Scientific name: |
Thunnus maccoyii |
Other names: |
Bluefin, southern bluefin, thon rouge de sud (Canada, France), atun del sur (Spain), minamimaguro, indo-maguro (Japan) |
Southern bluefin tuna is a worst choice tuna. A better alternative is albacore or skipjack tuna.
Southern bluefin tuna is a long-lived migratory species, found throughout the southern hemisphere, which can move thousands of kilometres in a year. It is a highly sought-after tuna species, due to its flesh being of high oil and low moisture content. Since 1996 its depleted status resulted in it being ranked by the IUCN Red List as critically endangered. Southern bluefin tuna breed in the Indian Ocean off western Australia, arriving in New Zealand in prime condition at around the age of 5 years old, where they are caught off the east coast by longlining and trolling.
Southern bluefin is caught using surface longlines. Stocks are severely over-fished and less than 10% of their unfished stock size remains. The concerns include the lack of a management plan, and the bycatch of seabirds, New Zealand fur seals, a range of shark species and non-target fish bycatch. An estimated 623 seabirds a year (including cryptic bycatch) are caught including white-capped albatross and Buller’s albatross. The fishery also catches about 100 fur seals annually and vulnerable sharks like porbeagle and mako.
Not certified under any scheme.
Over 90% of Southern bluefin tuna are exported to Japan where it is highly prized for sashimi and sushi. The export value of southern bluefin tuna was $13.6 million in 2015. The export value of all tuna and swordfish species combined was $42.3 million in 2015.
Asssessment output
No regional or fishing method difference.
| Score: | E |
| Population size: | Southern bluefin tuna are severely depleted – under 10% of the 1960 population. In 1996 the IUCN listed this species as Critically Endangered, the highest threat category. Current stock size estimate is 9%Bo. |
| Annual catch limit: | The annual New Zealand catch limit was increased to 987 tonnes from the 2011/12 year, out of a global “limit” of 14,647 tonnes set by the Convention on the Conservation of Southern Bluefin Tuna (CCSBT). |
| Recorded catch: | Reported landings of 825.6 tonnes in 2013/14. Estimated global catches reported in 2014 (11,911 t) were well below catches in the 1970s and 1980s. |
| Stock trends: | Declined to historically low size (4.5%) and estimated to have rebuilt to 9% with current recruitment. The biomass of adult fish “B10+ relative to initial is estimated to be 7% which is up from the estimate of 5% in 2011.” |
| MSY Status: | Well below the level necessary to produce the maximum sustainable yield. |
| The Ministry of Primary Industries assessment plenary report includes: |
“Recent recruitments are estimated to be well below the levels from 1950-1980, but have improved since the poor recruitments of 1999-2002.” “The stock remains at a very low state estimated to be 9% of the initial SSB, and below the level to produce maximum sustainable yield (MSY), however there has been some improvement since the 2011 stock assessment and the fishing mortality rate is below the level associated with MSY. B10+ relative to initial is estimated to be 7% which is up from the estimate of 5% in 2011. The current TAC has been set following the recommendation from the management procedure adopted in 2011.” (MPI 2015, p438-447) |
| Score: | D |
| Distribution: | Breeds south of Java (Indonesia) on the west coast of Australia. Distributed in the southern oceans between 10oS and 50oS, including New Zealand waters. |
| Maximum age (years): | 30+ |
| Age at sexual maturity: | 8-12 |
| Growth rate: | Moderate |
| Reproductive output: | Medium to very high |
| Age exploited: | 4 |
| Ability to recover: | Low to moderate |
| Score: | B |
| Fishing method(s): | Southern bluefin tuna is caught using pelagic longline. |
| Habitat damage: | No benthic impact |
| Habitat of particular significance: | Hasn’t been defined in New Zealand. |
| Bycatch: | Various sharks are caught in the longline fishery and, combined, make up over 90% of the bycatch by number. |
| Ecological effects: | Excessive removal of this large predator species can have considerable ecological implications. |
| Score: | E |
| Bycatch: | Catches seabirds, turtles, sharks and New Zealand fur seals. It is estimated that 623 seabirds (including cryptic bycatch) are caught including white-capped albatross and Buller’s albatross. Albatross species recorded killed in the fishery include Antipodean, Buller’s, Salvin’s, Gibson’s, Campbell, Chatham, black-browed and white-capped. Grey petrels are also caught. The southern bluefin tuna fishery also catches an estimated 100 fur seals a year (based on the last 5 years). These longline fisheries all catch significant shark bycatch which, combined, makes up over 90% of the bycatch number. These sharks include porbeagle, mako and blue which are all listed as vulnerable threatened species. |
| Score: | A |
| Management component: | Single species – southern hemisphere stock. |
| Score: | C |
| Quota Management Species: | Yes, in 2004. |
| Catch limits: | Yes, as a proportion of the ‘global limit’ set by the CCSBT. |
| Management plan: | Highly Migratory Species management plan for 2010-15 is out of date, and has yet to be reviewed and replaced. There is no operational plan and the old management plan lacks key environmental standards. The National Plans of Action on Seabirds and Sharks are more relevant but they are slow to be implemented. There is no international management plan and the Western and Central Pacific Fisheries Commission (WCPFC) has yet to apply effective measures to prevent over-fishing. |
| Stock assessment: | Quantitative stock assessment in 2011 by CCSBT. Assessments have been affected by the high level of unreported or illegal catch identified in 2005, principally by Japanese fishers, which went back over 20 years. |
| Research: | Research focus is limited to catch-at-age of southern bluefin tuna in the New Zealand catch. |
| Observer coverage: | About 21.4% of sets are observed but it is biased towards larger vessels. Observer coverage for small vessels is only 5.97% annually over last 5 years. |
Fisheries map
Taken from the Ministry for Primary Industries’ Plenary report for fisheries management.
References
Paste here.