Species' Linked Fates Provide Early Signs of Risk in Multi-Species Harvests

Many modern harvesting methods cause mortality to multiple species either intentionally or accidentally (by-catch).  While declining profits as a species’ population declines can prevent it from being depleted in a single-species harvest, multi-species harvests often pose a particularly severe threat as harvesting may remain profitable even as a population becomes depleted, provided other species remain relatively plentiful.  We show that the shared threat of multi-species harvesting links the short- and long-term fates of species in measurable ways, which can be exploited to provide assessments of both the current and potential future threats of extinction and depletion below biological thresholds to even the most data-poor species.  These assessments do not require lengthy time-series data, offering a unique opportunity to identify species at risk before they have declined.  Risk to each species is determined by its relative ability to withstand high harvest effort compared to economically important species.  We demonstrate the robustness of our approach to a variety of data-availability scenarios and show that risk to several species recently assessed as over-harvested and declining could have been identified decades earlier using our approach.  Our results demonstrate the potential of mechanistic approaches to provide early warning signs of threats for preventative conservation.