Interpreting Pacific halibut catch statistics in the British Columbia individual quota program

Abstract

An individual quota management program was implemented on Pacific halibut (Hippoglossus stenolepis) in Canada in 1991. Subsequent changes in fleet behavior influenced the interpretability of catch-per-unit-effort (CPUE) statistics. A regression analysis on Pacific halibut CPUE statistics collected from 1986 to 1994 indicates that year, season, area, vessel class, and gear type all significantly influence CPUE and that there are significant year x season, year x area, and other interactions. CPUE as an annual index of abundance appears to be influenced by changes in fish distribution and fleet behavior. Effort-weighted global CPUE estimates indicate a 38% increase in halibut density in years following implementation of the quota program, while seasonally adjusted area-weighted estimates show only a 16% increase. Two systematic scientific surveys conducted on a portion of this area in 1986 and 1993 showed a 132% increase in density, although high variation and bias in these estimates limited their significance. The composition of the fleet remained relatively stable over this period making interactions involving the factors of gear type and vessel size-class less significant. Results of this analysis proved useful in planning survey and assessment programs prior to implementing a similar quota program in Alaska.