Ghost Fishing in the Southeast Alaska Commercial Dungeness Crab Fishery

Entrapment of crabs by derelict crab pots (also known as ghost fishing) can be a significant consequence of commercial fishing. The prevalence of lost commercial pots and ghost-fishing entrapments was estimated for the commercial Dungeness crab Cancer magister fishery in southeastern Alaska during the 2009 and 2010 summer closures of the commercial season (16 August through 30 September). Teams of divers retrieved a random subsample of the derelict crab pots located using side-scan sonar. Altogether, we retrieved 123 derelict crab pots containing 215 entrapped Dungeness crabs. The densities of derelict crab pots varied from 1.5 to 10.1/km(2), while the densities of entrapped Dungeness crabs ranged from 0 to 54.5/km(2), depending on the area surveyed. Derelict crab pots were discovered to effectively ghost-fish for at least 7years, indicating that there are long-term cumulative impacts on Dungeness crab populations. The number of derelict crab pots and entrapped Dungeness crabs at each of the surveyed areas was highly correlated with the number of fishermen, the number of pot lifts, and annual harvest in numbers, allowing for extrapolation to a regionwide estimate of crab entrapment and derelict crab pot abundance. Overall, our findings show instantaneous entrapment of less than 1% of the commercial crab harvest with a cumulative annual loss of less than 3% of the regional commercial crab harvest. We challenge the efficacy of the biodegradable escape mechanism currently employed in commercial Dungeness crab pots in southeastern Alaska and present alternatives which may require further in situ or laboratory verification of their effectiveness.