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Bigeye tuna - Indian Ocean
Marine Resource  Fact Sheet
Stock status report 2020
Bigeye tuna - Indian Ocean
Fact Sheet Citation  
Bigeye tuna Indian Ocean
Owned byIndian Ocean Tuna Commission (IOTC) – More
Related observationsLocate in inventorydisplay tree map
 
Species:
FAO Names: en - Bigeye tuna, fr - Thon obèse(=Patudo), es - Patudo, ru - Тунец большеглазый

Fishery Indicators
Production: Catch
Geographic extent of Bigeye tuna - Indian Ocean
Main Descriptors
Considered a single stock: Yes        Management unit: Yes
Reference year: 2018
 
 
Biological State and Trend
State & Trend Descriptors
PartnerFIRMS
Exploitation rateSubject to overfishing (F2018/FMSY (plausible range) = 1.20 (0.70-2.05))Moderate fishing mortality
Abundance levelNot overfished (SB2018/SBMSY (plausible range) = 1.22 (0.82-1.81))Pre-exploitation biomass or high abundance
Habitat and Biology
Climatic zone: Temperate; Tropical.   Horizontal distribution: Oceanic.   Vertical distribution: Pelagic.  

Geographical Distribution
Jurisdictional distribution: Highly migratory

Water Area Overview
 
Geo References
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
TypeMeasureValueUnitTime period
ProductionCatch 6589tonnesAverage 1950 - 1959
Catch 22269tonnesAverage 1960 - 1969
Catch 31720tonnesAverage 1970 - 1979
Catch 58117tonnesAverage 1980 - 1989
Catch 120031tonnesAverage 1990 - 1999
Catch 136178tonnesAverage 2000 - 2009
Catch 95805tonnesAverage 2010 - 2019
Catch 94374tonnes2011
Catch 124759tonnes2012
Catch 113193tonnes2013
Catch 93056tonnes2014
Catch 96396tonnes2015
Catch 86849tonnes2016
Catch 90862tonnes2017
Catch 94750tonnes2018
Catch 78441tonnes2019
Catch 83449tonnes2020
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. 2020. Bigeye tuna. Executive Summary.  Click to openhttps://iotc.org/sites/default/files/Bigeye2020.pdf
IOTC–SC23 2020. Report of the 23rd Session of the IOTC Scientific Committee. Seychelles, 7 – 11 December 2020. IOTC–2020–SC23–R[E]: 211ppp.  Click to openhttps://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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