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Swordfish - South Atlantic
Marine Resource  Fact Sheet
Stock status report 2017
Swordfish - South Atlantic
Fact Sheet Citation  
Swordfish in the South Atlantic
Owned byInternational Commission for the Conservation of Atlantic Tunas (ICCAT) – More
Related observationsLocate in inventorydisplay tree map
 
Species:
FAO Names: en - Swordfish, fr - Espadon, es - Pez espada, ru - Меч-рыба
Geographic extent of Swordfish - South Atlantic
Main Descriptors
Considered a single stock: Yes        Spatial Scale: Sub-Regional
Management unit: Yes        Reference year: 2015
 
 
Biological State and Trend
State & Trend Descriptors
PartnerFIRMS
Exploitation rateFcur/FMSY = 0.98 range (0.70-1.36)Moderate fishing mortalityRed
Abundance levelBcur/BMSY = 0.72 range (0.53-1.01)Low abundance
History
 

The status of the South Atlantic swordfish stocks is based on the most recent analyses conducted in July 2017 by means of applying statistical modelling to the available data up to 2015. Complete information on the assessment can be found in the Report of the 2017 ICCAT Atlantic Swordfish Stock Assessment Session.
Habitat and Biology
Climatic zone: Temperate.   Horizontal distribution: Oceanic.   Vertical distribution: Pelagic.  


Swordfish (Xiphias gladius) are members of the family Xiphiidae and are in the suborder Scombroidei. They can reach a maximum weight in excess of 500 kg. They are distributed widely in the Atlantic Ocean and Mediterranean Sea. In the ICCAT Convention area, the management units of swordfish for assessment purposes are a separate Mediterranean group, and North and South Atlantic groups separated at 5°N. New genetic information was reviewed that indicated that the existing stock boundaries should be refined for the Atlantic and Mediterranean stocks. Swordfish feed on a wide variety of prey including groundfish, pelagic fish, deep-water fish, and invertebrates. They are believed to feed throughout the water column, and from electronic tagging studies, undertake extensive diel vertical migrations.

Swordfish mostly spawn in the western warm tropical and subtropical waters throughout the year, although seasonality has been reported in some of these areas. They are found in the colder temperate waters during summer and fall months. Young swordfish grow very rapidly, reaching about 140 cm LJFL (lower-jaw fork length) by age three, but grow slowly thereafter. Females grow faster than males and reach a larger maximum size. Tagging studies have shown that some swordfish can live up to 15 years. Swordfish are difficult to age, but about 50% of females were considered to be mature by age five, at a length of about 180 cm. However, the most recent information indicates a smaller length and age at maturity.

The analysis of the horizontal movements evidences seasonal patterns, with fish generally moving south by winter and returning to the temperate foraging grounds in spring. Broader areas of mixing between some eastern and western areas were also suggested. These new results obtained by pop-up satellite tags also fully confirm the previous knowledge that was available from fishery data: deep longline settings catch swordfish during the day-time as a by-catch, while shallow setting longliners target swordfish at night closer to the surface.

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


Swordfish is a temperate tuna widely distributed throughout the Atlantic Ocean and Mediterranean Sea, in coastal and offshore areas, mostly ranging from 50°N to 45°S.
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 swordfish cumulative catch (t) by gear, in the Convention area, shown on a decadal scale. The maps are scaled to the maximum catch observed during 1960-2016 (the last decade only covers 7 years).
Exploitation
 

Description of fisheries

South Atlantic

Due to the broad geographical distribution of Atlantic swordfish (Figure 1) in coastal and off-shore areas (mostly ranging from 50ºN to 45ºS), this species is available to a large number of fishing countries. Directed longline fisheries from Canada, EU-Spain, and the United States have operated since the late 1950s or early 1960s, and harpoon fisheries have existed at least since the late 1800s. Other directed swordfish fisheries include fleets from Brazil, Morocco, Namibia, EU-Portugal, South Africa, Uruguay, and Venezuela. The primary by-catch or opportunistic fisheries that take swordfish are tuna fleets from Chinese Taipei, Japan, Korea and EU-France. The tuna longline fishery started in 1956 and has operated throughout the Atlantic since then, with substantial catches of swordfish that are produced as a by-catch of tuna fisheries. The largest proportion of the Atlantic catches is made using surface-drifting longline. However, many additional gears are used, including traditional gillnets off the coast of western Africa. The trends in mean fish weight taken in the North and South Atlantic fisheries are shown in Figure 3.

The historical trend of catch (landings plus dead discards) can be divided in two periods: before and after 1980. The first one is characterized by relatively low catches, generally less than 5,000 t (with an average value of 1,700 t). After 1980, landings increased continuously up to a peak of 21,930 t in 1995, levels that are comparable to the peak of North Atlantic harvest (20,238 t in 1987). This increase of landings was, in part, due to progressive shifts of fishing effort to the South Atlantic, primarily from the North Atlantic, as well as other waters. Expansion of fishing activities by southern coastal countries, such as Brazil and Uruguay, also contributed to this increase in catches. The reduction in catch following the peak in 1995 resulted from regulations and was partly due to a shift to other oceans and target species. In 2017, the 10,512 t of reported catch was about 52% lower than the 1995 reported level (Table 1 and Figure 2). The SCRS received reports from Brazil and Uruguay that they have reduced their fishing effort directed towards swordfish in recent years. Uruguay recently received increased albacore quotas that may allow increased effort for swordfish in the near future.

Available catch per unit effort (CPUE) series for the South Atlantic swordfish were evaluated by the Committee and certain indices were identified as suitable for use in assessment models (Brazil, EU-Spain, Japan, South Africa, Uruguay). The available indices are illustrated in Figure 4.


Figure 2: Total swordfish catches reported to ICCAT (Task I) for the southern Atlantic stock including TAC.


Figure 3: Trends in mean weight (kg) for the North and South Atlantic swordfish stocks.
Assessment
 
Assessment Model

In 2017, evaluation of the status of the South Atlantic swordfish stock was assessed using two Bayesian biomass dynamics production models with process error (BSP2 and JABBA - Just Another Bayesian Biomass Assessment). Stock status and projections were determined from JABBA, while BSP2 was used mainly to provide several sensitivity analyses.

The results from both models for the South Atlantic swordfish were consistent. The final base case BSP2 model estimated that current biomass (B2015) was lower than BMSY (median = 0.64, 95% CIs = 0.43-1.00) and current F2015 was higher than FMSY (median = 1.15; 95% CIs = 0.61-1.82) (Figure 5). The final base case JABBA model estimated that B2015 was also below BMSY (median = 0.72, 95% CIs = 0.53-1.01) while F2015 was very close to FMSY (median = 0.98, 95% CIs = 0.70-1.36) (Figure 6).

Both models agreed that the southern swordfish stock biomass is overfished, and that overfishing is either occurring or current F is very close to FMSY. The Committee agreed that either one of the models (BSP2 or JABBA) could be used for management advice but given that both are very similar in structure and use of information only one should be used. Given that JABBA is written in open-source software with more capabilities for future evolutions, the Committee agreed that the management advice, including stock status and projections, should be based on JABBA model (Figure 7).


Figure 4: Standardized CPUEs series provided by CPCs for South Atlantic swordfish. The CPUE series were scaled to their mean for comparison purposes.


Figure 5: South Atlantic swordfish biomass and fishing mortality rates relative to MSY levels, from the BSP2 base case model. Dashed lines represent lower and upper 90% CIs.


Figure 6: South Atlantic swordfish biomass and fishing mortality rates relative to MSY levels, from the JABBA base case model. Grey areas represent lower and upper 95% CIs.


Figure 7: Kobe plots for the JABBA reference base case model for southern Atlantic swordfish. The solid blue circle is the estimated median point with the respective uncertainties in the terminal year (2015). The pie chart below represents the probabilities of stock being in the different color quadrants (red 47%, yellow 51%, green 2%).
Overall Assessment Results
Projection

Outlook

Projections were conducted for the final base case JABBA model under constant TAC scenarios of 4 to 16 thousand tons. Projections used reported catch as of July 2017 for 2016. For those CPCs whose reported catch was not yet available, it was assumed that their catch was the average of the last three years (2013-2015), giving a total catch of 10,002 t.

Although the median MSY was around 14,600 t, the 2015 biomass depletion level at B/BMSY = 0.72 would require catches be reduced to a level at or below 14,000 tons to rebuild the population to biomass levels that can produce MSY by the end of the projection period in 2028 (Figure 8).


Figure 8: Median trends of relative biomass (B/BMSY) for the projected South Atlantic swordfish stock based on the JABBA base case models under different constant catch scenarios (thousand tons).
Management
Management unit: Yes


Effects of current regulations

In 2017, the Committee provided information on the effectiveness of existing minimum size regulations. New catch regulations were implemented on the basis of Rec. 06-02, which entered into effect in 2007 (Rec. 08-02 extended the provisions of Rec. 06-02 to include 2009). Rec. 09-02 came into effect in 2010 and extended most of the provisions of Rec. 06-02 for one year only. Rec. 10-02 came into effect in 2011, and again extended those provisions for one year only, but with a slight reduction in total allowable catch (TAC). For the North and South Atlantic swordfish the most recent recommendations can be found in Rec. 17-02 and 17-03.

The total allowable catch in the South Atlantic for the years 2007 through 2009 was 17,000 t. The reported catch during that period averaged 13,674 t, and did not exceed the TAC in any year. In 2010, the TAC was reduced to 15,000 t and in 2018 it was reduced to 14,000. The reported catch since 2010 averaged 10, 837 t and did not exceed the TAC in any year.

There are two minimum size options that are applied to the entire Atlantic: 125 cm LJFL with a 15% tolerance, or 119 cm LJFL with zero tolerance and evaluation of the discards. Since the implementation of the minimum landing sizes in 2000, the estimate of percentage of swordfish less than 125 cm LJFL reported landed (in number) has been generally stable in the South Atlantic, the estimate was 18% in 2000, had a maximum of 19% in 2006 and decreased to 13% in 2015. The Committee notes that these estimations have high levels of substitutions for a significant portion of the total catch and are highly unreliable and biased unless CPCs fully report size samples from the entire catch.

The Committee also noted high values of hooking mortality (ranging between 78-88%) on small swordfish (<125 cm LJFL) on some surface longline fisheries targeting swordfish, with the post-release mortality of specimens discarded alive unknown. Recommend and evaluating other strategies to protect juvenile swordfish will need completeness of datasets on fishing effort and size data over the entire Atlantic and should take into account the effects on other species. In view of the Commission objective to protect small swordfish, the Committee therefore recommends that future work should be carried out to determine more precisely the spatial distribution and magnitude of fishing effort, size and sex distribution of undersized swordfish in the Atlantic, using high resolution observer data.


Management Advice

Tables 2, 3 and 4 show, respectively, the probabilities of maintaining the stock in the green quadrant of the Kobe plot, maintaining B>BMSY and maintaining F<FMSY, over a range of TAC options for South Atlantic swordfish over a period of 10 years. The current TAC of 15,000 t has a 26% probability of rebuilding the South Atlantic swordfish stock to within MSY reference levels by 2028, whereas a TAC of 14,000 t would have a 50% probability of rebuilding the stock.

The Committee also recognizes that the above advice does not account for removals associated with the actual mortality of unreported dead and live discards, quota carryovers (30% in the South Atlantic) nor quota transfers across the North and South stock management boundaries. The Committee emphasizes the importance of this uncertainty particularly given that the current estimated biomass is lower than BMSY.


SOUTH ATLANTIC SWORDFISH SUMMARY

Maximum Sustainable Yield

14,570 (12,962-16,123)1

Current (2017) TAC

14,000 t

Current (2017) Yield2

10,512 t

Yield in last year used in assessment (2015)3

10,227 t

BMSY

52,465 t (35,119-80,951)1

SSBMSY

Unknown

FMSY

0.28 (0.17-0.44)1

Relative Biomass (B2015/BMSY)

0.72 (0.53 - 1.01)4

Relative Fishing Mortality (F2015/FMSY)

0.98 (0.70 - 1.36)4

Stock Status (2015)

Overfished: YES
  Overfishing: NO
Management Measures in Effect

Country-specific TACs

[Rec. 17-03];

125/119 cm LJFL minimum size


1 From base case JABBA model with 95% CIs.

2 Provisional and subject to revision.

3 Based on catch data available in July 2017 for the stock assessment session.

4 Median and 95% quantiles from base case JABBA model.


Table 2: Estimated probabilities (%) that both the fishing mortality is below FMSY and biomass is above BMSY for South Atlantic swordfish from JABBA final base model.


Table 3: Estimated probabilities (%) that biomass is above BMSY for South Atlantic swordfish from JABBA final base model.


Table 4: Estimated probabilities (%) that fishing mortality is below FMSY for South Atlantic swordfish from JABBA final base model.
Source of information
 
Report for biennial period, 2016-17 PART I (2017) – Vol. 2 SCRS. Madrid, Spain 2018. Click to openhttps://www.iccat.int/Documents/BienRep/REP_EN_16-17_II-2.pdf
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