Shifts in Spatio-Temporal Fishing Behaviour in the Canadian Pacific Halibut Hook and Line Fishery as a Result of a Choke Species

On Wednesday, April 4, Tiare Boyes will defend her master’s thesis in Coastal and Marine Management. Her thesis is titled Shifts in Spatio-Temporal Fishing Behaviour in the Canadian Pacific Halibut Hook and Line Fishery as a Result of a Choke Species. The thesis presentation begins at 16:30 and is open to the public.

The thesis advisor is Robyn Forrest, Ph.D at the Fisheries and Oceans Canada Pacific Biological Station, Nanaimo BC, Canada. The external reader is Megan Peterson, Ph.D. from Seafood Watch and Sierra Nevada College.


Marine capture fisheries can be characterised by a combination of biological factors governing fish productivity and social factors governing fishers’ behaviours. Most fisheries science research has focused on the biological side of fisheries but few studies have attempted to combine quantitative analysis of fishing data with qualitative study of active fishing participants. Choke species, or species with a low quota allocation in contrast to their encounter rates, may present a particular challenge to management of multispecies fisheries. Choke species may restrict fishers’ ability to harvest other species, especially in the presence of at-sea monitoring, which prevents discarding of regulated species. This thesis combines a quantitative spatio-temporal analysis of the potential impact of a choke species on fishers’ behaviour in the British Columbian Pacific Halibut (Hippoglossus stenolepis) fishery with a qualitative analysis of fishers’ reactions to reductions in the quota of bycatch species, Yelloweye Rockfish (Sebastes ruberrimus). Novel criteria were employed to determine if Yelloweye Rockfish acts as a choke species within the Pacific Halibut fishery. Inter-annual and seasonal fishing effort dynamics were studied in years “prior” to (2007-2015) and “post” (2016-2017) a large reduction in the Total Allowable Catch (TAC) for Yelloweye Rockfish. A cluster analysis based on a previous study was developed to identify individual skippers’ “fishing opportunities” (i.e., individual fishing grounds on a fine spatial scale) and track usage of fishing opportunities in “prior” and “post” years. Interviews with five active skippers were conducted to corroborate interpretation of the data analysis. Results indicate that fishers have been successful in reducing their Yelloweye Rockfish catches since the TAC reductions, through a series of avoidance fishing tactics, including shifting into deeper waters, seasonal shifts and the decreased utilization of areas with high proportion of Yelloweye Rockfish in the catch. Studies such as this can help understanding of the potential spatio-temporal impacts of further TAC reductions for Yelloweye Rockfish. More broadly, this thesis improves understanding of strategies that fishers can employ to comply with catch regulations in monitored multispecies fisheries, which may help improve design of management strategies in the future.  


Tiare Boyes at the Ísafjörður harbor.