Distribution Characteristics and Influencing Factors of Fish Resources in the Offshore Waters South of Zhejiang

Abstract:

Based on fishery-independent survey data from 2016 to 2020 in the offshore waters south of Zhejiang, the relationship between fish resource density and environmental factors was explored using a generalized additive model, and the spatial and temporal distribution of fish resource density was predicted using the optimal models and environmental data of 2020. The results showed that the optimal models had deviances of 47.9%, 68.0%, 56.6% and 45.6% in spring, summer, autumn, and winter, respectively. The average slope of the cross-validation regression line was 0.74–1.02, and the model had good fitting and prediction abilities. Water temperature, salinity, and chlorophyll were significant factors that affected fish resource density in the offshore waters south of Zhejiang, and they had different influencing mechanisms in different seasons. In general, in summer and autumn, water temperature had a significant impact on fish resource density (P<0.01). And there is a negative correlation between water temperature and fish resource density in autumn (r= –0.225, P<0.05). In autumn, fish density increased with an increase in salinity, and in winter, fish density first increased and then decreased, reaching the maximum value at a salinity of 31.5. In spring, summer and autumn, chlorophyll was significantly correlated with fish resource density (P<0.05). Overall, the results showed that the fish resource density in autumn and winter was relatively lower than that in spring and summer in 2020. In spring, the fish resources in Wentai fishing ground were significantly greater than those in Yushan fishing ground. In summer, fish resources in Wentai and Yushan fishing grounds were relatively concentrated, primarily distributed at 27.8°~28.4°N, 121.7°~122.9°E and at 28.9°N, 122°E, respectively.