Growth and Mortality Estimation for Chub Mackerel based on Chinese data in the Convention Area of NPFC
As a highly migrate species, Chub mackerel is distributed in both the national waters of Japan and Russia and the high sea of Northwestern Pacific. The previous biology information used for stock assessment was almost based on results from Japanese fishery in its Exclusive Economic Zone. This research provides some analysis based the data from Chinese survey and fishery in the convention area. The parameters in the length-weight relationship of 2021-2023 were estimated to be 1.886~9.441×10-6for the condition factor a, and 3.03~3.32 for the growth parameter b, with significant temporal variations. Von Bertalanffy Growth parameters were estimated to be K=0.33~0.78, L=31~34 cm, and t0= -0.34 ~ -0.82. Both constant and age-specific natural mortality were calculated based on several empirical methods, while the M estimates ranged from 0.26 to 0.62 in different years, with geometrical mean to be 0.47. In conclusion, the results suggest obvious variations among different regions and years, indicating the non-stationarity of Chub mackerel’s life history traits. Based on this research, we strongly recommend the stock assessment for Chub mackerel using time-varying growth and mortality considering spatial heterogeneity.