Estimation of life history traits and stock status for Scomber japonicus based on data-limited method

The age-structure data is usually unavailable for most traditional fishery species in the East China Sea. The data-limited method is thus particularly important to understand life history and population dynamics of commercial fishes. At the offshore waters of southern Zhejiang, Chub mackerel (Scomber japonicus) is one of the dominant economic species. Based on fork length data from 2016 to 2020, we estimated its life history traits with the data-limited method, including the growth parameters and mortality coefficients. We further evaluated the status of Chub mackerel by the yield per recruitment (YPR) model. The results showed that the relationship between fork length (L) and body weight (W) based on 1606 samples was estimated to be W=4.18×10^-3L^3.28(R²=0.96). The asymptotic fork length L_∞ of Chub mackerel was 28.34 cm, the growth rate was 0.36 a^-1, and the initial theoretical age was -0.40 a. The total mortality was estimated as 1.67 a^-1, and the estimated natural mortality (M) was 0.85 a^-1. The fishing mortality (F) was 0.82 a^-1, and the development rate was 0.49. The current capture age was estimated to be 1.78 a, while the capture fork length was 15.44 cm. The YPR model results showed YPR value showed a trend of increasing and then decreasing with the increases of F. The values of biological reference points F_0.1 and F_max were 0.97 a^-1 and 4.55 a^-1, respectively, which were higher than the value of current F. The sensitivity analysis showed that the uncertainty of M greatly influenced the estimation results of YPR and biological reference points. A decrease in M significantly increased the YPR value, but F_0.1 and F_max decreased. The status of Chub mackerel stock at the offshore waters of southern Zhejiang is in good condition. However, the miniaturization of catch is intensifying. It is recommended to extend the capture fork length to 20 cm (the impact point age) to improve the quality of the catch, which would sustainably use the Chub mackerel resources.