Variation in the Catch Rate and Distribution of Swordtip Squid Uroteuthis edulis Associated with Factors of the Oceanic Environment n the Southern East China Sea

Abstract

Predictions from species distribution models are used to parameterize the environmental factors that influence the biology, distribution, and habitats of a species of interest. We fitted generalized additive models (GAMs) to spatiotemporal fishery data from torchlight fishing (2009-2013) to investigate the catch rates of swordtip squid Uroteuthis edulis in relation to changes in oceanographic conditions within the southern East China Sea, and we developed a habitat preference model. A high Jensen-Shannon divergence (JSD) value is considered to be an index of a thermal front. The results obtained using the selected GAMs revealed that the explained deviance in the catch rates pertaining to the oceanographic conditions was 45.10% throughout the year. All variables examined-sea surface temperature (SST), chlorophyll-a, sea surface height anomaly, and JSD-were statistically significant predictors (P < 0.05), and JSD explained the greatest amount of deviance (17.70%). The model predicted relatively high abundance of swordtip squid at 27-28 degrees N in the southern East China Sea during spring and a decrease from June to August. The high abundance occurred again in September and extended southwestwardly to a region including coastal mainland China. These results demonstrated that high swordtip squid abundance occurred in an SST range of 20.0-26.0 degrees C and a JSD range of 0.35-0.50 during spring around 27-28 degrees N, and movement toward the southwest corresponded with shifts in the Kuroshio front (26 degrees C isotherm) in summer and autumn.