Fisheries and Resources Monitoring System

Blue marlin - Indian Ocean
Marine Resource  Fact Sheet
Stock status report 2018
Blue marlin - Indian Ocean
Fact Sheet Citation  
Blue marlin Indian Ocean
Owned byIndian Ocean Tuna Commission (IOTC) – More
Related observationsLocate in inventorydisplay tree map
FAO Names: en - Blue marlin, fr - Makaire bleu, es - Aguja azul, ar - مقير أزرق أطلسيّ ، مكيرأزرق أطلسيّ, zh - 蓝枪鱼, ru - Марлин синий

Fishery Indicators
Production: Catch
Geographic extent of Blue marlin - 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) = 1.18 (0.80–1.71))High fishing mortality
Abundance levelNot overfished (B2015/BMSY (80% CI) = 1.11 (0.90–1.35))Intermediate 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 on stock structure is currently available in the Indian Ocean; thus for the purposes of assessment, one pan-ocean stock is assumed. However, spatial heterogeneity in stock indicators (catch–per–unit–effort trends) for other billfish species indicates that there is potential for localised depletion.
Fishery Indicators
TypeMeasureValueUnitTime period
ProductionCatch 2574tonnesAverage 1950 - 1959
Catch 3546tonnesAverage 1960 - 1969
Catch 3550tonnesAverage 1970 - 1979
Catch 5413tonnesAverage 1980 - 1989
Catch 9511tonnesAverage 1990 - 1999
Catch 10226tonnesAverage 2000 - 2009
Catch 8876tonnes2008
Catch 9004tonnes2009
Catch 9205tonnes2010
Catch 11484tonnes2011
Catch 14739tonnes2012
Catch 11865tonnes2013
Catch 10149tonnes2014
Catch 11636tonnes2015
Catch 12361tonnes2016
Catch 12029tonnes2017

A range of quantitative modelling methods (SS3, ASPIC and Bayesian state space Surplus Production Model) were applied to the Blue marlin in 2016. These models showed similar stock trajectories, and based on the weight-of evidence approach, the WPB agreed to use the results from the Bayesian state space Surplus Production Model for stock status advice. In any case, further work needs to be conducted in future years to improve these assessments.
Assessment Model
Type:  Biomass-aggregated
Bayesian Surplus Production Model – State-Space (BSP-SS)
A Stock-Production Model Incorporating Covariates (ASPIC)
Assessment Model
Type:  Age-structured
Stock Synthesis III (SS3)
Scientific Advice

The current catches of BUM [blue marlin] (average of 15400 t in the last 3 years, 2013-2015) are higher than MSY (11926 t) and the stock is currently being overfished (Fcurr > FMSY). In order to achieve the Commission objectives of being in the green zone of the Kobe Plot by 2025 (F2025 < FMSY and B2025 > BMSY) with at least a 50% chance, the catches of blue marlin would have to be reduced by 24% compared to the average of the last 3 years, to a maximum value of 11704 t.
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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