The Entangled Economics of Killer Whale Depredation in Western Alaska

Killer whale (Orcinus orca) depredation (whales removing or damaging fish caught on fishing gear) adversely impacts demersal longline fisheries in western Alaska. These interactions increase operating costs and reduce the profitability of longline fishing. This study synthesizes National Marine Fisheries Service observer data, sablefish longline survey and fishermen-collected depredation data to: 1) estimate the frequency of killer whale depredation; 2) estimate depredation-related catch per unit effort reductions; and 3) assess direct costs and opportunity costs incurred by longliners as a result of whale interactions. Average catch per unit effort reductions on depredated sets ranged from 35.1-69.3% for the observed longline fleet in all three management areas from 1998-2012. To compensate for depredation, fishermen set additional gear to catch the same amount of fish, and this increased fuel costs by an additional 82% per depredated set (average $433 additional fuel per depredated set). In a separate analysis with six longline vessels in 2011and 2012, killer whale depredation avoidance measures resulted in an average additional cost of $494 per depredated vessel-day for fuel and crew food. This assessment of killer whale depredation costs will help longline fishermen and managers consider the costs and benefits of depredation avoidance and alternative policy solutions.