Fisheries and Resources Monitoring System

Longtail tuna - Indian Ocean
Marine Resource  Fact Sheet
Stock status report 2018
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: 2015
Biological State and Trend
State & Trend Descriptors
Exploitation rateSubject to overfishing (F2015/FMSY (80% CI) = 1.04 (0.84–1.46) )High fishing mortality
Abundance levelOverfished (B2015/BMSY (80% CI) = 0.94 (0.68–1.16))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 3569tonnesAverage 1950 - 1959
Catch 7235tonnesAverage 1960 - 1969
Catch 12681tonnesAverage 1970 - 1979
Catch 35849tonnesAverage 1980 - 1989
Catch 59589tonnesAverage 1990 - 1999
Catch 94437tonnesAverage 2000 - 2009
Catch 105260tonnes2008
Catch 125601tonnes2009
Catch 141115tonnes2010
Catch 171405tonnes2011
Catch 175494tonnes2012
Catch 157157tonnes2013
Catch 147970tonnes2014
Catch 137161tonnes2015
Catch 132580tonnes2016
Catch 139950tonnes2017

The assessment in 2017 was conducted using the Optimised Catch Only Method (OCOM). Based on the weight-of-evidence available, the stock is considered to be both overfished and subject to overfishing.
Assessment Model
Type:  Biomass-aggregated
Optimised Catch Only Method (OCOM)
Scientific Advice

There is a substantial risk of exceeding MSY-based reference points by 2018 if catches are maintained at current (2015) levels. If catches are capped at current (2015) levels at the time of the assessment, the stock is expected to recover to levels above MSY reference points with at least a 50% probability by 2025.
Management unit: Yes
Source of information
IOTC–SC21 2018. Report of the 21st Session of the IOTC Scientific Committee. Seychelles, 3 – 7 December 2018. IOTC–2018–SC21–R[E]: 250 pp.  Click to open
All references to figures, tables and bibliography in the text are found within the source of information.
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