Stock Status and Conservation Information
(From ISC18 Plenary Report)
Click here to see the ISC17 stock status and conservation information.
Target and limit reference points have not yet been established for pelagic sharks by the WCPFC or the IATTC, the organizations responsible for management of pelagic sharks caught in international fisheries for tuna and tuna-like species in the Pacific Ocean.
Results of the reference case model showed that the spawning stock biomass was near a time-series high in the late 1970s, declined to its lowest level between 1990 to 1995, subsequently increased gradually to reach the time-series high again in 2005, and has since shown small fluctuations with no apparent trend (see ISC/17/ANNEX/13, Figure 1B) close to the time-series high. Recruitment has fluctuated around 37,000,000 age-0 sharks annually with no apparent trend (see ISC/17/ANNEX/13, Figure 1A). Stock status is reported in relation to maximum sustainable yield (MSY) based reference points. Based on these findings, the following information on the status of the North Pacific blue shark stock is provided:
- Female spawning biomass in 2015 (SSB2015) was 69% higher than at MSY and estimated to be 295,774 t (ISC/17/ANNEX/13, Table 1; Figure 1);
- The recent annual fishing mortality (F2012-2014) was estimated to be well below FMSY at approximately 38% of FMSY (ISC/17/ANNEX/13, Table 1; Figure 1); and
- The reference run produced terminal conditions that were predominately in the lower right quadrant of the Kobe plot (not overfished and overfishing not occurring) (ISC/17/ANNEX/13, Figure 2).
Future projections under different fishing mortality (F) harvest policies (status quo, +20%, -20%, FMSY) show that median BSH spawning biomass in the North Pacific will likely remain above SSBMSY in the foreseeable future (ISC/17/ANNEX/13, Table 2, Figure 3). Other potential reference points were not considered in these evaluations.
Improvements in the monitoring of blue shark catches and discards, through carefully designed observer programs and species-specific logbooks, as well as continued research into the fisheries, biology, and ecology of blue shark in the North Pacific are recommended.