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| Marine Resource Fact Sheet |
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| Blue marlin - Indian Ocean |
| | Data Ownership | | This document provided, maintained and owned by Indian Ocean Tuna Commission (IOTC) , is part of IOTC Stock Status Reports data collection. |
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| Related observations | Locate in inventory | | | | 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 IndicatorsProduction: Catch |
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| Geographic extent of Blue marlin - Indian Ocean Map tips - Click on
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| FAO Major Fishing Areas |
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| 51 | Indian Ocean, Western |
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| 57 | Indian Ocean, Eastern |
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| Main Descriptors | Considered a single stock: Yes Management unit: Yes
Reference year: 2015 |
| Considered a single stock: A group of individuals in a species occupying a well defined spatial range independent of other stocks of the same species. It can be affected by random dispersal movements and directed migrations due to seasonal or reproductive activity. |
| Spatial Scale: Spatial scale contains a standard term such as Global, Regional (e.g. for the whole Atlantic), sub-regional (e.g. for a part of the Atlantic), national, local (for sub-national levels). |
| Considered a management unit: An aquatic resource or fishery is declared as [Fishery] Management Unit if it is effectively the focus for the application of selected management methods and measures, within the broader framework of a management system. According to the FAO Glossary for Responsible Fishing, "a Fishery Management Unit (FMU) is a fishery or a portion of a fishery identified in a Fishery Management Plan (FMP) relevant to the FMP's management objectives." FMU's may be organised around fisheries biological, geographic, economic, technical, social or ecological dimensions , and the makeup and attribute of a fishery management unit depends mainly on the FMP's management objectives. |
| Jurisdictional distribution: Jurisdictional qualifier (e.g. "shared", "shared - highly migratory") of the aquatic resource related with its spatial distribution. |
| Environmental group: Classification of the aquatic resource according to the environmental group (e.g. pelagic invertebrate, or demersal fish) to which the species belong. |
| Reference Year: The Reference Year is the last year considered in the stock assessment and/or fishery status. |
| | | | | | Biological State and Trend Habitat and Biology Climatic zone: Temperate; Tropical. Horizontal distribution: Oceanic. Vertical distribution: Pelagic. Geographical Distribution Jurisdictional distribution: Highly migratory Geo References  | | Geographic extent of Blue marlin - Indian Ocean
| FAO Major Fishing Areas | 51: Indian Ocean, Western | | 57: Indian Ocean, Eastern |
| | | | | | Intersecting Major FAO areas and LME areas |
The following area codes have been found as intersecting the distribution of Blue marlin - Indian Ocean | FAO Major Fishing Areas | 51: Indian Ocean, Western | | 57: Indian Ocean, Eastern | | Large Marine Ecosystem Areas (LME) | 30: Agulhas Current | | 31: Somali Coastal Current | | 32: Arabian Sea | | 33: Red Sea | | 34: Bay of Bengal | | 38: Indonesian Sea | | 39: North Australian Shelf | | 42: Southeast Australian Shelf | | 43: Southwest Australian Shelf | | 44: West-Central Australian Shelf | | 45: Northwest Australian Shelf |
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 | Type | Measure | Value | Unit | Time period |
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| Production | Catch | 2574 | tonnes | Average 1950 - 1959 | | Catch | 3546 | tonnes | Average 1960 - 1969 | | Catch | 3550 | tonnes | Average 1970 - 1979 | | Catch | 5413 | tonnes | Average 1980 - 1989 | | Catch | 9511 | tonnes | Average 1990 - 1999 | | Catch | 10226 | tonnes | Average 2000 - 2009 | | Catch | 8876 | tonnes | 2008 | | Catch | 9004 | tonnes | 2009 | | Catch | 9205 | tonnes | 2010 | | Catch | 11484 | tonnes | 2011 | | Catch | 14739 | tonnes | 2012 | | Catch | 11865 | tonnes | 2013 | | Catch | 10149 | tonnes | 2014 | | Catch | 11636 | tonnes | 2015 | | Catch | 12361 | tonnes | 2016 | | Catch | 12029 | tonnes | 2017 |
Assessment 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 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.  https://iotc.org/sites/default/files/documents/2019/02/IOTC-2018-SC21-RE_FINAL_DO_NOT_MODIFY_Rev1.pdfBibliography All references to figures, tables and bibliography in the text are found within the source of information. |
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