Rapid declines across Australian fishery stocks indicate global sustainability targets will not be achieved without an expanded network of ‘no‐fishing’ reserves

Abstract

Abstract1. A continuing debate between environmental scientists and fisheries biologists on the sustainability of fisheries management practices, and the extent of fishing impacts on marine ecosystems, is unlikely to be resolved without fisheryindependent data spanning large geographic and temporal scales. Here, we compare continental-and decadal-scale trends in fisheries catches with underwater reef monitoring data for 533 sites around Australia, and find matching evidence of rapid fish-stock declines.2. Regardless of a high global ranking for fisheries sustainability, catches from Australian wild fisheries decreased by 31% over the past decade. The biomass of large fishes observed on underwater transects decreased significantly over the same period on fished reefs (36% decline) and in marine park zones that allow limited fishing (18% decline), but with a negligible overall change in no-fishing marine reserves. Populations of exploited fishes generally rose within marine reserves and declined outside the reserves, whereas unexploited species showed little difference in population trends within or outside reserves.3. Although changing climate and more precautionary fisheries management contribute to declining fish catches, fisheries-independent transect data suggest that excessive fishing also plays a major role.4. The large number of fishery stocks that remain unmanaged or have poor data, coupled with continuing declines in the stock biomass of managed fish species, indicate that Aichi Target 6 of the Convention on Biological Diversity (i.e. 'by 2020, all fish and invertebrate stocks and aquatic plants are managed and harvested sustainably') will not be achieved in Australia, or elsewhere.5. In order to maintain some naturally functioning food webs supported by large predators and associated ecosystem services in this era of changing climate, a greatly expanded network of effective, fully protected marine protected areas is needed that encompasses global marine biodiversity. The present globally unbalanced situation, with >98% of seas open to some form of fishing, deserves immediate multinational attention.

Underestimating the benefits of marine protected areas for the replenishment of fished populations

“…; Edgar et al . ). Fish length can vary twice as much inside MPAs as it does outside (Davidson ; Kleczkowski et al .…”

Generic solutions for data‐limited fishery assessments are not so simple

“…Yet, there remain examples of misapplication of empirical DLMs—specifically, the use of aggregated time series of catch or catch‐per‐unit‐effort—in the context of obtaining a regional or global estimate of sustainability. Edgar, Ward, and Stuart‐Smith's () use of aggregated catch time series across over 200 Australian fisheries, each normalized to its maximum value, to infer that Australian fisheries are in decline, acknowledges but fails to account for management intervention and large‐scale environmental changes, fails to weight each time series according to (for example) relative biomass and fails to acknowledge the lack of desirability of maximum catch as a reference point. The now‐classic Myers and Worm () claim of rapid worldwide depletion of predatory fish communities, based on analysis of nominal catch‐per‐unit‐effort data combined globally, was rebutted by Hampton, Sibert, Kleiber, Maunder, and Harley (), Maunder et al.…”

Comments on Edgar et al. (2018) paper for south‐western Australia

“…Edgar, Ward, and Stuart‐Smith () argue that Australian fishery stocks are suffering rapid declines and that to meet sustainability targets an expanded network of ‘no‐fishing’ reserves is required. The three lines of evidence used were underwater visual surveys (UVSs), Australian catches, and one case study.…”

“…Edgar et al () provide some valid points about improving fisheries stock assessment and management, including fishery‐independent data, fishing‐power changes, precautionary management, responding to changing harvestable biomass, collecting discard information, expansion of ecosystem‐based fisheries management, and transparency in stock assessments. However, the poor portrayal of fisheries assessment and management in Australia used to conclude that ‘a greatly expanded network of effective, fully‐protected marine protected areas (MPAs) is needed’, is not supported by the information provided or that available.…”

“…Edgar et al () make no assessment of whether the ~10% increase in catch from the mid‐1990s to 2005 represents an increase in abundance. Their focus starts with the year of peak catch (2005) and the decline over the following decade.…”