Assessment of Exploited Stock and Management Implications of Kingfish (Scomberomorus commerson) in the Omani Waters

The high demand and economic value of kingfish (Scomberomorus commerson) have led to intensive fishing of this species in the Omani waters. The increased fishing pressure has made the fishery vulnerable; hence, information on the current stock status is essential for the sustainability of the kingfish stock. Three length-based stock assessment approaches (TropFishR, spawning potential ratio, and Bayesian biomass method) were used to estimate growth, mortality, exploitation, spawning potential capacity, and relative biomass in relation to maximum sustainable yield (MSY). Asymptotic length (L∞) was 186.31 cm, and the growth coefficient (K) was 0.15 yr−1 for S. commerson. Fishing mortality was 0.45 yr−1, which was higher than natural mortality (M = 0.18 yr−1) and optimal fishing mortalities (F40% = 0.15 yr−1). The exploitation rate (E) was found to be 0.71 yr−1, higher than the optimum exploitation (E = 0.50), indicating a total overfishing of 42% of the S. commerson in Oman waters. The current length at first capture (Lc50 = 74.38 cm) was significantly smaller than the length at first maturity (Lm50 = 91.25 cm), indicating growth overfishing. The current spawning potential ratio (SPR) was 10%, which was significantly below the reference point (SPR = 20%), indicating that the stock was severely overfished. Biomass was critically low (B/Bo = 0.17), and lower than the reference point of 0.20. Additionally, the current biomass was 44% of Bmsy (B/Bmsy = 0.44), which is significantly lower than the reference point of 1, indicating that the stock biomass was below the maximum sustainable yield level, suggesting recruitment overfishing. Stock indicators revealed that the fishery was primarily targeting immature/juvenile fish, as well as older and larger fish, which indicated stocks were both growth- and recruitment-overfished. Therefore, carrying out commercial fishing for an optimum size range (118 to 144 cm) and reducing fishing pressure to a sustainable level (F = M, 0.18 yr−1) would sustain a healthy stock biomass of kingfish in Omani waters.