Status of stocks

Under the Magnuson-Stevens Act (MSA), Councils must identify status determination criteria (SDC) that can be used to decide whether overfishing is occurring (fishing mortality is above a maximum fishing mortality threshold, MFMT) or the stock is overfished (biomass is less than a minimum stock size threshold, MSST). They are derived from an estimate of maximum sustainable yield (MSY), “the largest long-term average catch or yield that can be taken from a stock or stock complex under prevailing ecological, environmental conditions and fishery technological characteristics (e.g., gear selectivity), and the distribution of catch among fleets.” Frequently MSY is difficult to estimate for HMS stocks, either due to stock dynamics or the lack of sufficient information to conduct a stock assessment. In those cases, proxy values may be determined for MSY and related status determination criteria. In general, the Council considers the biological reference points, or related proxies, adopted by regional fishery management organizations, to be the ‘best available science.’ The HMS FMP defines these thresholds as follows:

MFMTequals FMSY.  The overfishing limit (OFL) is the annual amount of catch that corresponds to the estimate of MFMT applied to a stock or stock complex’s abundance and is expressed in terms of numbers or weight of fish. Overfishing occurs when fishing mortality F is greater than the MFMT mortality or catch exceeds OFL for one year or more. 

MSSTis calculated as the greater of:

BMSST = (1-M)BMSY when M (natural mortality) ≤ 0.5, or

BMSST = 0.5BMSY      when M > 0.5

MSST or a reasonable proxy must be expressed in terms of spawning biomass or other reproductive potential.  Should the estimated size of an HMS stock in a given year fall below this threshold, the stock is considered overfished.

Additional information on status determination criteria and related management quantities may be found in Chapter 4 of the HMS FMP.

In the case of HMS in the Pacific, most stock assessments are conducted by several international organizations established through conventions that function akin to treaties among sovereign governments. This makes it difficult, if not impossible, for the U.S., or any participating country, to unilaterally peer review the assessments sponsored by these organizations. Therefore, NMFS employs “other peer review processes” to determine whether the assessments constitute the best scientific information available for these transboundary stocks (81 FR 54561; August 16, 2016), including through participation by the U.S. government in these organizations. Once NMFS makes a best scientific information available (BSIA) determination on the outputs of an assessment produced by an international organization, the agency uses this information to determine the status of stocks relative to SDC identified in the FMP for the purposes of domestic management. In instances where the use of proxies is necessary for making status determinations for domestic management based on the best scientific information available from internationally produced assessments, the Council and its advisory bodies may review and comment on the suitability of such proxies. International organizations that conduct stock assessments for HMS FMP management unit species are:

  • In the Eastern Pacific Ocean (EPO) scientific staff employed by the Inter-American Tropical Tuna Commission (IATTC) conduct stock assessments mainly for tropical tunas (bigeye, yellowfin, and skipjack) and some billfish (striped marlin, swordfish). The Fishery Status Reports summarize fisheries and stock status and the most recent stock assessment reports may be accessed on Scientific Advisory Committee (SAC) meeting webpages. All IATTC staff assessments and analyses are reviewed by the Scientific Advisory Committee.
  • In the Western and Central Pacific Ocean (WCPO), the Secretariat of the Pacific Community Oceanic Fisheries Program (SPC-OFP) conducts stock assessments as the science provider to the Western and Central Pacific Fisheries Commission (WCPFC). Like the IATTC, they tend to focus on the tropical tunas, but SPC has also completed stock assessments for species other than the tropical tunas. Their stock assessments may be accessed by visiting the SPC-OFP stock assessment webpage or webpages for relevant WCPFC Scientific Committee meetings.
  • In the North Pacific Ocean (NPO) the International Scientific Committee for Tuna and Tuna-like Species in the North Pacific Ocean (ISC) conducts stock assessments, also as a science provider for the WCPFC, and specifically that organization’s Northern Committee. The ISC has formed working groups for North Pacific albacore, Pacific bluefin tuna, billfish (marlins and swordfish), and sharks. Shark species of interest include blue, shortfin, mako, bigeye thresher, pelagic thresher, silky, oceanic whitetip, and hammerhead species. The ISC Plenary reviews assessments and analyses, and ISC annual Plenary Reports provide stock status updates and conservation recommendations. ISC stock assessments can be found on its Stock Assessment webpage.

In addition to stock assessments prepared by these international organizations, in 2016 NMFS Southwest Fisheries Science Center (SWFSC) scientists, in collaboration with scientists from Mexico, assessed the status of the stock of common thresher shark (Alopias vulpinus) along the West Coast of North America.

Based on these stock assessments, NMFS West Coast Region and Southwest Fisheries Science Center (SWFSC) make BSIA and status determinations for some but not all stocks of HMS FMP management unit species. These status determinations are presented to the Council as part of the biennial management process described in Chapter 5 in the HMS FMP. When appropriate, the Council’s SSC may provide advice on the basis for such determinations, which the Council may transmit as recommendations to NMFS. The Pacific Islands Regional Office and Pacific Islands Fisheries Science Center (PIFISC) are the lead in making status and BSIA determinations for Western and Central Pacific and may co-lead with the SWFSC for certain North Pacific-wide stocks (blue shark, shortfin mako shark).

The stock assessments upon which the status determination is based and resulting determinations are described below. (Status determinations are excerpted from Agenda Item I.4.a, Supplemental NMFS Report 1, September 2022 with pending determinations updated, as appropriate.)

Albacore (Thunnus alalunga)

Two albacore tuna stocks are defined and assessed in the Pacific Ocean, a North Pacific stock and a South Pacific stock. The North Pacific stock is managed under the HMS FMP.

The most recent stock assessment was completed by the ISC in 2023:

Stock Assessment of Albacore Tuna in the North Pacific Ocean in 2023. Report of the Albacore Working Group. International Scientific Committee for Tuna and Tuna-Like Species in the North Pacific Ocean. 12-17 July 2023.

The ISC23 (Plenary Report section 6.1.2) found that:

  1. The stock is likely not overfished relative to the threshold (30%SSBcurrent, F=0) and limit (14%SSBcurrent, F=0) reference points adopted by the WCPFC and IATTC;
  2. The stock is likely not experiencing overfishing relative to the adopted target reference point (F45%SPR); and
  3. Current fishing intensity (F2018-2020) is lower than the average fishing intensity from the 2002-2004 period (the reference level for IATTC Resolution C-05-02 and WCPFC CMM-2019-03).

Both the IATTC and WCPFC have adopted a harvest strategy for this stock that includes reference points and harvest control rules. See IATTC Resolution C-23-02.

The NMFS status determination is currently based on the 2020 ISC stock assessment but reaches the same conclusion, consistent with the framework in the HMS FMP, that the stock is not subject to overfishing nor overfished. The table below shows the reference points from the 2020 ISC stock assessment used for the current status determinations.

Overfishing
MFMT (FMSY or Proxy)Current FMSY or proxy quantity estimateCurrent F quantity estimateRFMO Ref. point (if adopted)F/FMSY ratioSubject to Overfishing?
FMSY0.83F2015-17 = 0.5NA0.6No
Overfished
BMSY or proxyCurrent BMSY or proxy estimateCurrent B quantity estimateMSST (1-MxBMSY or 0.5BMSY)Current B/MSSTRFMO Ref. point (if adopted)Overfished?
SSBMSY19,535 mtSSB2018 = 58,858 mt10,158 mt5.7920%SSBcurrent, F=0 =25,590 mtNo
Reference points used to determine stock status of North Pacific albacore tuna.

Pacific Bluefin Tuna (Thunnus orientalis)

Pacific bluefin tuna is considered a single stock across the North Pacific. However, its major spawning grounds occur in the Western Pacific in waters between the Ryukyu Islands in Japan and the east of Taiwan, in the southern portion of the Sea of Japan, and possibly the Kuroshio-Oyashio transition area in the coastal area of northeastern Japan. A portion of juvenile fish migrate from spawning grounds in the Western Pacific to forage in the California Current System before returning west at ages 3-7+ years. Since 1990, about 80% of the catch has occurred in waters around Japan, Korea, and Taiwan with almost all remaining catch occurring in waters off the west coasts of Mexico and the U.S. A small portion of the stock may migrate into waters in the Southwest Pacific and Indian Ocean. This single North Pacific stock is subject to management under the HMS FMP.

The most recent stock assessment was completed by the ISC in 2022:

Stock Assessment of Pacific Bluefin Tuna in the Pacific Ocean in 2022. ISC Pacific Bluefin Tuna Working Group. International Scientific Committee for Tuna and Tuna-Like Species in the North Pacific Ocean 12-18 July 2022.

The 2022 assessment was reviewed at ISC22. ISC23 forwarded its 2022 conclusions as follows (Plenary Report section 6.2):

  1. No biomass-based limit or target reference points have been adopted for PBF, but the PBF stock is overfished relative to the potential biomass-based reference points (20%SSB0) adopted for other tuna species by the IATTC and WCPFC. On the other hand, SSB reached its initial rebuilding target (SSBMED = 6.3%SSB0) in 2019, five years earlier than originally anticipated by the RFMOs; and
  2. No fishing mortality-based reference points have been adopted for PBF by the IATTC and WCPFC. The recent (2018-2020) F%SPR is estimated to produce a fishing intensity of 30.7%SPR and is below the level corresponding to overfishing for many F-based reference points proposed for tuna species, including SPR20%.

Both the IATTC and WCPFC have adopted a rebuilding plan as part of a long-term management framework. See IATTC Resolution C-23-01. The rebuilding plan includes two rebuilding targets: 1) SSBmed,1952-2014 (the median point estimate for 1952-2014) to be achieved by 2024 with at least 60% probability; and (2) 20%SSBF=0 to be achieved within 10 years of reaching the initial rebuilding target or by 2034, whichever is earlier, with at least 60% probability. Stock rebuilding is being accomplished through national/fishery catch limits for fish ≤30 kg and >30 kg. According to the 2022 stock assessment, the first rebuilding target has been met. The management framework also describes interim measures for the period between when the second rebuilding target is met (expected to be confirmed in 2024) and when the long-term harvest strategy is agreed to, based on management strategy evaluation results.

The current NMFS status determination is based on the 2022 ISC stock assessment and finds the stock is not subject to overfishing but is overfished, based on the framework in the HMS FMP. The table below shows the reference points from the 2022 ISC stock assessment used for the current status determinations.

Overfishing
MFMT (FMSY or Proxy)Current FMSY or proxy quantity estimateCurrent F quantity estimateRFMO Ref. point (if adopted)F/FMSY ratioSubject to Overfishing?
1-20%SPR0.81-SPR2018-20 = .693NA0.86625No
Overfished
BMSY or proxyCurrent BMSY or proxy estimateCurrent B quantity estimateMSST (1-MxBMSY or 0.5BMSY)Current B/MSSTRFMO Ref. point (if adopted)Overfished?
20%SSB0128,716 mtSSB20200 = 65,46496,5370.678NAYes
Reference points used to determine stock status of Pacific bluefin tuna.

Bigeye Tuna (Thunnus obesus)

Two bigeye tuna stocks are identified in the Pacific Ocean, the EPO stock and the WCPFO stock, defined by the IATTC and WCPFC Convention Areas. The stock managed under the HMS FMP is the EPO stock.

The most recent stock assessment for the EPO stock was completed by the IATTC scientific staff in 2020: 

Bigeye Tuna in the Eastern Pacific Ocean, 2019: Benchmark Assessment. Haikun Xu, Mark N. Maunder, Carolina Minte-Vera, Juan L. Valero, Cleridy Lennert-Cody, and Alexandre Aires-da-Silva. Prepared for the Eleventh Meeting of the Inter-American Tropical Tuna Commission (IATTC) Scientific Advisory Committee. Doc SAC-11-06.

As noted in Agenda Item E.3.a, Supplemental Joint NMFS SWFSC Report 1, September 2020: “In 2020, IATTC scientific staff used a new approach for assessing bigeye and yellowfin tuna in the eastern Pacific Ocean. IATTC scientific staff presented risk assessments for both stocks instead of base case assessments. The risk assessments show the probability of exceeding FMSY or SSBMSY as opposed to providing a base case model estimate for Fcurrent and SSBcurrent.” This presented challenges in using these assessments to develop the status determination criteria specified in the HMS FMP. NMFS concluded that it could identify MFMT proxies using the assessment results but could not identify suitable proxies for MSST. It requested the Council’s SSC review three alternative approaches for identifying these proxies. In its March 2021 report (Agenda Item H.5.a, Supplemental Joint SWFSC-NMFS Report 1) NMFS noted: “

In addition to the added complexity of interpreting the results of the probabilistic framework used in the 2020 benchmark assessment, the posterior distributions of P(FCUR>FMSY) and P(FCUR>FLIMIT) were also bimodal (i.e., one set of model results exceeds the reference point while another does not). For bigeye, there is a 50 percent probability that 2017-19 fishing mortality exceeds the MSY level (P(FCUR>FMSY) = 50%). Based on NMFS-suggested proxy for MFMT, EPO bigeye tuna would not be subject to overfishing. It may also be worth consideration that the recent assessment indicated a 5 percent probability that the IATTC’s F limit reference point has been exceeded (P(FCUR>FLIMIT) = 5%) (See Appendix A for more detail). To obtain these probabilities, the posterior distributions from individual models were weighted and combined.

Based on its review (through its HMS subcommittee), the SSC agreed that:

…applying the proxy for the Maximum Fishing Mortality Threshold outlined in Joint SWFSC-WCR NMFS Report 1 is a reasonable approach for these assessments. For the Minimum Stock Size Threshold (MSST), the SSC agrees that the second example under Alternative 3 is appropriate whenever the central values of natural mortality rate (M; either a fixed value or the median of a distribution for each individual model) are greater than 0.5 for all models in the ensemble. Option 1, whereby the assessment results include reference levels consistent with domestic SDC, is preferred in cases where some or all of these M central values are below 0.5 (including when M is age-dependent and this is true for a subset of ages). If only a small minority of the models have M central values below 0.5, the above proxy for MSST may still be acceptable. (Agenda Item H.5.a, Supplemental SSC Report 1, March 2021)

Given these considerations, NMFS made its overfishing and overfished determination based on the 2020 IATTC stock assessment , finding the stock is not subject to overfishing and not overfished.

MFMT (FMSY or Proxy)Current FMSY or proxy quantity estimateCurrent F quantity estimateRFMO Ref. point (if adopted)F/FMSY ratioSubject to Overfishing?
FMSYNANANAmedian of F2017-19/FMSY = 1.00No
BMSY or proxyCurrent BMSY or proxy estimateCurrent B quantity estimateMSST (1-MxBMSY or 0.5BMSY)Current B/MSSTRFMO Ref. point (if adopted)Overfished?
NANANANAS2020/0.5*SMSY= 1.84NANo
Reference points used for the current NMFS status determinations for EPO bigeye tuna. based on the 2020 IATTC stock assessment

Skipjack Tuna (Katsuwonus pelamis)

Two skipjack tuna stocks are identified in the Pacific Ocean, the EPO stock and the WCPO stock, defined by the IATTC and WCPFC Convention Areas. The stock managed under the HMS FMP is the EPO stock.

The most recent interim stock assessment for the EPO stock was conducted by the IATTC scientific staff in 2022:

Skipjack Tuna in the Eastern Pacific Ocean: Interim Assessment. Maunder, M, Xu, H., Minte-Vera, C., Valero, J.L., Lennert-Cody, C.E., and Aires-da-Silva, A. Prepared for the Thirteenth Meeting of the IATTC SAC, May 16-20, 2022, La Jolla, California USA. Doc SAC-13-07.

Although labeled interim by the IATTC scientific staff, the IATTC scientific staff concluded it was suitable for management use, but highlighted ongoing work needed to improve the model framework to reduce uncertainty in the results including the incorporation of tagging data. This assessment was reviewed by the SAC and considered by the IATTC. In terms of stock status, the assessment Executive Summary states:

  • The reference model estimated that the 2021 exploitation rate was slightly above status quo (average level of 2017-2019) as did over half of the sensitivity models ranging from being only slightly above to being 0.1 higher (except one model that estimated high exploitation rates).
  • The reference model and most of the sensitivity analyses estimate that the current biomass is above the target reference point and the fishing mortality is below the target fishing mortality.

These results indicate that the stock is not subject to overfishing nor overfished. Because the assessment results indicate that Fcurrent/FBtarget = 0.25 (i.e., less than 1), current fishing mortality is lower than the MFMT. Additionally, because the assessment results indicate that current spawning biomass is above BTARGET, it is also above the MSST for this stock. The current NMFS status determination is based on these results as shown in the table below.

Overfishing
MFMT (FMSY or Proxy)Current FMSY or proxy quantity estimateCurrent F quantity estimateRFMO Ref. point (if adopted)F/FMSY ratioSubject to Overfishing?
NAFBtarget, where Btarget = 0.3 SSB0NANA0.25No
Overfished
BMSY or proxyCurrent BMSY or proxy estimateCurrent B quantity estimateMSST (1-MxBMSY or 0.5BMSY)Current B/MSSTRFMO Ref. point (if adopted)Overfished?
30%SSB0NASB2021 = 26,871NAGreater than 1 since SBcurrent>30%SSB0 (or BMSY proxy)BMSY target, with 30%SSB0 as proxyNo
Reference points used for the current NMFS status status determination for EPO skipjack tuna based on the 2022 IATTC stock assessment.

Yellowfin Tuna (Thunnus albacares)

Two yellowfin tuna stocks are identified in the Pacific Ocean, the EPO stock and the WCPO stock, defined by the IATTC and WCPFC Convention Areas. The stock managed under the HMS FMP is the EPO stock.

The most recent assessment of the EPO stock was completed by IATTC scientific staff in 2020:

Yellowfin Tuna in the Eastern Pacific Ocean, 2019: Benchmark Assessment. Carolina Minte-Vera, Mark N. Maunder, Haikun Xu, Juan L. Valero, Cleridy E. Lennert-Cody, and Alexandre Aires-da-Silva. Prepared for the Eleventh Meeting of the Inter-American Tropical Tuna Commission (IATTC) Scientific Advisory Committee. Doc SAC-10-07.

This assessment integrated an ensemble of 12 different reference models tested against four different steepness assumptions s (0.7, 0.8, 0.9, and 1.0), for a total of 48 models. The assessment was used as the basis for a risk assessment by IATTC scientific staff (SAC-11-08 Rev1). “[T]he overall results of the risk analysis, which include all 48 reference models, indicate only a 9% probability that the fishing mortality corresponding to the maximum sustainable yield (FMSY) has been exceeded. There is a 12% probability that the spawning stock biomass corresponding to the maximum sustainable yield (SMSY) has been breached.”

In its November 2020 report (Agenda Item I.3.a, Supplemental NMFS Report 1) NMFS concluded:

The 2020 assessment indicates a 12 percent probability that spawning biomass at the beginning of 2020 (S) is below a maximum sustainable yield (MSY) level (i.e., P(SCUR<SMSY)= 12%), and a nine percent probability that 2017-19 fishing mortality exceeds the MSY level (i.e., P(FCUR>FMSY) = 9%). Because the IATTC’s target biomass threshold (SMSY) is more conservative than MSST (i.e., 1-M*BMSY, where M is natural mortality), the assessment results suggest that the EPO yellowfin tuna stock is unlikely to be overfished. Because the IATTC’s target fishing mortality threshold (FMSY) is the same reference level as MFMT, the assessment results suggest it is also unlikely that the stock is subject to overfishing. There is zero probability that both IATTC’s S and F limit reference points have been exceeded (P(SCUR<FLIMIT) = 0%; P(FCUR>FLIMIT) = 0%).

The current NMFS overfishing status determination is based on the 2020 IATTC stock assessment and finds the stock is not subject to overfishing, see the table below. Because of issues in deriving a proxy for MSST from a probabilistic assessment framework, the overfished status determination is based on the 2018 IATTC stock assessment (see Stock Assessment Report 20). Based on that assessment, NMFS finds the stock is not overfished, see the table below.

MFMT (FMSY or Proxy)Current FMSY or proxy quantity estimateCurrent F quantity estimateRFMO Ref. point (if adopted)F/FMSY ratioSubject to Overfishing?
FMSYNANANAmedian of F2017-19/Fmsy = 0.65No
Reference points used for the current NMFS overfishing status determination for EPO yellowfin tuna based on the 2020 IATTC stock assessment.
BMSY or proxyCurrent BMSY or proxy estimateCurrent B quantity estimateMSST (1-MxBMSY or 0.5BMSY)Current B/MSSTRFMO Ref. point (if adopted)Overfished?
SMSY (S= unitless spawning biomass index)3,634S = 3,925 (S= unitless spawning biomass index)1,8172.1NANo
Reference points used for the current NMFS overfished status determination for EPO yellowfin tuna based on the 2018 IATTC stock assessment.

Striped marlin (Kajikia audax)

Stock assessments have been performed on three striped marlin stocks in the Pacific Ocean: a northern EPO stock (assessed by the IATTC in 2009), a WCNPO stock (assessed by the ISC in 2023), and a Southwest Pacific Ocean stock (assessed by the SPC in 2019). The stock managed under the HMS FMP is the EPO stock.

The assessment for the northern EPO stock, completed by IATTC scientific staff in 2010 is: 

Assessment of Striped Marlin in the Eastern Pacific Ocean In 2008 and Outlook for the Future. Michael G. Hinton.  Inter-American Tropical Tuna Commission.  Document SAC-01-10 and also included in Stock Assessment Report 10.

Stock status as reported in the assessment for 2009, the terminal year of the assessment:

…the northern EPO stock of striped marlin is not being overfished [C(2009)/MSY = 0.36, Fmult = 6.4], and that the stock biomass is increasing from the low biomass (about 750 t) and SBR (about 0.16) observed in 2003. The estimates of biomass and SBR for 2009 were about 3,600 t and 0.31, respectively.

The results of the base case assessment indicate that at present the SBR for the stock is about 0.31, and that S(2009)/SMSY = 1.2, which indicates that the spawning biomass is above the level expected to support harvests at the estimated MSY of 2,000 t.

The results of the assessment (Fmult = 6.4) also indicate that levels of fishing effort are below those which would be expected to harvest striped marlin at the MSY level. Recent catches, which are estimated to be about 750 to 850 t, are about 40 percent of MSY. If harvests continue at this level, then it is expected that the biomass of the northern EPO stock of striped marlin will continue to increase over the near term.

The current NMFS status determination is based on the 2009 IATTC stock assessment and finds the stock is not subject to overfishing and is not overfished, based on the framework in the HMS FMP. The table below shows the reference points derived from the 2010 IATTC assessment used for the overfishing determination shows the reference points used for the overfished determination.

Overfishing
MFMT (FMSY or Proxy)Current FMSY or proxy quantity estimateCurrent F quantity estimateRFMO Ref. point (if adopted)F/FMSY ratioSubject to Overfishing?
FNANANA0.16No
Overfished
BMSY or proxyCurrent BMSY or proxy estimateCurrent B quantity estimateMSST (1-MxBMSY or 0.5BMSY)Current B/MSSTRFMO Ref. point (if adopted)Overfished?
SSBMSY1246 mtSSB2009 = 1488 mt623 mt2.3NANo
Reference points used for the current NMFS stock status determination for EPO striped marlin based on the 2010 IATTC stock assessment.

Swordfish (Xiphias gladius)

Three swordfish stocks have been assessed in the Pacific Ocean: A North Pacific Stock, a Southeast Pacific Ocean stock (south of 10°N in the IATTC Convention Area), and a southwest Pacific stock in the WCPFC Convention Area south of the equator. The North Pacific stock is the stock managed under the HMS FMP.

The most recent stock assessment for swordfish in the North Pacific was completed by the ISC Billfish Working Group in 2023:

Stock Assessment Report for Swordfish (Xiphias gladius) in the North Pacific Ocean Through 2021. ISC Billfish Working Group. Prepared for the Twenty-third Meeting of the ISC, July 12-17, 2023. The assessed stock is defined to be the waters of the North Pacific Ocean contained in the WCPFC Convention Area bounded by the equator and the waters of the IATTC Convention Area north of 10°N.

The following information on the status of this stock was provided by ISC23 (Plenary Report section 6.5):

  1. Female spawning stock biomass was estimated to be 35,778 mt in 2021, with a relative SSB ratio of SSB/SSBMSY = 2.18 in 2021;
  2. Estimated F (arithmetic average of F for ages 1 – 10) averaged roughly F=0.09 yr-1 during 2019-2021 with a relative fishing mortality of F/FMSY = 0.49 in 2021; and
  3. Relative to MSY-based reference points, overfishing is very likely not occurring (>99% probability) and the NPO SWO stock is very likely not overfished (>99% probability).

The current NMFS status determination is based on previous ISC stock assessment from 2018 but reaches comparable conclusions with respect to status. This assessment defined the stock boundaries somewhat differently, excluding a triangular area in the EPO, approximately bounded by a line extending southwest from Baja California, Mexico, to the equator and then eastwards to the coast of North America at 10°N. Using that assessment, NMFS found the stock is not subject to overfishing and is not overfished, based on the framework in the HMS FMP. The table below shows the reference points from the 2018 ISC stock assessment used for the current status determinations.

Overfishing
BMSY or proxyCurrent BMSY or proxy estimateCurrent B quantity estimateMSST (1-MxBMSY or 0.5BMSY)Current B/MSSTRFMO Ref. point (if adopted)
U (exploitation rate = catch/biomass)0.18F2012 = 0.19NA1.11Yes
Overfished
BMSY or proxyCurrent BMSY or proxy estimateCurrent B quantity estimateMSST (1-MxBMSY or 0.5BMSY)Current B/MSSTRFMO Ref. point (if adopted)Overfished?
BMSY31,200B2012 = 58,590 mt20,280 mt3*NANo
Reference points used for the current NMFS stock status determination for NPO swordfish based on the 2018 ISC stock assessment.

*For EPO swordfish, B2012/BMSY = 1.87 used for the status determination instead of B2012/BMSST = 3; status is the same, not overfished.

Blue shark (Prionace glauca)

Two blue shark stocks are recognized in the Pacific Ocean, a North Pacific stock and a South Pacific stock or stocks. (WCPFC conducted a stock assessment on the South Pacific stock in its Convention Area in 2021. IATTC is currently developing an assessment for the SEPO.) The North Pacific stock is subject to management under the HMS FMP.

The most recent NPO blue shark stock assessment was completed by the ISC in 2022:

Stock Assessment and Future Projections of Blue Shark in the North Pacific Ocean Through 2020. Report of the Shark Working Group. International Scientific Committee for Tuna and Tuna-like Species in the North Pacific Ocean. 12-18 July 2022.

The following information on the status of the NPO blue shark stock was provided by the ISC23 Plenary based on the 2022 stock assessment (Plenary Report section 6.3):

  1. Target and limit reference points have not been established for pelagic sharks in the Pacific Ocean. Stock status is reported in relation to MSY-based reference points;
  2. Median female SSB in 2020 (SSB2020) was estimated to be 1.170 of SSBMSY (80th percentile, 0.570 – 1.776) and is likely (63.5% probability) not in an overfished condition relative to MSY-based reference points;
  3. Recent annual F (F2017-2019) is estimated to be below FMSY and overfishing of the stock is very likely (91.9% probability) not occurring relative to MSY-based reference points; and
  4. The base case model results show that there is a 61.9% joint probability that NPO BSH stock is not in an overfished condition and that overfishing is not occurring relative to MSY-based reference points.

The pending NMFS status determination is based on the 2022 ISC stock assessment and finds the stock is not subject to overfishing and is not overfished, based on the framework in the HMS FMP. The table below shows the reference points from the 2022 ISC stock assessment used for the current status determinations.

Overfishing
MFMT (FMSY or Proxy)Current FMSY or proxy quantity estimateCurrent F quantity estimateRFMO Ref. point (if adopted)F/FMSY ratioSubject to Overfishing?
FMSY0.76F2017-19 = 0.33NA0.45No (pending)
Overfished
BMSY or proxyCurrent BMSY or proxy estimateCurrent B quantity estimateMSST (1-MxBMSY or 0.5BMSY)Current B/MSSTRFMO Ref. point (if adopted)Overfished?
Female SSBMSY83,545SSB2020 = 92,95463,494-71,0131.3-1.46NANo (pending)
Reference points used for the current NMFS stock status determination for NPO blue shark based on the 2022 ISC stock assessment.

Common Thresher Shark (Alopias vulpinus)

Although a pelagic species, common thresher sharks are relatively coastal, occurring primarily within 40-75 miles of land, over continental and insular shelves and slopes, and occupy cooler, more temperate waters. Although distributed around the Pacific basin (and circumglobally), an assessment has only been completed on the stock occurring off the west coast of North America (see below), which is the stock managed under the HMS FMP.

The most recent stock assessment was completed by NMFS in 2018: 

Status of Common Thresher Sharks, Alopias vulpinus, along the West Coast of North America: Updated Stock Assessment Based on Alternative Life History. Teo, S., Garcia Rodriguez, E. and Sosa-Nishizaki. O. U.S. Department of Commerce, NOAA Technical Memorandum NMFS-SWFSC-595. https://doi.org/10.7289/V5/TM-SWFSC-595

This is the first assessment completed for this stock. This assessment was peer reviewed in 2017 and revised in 2018. The assessment found:

The estimated fishing intensity (1-SPR) on common thresher sharks off the west coast of North America is currently relatively low at 0.097 (average of 2012 – 2014) and substantially below the estimated overfishing threshold (MFMT), with (1-SPR12-14)/(1-SPRMSY) at 0.21. Similarly, the estimated number of mature female sharks in 2014 (S2014) for this stock is at 62% of its unexploited level and is substantially larger than the estimated MSST, with S2014/MSST at 1.40. Thus, this stock of common thresher sharks is unlikely to be in an overfished condition nor experiencing overfishing. (Table references excluded.)

Based on the 2018 assessment NMFS determined the stock is not subject to overfishing and is not overfished, based on the framework in the HMS FMP. The table below shows the reference points from the 2018 NMFS stock assessment used for the current status determinations.

Overfishing
MFMT (FMSY or Proxy)Current FMSY or proxy quantity estimateCurrent F quantity estimateRFMO Ref. point (if adopted)F/FMSY ratioSubject to Overfishing?
1-SPRMSY0.451-SPR2012-14 = 0.097NA0.21No
Overfished
BMSY or proxyCurrent BMSY or proxy estimateCurrent B quantity estimateMSST (1-MxBMSY or 0.5BMSY)Current B/MSSTRFMO Ref. point (if adopted)Overfished?
SSBMSY101,500 mature femalesSSB = 136,800 mature females97,500 mature females1.4NANo
Reference points used for the current NMFS stock status determination for common thresher shark based on the 2018 NMFS stock assessment.

Shortfin Mako Shark (Isurus oxyrinchus)

A single shortfin mako shark stock is assumed in the NPO based on evidence from genetics, tagging studies, and lower catch rates of shortfin mako near the equator relative to temperate areas. The WCPFC completed a stock assessment for the stock within its Convention Area in the South Pacific. The NPO stock is managed under the HMS FMP.

The most recent assessment for the NPO stock was completed in 2018: 

Stock Assessment of Shortfin Mako Shark in the North Pacific Ocean through 2016. Report of the Shark Working Group. International Scientific Committee for Tuna and Tuna-like Species in the North Pacific Ocean. July 11-16, 2018, Yeosu, Republic of Korea. Additionally, the ISC completed an indicator analysis in 2021.

ISC23 endorsed the following stock status information based on the 2018 assessment (Plenary Report section 6.4):

  1. Target and limit reference points have not been established for pelagic sharks in the Pacific Ocean. Stock status is reported in relation to MSY-based reference points; and
  2. The results from the base case model and six sensitivity analyses that represent the most important sources of uncertainty in the assessment show that the NPO SMA stock is likely (>50%) not in an overfished condition and overfishing is likely (>50%) not occurring relative to MSY-based abundance and fishing intensity reference points.

Based on the 2018 ISC assessment, NMFS determined the stock is not subject to overfishing and is not overfished, based on the framework in the HMS FMP.

Overfishing
MFMT (FMSY or Proxy)Current FMSY or proxy quantity estimateCurrent F quantity estimateRFMO Ref. point (if adopted)F/FMSY ratioSubject to Overfishing?
1-SPRMSY0.261-SPRmsy2013-15 = 0.16NA0.62No
Overfished
BMSY or proxyCurrent BMSY or proxy estimateCurrent B quantity estimateMSST (1-MxBMSY or 0.5BMSY)Current B/MSSTRFMO Ref. point (if adopted)Overfished?
SAMSY633,700 female sharksSA2016 = 860,200 female sharks(1-0.128)x633700 = 552,586 female sharks1.6NANo
Reference points used for the current NMFS stock status determination for NPO shortfin mako shark based on the 2018 ISC stock assessment.

Dorado (Coryphaena hippurus)

Dorado, or mahi mahi, are found circumglobally in tropical and subtropical waters but stock structure in the Pacific is poorly understood. Throughout their range they are often found associated with both natural and manmade floating objects.  In the Eastern Pacific, dorado are most abundant off Mexico, Panama, Ecuador, Peru, and around the Galapagos Islands.  They move into U.S. waters as far north as Point Conception, California, primarily during warm water years. The exploratory stock assessment referenced below found “the available information does not provide strong evidence that there is more than one stock of dorado in the EPO, although there are indications of some spatial structure.” For the purposes of management under the HMS FMP, the stock is considered the portion of the population occurring in the EPO.

The IATTC conducted an exploratory assessment for a EPO stock south of the equator in 2016:

Exploratory Stock Assessment of Dorado (Coryphaena Hippurus) in the Southeastern Pacific Ocean (DRAFT). Alexandre Aires-da-Silva, Juan L. Valero, Mark. N. Maunder, Carolina Minte-Vera, Cleridy Lennert-Cody, Marlon H. Román, Jimmy Martínez-Ortiz, Edgar J. Torrejón-Magallanes and Miguel N. Carranza. Inter-American Tropical Tuna Commission, Scientific Advisory Committee Sixth Meeting. May 9-13, 2016.

Although, a single stock may occur over a larger area of the EPO, data were only sufficient to conduct the assessment on the population south of the equator, based on a “core area” located off Ecuador and Peru. The assessment executive summary concludes:

Although the assessment results contribute to knowledge about the population dynamics of dorado and its history of exploitation in the EPO, the IATTC staff is unable to draw conclusions about stock status, because no reference points, target or limit, have been defined for dorado in the EPO. Nonetheless, some management quantities are presented and discussed for consideration. Recent catches are near the estimates of maximum sustainable yield (MSY) from the stock assessment. However, yield-per-recruit (YPR) analyses show that the yield curve is very flat, and the fishing mortality required to achieve the MSY is poorly defined. A complementary study presents an exploratory management strategy evaluation (MSE) for dorado in the southern EPO. Overall, this study shows that Stock Synthesis is a promising tool for conducting stock assessments of this species in the EPO. More research is needed to refine the model and the data used, and to prioritize collection of new data for assessing dorado. Analyses expanding the spatial extent of the assessment and including data from more fisheries (e.g., Central America, Mexico, and Chile) could be considered in the future.

NMFS concluded that the status of the stock is unknown given the lack of data available to assess status.

Assessments for Other Pacific Ocean Stocks

Other stocks of HMS management unit species occur in the Pacific Ocean. These stocks are not managed under the HMS FMP. For reference the most recent assessments for these stocks are listed below.

Catches of HMS Management Unit Species in West Coast Fisheries

Except for North Pacific albacore, Pacific bluefin tuna, and swordfish, West Coast fisheries catch of HMS FMP management unit species has comprised less than one percent of stockwide catch. Historically, West Coast North Pacific albacore catch has been about one-fifth of the stockwide total. For Pacific bluefin tuna and swordfish it has been about 5% of stockwide catch. These catch fractions can inform considerations of the “relative impact of U.S. fishing vessels on the stock” when the Council considers responses to a notification that a stock is subject to overfishing or overfished “due to excessive international fishing pressure.” When notified by NMFS, Magnuson-Stevens Act section 304(i) requires the Council to develop recommendations for domestic regulations and international actions taking into account this relative impact.