Abstract
Fish community structure (FCS) of the Yellow Sea (YS) is affected by multiple pressures. Quantifying the responses of indicators of FCS (IFCSs) to pressures is a key aspect of ecosystem-based fisheries management. Quantitative methodology has hitherto been rarely applied to evaluate the performance of ecological indicators in response to physical and anthropogenic pressures and management actions. In this study, we adopted a quantitative and flexible framework to quantify the performance of IFCSs in the YS as well as to identify a suite of operational IFCSs to evaluate the status of the FCS via two state-space approaches. A total of 22 IFCSs were tested for their responses to three types of pressures including anthropogenic activities (fishing), large-scale climate change, and regional environmental variables. Our results indicate that the majority of IFCSs have good performance in terms of sensitivity in their responses to pressures, but weak performance in terms of robustness. The IFCSs tend to respond stronger to fishing than to large-scale climatic indices and regional environmental indices both in terms of sensitivity and robustness. A final indicator suite of five best-performing IFCSs was identified. The five IFCSs include total catch (ToC), mean trophic level (MTL), the ratio of catch of large predatory groups to total catch (LPC/ToC), mean temperature of catch (MTC) [or alternatively catch of small pelagic groups (SPC)], and functional evenness based on thermal groups (T-J′FD), all of which show regime shift patterns consistent with climate change. Compared to a reference period (1960–1964), the status of the current FCS has been obviously changed, and the long-term trajectories of the final indicator suite is consistent with that of fishing pressure. This study demonstrates the applicability of the indicator-testing framework in appraising the status of FCS, and facilitates moving towards ecosystem-based fisheries management in the YS.
Highlights
Threats to marine ecosystems consist of anthropogenic activities such as fishing, shipping, pollution, and species introductions (Jennings and Kaiser, 1998; Halpern et al, 2008), regional environmental changes in the pH, chlorophyll-a concentration, and sea surface temperature (Fabry et al, 2008; Solanki et al, 2015), and climate change (HoeghGuldberg and Bruno, 2010; Gissi et al, 2021)
None of the IFCSs showed a direct response to the regional environmental index (WD) and three large-scale climate indices (NPI, Monsoon Index (MOI), and Nino 4 Region (Nino 4))
None of the IFCSs scored more than 50% of the total score in terms of robustness, which resulted in weak performance for many IFCSs (Table 2)
Summary
Threats to marine ecosystems consist of anthropogenic activities such as fishing, shipping, pollution, and species introductions (Jennings and Kaiser, 1998; Halpern et al, 2008), regional environmental changes in the pH (ocean acidification), chlorophyll-a concentration, and sea surface temperature (Fabry et al, 2008; Solanki et al, 2015), and climate change (HoeghGuldberg and Bruno, 2010; Gissi et al, 2021). Overfishing typically caused miniaturization in the body size and truncation in age structure (Conover et al, 2005; Shan et al, 2012). The resources of some commercial fish species like rockfish (Sebastes spp.) showed obvious decline in recent decades (Link et al, 2009). Aside from overfishing, global warming has accelerated species extinction and altered biodiversity, further jeopardizing ecosystem structure (Urban, 2015). The ubiquitous biodiversity loss caused by climate change was pervasive in terrestrial, freshwater and marine ecosystems (Weiskopf et al, 2020). Extreme declines of fisheries resources and changes in compositions of fishery catches have threatened the sustainability of ecosystems and human well-being (Vörösmarty et al, 2010)
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