2007 IPHC harvest policy analysis: past, present, and future considerations

The IPHC harvest policy is updated to include the “slow up/fast down” fishery CEY adjustment and autocorrelated assessment error, and a range of spawning biomass thresholds considered. We conclude that a harvest rate of 0.20 in combination with a threshold reference point equal to 1.5 times the limit reference point (i.e., the point at which fishing ceases) provides the optimal combination of yield and spawning biomass conservation, under conditions of either density dependent growth or continued slow growth. The halibut female spawning stock is determined to be well above the minimum reference points, however the harvest rate has been over target for the past few years. Exploitable biomass is declining in all areas. This is occurring in the western regions as the stock is fished down from a lightly exploited state and in the eastern regions because of the passage of two exceptional year classes (1987 and 1988), as well as the buildup of the western area fisheries. Projections indicate that spawning biomass and exploitable biomass will both increase sharply if the incoming 1999 and 2000 year classes remain as strong as the assessment currently estimates them. The current slow growth rate of halibut may not reverse as numbers are fished down due to the large increase in the biomass of arrowtooth flounder.