Impacts of El Niño(2007) and La Niña(2015) events on spatial and temporal distribution of potential habitat of <italic>Scomber japonicus</italic> in the East China Sea

Abstract

Chub mackerel <italic>Scomber japonicus</italic> is one of economically important fish species in the ocean, and it is also an important fishing target for Chinese distant-water fishery. The resources of <italic>Scomber japonicus</italic> are strongly affected by environmental changes, thus understanding the response of changes in the habitat suitability of <italic>Scomber japonicus</italic> in the East China Sea to different anomalous climate conditions can help better know the stock dynamics of its resources and fishing grounds, and make sustainable exploitation of fishery resources of <italic>Scomber japonicus</italic>. According to the fishery data of <italic>Scomber japonicus</italic> obtained from National Data Center for Distant-water Fisheries of China at Shanghai Ocean University, combined with three key environmental factors: sea surface temperature (SST), sea surface height (SSH) and net primary productivity (NPP), this study investigated and compared the differences in the habitat of <italic>Scomber japonicus</italic> in the East China Sea between 2007 (a La Niña year) and 2015 (an El Niño year), based on the method of arithmetic average habitat suitability index (HSI) modeling analysis. The results showed that the catch, fishing effort and CPUE (catch per unit effort) of <italic>Scomber japonicus</italic> in the La Niña year (2007) was higher than those in the El Niño year (2015). The latitudinal gravity centers of fishing ground (LATG) in 2007 were in the northern waters compared with that of 2015. Comparing the environmental conditions between the two years, it was found that the spatial distributions of SST, SSH and NPP from July to September in 2007 were significantly different from those in 2015. The habitat modeling analysis indicated that the environmental conditions in 2007 were favorable for the formation of high-quality habitat for <italic>Scomber japonicas</italic>. Moreover, the areas of suitable habitat (HSI>0.6) from July to September in 2007 were significantly larger than that in 2015, and the location of suitable habitats in 2007 was northward compared with 2015, leading to the LATG in 2007 more northerly. Our findings suggested that La Niña and El Niño events strongly affected the ranges and spatial distributions of suitable habitats of <italic>Scomber japonicus</italic> in the East China Sea and the impacts showed large differences under different climate variabilities.