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| Marine Resource Fact Sheet |
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| Bigeye tuna - Indian Ocean |
| | Data Ownership | | This document provided, maintained and owned by Indian Ocean Tuna Commission (IOTC) , is part of IOTC Stock Status Reports data collection. |
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| Related observations | Locate in inventory | | | | Species: | | FAO Names: en - Bigeye tuna, fr - Thon obèse(=Patudo), es - Patudo, ru - Тунец большеглазый |
Fishery IndicatorsProduction: Catch |
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| Geographic extent of Bigeye tuna - Indian Ocean
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| FAO Major Fishing Areas |
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| 51 | Indian Ocean, Western |
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| 57 | Indian Ocean, Eastern |
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| Main Descriptors | Considered a single stock: Yes
Management unit: Yes
Reference year: 2018 |
| Considered a single stock: A group of individuals in a species occupying a well defined spatial range independent of other stocks of the same species. It can be affected by random dispersal movements and directed migrations due to seasonal or reproductive activity. |
| Spatial Scale: Spatial scale contains a standard term such as Global, Regional (e.g. for the whole Atlantic), sub-regional (e.g. for a part of the Atlantic), national, local (for sub-national levels). |
| Considered a management unit: An aquatic resource or fishery is
declared as [Fishery] Management Unit if it is
effectively the focus for the application of selected
management methods and measures, within the broader
framework of a management system. According to the FAO
Glossary for Responsible Fishing, "a Fishery Management
Unit (FMU) is a fishery or a portion of a fishery
identified in a Fishery Management Plan (FMP) relevant
to the FMP's management objectives." FMU's may be
organised around fisheries biological, geographic,
economic, technical, social or ecological dimensions ,
and the makeup and attribute of a fishery management
unit depends mainly on the FMP's management
objectives. |
| Jurisdictional distribution: Jurisdictional qualifier (e.g.
"shared", "shared - highly migratory") of the aquatic
resource related with its spatial distribution. |
| Environmental group: Classification of the aquatic
resource according to the environmental group (e.g.
pelagic invertebrate, or demersal fish) to which the
species belong. |
| Reference Year: The Reference Year is the last year considered in the stock assessment and/or fishery status. |
| | | | | | Biological State and Trend Habitat and Biology Climatic zone: Temperate; Tropical. Horizontal distribution: Oceanic. Vertical distribution: Pelagic. Geographical Distribution Jurisdictional distribution: Highly migratory Geo References  | | Geographic extent of Bigeye tuna - Indian Ocean
| FAO Major Fishing Areas | 51: Indian Ocean, Western | | 57: Indian Ocean, Eastern |
| | | | | | Intersecting Major FAO areas and LME areas |
The following area codes have been found as intersecting the distribution of Bigeye tuna - Indian Ocean | FAO Major Fishing Areas | 51:
Indian Ocean, Western | | 57:
Indian Ocean, Eastern | | Large Marine Ecosystem Areas (LME) | 30: Agulhas Current | | 31: Somali Coastal Current | | 32: Arabian Sea | | 33: Red Sea | | 34: Bay of Bengal | | 38: Indonesian Sea | | 39: North Australian Shelf | | 42: Southeast Australian Shelf | | 43: Southwest Australian Shelf | | 44: West-Central Australian Shelf | | 45: Northwest Australian Shelf |
Resource Structure Considered a single stock: Yes The tag recoveries from the RTTP-IO [Regional Tuna Tagging Project-Indian Ocean] provide evidence of rapid and large scale movements of juvenile bigeye tuna in the Indian Ocean, thus supporting the current assumption of a single stock for the Indian Ocean. Exploitation Fishery Indicators | Type | Measure | Value | Unit | Time period |
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| Production | Catch | 6589 | tonnes | Average 1950 - 1959 | | Catch | 22269 | tonnes | Average 1960 - 1969 | | Catch | 31720 | tonnes | Average 1970 - 1979 | | Catch | 58117 | tonnes | Average 1980 - 1989 | | Catch | 120031 | tonnes | Average 1990 - 1999 | | Catch | 136178 | tonnes | Average 2000 - 2009 | | Catch | 95805 | tonnes | Average 2010 - 2019 | | Catch | 94374 | tonnes | 2011 | | Catch | 124759 | tonnes | 2012 | | Catch | 113193 | tonnes | 2013 | | Catch | 93056 | tonnes | 2014 | | Catch | 96396 | tonnes | 2015 | | Catch | 86849 | tonnes | 2016 | | Catch | 90862 | tonnes | 2017 | | Catch | 94750 | tonnes | 2018 | | Catch | 78441 | tonnes | 2019 | | Catch | 83449 | tonnes | 2020 |
Assessment In 2019 a new stock assessment was carried out for bigeye tuna in the IOTC area of competence to update the stock status undertaken in 2016. Two models were applied to the bigeye stock (JABBA and Stock Synthesis (SS3)).The reported stock status is based on the SS3 model formulation using a grid of 18 model configurations designed to capture the uncertainty on stock recruitment relationship, the influence of tagging information and selectivity of longline fleets. On the weight-of-evidence available in 2019, the bigeye tuna stock is determined to be not overfished but subject to overfishing. Assessment Model Type: Age-structured Stock Synthesis III (SS3) Scientific Advice The stock status determination changed qualitatively in 2019 to not overfished but subject to overfishing. If catches remain at 2018 levels there is a risk of breaching MSY reference points with 58.9% and 60.8% probability in 2021 and 2028. Maintaining catches of at least 10% below 2018 levels will likely reduce the probabilities of breaching reference levels to 49.1% in 2028. Continued monitoring and improvement in data collection, reporting and analyses is required to reduce the uncertainty in assessments. Management Management unit: Yes Source of information IOTC–SC23 2020. Report of the 23rd Session of the IOTC Scientific Committee. Seychelles, 7 – 11 December 2020. IOTC–2020–SC23–R[E]: 211ppp.  https://www.iotc.org/sites/default/files/documents/2021/06/IOTC-2020-SC23-RE_Rev1.pdfBibliography All references to figures, tables and bibliography in the text are found within the source of information. |
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