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Xiphias gladius

Method of production - Caught at sea
Capture method - Longline
Capture area - Indian Ocean (FAO 51,57)
Stock area - Indian Ocean
Stock detail - All Areas
Certification -
Fish type - Oily fish

Sustainability rating Click for explaination of rating

This fish, caught by the methods and in the area listed above, is not the most sustainable choice of fish to eat. Click on the rating icon above to read more and on the alternatives tab below to find more sustainable fish to eat.

Sustainability overview

Swordfish has a low resilience to overfishing. The Indian Ocean stock is quite healthy with fishing biomass and fishing mortality above and below respective reference points, though recent provisional catches have been slightly above the maximum sustainable yield. Swordfish is primarily taken in either targeted longline fisheries, or those targeting tuna. Pelagic longline fisheries encounter a significant proportion of bycatch of vulnerable species including sharks, turtles and sea birds. Whilst there are mitigation measures to reduce this, widespread implementation and monitoring is deficient and maintaining current effort will likely further reduce populations of these species. Monitoring and reporting of interactions with vulnerable bycatch species needs improvement across all fleets. Poor catch reporting has also been noted for a number of countries accessing this fishery so it is important to only source from fisheries that are well regulated by their flag state.

Commercial buyers should establish what measures the flag state and fleet relating to their source is taking to improve data collection, research, monitoring and enforcement of their fisheries and specify the need to see ongoing, demonstrable improvements. Large buyers should consider supporting such improvements. MCS also advocates specifying the need for supplying vessels to register on the ISSF Proactive Vessel Register.


Swordfish is the only member of the family Xiphiidae. It is a highly migratory species, moving towards temperate or cold waters in summer to feed and returning to warmer waters to spawn. They are apex predators that feed opportunistically. Squids and fishes are major prey items. In the Atlantic, spawning takes place in spring in the southern Sargasso Sea. In the Pacific, spawning occurs during spring and summer, and in the Mediterranean between June-August. Usually solitary, it forms large schools during spawning. A fast growing fish, swordfish begin to mature at two years of age, when they are about 150 to 170 cm in length, and by age four all are mature. They can attain a maximum size of 4.5m and a weight of 650kg. Swordfish tolerate temperatures of about 5 to 27C, but their optimum range is about 18 to 22C, and larvae have been found only at temperatures exceeding 24C.

Stock information

Stock area
Indian Ocean

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Stock information
Indian Ocean stocks are managed by the Indian Ocean Tuna Commission (IOTC). Between 1950 and 1980, catches of swordfish in the Indian Ocean slowly increased as the level of coastal state and distant water fishing nation longline effort targeting tunas and sharks increased. Swordfish were not targeted by industrial longline fisheries before the early 1990s, however with the introduction of night fishing using longlines baited with squid and light sticks, catches increased post 1990. Piracy in the western Indian Ocean has significantly reduced longlining effort in the region since 2004, which has had a positive influence on the stock. The latest stock assessment was carried out in 2014 and updated in 2015. It indicates that the stock was neither overfished (Spawning Biomass, SB, at 3.10 SBmsy) nor experiencing overfishing (Fishing mortality, F, at 0.34 Fmsy). Spawning stock biomass in 2013 was estimated to be 58-89% of the unfished levels. However, the provisional catch for 2015 is 41,760t, higher than the 2014 catch of 34,822t, the five year average of 31,900t, and the estimated maximum sustainable yield of 39,400t. There is a very low risk (less than 1%) of the stock undergoing overfishing or becoming overfished if catches are maintained at 2011-2013 average levels (27,809t).

The southwest component has previously been subject to intense fishing pressure and up until 2016 was treated separately to the rest of the IOTC swordfish stock.


Swordfish stocks range across and are accessed by numerous coastal states, making harmonised and effective management of these individual stocks very difficult. To try and achieve this, Intergovernmental Regional Fisheries Management Organisations (RFMOs) have been established; for this stock it is the Indian Ocean Tuna Commission (IOTC). There are five main tuna RFMOs worldwide and it is their responsibility to carry out data collection, scientific monitoring and management of these fisheries. Whilst the RFMOs are responsible for the development of management and conservation measures, the degree to which they are implemented, monitored and enforced still varies significantly between coastal states. For this reason, it is important to choose tuna that has been caught by vessels that are well regulated by their flag state. Swordfish catch and/or effort data is poor or unknown for the following countries/fisheries: Drifting gillnet fisheries of Iran and Pakistan; artisanal and industrial longline fisheries of Indonesia; and the artisanal and industrial longline fisheries of India. Approximately 3% of the Indian Ocean swordfish catch is taken by vessels operating under flags of various non-reporting countries .

There is no harvest control rule that has been developed for the stock. The most recent catches (41,760 t in 2015) are 2,360 t above the MSY level (39,400 t). The scientific committee recommended that catches in 2017 be reduced to less than MSY (39,400 t). An updated stock assessment is scheduled in 2017, and more concrete advice should be developed after that.

The main management measure for the stock is a freeze on capacity to 2007 levels which extends to vessels greater than 24m in length, or vessels under this length operating in international waters. Additional measures may be needed in the southwest to prevent localised effort catches exceeding recommended levels and reversing stock recovery. Continued monitoring and improvement in data collection, reporting and analysis is required to reduce the uncertainty in stock assessments.

IOTC conservation and management measures of note include:

A one month closure for purse seiners and longliners over 24m and small vessels fishing in an area of the High Sea. The closure has had little effect on the status of IO tuna stocks though.

5% regional observer coverage is required for all vessels over 24m and for vessels under 24m fishing outside of their Exclusive Economic Zone (EEZ).

To help address IUU, the IOTC maintains an active vessel register and an IUU Vessel List; and prohibits transhipments for large scale vessels at sea unless part of the Programme to Monitor Transhipments at Sea and monitored by an IOTC observer.

Capture information

Approximately 85% of the swordfish catch in the Indian Ocean is taken in pelagic longline fisheries. The main fleets are Indonesia (fresh longline): 20%; Taiwan, China (longline): 17%; Sri Lanka (longline-gillnet): 12%; EU, Spain (swordfish targeted longline): 12%. Pelagic longlining is associated with the incidental capture and mortality of vulnerable sharks, turtles and sea birds. A number of threatened seabirds can interact with fisheries in the Indian Ocean including the critically endangered Amsterdam albatross (who live on Amsterdam Island in the southern Indian Ocean), shy albatross and the black-browed and wandering albatrosses. The IOTC require longline fisheries to employ two bird bycatch mitigation measures e.g.. bird scaring lines, dyed bait, weighted branch line, night setting, underwater setting chute, yet monitoring and reporting is deficient. Similarly, countries are required to develop conservation and management measures for turtles and vulnerable shark species which includes the prohibition to retain, tranship or land certain species and requires details of interactions with these species to be logged. This already applies to thresher sharks and, as in most tuna RFMOS, oceanic whitetip sharks. Monitoring and reporting for these measures is deficient and several countries have failed to implement national plans for sharks, seabirds and turtles as re required (although the shark plan is not binding in India as they have objected to the measure). In 2016 the scientific committee recommended better monitoring and a precautionary approach to management of shark species. Maintaining current catch and effort on these species will most likely further reduce their populations.

In 2016 IOTC introduced a number of resolutions to improve compliance with existing management measures, e.g. observer coverage, catch and effort reporting, support for countries to implement measures. Click here to see which countries have and have not fully implemented plans and actions for seabirds, sharks and marine turtles:

Read more about capture methods

Froese, R. and D. Pauly. Editors. 2016. FishBase. Available at [Accessed Dec 2016].

IOTC, 2016. Conservation and management measures. Available at [Accessed Dec 2016].

IOTC, 2016. Status of the Indian Ocean swordfish (SWO: Xiphias gladius) resource. Executive summary. Available at [Accessed Dec 2016].

ISSF, 2016. Status of the world fisheries for tuna: Management of tuna stocks and fisheries, 2016. ISSF Technical Report 2016-14.International Seafood Sustainability Foundation, Washington, D.C., USA. Available at [Accessed Nov 2016].

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