The spawning periods, sex ratio and length at first maturity were determined for six commercially important finfish species collected from Oman’s industrial trawl fishery. During 1 year of monthly sampling, biological data were collected on 5586 fish. ANCOVA was used to compare the length–weight relationships between sexes. There were sex-specific differences in length-weight relationships for three of the six species examined. One serranid, Epinephelus diacanthus, and a sparid, Pagellus affinis, had sex ratios significantly different from the expected ratio of 1 : 1. Size–frequency data revealed more male fish in the larger size classes for E. diacanthus, P. affinis and Nemipterus japonicus. Data on the development of female gonads and Gonado-somatic Index (GSI) revealed that the six species spawned at different times of the year. With the exception of female E. diacanthus, all fish had low GSI values during the onset of the summer monsoon period in June. The proportion of immature vs mature fish in the sample differed among species. For two species, Lethrinus nebulosus and Cheimerius nufar, more than 40% of the fish sampled (both sexes) were immature. Approximately 33% female and 41% male P. affinis were also immature. Management options such as temporal and area closures are discussed in light of the large number of immature fish caught by the fishery.

The spawning periods, sex ratio and length at first maturity were determined for six commercially important finfish species collected from Oman’s industrial trawl fishery. During 1 year of monthly sampling, biological data were collected on 5586 fish. ANCOVA was used to compare the length–weight...