Status summary for species of tuna and tuna-like species under the IOTC mandate, as well as other species impacted by IOTC fisheries

Each link below allows you to download a PDF version of the Executive summary on the status of the species.
(see Key table for Stock Status Colours at the bottom of the page)

2025-2029: Schedule of future Stock Assessments (PDF file)

Temperate and tropical tunas

These are the main stocks being exploited by large-scale industrial, and to a lesser extent, artisanal fisheries throughout the Indian Ocean, both on the high seas and in the EEZ of coastal states.

	Stock Status	Executive Summary	Supporting information
Albacore (Thunnus alalunga)	85%*
Bigeye tuna (Thunnus obesus)	79%
Skipjack tuna (Katsuwonus pelamis)	70%
Yellowfin tuna (Thunnus albacares)	89%

*Estimated probability that the stock is in the respective quadrant of the Kobe plot, derived from the confidence intervals associated with the current stock status (SS3 stock assessment model).

Billfish

These are the billfish species being exploited by industrial and artisanal fisheries throughout the Indian Ocean, both on the high seas and in the EEZ of coastal states. The marlins and sailfish are not usually targeted by most fleets, but are caught and retained as a byproduct by the main industrial fisheries. They are important for localised small-scale and artisanal fisheries or as targets in recreational fisheries.

	Stock Status	Executive Summary	Supporting information
Swordfish (Xiphias gladius)	97%*
Black marlin (Istiompax indica)	62%
Blue marlin (Makaira nigricans)	72%
Striped marlin (Kajikia audax)	100%
Indo-Pacific sailfish (Istiophorus platypterus)	54%

*Estimated probability that the stock is in the respective quadrant of the Kobe plot, derived from the confidence intervals associated with the current stock status.

Neritic tunas and mackerels (seerfishes)

The six species under the IOTC mandate have become as important or more important than the three tropical tuna species (bigeye tuna, skipjack tuna and yellowfin tuna) to most IOTC coastal states with a total estimated catch of about 600,000 t being landed in recent years. They are caught primarily by coastal fisheries, including small-scale industrial and artisanal fisheries. They are almost always caught within the EEZs of Indian Ocean coastal states. Historically, catches were often reported as aggregates of various species, making it difficult to obtain appropriate data for stock assessment analyses.

	Stock Status	Executive Summary	Supporting information
Bullet tuna (Auxis rochei)
Frigate tuna (Auxis thazard)
Kawakawa (Euthynnus affinis)	27%
Longtail tuna (Thunnus tonggol)	35%
Indo-Pacific king mackerel (Scomberomorus guttatus)	27%
Narrow-barred Spanish mackerel (Scomberomorus commerson)	31%

Sharks

Although sharks are not part of the 16 species directly under the IOTC mandate, sharks are frequently caught in association with fisheries targeting IOTC species. Some fleets are known to actively target both sharks and IOTC species simultaneously. As such, IOTC Contracting Parties and Cooperating non-Contracting Parties are required to report information at the same level of detail as for the 16 species directly under the IOTC mandate. The following are the main species caught in IOTC fisheries, although the list is not exhaustive.

	Stock Status	Executive Summary	Supporting information
Blue shark (Prionace glauca)	99.99%
Oceanic whitetip shark (Carcharhinus longimanus)
Scalloped hammerhead shark (Sphyrna lewini)
Shortfin mako shark (Isurus oxyrinchus)
Silky shark (Carcharhinus falciformis)
Bigeye thresher shark (Alopias superciliosus)
Pelagic thresher shark (Alopias pelagicus)
Porbeagle shark (Lamna nasus)

Marine turtles

Reporting of interactions with IOTC fisheries is required by the Commission.

	Stock Status	Executive Summary	Supporting information
Marine turtles (6 species)

Seabirds

Reporting of interactions with IOTC fisheries is required by the Commission.

	Stock Status	Executive Summary	Supporting information
Seabirds (various species)

Cetaceans

Reporting of interactions with IOTC fisheries is required by the Commission.

	Stock Status	Executive Summary	Supporting information
Cetaceans (various species)