Marlin, blue

Makaira nigricans

Method of production — Caught at sea
Capture method — Longline
Capture area — Atlantic Ocean (FAO 21,27,31,34,41,47)
Stock area — All Areas
Stock detail — All Areas
Picture of Marlin, blue

Sustainability rating five info

Sustainability overview

An important commercial and artisanal species, blue marlin in the Atlantic has been overfished for many years. It is primarily caught as bycatch in longline and purse seine fisheries targeting tuna and swordfish. Stocks are slowly recovering due to reduced effort and regulations limiting landings, however, this may be increasing discards. There is considerable under reporting of catches from growing artisanal fleets which may hinder recovery efforts. The species is listed as Vulnerable by the International Union for the Conservation of Nature (IUCN) and more research is necessary to better understand the life history characteristics of the species.

MCS recommends avoiding products from red rated tuna and billfish fisheries.

Biology

Blue marlin are highly migratory and are found throughout tropical and temperate waters worldwide. Migrations include trans-Atlantic as well as trans-equatorial movements. They are usually solitary, large predators with an average weight of 100-175 kgs. Sexually mature at 2-4 years, they spawn in tropical and sub-tropical waters in the summer and autumn, and are found in colder temperate waters during the winter. Young marlin are one of, if not the, fastest growing of all bony fish.

Stock information

Stock Area

All Areas

Stock information

Atlantic marlin stocks are managed by ICCAT - the International Commission for the Conservation of Atlantic Tuna. The stock has been overfished for the last 10-15 years, and the last assessment undertaken in 2011 indicated that the fishery was in an overfished state and is subject to overfishing. The fishery is in need of an updated stock assessment. At the time of the last assessment, it was noted that unless the catches of 3,358 t (2010) were substantially reduced, the stock will continue to decline. Reported catches have reduced in recent years yet there are concerns over significant unreported catches, particularly in artisanal fisheries. Over the last 20 years, Antillean artisanal fleets have increased the use of Moored Fish Aggregating Devices (MFADs) to capture pelagic fish. Catches of blue marlin caught around MFADs are known to be significant and increasing in some areas, however reports to ICCAT on these catches are incomplete. Furthermore, the Scientific Committee is concerned with the significant increase in the contribution from non-industrial fisheries to the total blue marlin harvest and that these fisheries are not fully accounted for in the current ICCAT database.

Blue marlin are listed globally as Vulnerable by the International Union for the Conservation of Nature (IUCN), and Endangered in the Gulf of Mexico.

Management

Marlin, like most tuna stocks range across and are fished by numerous coastal states, making harmonised and effective management of these individual stocks very difficult. As a result, intergovernmental Regional Fisheries Management Organisations (RFMOs) have been established. There are five main tuna RFMOs worldwide and it is their responsibility to carry out data collection, scientific monitoring and management of these fisheries. Blue marlin in the Atlantic is assessed by the International Commission for the Conservation of Atlantic Tunas (ICCAT). 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. There remain large data deficiencies in most tuna and billfish fisheries, particularly with regards to fine scale spatial and temporal data for both target and especially for vulnerable bycatch species.
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In 2006, ICCAT limited member state landings of blue marlin by purse seine and longline vessels to no more than 50% of the 1996 or 1999 landing levels, whichever was greater. Furthermore, in 2012, a TAC of 2,000t for 2013, 2014 and 2015, and this was subsequently extended to 2016, 2017, and 2018. The current management plan has the potential of recovering the blue marlin stock to the BMSY level if properly conducted. However, the scientific committee has expressed its concern on the effectiveness of such measures in light of severe under reporting currently occurring in some fisheries and noted that unless such non-compliance issues are properly addressed, the adoption of additional measures might be rendered ineffective. Although uncertain, the results of the 2011 stock assessment indicated that if the latest known catch levels of blue marlin (3,358 t in 2010, as in the time of the stock assessment) are not substantially reduced, the stock will continue to decline further.

Currently, four countries (Brazil, Canada, Mexico, and the United States) mandate or encourage the use of circle hooks on their pelagic longline fleets as an effective measure at reducing marlin mortality, whilst not reducing target species landings. Such measure should be considered for adoption by all longline fleets that encounter marlin. Selected ICCAT management and conservation measures regarding tuna and billfish longline fisheries include:

ICCAT have developed an IUU vessel register and a register of vessels authorised to undertake transhipments at sea. Additionally, transhipments at sea can only take place if an ICCAT Observer is on-board the receiving vessel. ICCAT have developed a vessel register for vessels over 20m in length.

ICCAT has noted that the current mandatory level of observer coverage of 5% has not been implemented by many of the fleets and in 2016, updated their recommendation for a minimum of 5% observer coverage of fishing effort in each of the pelagic longline, purse seine, bait boat, traps, gillnet and trawl fisheries.

Capture Information

Blue marlin in the Atlantic are mainly landed as by-catch in longline fisheries for tuna and swordfish, and to a lesser extent as bycatch in purse seine fisheries and in directed recreational and artisanal fisheries. Recent reports from purse seine fleets in West Africa suggest that blue marlin is more commonly caught with tuna schools associated with FADs than with free tuna schools. Pelagic longlines in the Atlantic need to reduce their interactions with vulnerable species including large sharks, turtles, birds and some billfish species like blue marlin. It is positive to see Brazil, Canada, Mexico and the U.S. mandating or encouraging the use of circle hooks to reduce mortality of blue marlin. Such measures should be considered for adoption more widely.

There are a range of measures that are available and required to be employed to reduce bycatch and mortality of vulnerable non-target species including: circle and/or barbless hooks to prevent turtle capture; chemical, magnetic and rare earth metal shark deterrents; and bird scaring lines for vessels south of 20 degrees S. South of 25 degrees S, longline vessels must use at least two of the following: night setting, bird-scaring lines or line weighting. In the Mediterranean, seabird mitigation measures are voluntary. Several species of albatross are threatened with extinction, and whilst there have been many advances in reducing interactions with longline fisheries, it is not clear how effective these have been. There is also a prohibition to retain at risk shark species including: bigeye thresher, oceanic whitetip, hammerhead, silky and porbeagle sharks. This has been in place for over four years, yet ICCAT has not received records of compliance from the majority of member states. Porbeagle is significantly overfished, and whilst there is a zero EU TAC for Porbeagle, it is still caught incidentally and discarded, and also landed by other fleets. In 2016 additional measures for blue shark were introduced, mainly focussed on improved data recording, with potential to introduce Harvest Control Rules. Monitoring of bycatch is deficient in these fisheries and the scientific committee strongly recommends improvements in data collection.

In 2016, work was begun to improve ICCAT's understanding of the trophic ecology of pelagic ecosystems that are important and unique for species managed in this area. ICCAT also introduced a number of recommendations to improve compliance and reporting.

ICCAT has noted that the current mandatory level of observer coverage of 5% has not been implemented by many of the fleets and in 2016, updated their recommendation for a minimum of 5% observer coverage of fishing effort in each of the pelagic longline, purse seine, bait boat, traps, gillnet and trawl fisheries.

References

Collette, B., Acero, A., Amorim, A.F., Boustany, A., Canales Ramirez, C., Cardenas, G., Carpenter, K.E., de Oliveira Leite Jr., N., Di Natale, A., Die, D., Fox, W., Fredou, F.L., Graves, J., Guzman-Mora, A., Viera Hazin, F.H., Hinton, M., Juan Jorda, M., Minte Vera, C., Miyabe, N., Montano Cruz, R., Nelson, R., Oxenford, H., Restrepo, V., Salas, E., Schaefer, K., Schratwieser, J., Serra, R., Sun, C., Teixeira Lessa, R.P., Pires Ferreira Travassos, P.E., Uozumi, Y. & Yanez, E., 2011. Makaira nigricans. The IUCN Red List of Threatened Species 2011: e.T170314A6743776. Available at http://dx.doi.org/10.2305/IUCN.UK.2011-2.RLTS.T170314A6743776.en [Accessed Dec 2016].

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

ICCAT, 2016. Resolutions, recommendations and other decisions. Available at https://www.iccat.int/en/RecsRegs.asp [Accessed Dec 2016].

ICCAT, 2016. Report of the standing committee on research and statistics. Madrid, Spain 3 to 7, October 2016. Available at https://www.iccat.int/Documents/Meetings/Docs/2016_SCRS_ENG.pdf [Accessed Nov 2016].

ISSF, 2016. ISSF Tuna stock status update, 2016: Status of the world fisheries for tuna. ISSF Technical Report 2016-05B. International Seafood Sustainability Foundation, Washington, D.C., USA. Available at http://iss-foundation.org/knowledge-tools/technical-and-meeting-reports/download-info/issf-2016-05b-status-of-the-world-fisheries-for-tuna-nov-2016/ [Accessed Nov 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 http://iss-foundation.org/downloads/13305/ [Accessed Nov 2016].