Stock Status and Conservation Advice
(From ISC12 Plenary Report)
The Albacore Working Group (ALBWG) noted that it has not received any new information since the 2011 stock assessment that would require a change to previous (2011) conservation information. Therefore, the ALBWG offers no new recommendations on conservation above, beyond that provided by ISC11:
- The stock is considered to be healthy at average historical recruitment levels and fishing mortality (F2006-2008).
- Sustainability is not threatened by overfishing as the F2006-2008level (current F) is about 71% of FSSB-ATHL and the stock is expected to fluctuate around the long-term median SSB (~400,000 t) in the short- and long-term future.
- If future recruitment declines by about 25% below average historical recruitment levels, then the risk of SSB falling below the SSB-ATHL threshold with F2006-2008 levels increases to 54% indicating that the impact on the stock is unlikely to be sustainable.
- Increasing F beyond F2006-2008 levels (current F) will not result in proportional increases in yield as a result of the population dynamics of this stock.
- The current assessment results confirm that F has declined relative to the 2006 assessment, which is consistent with the intent of the previous (2006) WG recommendation.
Pacific Bluefin Tuna (From 2012 Intercessional Plenary Meeting)
Based on the reference point ratios, overfishing is occurring (see F-based ratios in Table 1) and the stock is heavily overfished (see depletion ratios in Table 1). Model estimates of 2010 spawning stock biomass (SSB) are at or near their lowest level and SSB has been declining for over a decade; however, there is no evidence of reduced recruitment.
The current (2010) PBF biomass level is near historically low biomass levels and experiencing high exploitation levels above all biological reference points (BRPs) commonly used by fisheries managers. Based on projection results, extending the status quo (2007-2009) fishing levels is unlikely to improve the stock condition.
Recently implemented WCPFC (entered into force in 2011) and IATTC (entered into force in 2012) conservation and management measures combined with additional Japanese voluntary domestic regulations aimed at reducing mortality, if properly implemented and enforced, are expected to contribute to improvements in PBF stock status. Based on those findings, it should be noted that implementation of catch limits is particularly effective in increasing future SSB when strong recruitment occurs. It is also important to note that if recruitment is less favorable, a reduction of F could be more effective than catch limits to reduce the risk of the stock declining.
The ISC requires advice from the WCPFC regarding which reference point managers prefer so that it can provide the most useful scientific advice. Until which time a decision is rendered, the ISC will continue to provide a suite of potential biological reference points for managers to consider.
The ISC provides the following scientific information as conservation advice:
- Fishing at FMSY would lead to spawning biomass increases of roughly 45% to 72% from 2012 to 2017.
- Fishing at a constant catch of 2,500 mt would lead to potential increases in spawning biomass of 133% to 223% by 2017.
- Fishing at a constant catch of 3,600 mt would lead to potential increases in spawning biomass of 48% and 120% by 2017.
- Fishing at the current fishing mortality rate would lead to spawning biomass increases of 14% to 29% by 2017,
- Fishing at the average 2001-2003 fishing mortality rate would lead to a spawning biomass decrease of 2% under recent recruitment to an increase of 6% under the stock-recruitment curve assumption by 2017.
The WCNPO (Western and Central North Pacific) and EPO (Eastern North Pacific) stocks of swordfish are healthy and above the level required to sustain recent catches.