|Scientific Name:||Thunnus thynnus (Linnaeus, 1758)|
Scomber thynnus Linnaeus, 1758
Thunnus vulgaris Cuvier, 1832
Thynnus linnei Malm, 1877
Thynnus mediterraneus Risso, 1827
Thynnus secundodorsalis Storer, 1855
|Taxonomic Source(s):||Eschmeyer, W.N. (ed.). 2015. Catalog of Fishes. Updated 7 January 2015. Available at: http://researcharchive.calacademy.org/research/ichthyology/catalog/fishcatmain.asp. (Accessed: 7 January 2015).|
|Taxonomic Notes:||This is now considered to be a separate species from the Pacific Bluefin, Thunnus orientalis (Collette 1999).|
|Red List Category & Criteria:||Near Threatened (Regional assessment) ver 3.1|
|Assessor(s):||Collette, B.B., Fernandes, P. & Heessen, H.|
|Reviewer(s):||Ralph, G. & Allen, D.J.|
|Contributor(s):||Amorim, A.F., Boustany, A., Carpenter, K.E., Di Natale, A., Die, D., Fox, W., Fredou, F.L., Graves, J., Hinton, M., Juan Jorda, M., Kada, O., Minte Vera, C., Miyabe, N., Nelson, R., Oxenford, H., Pires Ferreira Travassos, P.E., Pollard, D.A., Restrepo, V., Schratwieser, J., Teixeira Lessa, R.P., Uozumi, Y., Viera Hazin, F.H. & de Oliveira Leite Jr., N.|
European Regional Assessment: Near Threatened (NT)
In European waters, Thunnus thynnus is found in the eastern Atlantic Ocean from Norway to the Canary Islands, and present in the Mediterranean Sea. The sub-population in the Black Sea is now extinct, however the causes of this are not fully understood. There are currently three known spawning areas, one aggregation in the Gulf of Mexico and at least two separate spawning aggregations in the Mediterranean Sea (Riccioni et al. 2010, 2013), however there is exchange between the eastern and western populations, and recent work detected several subpopulations in the Mediterranean Sea (Riccioni et al. 2013).
The fish is a highly valued species, particularly for the Japanese sashimi markets. Historically, it has been heavily overfished throughout its range, resulting in substantial declines in the population. Environmental conditions in the Black Sea have contributed to a range contractions of 46% since 1960 (Worm and Tittensor 2011), greater than any other pelagic species.
The most recent stock assessment for T. thynnus suggests that the recent management efforts to reduce the fishing mortality on the eastern Atlantic Bluefin Tuna are working; overfishing is no longer occurring but the stock remains overfished. The estimated spawning stock biomass (SSB) has increased over the past three generation lengths (21 years), and is currently close to exceeding the maximum SSB in the time series (1957-1959) depending on the model specifications. The current assessment, if it is correct, would lead to Least Concern. However, the virtual population analysis (VPA) methodology is completely dependent on the reported landings, which are uncertain, and the trend is driven by data from the last two years which, in a VPA, are the least reliable of the time series. Therefore, T. thynnus is assessed as Near Threatened in the European marine region. It is inferred that cessation of fishery management interventions that reduce fishing mortality would rapidly (within ten years) lead to population declines exceeding 30%. Management of the eastern Atlantic stock is essential to the future of this species, as it represents the majority of this species' global population, and populations in the European region are considered conservation dependent.
There remains an urgent need to have more reliable and complete size frequency data for the species in European waters. Tagging programs, fishery independent surveys and mining of historical data will all contribute to a better understanding of the status of this species.
|Range Description:||Thunnus thynnus is restricted to the Atlantic Ocean, where it is primarily found in the North Atlantic. In the eastern Atlantic, it is present from Norway to the Canary Islands. It is also present in the Mediterranean Sea. The fish was historically present in the Black Sea and its presence there was well documented in ancient times, but no individuals have been seen or caught since the 1980s (MacKenzie and Mariani 2012). An analysis of present over historical ranges concluded that Atlantic Bluefin Tuna has shown larger range contractions (minus 46% since 1960) than any other pelagic species (Worm and Tittensor 2011).|
In the eastern Atlantic, the fish is also reported from Mauritania (Maigret and Ly 1986) and off South Africa (Collette and Nauen 1983). This species was present in the western Atlantic from Canada to Brazil, including the Gulf of Mexico and the Caribbean Sea, although the bulk of the population off Brazil has now disappeared (Porch 2005, Takeuchi et al. 2009, Worm and Tittensor 2011). However over the last 20 to 36 years, the species has not been recorded off the coast of Brazil (R. Lessa and A.F. Amorim pers. comm. 2010) and there are no records of Bluefin Tuna in southern Brazil in the 21st century (M.A. Gasalla pers. comm. 2010).
Native:Åland Islands; Albania; Algeria; Belgium; Bosnia and Herzegovina; Croatia; Cyprus; Denmark; Egypt (Egypt (African part), Sinai); Estonia; Faroe Islands; Finland; France (Corsica, France (mainland)); Germany; Gibraltar; Greece (East Aegean Is., Greece (mainland), Kriti); Guernsey; Ireland; Isle of Man; Israel; Italy (Italy (mainland), Sardegna, Sicilia); Jersey; Latvia; Lebanon; Libya; Lithuania; Malta; Monaco; Montenegro; Morocco; Netherlands; Norway; Palestinian Territory, Occupied; Poland; Portugal (Azores, Madeira, Portugal (mainland), Selvagens); Romania; Slovenia; Spain (Baleares, Canary Is., Spain (mainland), Spanish North African Territories); Sweden; Syrian Arab Republic; Tunisia; Turkey (Turkey-in-Asia, Turkey-in-Europe); United Kingdom (Great Britain, Northern Ireland)
Possibly extinct:Bulgaria; Hungary
|FAO Marine Fishing Areas:|
Atlantic – northeast; Atlantic – eastern central; Mediterranean and Black Sea
|Population:||This species has become rare relative to historical levels because of massive overfishing (Fromentin and Powers 2005, Majkowski 2007, MacKenzie et al. 2009).|
Genetic differentiation and homing to breeding sites indicates that there are at least three reproductively isolated stocks (Boustany et al. 2008, Carlsson et al. 2007), although there is considerable trans-Atlantic migration of individuals between the Mediterranean and western North Atlantic stocks (Rooker et al. 2008, Dickhut et al. 2009). Mixed western and eastern Bluefin Tuna are found from Labrador and Newfoundland south into the Gulf of Mexico and the Caribbean Sea. Eastern Atlantic Bluefin Tuna are also found from Norway south to the Canary Islands and the Mediterranean Sea. There is a distinct Mediterranean/East Atlantic stock but there is some mixing with the western Atlantic stock in the North Atlantic (Block et al. 2005); in addition, there are genetically recognizable populations within the Mediterranean (Riccione et al. 2010).
Worldwide reported landings show fluctuating, but relatively stable landings from 1950–1993, of between 15,000 and 39,000 tonnes per year. Reported catches increased to a peak of 52,785 tonnes in 1996, and then fell again to 38,830 tonnes in 2006 (FAO 2009). However, in many regions, the catch statistics for this species are considered to be unreliable because catches are not reported from some countries and landings data are confounded by ranching harvests occurring months to years after the fish have been caught (STEFC 2009). Based on the most recent stock assessment (ICCAT 2010), the summed SBB biomass for both the Eastern and Western Atlantic stocks has declined at least 51% since 1970.
Eastern Atlantic and Mediterranean stock
The most recent stock assessment suggests that overfishing is no longer occurring, as the current fishing mortality is less than the target fishing mortality (Fcurrent/FMSY = 0.36-0.70); however the stock remains overfished, as the current biomass is less than the target biomass (Bcurrent/BMSY = 0.63-0.76) (ISSF 2013).
In the Eastern Atlantic and Mediterranean stock, the reported catch from 2000–2011 averaged 25,000 tonnes/year (ICCAT 2014). The high mortality for large Bluefin Tuna is consistent with an apparent shift in targeting larger individuals destined for fattening and/or farming in the region. A quota system has been put in place to set levels for maximum sustainable yield (MSY) of 30,000-36,000 mt, and have set the TAC at 13,400 for 2014 (ISSF 2013). The current management structure has established TACs for the entire Mediterranean; however, recent genetic studies suggest multiple populations within the Mediterranean (Riccione et al. 2010). This is problematic because there is the potential for overfishing of segments of the Mediterranean population. In addition, information available has demonstrated that catches of Bluefin Tuna from the East Atlantic and Mediterranean were seriously under-reported between the mid-1990s through 2007. The lack of compliance with TAC and underreporting of the catch may have severely undermined the conservation of the stock (ISSF 2013).
In the most recent stock assessment (ICCAT SCRS 2012), final estimated spawning biomass differs slightly between the satisfactory model runs. The spawning biomass peaked at over 300,000 tonnes in the late 1950s and early 1970s, followed by a decline. Under all runs, the biomass continued to decline slightly to about 150,000–200,000 tonnes around 2005, followed by a substantial increase through 2011 to 300,000-500,000 tonnes (ISSF 2013).
Considering all runs, there was substantial variability in current estimates of SSB: the recent (2009–2011) SSB ranged from 16% less to 52% more than the highest estimated SSB levels (1957–1959).
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||This is a pelagic, oceanodromous species, that seasonally can be found close to shore and can tolerate a wide range of temperatures. This species schools by size, sometimes together with Albacore, Yellowfin, Bigeye, Skipjack etc. It preys on small schooling fishes (anchovies, sauries, hakes) or on squids and red crabs. A recent study on the Mediterranean diet of this species provided evidence that juveniles prey mainly on zooplankton and small pelagic coastal fishes, sub-adults prey on medium pelagic fishes, shrimps and cephalopods, while adults prey mainly on cephalopods and larger fishes (Sarà and Sarà 2007).|
This species has a maximum size over 300 cm fork length (FL), but is more common to 200 cm. Longevity is at least 35 years and possibly to 50 years (Santamaria et al. 2009).
In the Western Atlantic, this species spawns in the Gulf of Mexico from mid-April to early June at temperatures of 22.6–27.5°C, starting at age 8–10 years at around 200 cm (FL), although most individuals first spawn closer to age 12 (Rooker et al. 2007, Rooker et al. 2008, Boustany et al. 2008, Diaz et al. 2009, Collette 2010). Recently, a few larvae were collected northeast of Campeche Bank suggesting that they were spawned outside of the Gulf of Mexico (Muhling et al. 2011). Maximum age is around 32 years (Neilson and Compana 2008), although age composition structure has also changed over time (e.g., there are more younger individuals). For the most recent stock assessment, an age of first maturity was estimated to be approximately 145 kg or about age nine years in the Gulf of Mexico (SRCS ICCAT 2010). For the western Atlantic stock, the generation length is therefore estimated to be approximately 13 years based on average survivorship and fecundity across known scombrid stocks (Collette et al. 2011).
The Eastern Atlantic stock spawns in the Mediterranean Sea from May to August at temperatures of 22.5–25.5°C, starting at age three years and full recruitment is reached by age five years. There are distinct behaviours during the spawning time, most noticeably with changes in diving times and depths. Estimated relative batch fecundity is greater (more than 90 oocytes/g of body weight) than estimated for other tunas in the genus Thunnus (Sissenwine et al. 1998, Corriero et al. 2003, Rooker et al. 2007, Boustany et al. 2008, Rooker et al. 2008, Collette 2010). Fromentin and Powers (2005) reported that there is spawning site fidelity for this species both in the Mediterranean Sea and in the Gulf of Mexico. There are at least two separate spawning aggregations in the Mediterranean Sea (Riccioni et al. 2010, 2013). In addition, there are genetically recognizable populations within the Mediterranean (Riccioni et al. 2010, 2013).
Median sexual maturity in the Mediterranean Sea was reached at 103.6 cm (FL), and females weighing between 270 and 300 kg produce as many as 10 million eggs per spawning season (Corriero et al. 2005).
In the Eastern Atlantic stock and in the Mediterranean Sea, age of first maturity is about 3–5 years (115–121 cm FL), with a longevity of 35 years or more (Corriero et al. 2003, Santamaria et al. 2009, Rooker et al. 2007, Rooker et al. 2008). For the most recent stock assessment, an age of first maturity was estimated to be approximately 25 kg or age four years in the Mediterranean (SRCS ICCAT 2010). For the eastern Atlantic stock, the generation length is therefore estimated to be approximately seven years based on average survivorship and fecundity across known scombrid stocks (Collette et al. 2011).
Maximum Size (in cms) 458 (TL). The all-tackle angling record is of a 678.58 kg fish caught off Aulds Cove, Nova Scotia, Canada in 1979 (IGFA 2014).
|Generation Length (years):||7-13|
|Movement patterns:||Full Migrant|
|Congregatory:||Congregatory (and dispersive)|
|Use and Trade:||This is a highly valued species for the Japanese sashimi markets, which has led to severe overfishing in both the Eastern and Western Atlantic. It is also an important gamefish particularly in the United States and Canada.|
Thunnus thynnus is an important commercial food fish and is specifically targeted in fisheries. This species is mainly caught by purse-seine, longline and traps. Historically, it has been heavily overfished throughout its range resulting in substantial declines in the populations. In addition, T. thynnus is also used for commercial fish farming in the Mediterranean Sea (Forrestal et al. 2012), where juveniles are caught and raised in pens. This may pose substantial threats to the population of T. thynnus for a number of reasons. Individuals are removed from the breeding stock, and this is not always adequately accounted for in the landings statistics. The conversion ratio of forage fish to tuna flesh is highly inefficient, and thus raising tunas is depleting small pelagic fish stocks which might otherwise be food for wild populations of tunas and other large pelagic species.
In addition, there is evidence of localized pollution from maintaining the large pens, which may also be impacting spawning tunas and other species in the Mediterranean. Rearing in captivity may also impact the reproductive function of adults through changes in germ cell proliferation and apoptosis (Zupa et al. 2013), which may explain why spawning occurred every day in cages in the Balearic Sea in June 2010, but few or no larvae were found (Reglero et al. 2013).
The population in the Black Sea appears to have been extirpated, though the direct cause is unclear. Overexploitation, shipping noise, and changed environmental conditions have been implicated, but the mechanisms are obscure, largely undocumented, and unquantified (MacKenzie and Mariani 2012).
There are several conservation measures for this species mainly based on regulation of fisheries activities. The International Commission for the Conservation of the Atlantic Tuna (ICCAT) was established in 1967. Fisheries quotas have been in place since 1982, and a comprehensive pluri-annual recovery action plan adopted by the ICCAT contracting parties in 2007, including time closure for fishing activities and mandated reduction in fishing capacity. However, many conservation measures are not fully enforced and illegal catch continues. Enforcement of the existing measures is needed to prevent extinction of this species. Also, although the Bluefin Tuna probably has more data collected on it than most other fish species, uncertainties in the data make much of it unreliable. It is crucial to improve the quality of data if fisheries managers are going to be able to improve their methods.
Eastern Atlantic and Mediterranean
For EU Member States, driftnet fishing for tuna has been banned since 1st January 2002, while the ban entered into force in 2004 for all the other Contracting Parties to ICCAT, as well as the GFCM Member States, but a driftnet fishing activity is still officially permitted in Morocco. The ICCAT further believes that a time area closure could greatly facilitate the implementation and the monitoring of rebuilding strategies. In 2006, ICCAT established a management plan to rebuild the stock to BMSY by 2022 with 50% or greater probability (ICCAT SCRS 2006: Rec. 06-05). As various issues related to implementation of the plan have come up, the plan has been amended and strengthened every year since. In 2009, ICCAT (ICCAT 2009: Rec. 09-06) the Commission established a total allowable catch for eastern Atlantic and Mediterranean Bluefin Tuna at 13,500 t for 2010. The current management plan (ICCAT 2010: Rec. 10-04) calls for rebuilding to be achieved with at least 60% probability. It includes a number of conservation measures (country-specific TACs, minimum size limit, closed fishing seasons, management controls of fishing and farming capacity) as well as Monitoring, Control and Surveillance (MCS) measures (vessel registers, vessel monitoring systems, observer programs, transshipment prohibitions, weekly catch reporting, etc.). ICCAT has also approved a research program with different components aimed at improving data and knowledge of Bluefin Tuna biology and behaviour. It is still early to see what practical improvements these efforts will have on rebuilding the stock and improving stock assessments, but it is generally agreed that investments in research and MCS need to be sustained if overfishing is to be avoided.
Deferring effective management measures will likely result in even more stringent measures being necessary in the future to achieve the ICCAT objectives. STECF agrees with the ICCAT-SCRS (2006) that the minimum catch size should be set at 25 kg in order to avoid misreporting and/or discarded catches of mature fish between 25 kg and 30 kg. There remains an urgent need to have more reliable and complete size frequency data (particularly, but not only, for early year-classes 1–3) for the period following the introduction of a TAC in the Mediterranean. Tagging programs, fishery independent surveys and mining of historical data will all contribute to a better understanding of the status of this species and should be encouraged (STECF 2009).
SCRS undertook a reassessment of the fish in 2014 (STECF 2014), recognising that there are considerable data limitations, not least the level of underestimated and underrecorded catches, especially up to 2007. In Recommendations (Res. 09-06, 10-04, 12-03, and 13-07) the STECF established a total allowable catch for eastern Atlantic and Mediterranean bluefin tuna of between 12,900 t and 13,500 t since 2010. Additionally, in the Commission required (Rec. 09-06) that the SCRS provide the scientific basis for the Commission to establish a recovery plan with the goal of achieving BMSY through 2022 with at least 60% of probability.
Thunnus thynnus was assessed as Endangered globally (IUCN 2011) and in the Mediterranean (Abdul Malak et al. 2011).
|Citation:||Collette, B.B., Fernandes, P. & Heessen, H. 2015. Thunnus thynnus. The IUCN Red List of Threatened Species 2015: e.T21860A97778482.Downloaded on 19 September 2018.|
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