Evaluating harvest control rules for bigeye tuna (Thunnus obesus) and yellowfin tuna (Thunnus albacares) fisheries in the Indian Ocean

Evaluating harvest control rules for bigeye tuna (Thunnus obesus) and yellowfin tuna (Thunnus albacares) fisheries in the Indian Ocean

Year of publication 2013

Product type Document

Edition 1

Synopsis (short abstract) Bigeye tu (Thunnus obesus) and yellowfin tu (Thunnus albacares) support two of the most important fisheries in the Indian Ocean. However, there is little research evaluating harvest control rules (HCRs) for their magement. In this study we evaluated four HCRs, ‘knife-edged’, ‘linear’, ‘convex’, and ‘concave’, for these two species. These four HCRs defined magement rules for how annual fishing mortality should be adjusted based on perceived stock status. Fishing mortality was adjusted linearly, c onvexly and concavely for the ‘linear’, ‘convex’, and ‘concave’ HCRs, respectively when the current spawning stock biomass (SSB) was between the limit and target SSB-based biological reference points (BRPs). Two age-structured operating models were developed to simulate fisheries maged under these HCRs for a 25-year magement period. Implementation and process errors, and uncertainties in key fisheries parameters were considered as sources of uncertainty in this study. All four HCRs were found to be effective in driving both stocks to the status defined by maximum sustaible yield-based BRPs. The ‘knife-edged’ HCR, which has constant fishing mortality but switches fishing mortality to 0 when stock biomass is below the limit SSB-based BRP, led to relatively poor performance. Our results indicate that a simulation study is needed to evaluate the performance of BRPs and HCRs in maging bigeye tu and yellowfin tu fisheries in the Indian Ocean.

Meeting Session Number 15

Language English