Fisheries and Resources Monitoring System

Bigeye tuna - Indian Ocean
Marine Resource  Fact Sheet
Stock status report 2016
Bigeye tuna - Indian Ocean
Fact Sheet Citation  
Bigeye tuna Indian Ocean
Owned byIndian Ocean Tuna Commission (IOTC) – More
Related observationsLocate in inventorydisplay tree map
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: 2015
Biological State and Trend
State & Trend Descriptors
Exploitation rateNot subject to overfishing (F2015/FMSY (plausible range) = 0.76 (0.49–1.03))Moderate fishing mortality
Abundance levelNot overfished (SB2015/SBMSY (plausible range) = 1.29 (1.07–1.51))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. 
Fishery Indicators
TypeMeasureValueUnitTime period
ProductionCatch 6589tonnesAverage 1950 - 1959
Catch 22269tonnesAverage 1960 - 1969
Catch 31720tonnesAverage 1970 - 1979
Catch 58118tonnesAverage 1980 - 1989
Catch 120419tonnesAverage 1990 - 1999
Catch 136194tonnesAverage 2000 - 2009
Catch 132813tonnes2006
Catch 138255tonnes2007
Catch 122516tonnes2008
Catch 118801tonnes2009
Catch 85368tonnes2010
Catch 92712tonnes2011
Catch 120418tonnes2012
Catch 110844tonnes2013
Catch 90856tonnes2014
Catch 92736tonnes2015

In 2016, six models were applied to 2016 bigeye tuna stock assessment, the majority of which gave qualitatively similar results. Stock status is based on the Stock Synthesis III model formulation. On the weight-of-evidence available in 2016, the bigeye tuna stock is determined to be not overfished and is not subject to overfishing.
Assessment Model
Type:  Age-structured
Age structured assessment program (ASAP)
Statistical-Catch-At-Age (SCAA)
Stock Synthesis III (SS3)
Assessment Model
Type:  Biomass-aggregated
Biomass Dynamic Model (BDM)
A Stock-Production Model Incorporating Covariates (ASPIC)
Bayesian State-Space Production model (BSPM)
Scientific Advice

The stock status determination did not qualitatively change in 2016, but is somewhat less optimistic than in 2013. If catch remains below the estimated MSY levels estimated for the current mix of fisheries, then immediate management measures are not required. However, increased catch or increases in the mortality on immature fish will likely increase the probabilities of breaching reference levels in the future. Continued monitoring and improvement in data collection, reporting and analysis is required to reduce the uncertainty in assessments (Table 2).
Management unit: Yes
Source of information
IOTC–WPTT18 2016. Report of the 18th Session of the IOTC Working Party on Tropical Tunas. Seychelles, 5-10 November 2016. IOTC–2016–WPTT18– R[E]: 126 pp.  Click to open
Bigeye tuna supporting information for the 17th Session of the IOTC Working Party on Tropical Tunas. 2016.  Click to open
All references to figures, tables and bibliography in the text are found within the source of information.
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