Comparison of threat and exploitation status in North-East Atlantic marine populations

Abstract

1. Threat listing of exploited marine species has been controversial because of the scientific uncertainty of extinction risk as well as the social, economic and political costs of management procedures that may be triggered by designation of species as threatened. 2. We applied three sets of threat criteria to 76 stocks (populations) of 21 exploited marine fish and invertebrate species. Two criteria sets were based on decline rates: World Conservation Union (IUCN A1) and the American Fisheries Society (AFS). The third set of criteria, based on population viability (IUCN E), was assessed using non-parametric simulation and two diffusion approximation methods. 3. We compared extinction risk outcomes (threatened or not) against the exploitation status of each stock as reported in fish stock assessments (inside or outside safe biological limits). For each combination of threat and exploitation we assessed the rate of hits, misses and false alarms. 4. Our analyses suggest that decline rate criteria provide risk categorizations consistent with population viability analyses when applied to exploited marine stocks. Nearly a quarter of the fish and invertebrate populations (n = 18) considered met one or more of the threat criteria. 5. None of the threat metrics produced false alarms, where sustainably exploited stocks were categorized as threatened. The quantitative IUCN E metrics produced higher hit rates than the decline rate metrics (IUCN A1 and AFS) and all of the metrics produced similar miss rates. However, the IUCN E methods could be applied to fewer stocks (12-14) compared with IUCN A1 decline rate and AFS criteria, both of which could be applied all 76 stocks. 6. Synthesis and applications. Threat criteria provide warnings of population collapse that are consistent with those provided in fisheries stock assessments. Our results suggest that scientists with different backgrounds and objectives should usually be able to agree on the stocks for which the most urgent management action is needed. Moreover, IUCN A1 decline rate metrics may provide useful indicators of population status when the information needed for full fisheries stock assessment is not available. © 2005 British Ecological Society.