Fisheries and Resources Monitoring System

Longtail tuna - Indian Ocean
Marine Resource  Fact Sheet
Stock status report 2016
Longtail tuna - Indian Ocean
Fact Sheet Citation  
Longtail tuna Indian Ocean
Owned byIndian Ocean Tuna Commission (IOTC) – More
Related observationsLocate in inventorydisplay tree map
FAO Names: en - Longtail tuna, fr - Thon mignon, es - Atún tongol

Fishery Indicators
Production: Catch
Geographic extent of Longtail tuna - Indian Ocean
Main Descriptors
Considered a single stock: Yes        Management unit: Yes
Reference year: 2014
Biological State and Trend
State & Trend Descriptors
Exploitation rateSubject to overfishing (F2014/FMSY (80% CI) = 1.03 (0.88–1.26))High fishing mortality
Abundance levelOverfished (B2014/BMSY (80% CI) = 0.99 (0.78–1.19))Low 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

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.
Fishery Indicators
TypeMeasureValueUnitTime period
ProductionCatch 3573tonnesAverage 1950 - 1959
Catch 7239tonnesAverage 1960 - 1969
Catch 12727tonnesAverage 1970 - 1979
Catch 36141tonnesAverage 1980 - 1989
Catch 59590tonnesAverage 1990 - 1999
Catch 94437tonnesAverage 2000 - 2009
Catch 78498tonnes2005
Catch 89081tonnes2006
Catch 109851tonnes2007
Catch 105260tonnes2008
Catch 125601tonnes2009
Catch 141115tonnes2010
Catch 171496tonnes2011
Catch 175459tonnes2012
Catch 157656tonnes2013
Catch 146751tonnes2014

Two assessment approaches were applied to Longtail tuna in 2016, a traditional Catch-MSY model and an Optimised Catch Only Method (OCOM). The approaches provided similar estimates of MSY and the same stock status advice. For final reporting and stock status advice the OCOM model was used. 
Assessment Model
Type:  Biomass-aggregated
Optimised Catch Only Method (OCOM)
Scientific Advice

There is a continued high risk of exceeding MSY-based reference points by 2017 if catches are maintained at current (2014) levels. (69% risk that B2017<BMSY, and 81% risk that F 2017>FMSY). If catches are reduced by 10% this risk is lowered to 27% probability B2017<BMSY and 39% probability F2017>FMSY). If the Commission wishes to recover the stock to levels above the MSY reference points, the Scientific Committee recommends catches should be reduced by approximately 10% of current levels which corresponds to catches somewhat below MSY in order to recover the status of the stock in line with the decision framework described in Resolution 15/10.
Management unit: Yes
Source of information
IOTC–WPNT06 2016. Report of the 6th Session of the IOTC Working Party on Neritic Tunas. Mahe, Seychelles 21 – 24 June 2016. IOTC–2016–WPNT06– R[E]: 89 pp.  Click to open
Longtail tuna supporting information for the 6th Session of the IOTC Working Party on Neritic Tunas. 2016.  Click to open
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