield-per-recruit analysis, Emax was estimated as 0.79, confirming that the stock is under optimum exploitation.