Is the population of kingfish (Scomberomorus commerson) in the northern Persian Gulf really under pressure from overfishing?

Abstract

Quantifying the population dynamics of marine species is difficult when good, comprehensive data are not available. We sought to determine if the kingfish Scomberomorus commerson stock in the Persian Gulf was overfished. The ICES data-limited assessment framework was used to provide precautionary advice, with a 20% decrease advised in situations where only catch or bycatch data were available. The length-based Bayesian biomass (LBB) was used to model fork length from landing records of licensed fishers in the Khuzestan Province during 2002–2018, which had increased despite sought being overexploited. Most kingfish were immature and smaller than optimum length of the catch (L_c-opt = 88 cm) and optimum length (L_opt = 104 cm). Relative biomass (B/B_msy) ranged 0.62–0.66 and exceeded 0.5. The B/B_msy ratio (1.25) was >1.1. The stock appeared to be healthy and exploitable, but wide confidence intervals of the B/B_msy ratio complicated interpretation of stock status. The kingfish stock appeared to use waters of the study area as a spawning and nursery ground, so many young immature individuals were present. If current exploitation of young individuals continues, this the stock will eventually be overfished. Long-term increases in the catch of young immature kingfish can have a side effect on stock maturation and recruitment. We recommend that the mesh size of fishing gear be selected based on optimum length, to enhance economic, and commercial viability of the kingfish fishery.