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Marine Resource Fact Sheet |
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Longtail tuna - Indian Ocean |
Longtail 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 - Longtail tuna, fr - Thon mignon, es - Atún tongol |
Fishery IndicatorsProduction: Catch |
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| Geographic extent of Longtail 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: 2019 |
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 Longtail 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 Longtail 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 No information is available on the stock structure of longtail tuna in the Indian Ocean. The IOTC coordinated Stock Structure Project, which commenced in early-2015, aims to supplement gaps in the existing knowledge on biological data, and in particular provide an insight on whether neritic tuna and tuna like species should be considered as a single Indian Ocean stock. Exploitation Fishery Indicators Type | Measure | Value | Unit | Time period |
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Production | Catch | 3564 | tonnes | Average 1950 - 1959 | Catch | 7230 | tonnes | Average 1960 - 1969 | Catch | 12681 | tonnes | Average 1970 - 1979 | Catch | 35901 | tonnes | Average 1980 - 1989 | Catch | 58852 | tonnes | Average 1990 - 1999 | Catch | 96029 | tonnes | Average 2000 - 2009 | Catch | 147223 | tonnes | Average 2010 - 2019 | Catch | 171633 | tonnes | 2011 | Catch | 176724 | tonnes | 2012 | Catch | 158193 | tonnes | 2013 | Catch | 148661 | tonnes | 2014 | Catch | 140008 | tonnes | 2015 | Catch | 141352 | tonnes | 2016 | Catch | 144970 | tonnes | 2017 | Catch | 136154 | tonnes | 2018 | Catch | 112914 | tonnes | 2019 | Catch | 132529 | tonnes | 2020 |
Assessment No new assessment was conducted for longtail tuna in 2021 and so the results are based on the assessment carried out in 2020 using the Optimised Catch-Only Method (OCOM). Analysis using the OCOM indicates that the stock is being exploited at a rate that exceeded FMSY in recent years and that the stock appears to be below BMSY and above FMSY (76% of plausible models runs) (Fig. 2). Catches were above MSY between 2010 and 2018 but steadily declined from 2012 to were less than 113,000 t in 2019, below the estimated MSY (Fig. 1). The F2018/FMSY ratio is slightly higher than previous estimates. The estimate of the B2018 /BMSY ratio (0.69) was lower than in previous years, reflecting declining abundance. An assessment using a biomass dynamic model incorporating gillnet CPUE indices was also undertaken in 2020 and results were consistent with OCOM in terms of status. Therefore, based on the weight-of-evidence currently available, the stock is considered to be both overfished and subject to overfishing (Table 1; Fig. 2). Assessment Model Type: Biomass-aggregated Optimised Catch Only Method (OCOM) Scientific Advice The catch in 2019 was below the estimated MSY but the exploitation rate has been increasing over the last few years, as a result of the declining abundance. Despite the substantial uncertainties, this suggests that the stock is very close to being fished at MSY levels and that higher catches may not be sustained. A precautionary approach to management is recommended. 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]: 211pp. https://www.iotc.org/sites/default/files/documents/2021/06/IOTC-2020-SC23-RE_Rev1.pdf Bibliography All references to figures, tables and bibliography in the text are found within the source of information. |
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