Fisheries and Resources Monitoring System

Albacore - Northern Pacific
Fact Sheet Title  Fact Sheet
Stock status report 2022
Albacore - Northern Pacific
Fact Sheet Citation  
Owned byInter-American Tropical Tuna Commission (IATTC) – ownership
ident Blockident Blockdisplay tree map
Species List:
Species Ref: en - Albacore, fr - Germon, es - Atún blanco, ru - Тунец длинноперый
ident Block Albacore - Northern Pacific
Aq Res
Biological Stock: Yes         Value: Regional
Management unit: Yes        Reference year: 2021
Aq Res State Trend
Aq Res State Trend
Aq Res State Trend Aq Res State Trend
Aq Res State TrendModerate fishing mortalityModerate fishing mortalityGreen
Aq Res State TrendPre-exploitation biomass or high abundancePre-exploitation biomass or high abundance
Aq Res State Trend
Aq Res State TrendModerately exploited
Habitat Bio
Bottom Type: Unspecified.   Depth Zone: Abyssal ( >1000m).   Horizontal Dist: Oceanic.   Vertical Dist: Pelagic.  

Geo Dist
Geo Dist: Highly migratory

Water Area Overview
Spatial Scale: Regional

Water Area Overview
Aq Res Struct
Biological Stock: Yes

Data provided by the relevant CPCs on catches of albacore, by gear and area (north and south of the equator), are shown in (Table A-6), and for the entire EPO are in (Table A-2a). A portion of the albacore catch is taken by troll vessels (LTL), included under “Other gears” (OTR) in Table A-2a.

There are two stocks of albacore in the Pacific Ocean, one in the northern hemisphere and the other in the southern hemisphere. Albacore are caught by longline gear in most of the North and South Pacific, but not often between about 10°N and 5°S, by trolling gear in the eastern and central North and South Pacific, and by pole-and-line gear in the western North Pacific. In the North Pacific, about 40% of the catch is taken by pole-and-line and troll fisheries that catch smaller, younger albacore, and about 50% was taken by longline. In the South Pacific, almost all the albacore is taken by longline. The total annual catches of South Pacific albacore ranged from about 25,000 to 50,000 t during the 1980s and 1990s but increased after that and peaked at about 94,500 t in 2017, declining slightly after that. During 2018-2020, the albacore catches in the south Pacific averaged about 80,500 t (Figure F-1a),
Figure F-1a: Retained catches of South Pacific albacore, by region. EPO catches broken down by gear: LL: longline; LTL: troll; OTR: other.

of which about 25% was taken in the eastern Pacific Ocean (EPO), a decline of about 6,500 t from the average for 2017-2019. The total annual catches of North Pacific albacore peaked in 1976 at about 125,000 t, declined to about 38,000 t in 1991, and then increased to about 126,000 t in 1999 (Figure F-1b).
Figure F-1b: Retained catches of North Pacific albacore, by region. EPO catches broken down by gear: LL: longline; LTL: troll; OTR: other.

They declined again in the early 2000s, then recovered. Since 2012 catches have declined on average 5% a year from about 92,000 to about 52,000 t in 2020. The catches averaged about 54,500 t in 2018-2020, of which 23% was taken in the EPO. Those declines in catches coincide with decline in effort in the north EPO (Figure F-2).
Figure F-2: Effort in vessel-days and number of vessels for the North Pacific albacore tuna in the eastern Pacific Ocean.

Juvenile and adult albacore are caught mostly in the Kuroshio Current, the North Pacific Transition Zone, and the California Current in the North Pacific and in the Subtropical Convergence Zone in the South Pacific, but spawning occurs in tropical and subtropical waters, centering around 20°N and 20°S latitudes. North Pacific albacore are believed to spawn between March and July in the western and central Pacific.

The movements of North Pacific albacore are strongly influenced by oceanic conditions, and migrating albacore tend to concentrate along oceanic fronts in the North Pacific Transition Zone. Most of the catches are made in water temperatures between about 15° and 19.5°C. Details of the migration remain unclear, but juvenile fish (2- to 5-year-olds) are believed to move into the eastern Pacific Ocean (EPO) in the spring and early summer, and return to the western and central Pacific, perhaps annually, in the late fall and winter, where they tend to remain as they mature. This pattern may be complicated by sex-related movements of large adult fish (fork length (FL) >125 cm), which are predominately male, to areas south of 20°N. The significance of such movements for the demographic dynamics of this stock are uncertain at present.

Less is known about the movements of albacore in the South Pacific Ocean. The juveniles move southward from the tropics when they are about 35 cm long, and then eastward along the Subtropical Convergence Zone to about 130°W. When the fish approach maturity they return to tropical waters, where they spawn. Recoveries of tagged fish released in areas east of 155°W were usually made at locations to the east and north of the release site, whereas those of fish released west of 155°W were usually made at locations to the west and north of the release site.

The most recent published stock assessments for the South and North Pacific stocks of albacore are from 2021 and 2020, respectively. The assessments indicate that it is not likely that either stock is overfished or that overfishing is taking place.

See also fishery fact sheet:EPO Tunas and billfishes fishery
EPO Tunas and billfishes fishery: Retained catches of North Pacific albacore, by region. EPO catches broken down by gear: LL: longline; LTL: troll; OTR: other.
Bio Assess

The last stock assessment for North Pacific albacore completed in 2020 by the Albacore Working Group (ALBWG) of the International Scientific Committee for Tuna and Tuna-like Species in the North Pacific Ocean (ISC) (ISC/20/Annex/12, SAC-11-INF-I). A new assessment is planned for 2023. The north Pacific albacore tuna stock has been exploited for a long time, the catches were the highest in 1976 (about 127,000 t) and the lowest in 1991 (about 37,000 t). During the assessment period (1994-2018), the highest catches were in 1999 (about 119,000 t) and the lowest in 2018 (about 57,600 t). About 2/3 of the catches come from surface fisheries (troll and pole-and-line) that harvest mainly juveniles, and the rest from longline fisheries.

The assessment was done using the “best model” approach. The working group concluded that the stock was not experiencing overfishing and was probably not overfished (Figure F-3)

Figure F-3 Kobe plot showing the status of the north Pacific albacore (Thunnus alalunga) stock relative to the 20% of the dynamic spawning biomass with no fishing and corresponding fishing intensity (F20%), with 95% confidence intervals: (A) Base-case trajectory (start year, 1994, is a triangle and terminal year, 2018, is a circle). (B) Final year for base-case model (black), sensitivity model with different growth assumptions (blue), update of the 2017 model to 2020 data (red) (SAC-11-INF-I).

(Table F-1). The current depletion is 0.46 (SSB2018/SSB_d, where SSB_d is the dynamic spawning stock biomass without fishing for 2018). The ratio of SSB2018/SMSY = 3.01. The relative current fishing mortality is F2015-2017/F50%= 1, F2015-2017/F20% =0.62, F2015-2017/FMSY =0.60 (Table F-1). Ten years projections with either constant catch (average of 2013-2017, 69,000 t) or constant fishing mortality (at the F2015-2017 level) predicted an increase in the female spawning biomass.

The current IATTC conservation and management measures for north Pacific albacore (Resolutions C-05-02, C-13-03 and C-18-03) are based on maintaining the fishing effort below the 2002-2004 levels. The effort levels in eastern Pacific Ocean for 2018-2020 were 63% and 65% of those in 2002-2004, for vessel-days and number of vessels respectively, and are showing a declining trend in the last 10 years (Figure F-2).
Figure F-2: Effort in vessel-days and number of vessels for the North Pacific albacore tuna in the eastern Pacific Ocean.

The Working Group finished a Management Strategy Evaluation (MSE) for the North Pacific albacore stock and presented the results to the stakeholders in regional workshops. The first round of the MSE was concluded and reported during the 4th ISC ALB MSE workshop in March 2019 (ISC/19/ANNEX/06). Several operating models were developed, and equal weights were assumed for all alternative operating models when evaluating the harvest control rules, HCRs. Additional work was conducted in a second round of the MSE, when mixed control rules were tested (under mixed control, longline fleets are subject to a total allowable catch, TAC, whereas surface fleets are managed with a total allowable effort, TAE) and the effect of a “ghost fleet” (a fleet with undeclared catch) was evaluated. The results of the MSE were included in a recorded presentation for the SAC-12 meeting (SAC-12 INF-C, SAC-12-INF-C presentation) and were presented at the 2021 ISC plenary (ISC).

The following management objectives for the North Pacific albacore tuna were developed in the context of the MSE process and were adopted by the IATTC in 2020 (IATTC-95).

Overarching objective: maintain the viability and sustainability of the current NPALB stock and fisheries.

1. Maintain spawning biomass above the limit reference point

2. Maintain total biomass, with reasonable variability, around the historical average depletion of total biomass

3. Maintain harvest ratios by fishery (fraction of fishing impact with respect to SSB) at historical average

4. Maintain catches by fishery above average historical catch

5. If a change in total allowable effort and/or total allowable catch occurs, the rate of change should be relatively gradual

6. Maintain F at the target value with reasonable variability

The MSE process included input from managers and stakeholders and extensive simulation work. Candidate harvest control rules (HCRs) were suggested by managers and stakeholders. All HRCs are based on inputs from the assessment model and included target, limit, and threshold reference points, all based on dynamic quantities that take into consideration temporal variation in selectivity and recruitment. Based on the estimated status of the stock, the HRC specifies whether a management action to control fishing is needed. The management actions tested were mixed control or Total Allowable Catch (TAC). Under mixed control, surface fisheries (EPO troll and pole-and-line, and Japanese pole-and-line) are managed via effort control, while longline fisheries are managed via a TAC.

Sixteen HCRs were tested under several scenarios ranging from low to high productivity of the stock, of which four (which were deemed a good representation of the plausible mechanisms operating in the population) were retained to present the results. The performance of the HCRs under those scenarios was measured through indicators consisting of quantitative representations of the overall management objectives adopted for the fishery.

The main results of the MSE were (ISC/21/ANNEX/11):

1. All HCRs were able to maintain the stock above the level considered undesirable (i.e., above WCPFC’s limit reference point (20% SSB0), the IATTC limit reference point used for tropical tunas (7.7% SSB0)), with more than 92% probability (for mixed controls) or 86% probability (for TAC control), even in the event of undeclared catches from an unknown fleet.

2. For all HCRs, mixed control maintained higher and less variable stock biomass than TAC control as the catches of surface fleets under effort control responded quickly to changes in biomass and their catch levels were not impacted by assessment errors in biomass estimates. Mixed control performs better under all indicators in the scenario of low productivity than TAC controls.

3. HCRs with the LRP and SSBthreshold reference points closer to the SSB associated with TRP resulted in a higher frequency of management interventions (that is, HCRs with 30% SSB0 as threshold and F50%SSB as target, and HCRs 20% SSB0 as threshold and F40%SSB as target).

4. HCRs that used F40%SSB as TRP produced more variable catches (but higher median catches) than HCRs that used F50%SSB under TAC control.

In addition, the results of adding a ghost fleet showed that all HCRs succeeded in maintaining the stock at healthy levels, but the catches of the other fleets decreased to compensate for the increase in fishing mortality.

The next step in the MSE process is the adoption of a HCR by the Commission in coordination with the Western and Central Pacific Fisheries Commission taking into account the performance of the tested HCRs to fullfil the management objectives.

The staff will work with the ALBWG to complete the 2023 stock assessment of North Pacific albacore tuna.
Management unit: Yes
Inter-American Tropical Tuna Commission (IATTC). “Report on tuna fishery, stocks, and ecosystem in the Eastern Pacific Ocean in 2021. Inter-American Tropical Tuna Commission. Fishery Status Report. IATTC 2022.” Click to open,-stocks,-and-ecosystem-in-the-Eastern-Pacific-Ocean-in-2021-(1).pdf
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