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Blue marlin - Indian Ocean
Marine Resource  Fact Sheet
Stock status report 2021
Blue marlin - Indian Ocean
Fact Sheet Citation  
Blue marlin Indian Ocean
Owned byIndian Ocean Tuna Commission (IOTC) – More
Related observationsLocate in inventorydisplay tree map
 
Species:
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: 2017
 
 
Biological State and Trend
State & Trend Descriptors
PartnerFIRMS
Exploitation rateSubject to overfishing (F2017/FMSY (80% CI) = 1.47 (0.96 – 2.35))High fishing mortality
Abundance levelOverfished (B2017/BMSY (80% CI) = 0.82 (0.56 – 1.15))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.
Exploitation
 
Fishery Indicators
TypeMeasureValueUnitTime period
ProductionCatch 2574tonnesAverage 1950 - 1959
Catch 3546tonnesAverage 1960 - 1969
Catch 3550tonnesAverage 1970 - 1979
Catch 5113tonnesAverage 1980 - 1989
Catch 7629tonnesAverage 1990 - 1999
Catch 8696tonnesAverage 2000 - 2009
Catch 8987tonnesAverage 2010 - 2019
Catch 9018tonnes2011
Catch 11965tonnes2012
Catch 8577tonnes2013
Catch 6955tonnes2014
Catch 8506tonnes2015
Catch 9701tonnes2016
Catch 9889tonnes2017
Catch 8536tonnes2018
Catch 8424tonnes2019
Catch 6956tonnes2020
Assessment
 

No new stock assessment for blue marlin was carried out in 2021 so the stock status is based on the 2019 assessment conducted using the Bayesian State-Space Surplus Production model JABBA which suggests that there is an 87% probability that the Indian Ocean blue marlin stock in 2017 is in the red zone of the Kobe plot, indicating the stock is overfished and subject to overfishing (B2017/BMSY=0.82 and F2017/FMSY=1.47) as shown in Table 1 and Fig. 2. The most recent catch is lower than the estimate of MSY (Catch2019 = 8,486 t; MSY = 9,984 t). The previous assessment of blue marlin concluded that in 2015 the stock was subject to overfishing but not overfished. The change in stock status can be attributed to increased catches for the period 2015-2017 as well as improved standardisation of CPUE indices, which includes the area disaggregation of JPN and TWN indices to account for fleet dynamics.
Assessment Model
Type:  Biomass-aggregated
JABBA Model
Scientific Advice

The current catches of blue marlin (average of 8,701 t in the last 5 years, 2016-2020) are lower than MSY (9,984 t). The assessment conducted in 2017 indicated that the stock was overfished and subject to overfishing. In order to achieve the Commission objectives of being in the green zone of the Kobe Plot by 2027 (F2027 < FMSY and B2027 > BMSY) with at least a 60% chance, the catches of blue marlin would have to be reduced by 35% compared to the average of the last 3 years, to a maximum value of approximately 7,800 t.
Management
Management unit: Yes
Source of information
 
IOTC–SC23 2020. Report of the 23rd Session of the IOTC Scientific Committee. Seychelles, 7 – 11 December 2020. IOTC–2020–SC23–R[E]: 211pp.  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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