Fisheries and Resources Monitoring System

EspañolFrançais
Swordfish - South Atlantic
Marine Resource  Fact Sheet
Stock status report 2013
Swordfish - South Atlantic
Fact Sheet Citation  
Southern Atlantic swordfish
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: Regional
Management unit: Yes        Reference year: 2011
 
 
Biological State and Trend
State & Trend Descriptors
PartnerFIRMS
Exploitation rateF2011/FMSY = Unknown, but likely below 1Moderate fishing mortalityGreen
Abundance levelB2011/BMSY = Unknown, but likely aboveIntermediate abundance
History
 

The status of the South Atlantic swordfish stocks was assessed in September 2013, by means of applying statistical modelling to the available data up to 2011. Complete information on the assessment can be found in the Report of the 2013 ICCAT Swordfish Stock Assessment Meeting (SCRS/2013/019). Other information relevant to Atlantic swordfish is presented in the Report of the Sub-Committee on Statistics, included as Appendix 7 to this SCRS Report, and recommendations pertinent to Atlantic swordfish are presented in Item 17.


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. This stock separation is supported by recent genetic analyses. However, the precise boundaries between stocks are uncertain. 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 recent 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 180cm. However, the most recent information indicates a smaller length and age at maturity.

New length-weight relationships were proposed for the North Atlantic, but these will be considered interim solutions until further analysis is conducted with new and more recent data..

The Committee reviewed document SCRS/2013/151 which presented the horizontal tracking of 21 swordfish tagged with pop-up satellite tags in the central and eastern North Atlantic. The analysis of the horizontal movements evidenced 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 fully confirm the previous knowledge that was available from fishery data: deep longline catch swordfish during the day time as a by-catch, while shallow longliners target swordfish at night in very shallow waters.

The Committee also reviewed document SCRS/2013/161 that demonstrated a significant relation between temperate fishery CPUE residuals and the size of the Atlantic Warm Pool (AWP), which was shown to be highly correlated with the Atlantic Multidecadal Oscillation (AMO). This supported the information provided in Sunby et al. (2013), that described the occurrence of swordfish (1.5 to 2.65 m) off the Norwegian coast (58 to 70ºN latitude) from 1967 to 2011. The effect of AWP was thought to be responsible for conflicting signals in the CPUEs from the northern temperate and tropical regions. Further analysis and hypothesis testing was recommended to determine if this relationship was due to a swordfish temperature preference, a change in prey distribution, or perhaps both.


Geographical Distribution
Jurisdictional distribution: Highly migratory


Swordfish are distributed widely in the Atlantic Ocean and Mediterranean Sea, in coastal and offshore areas, mostly ranging from 45ºN to 45ºS,and range from Canada to Argentina on the western side, and from Norway to South Africa on the eastern side (Figure 1).
Water Area Overview
Spatial Scale: Regional

Geo References
Resource Structure
Considered a single stock: Yes


A Workshop on swordfish stock structure took place in Crete in early 2006, in response to Resolution by ICCAT on the clarification of the stock structure and boundaries between the swordfish stocks in the Atlantic [Res. 99-03], at which 13 scientific documents on swordfish biology were presented. The results of the research presented gave general support to the stock structure currently assumed for Atlantic Swordfish (Mediterranean and North and South Atlantic stocks). The Workshop agreed that the precise delimitation between these three stocks cannot be improved upon without intensified collaborative and multi-disciplinary research. Similarly, the classification of swordfish caught near the boundaries to their stock of origin is subject to uncertainty and cannot be made accurately without intensified collaborative and multi-disciplinary research taking into account fine-scale (e.g., 1º squares) and quarterly sampling strata. The Workshop also noted that while there was some mixing between Atlantic and Mediterranean stocks near the Straits of Gibraltar, there was strong evidence that the Mediterranean is genetically distinct from the Atlantic, Pacific and Indian Ocean stocks.

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. However, the precise boundaries between stocks are uncertain, and mixing is expected to be highest at the boundary in the tropical zone.
Figure 1 Geographic distribution of swordfish cumulative catch (t) by gear, in the Convention area, shown on a decadal scale. The maps (a-f) are scaled to the maximum catch observed during 1950-2009. Map g is scaled to the maximum catch observed from 2010-2011.
Exploitation
 

Description of fisheries

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, EC-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, EC-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 EC-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 historical trend of swordfish South Atlantic catch (landings plus dead discards) (Table 1 and Figure 2) 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 2,300 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 (20,236 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 partly due to a shift to other oceans and target species. In 2012, the 10,180 t reported catches were about 54 % lower than the 1995 reported level. The SCRS received reports from Brazil and Uruguay that those CPCs 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.

Six data sets of relative abundance indices (Brazil, Japan, Spain, Uruguay, South Africa and Chinese Taipei) were made available to the Committee. These CPUE indices were standardized using various analytical approaches. The standardized CPUE series presented show different trends and high variability which indicates that at least some are not depicting trends in the abundances of the stock. The available indices are illustrated in Figure 3. Two combined indices were produced (Figure 4), one excluding Brazil and the other excluding both Brazil and Chinese Taipei data series.

Many of the indices of abundance were affected by changes in gear technology and management that could not be accounted for in the CPUE standardization, and therefore had to be split. Splitting the indices reduces the abundance signal and, to the degree possible continuity of the indices can be maintained, it will increase the reliability of the assessment results.

The trends in mean fish weight taken in the North and South Atlantic fisheries is shown in Figure 5.

Discards

Since 1991, several fleets have reported dead discards (see Table 1). The volume of Atlantic-wide reported discards since then has ranged from 215 t to 1,139 t per year. Reported annual dead discards (in tonnes) have been declining in recent years.


Figure 2. South Atlantic swordfish catches and TAC (t).
Figure 3. Standardized CPUEs series provided by CPCs for the for South Atlantic swordfish, The CPUE series were scaled to their mean for the overlapping years.
Figure 4. South Atlantic swordfish combined standardized CPUE indices.
Figure 5. Trends in mean weight (kg) for the entire North and South Atlantic swordfish stocks. The information for 2010 is being reviewed and should be considered preliminary.
Assessment
 
Assessment Model
South Atlantic
Results

In 2009, evaluation of the status of the South Atlantic swordfish stock was assessed using a ‘Catch only’ model. During the 2013 stock assessment two platforms were used to provide stock status advice for the South Atlantic swordfish stock (i.e. ASPIC and BSP2).

The results of both models indicated that there was a conflicting signal for several of the indices used and substantial conflict between the landings history and the indices. Consequently the Committee had low confidence in the estimation of the absolute productivity level of the stock or on MSY-related benchmarks. Both models had similar difficulties estimating these quantities but both offered useful status advice. Consequently each platform provided a reference model on which the stock status was based.

Both models had similar trajectories of fishing mortality and biomass (Figure 6 and 7) but differed in their absolute levels and their status relative to benchmarks (Figure 8). Hence the two models differ in their view of current stock status, with ASPIC estimating the stock to be overfished (B2011/BMSY =0.98) but not undergoing overfishing (F2011/FMSY =0.84), and BSP, neither overfished (B2011/BMSY =1.38), nor overfishing (F2011/FMSY =0.47). Though, it should be noted that there is considerable uncertainty around any of these point estimates.

The groups choose to base stock status determination on a combination of model output and ancillary information, of which two pieces of information are informative. First, total removals (1950-2011) for the South Atlantic stock have been only 73% of the total removals for the North Atlantic stock for the same time period. Second the mean weight for the South (Figure 9) is larger than for the North. Assuming similar production dynamics, both indicators would suggest a lower exploitation rate for the South stock than for the North. Hence, while the Committee does not believe it can estimate the absolute productivity of the stock without improved scientific information, the Committee believes that the stock is not overfished.


Figure 6: South Atlantic swordfish B/BMSY and F/FMSY estimated by ASPIC, dashed lines are the lower and upper 80 percentiles of the bootstrap runs.
Figure 7: South Atlantic swordfish B/BMSY and F/FMSY estimated by BSP2. Posterior median and 90% intervals are plotted.
Figure 8: Kobe plots for the BSP reference model for southern Atlantic swordfish. The diamonds show the level of uncertainty and the line represents the trajectories of the status of the stocks of B/BMSY and F/FMSY, 1950-2011.
Figure 9: Kobe plots for the ASPIC reference model for southern Atlantic swordfish. The diamonds show the level of uncertainty and the line represents the trajectories of the status of the stocks of B/BMSY and F/FMSY, 1950-2011.
Overall Assessment Results
Projection

Outlook

South Atlantic

The Committee considered that the ASPIC and BSP estimated benchmarks were unreliable due to the conflicting signal between the catch data and the CPUE time series available to the Committee. Hence, it is unknown whether it is possible to obtain substantially higher yields from the stock as BSP suggests or whether the stock is fully exploited as suggested by ASPIC. Until improved scientific information is available in the form of more consistent indices, tagging studies to estimate fishing mortality or abundance or other improved information, this uncertainty may remain.


Management
Management unit: Yes


Effects of current regulations

In 2006, 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 South Atlantic, the most recent recommendation can be found in Rec. 09-03, which establishes a three year management plan for that stock.

Catch limits
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 13,482 t, and did not exceed the TAC in any year. In 2010, the TAC was reduced to 15,000 t, compared with 2012 catch of 10,180 t. Reports for 2012 are considered provisional and subject to change.

Minimum size limits
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.

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.

For the 2006-2008 period, the estimate of the percentage of swordfish reported landed (throughout the Atlantic) less than 125 cm LJFL was about 24% (in number) overall for all nations fishing in the Atlantic (28% in the northern stock and 20% in southern stock). If this calculation is made using reported landings plus estimated dead discards, then the percentage less than 125 cm LJFL would be of the same order given the relatively small amount of discards reported. These estimates are based on the overall catch at size, which have high levels of substitutions for a significant portion of the total catch.

Other implications
The Committee is concerned that in some cases national regulations have resulted in the unreported discarding of swordfish caught in the North stock and, to a certain extent, could have influenced similar behavior of the fleet that fishes the South Atlantic swordfish stock. The Committee considers that these regulations may have had a detrimental effect on the availability and consistency of scientific data on catches, sizes and CPUE indices of some of the Atlantic fleets. The Committee expressed its serious concern over this limitation on data for future assessments.


Management Advice



South Atlantic

Considering the unquantified uncertainties and the lack of signal in the data for the southern Atlantic swordfish stock, and until sufficiently more research has been conducted to reduce the high uncertainty in stock status, the Committee did not have sufficient confidence in the assessment results to change the previous recommendation to limit catches to no more than 15,000 t.



SOUTH ATLANTIC SWORDFISH SUMMARY

 

 

 

 

Maximum Sustainable Yield

 

Unknown

 

Current (2012) TAC

 

15,000 t

 

Current (2012) Yield1

 

10,180 t

 

Yield in last year of assessment (2011)

 

11,055 t2

 

BMSY

 

Unknown

 

FMSY

 

Unknown

 

Relative Biomass (B2011/SSBMSY1 )

 

Unknown, but likely above 1 3

 

Relative Fishing Mortality (F2011/FMSY1)

 

Unknown, but likely below 1 3

 

Stock Status

 

Overfished: NO3

 

 

 

Overfishing: NO

 

Management measures in effect:

 

Country-specific TACs [Rec. 12-01]
125/119cm LJFL minimum size:

 

1 Provisional and subject to revision.
2 As of 5 September 2013.
3 This determination is based on the models and the ancillary information (e.g. catch trends, mean weight trends).
Source of information
 
Report of the Standing Committee on research and Statistics (SCRS) . “Atlantic Swordfish, executive summaries.” Madrid, Spain September 30 to October 4, 2013. Click to openhttp://www.iccat.int/Documents/BienRep/REP_EN_12-13_II_2.pdf
powered by FIGIS  © FAO, 2019
Powered by FIGIS
crawl