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Albacore - North Atlantic
Marine Resource  Fact Sheet
Stock status report 2016
Albacore - North Atlantic
Fact Sheet Citation  
Albacore in the North Atlantic
Owned byInternational Commission for the Conservation of Atlantic Tunas (ICCAT) – More
Related observationsLocate in inventorydisplay tree map
 
Species:
FAO Names: en - Albacore, fr - Germon, es - Atún blanco, ru - Тунец длинноперый
Geographic extent of Albacore - North Atlantic
Main Descriptors
Considered a single stock: Yes        Spatial Scale: Sub-Regional
Management unit: Yes        Reference year: 2014
 
 
Biological State and Trend
State & Trend Descriptors
PartnerFIRMS
Exploitation rateF2014/FMSY = 0.54 range (0.35-0.72)No or low fishing mortalityGreen
Abundance levelB2015/BMSY = 1.36 range (1.05-1.78)Intermediate abundance
History
 

The status of the North and South Atlantic albacore stocks is based on the most recent analyses conducted in May 2016 by means of using the available data up to 2014. Complete information on the assessment can be found in the Report of the 2016 ICCAT North and South Atlantic Albacore Stock Assessment Meeting.
Habitat and Biology
Climatic zone: Temperate.   Horizontal distribution: Oceanic.   Vertical distribution: Pelagic.  


Albacore is a temperate tuna widely distributed throughout the Atlantic Ocean and Mediterranean Sea. On the basis of the biological information available for assessment purposes, the existence of three stocks is assumed: northern and southern Atlantic stocks (separated at 5ºN) and a Mediterranean stock. However, some studies support the hypothesis that various sub populations of albacore exist in the North Atlantic and Mediterranean. Likewise, there is likely intermingling of Indian Ocean and South Atlantic immature albacore which needs further research.

Scientific studies on albacore stocks, in the North Atlantic, North Pacific and the Mediterranean, suggest that environmental variability may have a serious potential impact on albacore stocks, affecting fisheries by changing the fishing grounds, as well as productivity levels and potential MSY of the stocks. Those yet sufficiently unexplored aspects might explain recently observed changes in fisheries, such as the lack of availability of the resource in the Bay of Biscay in some years, or the apparent decline in the estimated recruitment which are demanding focussed research.

The expected life-span for albacore is around 15 years. While albacore is a temperate species, spawning in the Atlantic occurs in tropical waters. Present available knowledge on habitat, distribution, spawning areas and maturity of Atlantic albacore is based on limited studies, mostly from past decades. In the Mediterranean, there is a need to integrate different available studies so as to better characterize growth of Mediterranean albacore. Besides some additional recent studies on maturity, in general, there is poor knowledge about Mediterranean albacore biology and ecology.

More information on albacore biology and ecology is published in the ICCAT Manual.
Geographical Distribution
Jurisdictional distribution: Highly migratory


Albacore is a temperate tuna widely distributed throughout the Atlantic Ocean and Mediterranean Sea.
Water Area Overview
Spatial Scale: Sub-Regional

Geo References
Resource Structure
Considered a single stock: Yes


On the basis of the biological information available for assessment purposes, the existence of three stocks is assumed: northern and southern Atlantic stocks (separated at 5ºN) and Mediterranean stock (Figure 1).
Figure 1 Geographic distribution of albacore accumulated catch by major gears and decade (1960-2014). Baitboat and troll catches prior to the 1990s, these catches were assigned to only one 5ºx5º stratum in the Bay of Biscay. Plots are scaled to the maximum catch observed from 1960 to 2014 (last decade only covers 5 years).
Exploitation
 

Description of fisheries



North Atlantic

The northern stock is exploited by surface fisheries targeting mainly immature and sub-adult fish (50 cm to 90 cm FL) and longline fisheries targeting immature and adult albacore (60 cm to 130 cm FL). The main surface fisheries are carried out by EU fleets (Ireland, France, Portugal and Spain) in the Bay of Biscay, in the adjacent waters of the northeast Atlantic and in the vicinity of the Canary and Azores Islands in summer and autumn. The main longline fleet is the Chinese Taipei fleet which operates in the central and western North Atlantic year round. However, Chinese Taipei fishing effort decreased in late 1980s due to a shift towards targeting on tropical tuna, and then continued at this lower level to the present. Over time, the relative contribution of different fleets to the total catch of North Atlantic albacore has changed, which resulted in differential effects on the age structure of the stock. Since the 1980s, a significant reduction of the effective albacore area fished was observed for both longline and surface fisheries.



Total reported landings, steadily increased since 1930 to peak above 60,000t in the early 1960s, declining afterwards, largely due to a reduction of fishing effort by the traditional surface (troll and baitboat) and longline fisheries (Table 1; Figure 2). Some stabilization was observed in the 1990s, mainly due to increased effort and catch by new surface fisheries (driftnet and mid-water pair pelagic trawl), with a maximum catch in 2006 at 36,989 t and, since then, a decreasing trend of catch is observed in the North Atlantic. The total catch in 2015 was 25,450 t, and the average catch in the last five years has remained about 24,000 t, above the historical minimum of around 15,000 t recorded in 2009. During these years, the surface fisheries contributed to approximately 80% of the total catch (Table 1). The reported catch for 2015, when compared with the average of the last five years, was similar for EU Ireland, increased (around 20%) for EU-Spain, and decreased (around 10%) for EU-France.

Longline catch contributed to approximately 20% of the total catch during the last five years. During the last decades, both Chinese Taipei and Japan have reduced their fishing effort directed to albacore. In the case of Japan, albacore was taken mainly as by-catch. The catch reported in 2015 for Japan was below the last 5 year average, while for Chinese Taipei it was above.

The trend in mean weight for northern albacore remained stable between 1975 and 2014, ranging between 7 and 11 kg. The mean weight for surface fleets (baitboat and troll) showed a stable trend with an average of 7 kg (range of 4 to 10 kg), and for longline fleets it showed no clear trend with an average of 19 kg, but some important fluctuations between 15 and 26 kg since the 1990 (Figure 3).
Figure 2 Total albacore catches reported to ICCAT (Task I) by gear for the northern Atlantic stock including TAC.
Figure 3 Mean weight trend by surface and longline fisheries in Nouth Atlantic stock.
Assessment
 
Assessment Model

In the 2013 stock assessment, several model formulations (Multifan-CL, Stock Synthesis, VPA and ASPIC) with varying degrees of complexity were used. This allowed the modeling of different scenarios that represented different hypotheses, and the characterization of the uncertainty around the stock status. The results showed that although the range of estimated management benchmarks was relatively wide, most models were in agreement that the stock was overfished, and no model indicated that the stock was undergoing overfishing. These models from all the various platforms showed a general drop in stock biomass from 1930 to about 1990 and an increasing trend in biomass starting in around 2000. Likewise, most models within all configurations showed a peak in fishing mortality in around 1990 with a decreasing trend thereafter. The analyses conducted in 2013 involved a large amount of data preparation and scrutiny, and the Committee suggested that future assessment updates could be conducted using simpler models (e.g. production models).

Thus, in 2016 a production model was used to assess the stock status. A thorough revision of North Atlantic Task I data was conducted and catch rate analyses were improved and updated with new information for the northern albacore fisheries. Decisions on the final specifications of the base case model were guided by first principles (e.g. knowledge of the fisheries) and data exploration (e.g. correlation between indices). The results of these efforts are reflected in the following summaries of stock status that analyzed data through 2014.

Four longline and one baitboat CPUE indices were selected to be used in a production model framework. The Committee lacked a basis to decide which CPUE series could best represent abundance. In fact, it was assumed that different CPUE series reflected local abundance available to different fleets operating in different areas, and that overall they represented the global population trend. On this basis, the Committee agreed to use all the 5 CPUEs jointly in the base case scenario, and to weight them equally. Despite their variable pattern, these indices showed an overall increasing trend towards the end of the time series (Figure 4), which could be reflecting the increasing trend of the stock during this period of relatively low catch. The Chinese Taipei longline index showed the steepest increase during the last years of the series.

The biomass dynamic model results for the base case suggest a biomass drop between 1930 and the 1990s and a recovery since then, while fishing mortality decreases. Relative to MSY benchmarks, the base case scenario estimates that the stock remained slightly overfished with B below BMSY during the 1980s and 1990s, but now has recovered to levels well above BMSY (Figure 5). Peak relative fishing mortality levels in the order of 1.4 were observed in the early 1980s but overfishing stopped in the 1990s, current F2014/FMSY ratio being 0.54. The uncertainty around the current stock status has a clear shape determined by the strong correlation between parameters estimated by the production model. The probability of the stock currently being in the green area of the Kobe plot (not overfished and not undergoing overfishing, F<FMSY and B>BMSY) is 96.8% while the probability of being in the yellow area (overfished, B<BMSY) is 3.2%. The probability of being in the red area (overfished and undergoing overfishing, F>FMSY and B<BMSY) is 0% (Figure 6).



Sensitivity analyses revealed that recent stock status indicators are sensitive to different modelling assumptions as well as the choice of the CPUE series. When a logistic function was assumed in the biomass dynamic model lower values of B/BMSY were predicted over the whole time series, while excluding the Chinese-Taipei longline CPUE resulted in much larger values of B/BMSY in the recent period. Other sensitivity analyses did not show strong deviations from the base case. However, although the recent status varied across scenarios, all predicted the stock to be in the green quadrant. Finally, the Committee noted that the B/BMSY trajectory showed a strong retrospective pattern that might imply that the current stock status is overestimated, although all the retrospective trajectories showed an improvement in stock status in the most recent period.

In summary, the available information indicates that the stock has improved and is most likely in the green area of the Kobe plot, although the exact condition of the stock is not well determined.
Figure 4 North Atlantic Albacore. Standardized catch rate indices used in the 2016 stock assessment from the surface fisheries, which take mostly juvenile fish, and from the longline fisheries, which take mostly adult fish.
Figure 5 North Atlantic Albacore. Joint trajectories of B/BMSY and F/FMSY over time (1930-2014) and current stock status according to the Base Case biomass dynamic model. Dots represent the uncertainty on the estimated 2014 stock status..
Figure 6 North Atlantic albacore probability of being overfished and overfishing (red, 0%), of being neither overfished nor overfishing (green, 96.8%), and of being overfished (yellow, 3.2%), according to the Base Case.
Overall Assessment Results
Projection

Outlook

Following previous practice during the 2013 assessment and considering Rec. 13-05 and Rec. 15-04 that request to further develop a Limit Reference Point (LRP) and Harvest Control Rules (HCR) for north Atlantic albacore, the estimated population was projected under both alternative TACs and HCRs, as combinations of target fishing mortality (FTAR), threshold biomass (BTHRESH) and an interim biomass limit reference point (BLIM) of 0.4 BMSY that should be further tested (Figure 7). The projections assuming catch levels similar to those observed during the last five years (approximately 24,000 t) or the current TAC (28,000 t) suggest that biomass would continue to increase and are likely sustainable. The Committee noted that the new projections suggest higher sustainable catch levels compared to most of the previous assessments. However, the Committee has little trust in the absolute biomass estimate and the projections did not fully account for many other sources of uncertainty (i.e. model structure and assumptions) that need further evaluation. Thus, the Committee did not have confidence in the projections and the Kobe 2 Strategy Matrix and decided not to provide or use these analyses for advice.




Figure 7 Generic form of the HCR recommended by SCRS (SCRS, 2011). Blim is the limit biomass reference point, BThreshold is the biomass point at which increasingly strict management actions should be taken as biomass decreases and Ftarget, the target fishing mortality rate to be applied to achieve the management objective [Rec. 15-04].
Management
Management unit: Yes


Effects of current regulations

In 2013, the Commission established a TAC for 2014-2016 of 28,000 t [Rec. 13-05], but included several provisions that allow the catch to exceed this level. The Committee noted that, since the establishment of the TAC in the year 2001, catch remained substantially below the TAC in all but two years (Figure 2). This might have accelerated rebuilding over the last decade, but the Committee did not test the effect of perfect implementation of the TAC.

Furthermore, Rec. [98-08] that limits fishing capacity to the average of 1993-1995, remains in force. The effect of this recommendation has not been evaluated but a general decrease of fishing mortality is observed since its implementation.
Management Advice

Recommendation 15-04 sets the objective of maintaining the stock in the green area of the Kobe plot with a 60% probability while maximizing long-term yield, and, if B<BMSY, to recover it by 2020 at the latest, while maximizing average catch and minimizing inter-annual fluctuations in TAC levels. The simulations conducted so far suggest that HCRs with combinations of F targets below FMSY together with BTHRESHOLD values below BMSY allow for reasonably good compromises between sustainability targets and fishery profit and stability, and may have the potential to meet the management objectives as outlined in Rec. [15-04]. However, although some of these Harvest Control Rules have been tested in an MSE framework against a broad range of sometimes conflicting objectives, further work is needed to fully test them against a fuller range of uncertainties.

The Committee has noted that the relative abundance of north Atlantic albacore has continued to increase over the last decades and is likely somewhere in the green area of the Kobe plot. However, without additional information, the magnitude of the recovery is not well determined and remains sensitive to many different assumptions. This undermines the ability of the Committee to reliably quantify the effects of future TAC or HCR scenarios on the status of the stock, until more sources of uncertainty and the robustness of the advice are evaluated in the future through MSE and/or benchmark stock assessment after accumulating sufficient new information. The projections assuming catch levels similar to those observed during the last five years (approximately 24,000 t) or the current TAC (28,000 t) suggest that biomass would continue to increase and are likely sustainable. Based on the analyses conducted in 2016 as well as in 2013, the Committee believes that the current TAC would maintain the long-term objectives of the Commission as specified in Rec. 15-04. Given the uncertainty around the current stock status and the projections, the Committee is unable to advice on risks associated with an increase in the TAC. Therefore, the Committee does not recommend an increase of the TAC. Further, the Committee reminds the Commission that our ability to monitor changes in stock abundance is currently limited due to incomplete fishery dependent information. Thus, it is desirable to pursue alternative fishery independent tools to provide improved bases for monitoring stock condition.



NORTH ATLANTIC ALBACORE SUMMARY
Maximum Sustainable Yield 37,082 t (35,396-42,364)1
Current (2016) TAC 28,000 t
Current (2015) Yield 25,450 t
Yield in last year of assessment (2014) 26,651 t
BMSY 407,567 t (366,309-463,685)1
FMSY 0.097 (0.079-0.109)1
B2015/BMSY1
B2015/Blim2
1.36(1.05-1.78)
3.4
F2014/FMSY 0.54 (0.35-0.72)1
Stock Status Overfished: NO
Overfishing: NO
Management measures in effect:

[Rec. 98-08]: Limit number of vessels to 1993-1995 average.

[Rec. 13-05]: TAC of 28,000 t

for 2014-2016.

[Rec. 15-04]: Management objective is to keep the stock in (or rebuild it to) the green area of the Kobe plot with 60% probability, while maximizing catch and reducing variability of TAC.


1 Median and 80% CI for the base case.
2 The proposed interim BLIM is 0.4*BMSY.
Source of information
 
Standing Committee on Research and Statistics (SCRS). “Albacore, Executive Summary.” Madrid, Spain October 3 - 7 2016. ICCAT Click to openhttp://www.iccat.int/Documents/Meetings/Docs/2016_SCRS_ENG.pdf
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