Seasonal and spatial distribution of AmphiOctopus fangsiao and Octopus variabilis in the southern Yellow and East China Seas: Fisheries management implications based on climate scenario predictions

Abstract

AmphiOctopus fangsiao and Octopus variabilis are economically important species that dominate the northwest Pacific cephalopod communities. However, little is known about their seasonal and spatial distributions in the southern Yellow Sea and East China Sea. This study aimed to identify the seasonal and spatial distributions of A. fangsiao and O. variabilis, explore potential relationships with environmental variables, and predict annual mean habitat variations under different climate scenarios. Our findings revealed that A. fangsiao was concentrated in the southern Yellow Sea in spring, in the Zhoushan fishing ground near the Yangtze River Estuary in summer, expanded to the entire East China Sea in autumn, and migrated offshore in winter. In contrast, O. variabilis was concentrated in the Zhoushan fishing grounds in spring, moved eastward in summer, shifted southward to the Yushan fishing grounds in autumn, and moved farther south to the Yushan-Wentai-Mindong fishing grounds in winter. Additionally, we predicted the most suitable sea bottom temperature (SBT) for A. fangsiao to be 10–25°C, with sea bottom salinity (SBS) of 29–31 ‰, whereas for O. variabilis, the most suitable SBT was 27°C, with an SBS of 34–35 ‰. Our results showed that under different climate change scenarios, the annual mean habitat area of A. fangsiao will decrease under SSP1–2.6 by 2050, and increase under SSP1–2.6 by 2100, whereas the area will shrink significantly under the SSP5–5.8 scenario by both 2050 and 2100. Moreover, the annual mean habitat of O. variabilis will shift northward offshore under SSP1–2.6 scenario by 2050 and 2100, as well as under SSP5–8.5 by 2050, but will shrink significantly under SSP5–8.5 by 2100. These results may provide guidance for sustainable fishing and management of both species by specifically incorporating climate change.