Global Trends in the Threat Potential of Multispecies Fisheries

Multispecies fisheries can pose severe threats of overfishing or extinction to weak stocks and by-catch species caught along with more resilient and economically important species that support large fishing efforts.  A new tool called the Eventual Threat Index was recently developed to measure the potential of current fishing practices to pose long-term threats to a by-catch species or weak stock - by measuring its average vulnerability to depletion relative to the socioeconomically important species limiting long-term effort in its fisheries.  We apply this approach globally, where data is available, to tunas, billfish, groundfish, sharks, and marine turtles, finding threat potentials to be widespread and in many cases severe, though also largely in decline. We present and discuss evidence that declines in the worldwide threat potential of multispecies fisheries may be driven both by improvements in management and diversification of fishing fleets.  Our results highlight some important global trends in multispecies fishing threats, and demonstrate how such trends can be effectively monitored using the Eventual Threat Index.