The role of catch shares in Pacific halibut bycatch reduction in the U.S. West Coast bottom trawl fishery

Pacific halibut (Hippoglossus stenolepis) are a valuable target species in the U.S. and Canada, but are also caught as bycatch in other groundfish fisheries. In 2011, a catch shares (CS) management program was implemented in the U.S. west coast limited entry (LE) bottom trawl fishery, shifting responsibility for catch limits, including P. halibut bycatch, from the fleet to individual vessels. After CS implementation, P. halibut bycatch decreased significantly from an annual mean of 312.5 metric tons (mt) (2007-2010) to 65.6 mt (2011-2014). I hypothesized that this reduction in P. halibut bycatch resulted from changes in fishing behavior initiated by the shift to CS. I evaluated changes in variables associated with P. halibut bycatch, including fishing latitude, depth, duration, and catch of correlated species, before and after CS implementation. Comparisons of associated variables under LE versus CS management showed that significant changes to all variables occurred after CS implementation. To predict and compare relative P. halibut bycatch among LE versus CS hauls, I modeled how associated variables predicted P. halibut encounters, bycatch weight, and mortality for LE data, and re-ran these models for CS data. My results indicate that the relationship between predictor variables and P. halibut bycatch changed under CS from what was observed in the LE fleet. These changed relationships suggest that fishers altered their behavior following the management shift, likely contributing to the reduction in P. halibut bycatch under CS management. This work will help the Pacific Fishery Management Council and International Pacific Halibut Commission understand how CS has changed fishing behavior and P. halibut bycatch in bottom trawl fisheries.Bachelor of Scienc