Assessment of Population Dynamics and Fishery Exploitation of Narrow-Barred Spanish Mackerel (Scomberomorus commerson) in Iranian Waters

The population dynamics and exploitation ratios of the narrow-barred Spanish mackerel (Scomberomorus commerson, Lacépède, 1800) were investigated from August 2020 to February 2023, with data collected from three landing sites (Bushehr, Bandar Abbas, and Chabahar) of Iran waters. During the study period, only length was measured for 6504 specimens and both the length and weight were measured for 504 specimens. The mean fork length of the samples was 86 ± 20 cm, and the mean weight was 6230 ± 3742 g. The relationship between length and weight for the total samples was described by the equation W = 0.022 × CL2.76 (n = 504, R2 = 0.90, 95% C.I. for b = 2.52–2.91). The population dynamics indices for S. commerson were as follows: infinite length (Linf) = 173 cm, natural mortality (M) = 0.47 per year, growth coefficient (K) = 0.52 per year, total mortality (Z) = 1.42 ± 0.06 (95% C.I. = 1.36–1.48), fishing mortality (F) = 0.95 per year, and exploitation coefficient (E) = 0.67. The exploitation rate (U) and total stock at the beginning of the year (B0) were 0.6 and 48,333 tons, respectively. The annual average standing stock (Bt) was estimated at 30,526 tons. The exploitation ratio for maximum sustainable yield (EMSY) was 0.50, and fishing mortality at maximum sustainable yield (FMSY) was 1.5. The estimated range for maximum sustainable yield (MSY, in 1000 tons), the B/BMSY ratio, F/FMSY ratio, and saturation (S) ratio of S. commerson in the Iranian part of the Persian Gulf and the Sea of Oman was 20 (17–25), 1.55 (1.25–1.73), 0.90 (0.8–1.12), and 0.45, respectively. The stock of S. commerson is approaching overfishing in Iran waters, imposing immediate management actions to reduce catch and fishing effort.