An evaluation of criteria for assessing conservation status of Fraser River sockeye salmon conservation units.

Fisheries management agencies and conservation organizations use various criteria to determine whether fish populations are a conservation concern. By conducting retrospective analyses using historical data for 18 Fraser River (B.C.) sockeye salmon conservation units (CUs), we evaluated the effectiveness of 20 criteria that measure time trends in spawner abundance to determine how likely they are to correctly categorize conservation status of salmon populations. We used a Receiver Operating Characteristic (ROC) approach to quantify the probability of each criterion correctly distinguishing between a declining and non-declining CU. Those criteria that measured the extent of decline from an estimated historical baseline were most reliable and consistently outperformed the widely used International Union for the Conservation of Nature (IUCN) criterion of percent decline in abundance over the most recent three generations. We therefore urge scientists to evaluate the statistical performance of their criteria for classifying conservation status before applying them in decision making.