In 2015, the IATTC updated their 2013 stock assessment which indicated the population had slightly improved since the last assessment . The results indicate that the spawning biomass has improved a little in recent years and at the start of 2015 was slightly overfished, but not subject to overfishing. The is considerable uncertainty in this assessment and it is suggested that the stock may now be moving from a regime of high productivity to an intermediate one and it is recommended that fishing mortality not be increased. Purse seines set on free schooling tuna as opposed to being associated with Fish Aggregation Devices (FADs) or dolphins represent the most selective fisheries.
Commercial buyers should establish what measures the flag state and fleet relating to their source is taking to reduce impacts to and improve reporting of interactions with vulnerable species. This is particularly important for the dolphin associated purse seine fishery which needs to increase efforts to reduce dolphin mortality to zero as soon as possible. Large buyers should consider supporting such improvements. MCS also advocates specifying the need for supplying vessels, in particular purse seiners, to register on the ISSF Proactive Vessel Register.
Tuna belong to the family Scombridae. They are large, oceanic fish and are seasonally migratory, some making trans-oceanic journeys. Yellowfin are found throughout the world's tropical and subtropical seas, except the Mediterranean. They often form large, size specific schools, frequently associated with dolphins or floating objects. Yellowfin is a large fast growing species, reaching maximum sizes of 240cm in length, 200kg in weight and an age of 8 years. They mature when 2 to 5 years old and mainly spawn in summer. Smaller fish are mainly limited to surface waters, while larger fish are found in surface and deeper waters, but rarely below 250m. Yellowfin has medium resilience to fishing.
Yellowfin stocks in the Eastern Pacific Ocean (EPO) are managed and assessed by the Inter-American Tropical Tuna Commission (IATTC). In 2014, catches were approximately 233,566t which is roughly equal to the previous five year average of 234,178t and below the estimated Maximum Sustainable Yield (MSY) of 275,258t. In 2015, the IATTC updated their 2013 stock assessment and indicated that both spawning biomass and fishing mortality had slightly improved since the last assessment, yet uncertainty remained about recent and future levels of recruitment and biomass. The scientific committee note that there have been two, and possibly three different productivity regimes, and the MSY levels and the biomasses corresponding to the MSY may differ among the regimes. The population may have switched in the last ten years from a high to an intermediate productivity regime. The results indicate that the spawning biomass has improved a little in recent years and at the start of 2015 is slightly below that which would produce MSY (0.99Bmsy) and is therefore slightly overfished. Recent fishing mortality (2012-2014) was below Fmsy (0.86Fmsy) indicating that the stock is not being subject to overfishing. It is noted though that if a stock-recruitment relationship is assumed, the outlook is more pessimistic, and current effort would be estimated to be above the MSY level. It is also noted that MSY could be increased by reducing fishing mortality in fisheries which take juveniles.
Most tuna 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. There are five main tuna RFMOs worldwide and it is their responsibility to carry out data collection, scientific monitoring and management of these fisheries. Eastern Pacific Ocean bigeye tuna is managed and assessed by the Inter-American Tropical Tuna Commission (IATTC). 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. There is a Marine Stewardship Council (MSC) certified sustainable and well managed pole and line fishery for skipjack, yellowfin and bigeye based on the California Peninsula, Mexico.
There is no harvest control defined for yellowfin in the EPO and the IATTC has adopted interim target reference points of Fmsy and Bmsy. The latest assessment states that 'maintaining the fishing mortality below the MSY level would result in only a marginal decrease in the long-term average yield, with the benefit of a relatively large increase in the spawning biomass' so it would seem wise to not increase effort in the fishery. The main stock conservation measures established includes: a 62-day closure for purse seiners greater than 182 tons capacity; a seasonal closure of the purse seine fishery in an area known as "El Corralito", west of the Galapagos Islands, where catch rates of small bigeye are high; and a full retention requirement for bigeye, skipjack and yellowfin tunas for all purse seine vessels and there is 100% observer coverage on large purse seiners and 5% coverage on large longliners.
To help address IUU, the IATTC maintains an IUU Vessel List and prohibits transhipments at sea for most vessels (Some exemptions apply) and requires most other transhipments to be documented and observed as part of the regional observer programme.
Longline catches of yellowfin in the Eastern Pacific Ocean have been steadily decreasing and in roughly represent 4% of the total retained catch. Longlining targets larger, mature fish yet is often associated with the bycatch of vulnerable species such as seabirds, turtles and sharks. To help address this, the IATTC require: that longliners over 20m in length use at least two prescribed seabird mitigation measures (e.g. tori line, dyed bait, weighted branch line, night setting, underwater setting chute); for vessels to carry line cutters and de-hookers to promptly release turtles or to foster to recovery any sick or comatose turtles captured; permissible sharks are to be fully utilized and no more than 5% of fins to total shark weight can be retained with a prohibition to land oceanic whitetip sharks; and countries to develop national plans of action to address the bycatch of sharks, turtles and seabirds. Monitoring and reporting is deficient in many fisheries however, and the effectiveness of these various measures has not been evaluated. The IATTC requires 5% observer coverage on longliners greater than 20m in length.
Monitoring and reporting of interactions with vulnerable species in particular needs to be improved.
Based on method of production, fish type, and consumer rating: only fish rated 2 and below are included as an alternative in the list below . Click on a name to show the sustainable options available.
Froese, R. and Pauly, D. Editors, 2015. FishBase. Available at www.fishbase.org [Accessed Dec 2015].
IATTC, 2015. Active IATTC and AIDCP Resolutions and Recommendations. Available at http://www.iattc.org/ResolutionsActiveENG.htm [Accessed Dec 2015].
IATTC, 2015. Status of yellowfin tuna in the Eastern Pacific Ocean in 2014 and outlook for the future. Available at http://www.iattc.org/Meetings/Meetings2015/6SAC/PDFs/SAC-06-06-YFT-assessment-2014.pdf [Accessed Dec 2015].
ISSF, 2015. Status of the world fisheries for tuna: management of tuna stocks and fisheries. Nov 2015 Update. Available at http://iss-foundation.org/knowledge-tools/reports/technical-reports/download-info/issf-technical-report-2015-03-a-status-of-the-world-fisheries-for-tuna-november-2015/ [Accessed Dec 2015].
Sign up to get all the latest marine related news from MCS
The UK charity for the protection of our seas, shores and wildlife.