Spatiotemporal Characteristics of Small Yellow Croaker Fishing Grounds During the Spawning Period in the Offshore Waters of Jiangsu Province, China

This study aimed to analyze the impact of marine environmental changes on fish resources and understand the distribution variations of small yellow croaker (Larimichthys polyactis) during the spawning season in the offshore waters of Jiangsu Province, China. To this end, the spatiotemporal characteristics of L. polyactis during May (the spawning month) were determined from bottom trawl survey data and marine remote sensing environmental data collected from 2009 to 2020. The spatiotemporal distribution of L. polyactis and the effects of environmental factors on this distribution were then estimated using species distribution models (SDMs). After evaluating the performances of three SDMs—generalized linear model, generalized additive model (GAM), and random forest model—the GAM was identified as the optimal model with the highest explanatory power and the best fit to the observed spatiotemporal distribution. The relative abundance of L. polyactis during its spawning period exhibited considerable interannual variations from 2009 to 2020. The fish were mainly aggregated in the central and southern part of the Lvsi Fishing Ground (approximately 31.5°N—33.0°N, 121.0°E—122.5°E) and the southern part of the Haizhou Bay Fishing Ground (approximately 33.5°N—34.5°N, 120°E—121°E). The distribution extent in the northern Haizhou Bay and southern Lvsi Fishing Ground areas significantly contracted in 2013, 2016, 2019, and 2020. During these years, the distribution center shifted southward in the southern Lvsi Fishing Ground and westward in the northern Haizhou Bay Fishing Ground. The GAM identified seven key environmental factors affecting the relative abundance of L. polyactis during the spawning period: sea surface salinity (SSS), sea surface height (SSH), chlorophyll a concentration, bottom temperature (BT), depth, eastward current velocity, and pH. Among these factors, SSS, SSH, and BT exerted the greatest influence, with contributions of 27.3%, 7.7%, and 3.6%, respectively. The yield with a one-year lag of L. polyactis in the Jiangsu Province waters was significantly negatively correlated with the latitude of the distribution center of high-value areas in the northern Haizhou Bay and significantly positively correlated with the mean value in the northern area. Conversely, it was significantly positively correlated with the longitude of the distribution center of high-value areas in the southern Lvsi Fishing Ground and significantly negatively correlated with the mean value in the southern area. Our findings suggest that a decrease in spawning habitat suitability may lead to reduced L. polyactis catches in the following year. Under current fishing pressure, unfavorable climatic conditions during the spawning period may adversely affect L. polyactis production.