Distribution of Japanese Scad (Decapterus maruadsi) and Its Relationship with Environmental Factors in the Coast Waters of Southern Zhejiang Based on the Tweedie-GAM

This study used Tweedie-GAM to evaluate the distribution characteristics of Japanese scad (Decapterus maruadsi) in spring, summer, and autumn (from 2015 to 2020) and its relationship with marine environmental factors. The fishery resources data from the southern Zhejiang coastal waters were combined with the hydrological environment survey data collected simultaneously. The results showed significant differences in the Japanese scad spatial distribution in different seasons. Japanese scad is mainly concentrated in the nearshore waters in spring and concentrated primarily on the south and north regions of the Zhejiang southern waters in summer, showing a "high on both sides, low in the middle" pattern. The distribution pattern in autumn is opposite to that in spring, wherein the Japanese scad mainly concentrated in open waters. There are some differences in the key influencing factors of Japanese scad in different seasons. In spring, with a range of 19.5~25.0 ℃, the resource density firstly showed an increasing trend and then decreased with the rise in water temperature, peaking at 22.7 ℃. During summer, the water temperature reached 28.0~30.3 ℃, and the resource density showed the maximum value when the salinity was 32.3. In autumn, the resource density showed a decreasing trend and later increased with the increment in the water salinity, with a minimum value of 29.8. The relationship between resource density and water depth remained stable, showing a multi-wavy nonlinear relationship, with an overall increasing trend and later stable pattern. This study revealed the relationship between the Japanese scad's temporal and spatial distribution characteristics and environmental factors. It provides a research reference for the conservation, management, and sustainable utilization of Japanese scad in the coastal waters of southern Zhejiang.