Length at maturity and biological traits of nine commercially important fishes off the Saudi Coast, Arabian Gulf

The length–weight relationship, condition factor, gonadosomatic index, and length at reproductive maturity of nine commercially important fish species in the Arabian Gulf were assessed in a sample of 5,030 specimens, all collected in a 2-year period at the commercial harbor in Jubail, Saudi Arabia. The b value for length–weight relationship varied from 2.72 to 3.20, while length at first maturity ranged from 20.68 to 39.34 cm and length at 90 % maturity from 26.02 to 72.86 cm. At a 95 % confidence interval, all species showed a tendency toward allometric growth except for the male populations of Epinephelus areolatus, Lethrinus lentjan, and Siganus canaliculatus and the female populations of Carangoides bajad and Rhabdosargus haffara, which tended toward isometric growth. Among other results, the mean relative condition factor ranged from 0.99 to 1.10, which reflects the satisfactory growth of all species studied. Last, monthly variation in the gonadosomatic index revealed high values from February to June for most species, although Rhabdosargus haffara and Argyrops spinifer showed maximum spawning activity from October to February, indicating yearly spawning for those species. Length at first maturity ranged from 20.68 to 39.34 cm, while length at 90 % maturity varied between 26.02 and 72.86 cm.