Length-weight and length-length relationships, condition factors and optimal length of some fish species from the Persian Gulf and Oman Sea

Length-weight relationships (LWRs), relative condition factor (K_rel), relative weight (Wr) and optimal length (L_opt) were calculated for five important commercial fishes from Iranian waters of the Persian Gulf and Oman Sea. Samples were collected from 2011 and December 2012 in 11 stations in three Iranian provinces (Hormuzgan, Khozestan and Sistan and baluchestan) using trawl and gillnets. Also, length-length relationships (LLRs) for Pampus argenteus and Scomberomorus commerson were computed. The values of the exponent b in the length-weight relationship ranged from 2.593 for S. commerson to 2.995 for P. argenteus. K_rel varied between 1.01 ± 0.08 for Parastromateus niger and 1.06 ± 0.41 for P. argenteus. Also, W_r ranged from 59.12 ± 47.74% for S. commerson to 107.78 ± 107.29% for Eleutheronema tetradactylum. The L_opt were calculated for all five species. A negative allometric growth was found in S. commerson, while other four species (E. tetradactylum, Otolithes ruber, P. niger and P. argenteus) had isometric growth. The length-weight and length-length relationships presented here are for the first time in the Iranian coastal waters of the Persian Gulf and Oman Sea, which can provide a basis for fisheries management.