Long-Term Variability of Piscivorous Fish in China Seas Under Climate Change With Implication for Fisheries Management

Dan Liu,Jianchao Li,Kuowei Lan,Zhenjiang Ye,Shijie Zhou,Shuyang Ma,Peng Sun,Caihong Fu,Yongjun Tian

doi:10.3389/fmars.2021.581952

Abstract

Due to persistent fishing expansion in the China Seas over the past six decades, fisheries resources have been over-exploited; as a result, exploited fish have become smaller in size and younger in age. Marine piscivorous fish constituted a large portion of Chinese fisheries catch, long-term variability of which has rarely been investigated despite intense fishing pressure and climate change. In this study, we attempt to identify their responses to climate change and fishing activities and to provide scientific basis for sustainable exploitation of these resources. Seven taxa from pelagic to demersal species inhabiting either cold-water or warm-water were selected to represent the piscivorous fish assemblage in the China Seas. Total catch of these piscivorous fish in the China Seas increased during the early 1990s, stabilizing around 1.2 million tons after 1997. Principal component analysis (PCA) showed evident interannual-decadal variabilities in the catch of these fish with step changes around 1985/86 and 1997/98. Individual taxa, however, showed different trends in catches with sharks, rays, and lizardfishes manifesting downward trends while Pacific cod, eels, and hairtail increasing. Common dolphinfish and Japanese-Spanish mackerel increased largely in the 1990s but declined slightly during the 2000s. Although there were temporal overlaps between climate change and fishing variabilities, results of gradient forest analyses indicated that fishing effort imposed the most important influence on piscivorous fish. And among all climate variables explored in this study, sea surface temperature (SST) especially that of the East China Sea, had greatest impacts on variations in piscivorous fish catch, which may have been gradually exacerbated by the continued high fishing intensity. In addition, significant changes were identified in the life history traits in the species we evaluated, such as reduced average body sizes and truncated age compositions, strongly indicating the effect of fishing. We therefore advocate precautionary fishery practices under climate change.

Highlights

Monitoring and understanding long-term variabilities in marine ecosystems have become global concern (Ding et al, 2016, 2017)
The engine power of Chinese marine fishing boats increased continuously after 1955 and is much higher than it was in the early decades of the time series, it showed slight decline in recent years; the number of fishing boats simultaneously increased after 1955 but declined in the early 2000s (Figure 2B)
The estimated CPUE dropped sharply in the 1950s remained below 50 tons per boat or 80 tons per 100 kw, which indicated over exploitation in the China Seas

Summary

Introduction

Monitoring and understanding long-term variabilities in marine ecosystems have become global concern (Ding et al, 2016, 2017). Marine ecosystems respond to climate changes over a wide range of spatial and temporal scales. The warming trend is strongly modifying the key marine ecological processes (Bennett et al, 2015), as well as rapidly breaking down long-standing biogeographic boundaries and causing species redistribution at a global scale (Hobday et al, 2015), which contributes to the erosion of ecosystem resilience (Graham et al, 2015). A recent study indicates that historical warming has large impacts on marine fisheries production (Free et al, 2019)

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Discussion

Conclusion