The Catch of Tropical Tunafish in Indian Ocean (IO).

 

About 23 percent of the world’s tuna production comes from the Indian Ocean (IO)– FAO Major Fishing Areas 51 and 57–making it the second most important region for tuna fishing after the Western and Central Pacific Ocean. Catches of skipjack, yellowfin, bigeye and albacore tuna in 2023 totaled approximately 1 237 000 tonnes, a 1 percent decrease from 2022. The total catch generally declined after 2005, when a record 1.25 million tonnes were caught, followed by an increase in recent years which has brought catches back to 2005 levels (FIGURE E.1.16). Catches of southern bluefin tuna occur primarily in the IO Area of Competence. However, due to their distribution across three oceans, this stock is covered below under a separate section on the CCSBT convention area.

The catch of tropical tunas and albacore tuna in the IO steadily increased, reaching 200 000 tonnes in the early 1980s. It then rose rapidly to 500 000 tonnes in 1988 with the advent of the purse-seine fishery in the mid-1980s. Catches continued increasing quickly, reaching 600 000 tonnes in 1991, 700 000 tonnes in 1992, 800 000 tonnes in 1993, 900 000 tonnes in 1999, and 1.0 million tonnes in 2002. The highest recorded catch of 1.25 million tonnes was reached in 2005. Since then, catches declined until 2015 but have increased again, returning to 2005 levels in recent years (2022 and 2023) (FIGURE E.1.16). The average tuna catch over the last five-year period (2019–2023) was 1 181 710 tonnes. During this period, skipjack tuna accounted for 53 percent of the total catch by weight, followed by yellowfin tuna (36 percent), bigeye tuna (8 percent) and albacore tuna (3 percent). Purse-seine vessels caught 42 percent of the total catch, followed by other fishing gears including handlines, trolling lines, coastal drifting longlines, and all other fishing gears used in coastal areas (22 percent), gillnets (15 percent), pole-and-line (12 percent), and longlines (9 percent). Skipjack tuna catches continuously increased, peaking at around 0.6 million tonnes in 2006, then declined before rising again in 2016. They reached a record high of 0.69 million tonnes in 2023. Meanwhile, the yellowfin tuna catch reached its highest level in 2004, totaling about 0.54 million tonnes. Since then, catches have declined, stabilizing at about 0.4–0.45 million tonnes over the last ten years (FIGURE E.1.16). Bigeye tuna has a similar catch history to yellowfin tuna, with catches increasing until reaching a record high of 137 000 tonnes in 2004, followed by a decline. However, albacore tuna exhibited different trends, peaking in 2013 at 50 000 tonnes and then fluctuating between 35 000 tonnes and 48 000 tonnes.

BIGEYE TUNA Bigeye tuna catches in 2023 were about 105 877 tonnes, a 17 percent increase from 2022. For the period 2019–2023, the main fishing gear is purse seine (43 percent), followed by longline (37 percent). Longline catches have declined dramatically from a high in 2004 (FIGURE E.1.17), due to vessels moving away from the main fishing grounds to avoid piracy, though they increased sharply in 2012 only to decrease again since then. In contrast, catches from purse-seine vessels have been relatively stable since 2000, with the exception of 2018 and 2021–2023 during which catches were elevated: the catch in 2023 is the highest in the record (52 000 tonnes). 

YELLOWFIN TUNA Yellowfin tuna catches in 2023 were about 401 364 tonnes, an 8 percent decrease from 2022. The main fishing gears for yellowfin tuna for the 2019–2023 period are purse seine (30 percent of the catch), followed by handlines (27 percent), gillnets (15 percent), other line fisheries such as troll and coastal longline (15 percent), longline (9 percent) and poleand-line (3 percent) (FIGURE E.1.17). Catches by gillnet (15 percent) and miscellaneous line gears (42 percent including handline, troll and coastal longline) have become increasingly important in recent years. Catches by these gears are poorly estimated. Catches from pole-and-line vessels (3 percent) have been relatively stable. Overall, catches have declined by 26 percent from a record high of 540 000 tonnes in 2004; but annual catches have stayed above 400 000 tonnes since 2012, and another peak of over 450 000 tonnes was reached in 2018–2019. 

SKIPJACK TUNA Skipjack tuna catches in the IO in 2023 were about 688 679 tonnes, a 2 percent increase from 2022. Purse seine (54 percent), pole-and-line (20 percent) and gillnets (17 percent) dominate the catches, with other miscellaneous gears catching around 9 percent (FIGURE E.1.17). Pole-and-line, purse-seine and gillnet catches decreased since the mid-2000s for about a decade, but show an increasing trend after 2012, notably so for purse seine. 

ALBACORE TUNA Albacore tuna catches in the IO in 2023 were about 41 680 tonnes, a 15 percent decrease from 2022. Almost all catches are made by pelagic longlines (83 percent) while the contribution of other miscellaneous gears is around 17 percent (FIGURE E.1.17)

BIGEYE TUNA The latest assessment conducted by the Scientific Committee in 2022 (IOTC, 2024) indicated that the stock is overfished and overfishing is taking place (TABLE E.1.5 and FIGURE E.1.18). The 2022 and 2023 catch (both around 100 000 tonnes) were above the MSY level and above the TAC for 2024–2025 (80 583 tonnes). 

YELLOWFIN TUNA In 2024 a new stock assessment was carried out for yellowfin tuna in the IOTC area of competence which resulted in a more optimistic stock status than the 2021 model (IOTC, 2024). This was mostly due to the new abundance index derived from the joint catch per unit effort (CPUE) estimated for longline fleets which was significantly different from the index used in 2021, suggesting a marked increase of abundance for yellowfin in the last three years (2021–2023). The new stock assessment indicated that the stock is not overfished and overfishing is not occurring. According to the 2024 assessment, the total catch has remained within the estimated range of MSY since 2007 (i.e. between 402 000 tonnes and 427 000 tonnes), with the exception of 2018 (443 252 tonnes) and 2019 (450 586 tonnes), the latter being the largest catch since 2006 and above the estimated recent MSY value. However, there is considerable uncertainty related to the new CPUE that requires further exploration. 

SKIPJACK TUNA The most recent stock assessment of skipjack tuna was conducted in 2023 (IOTC, 2024) and indicated that the stock is not overfished and overfishing is not occurring. The catch in 2023 (688 680 tonnes) was larger than the estimated median value of MSY (584 800 tonnes); if this catch trend continues, overfishing might occur

ALBACORE TUNA The latest assessment was performed in 2022 (IOTC, 2024) and indicated that the stock is not overfished and overfishing is not occurring. However, there is considerable uncertainty associated with the latest stock assessment.

BIGEYE TUNA Indian Ocean bigeye tuna is managed by a management procedure (IOTC Res 22/03) with the objective of maintaining the stock with 60 percent probability in the green zone of the Kobe plot while maximizing the average catch from the fishery and reducing the variation in the TAC between management periods (15 percent TAC change limit). 

YELLOWFIN TUNA There is no management procedure. 

SKIPJACK TUNA The skipjack tuna in the IO is managed through a management procedure (IOTC Res 24/07) with the objective to have at least 50 percent probability that the spawning stock biomass achieves the target biomass level of 40 percent SSB0 by 2034–2038, is maintained above the biomass of SSBMSY with very high probability, is maintained above the biomass of 20 percent of SSB0 at all times, and a maximum increase in TAC of 15 percent and a maximum decrease of 10 percent relative to the previous TAC. 

ALBACORE TUNA There is no management procedure.

BIGEYE TUNA The only conservation measure established by the IOTC specifically for bigeye tuna is Resolution 23/04, which establishes catch limits by contracting parties or cooperating non-contracting parties (CPCs) as per the management procedure (Res. 22/03) and Resolution 01/06 concerning IOTC bigeye tuna statistical document programme.

 YELLOWFIN TUNA Resolution 21/01 establishes an interim plan for rebuilding the IO yellowfin tuna stock in the IOTC area of competence. This plan details yellowfin tuna catch limits and provisions, requiring that CPCs whose fleets exceed their catch limits will have that overcatch deducted from their annual limits in future years. Moreover, Resolution 21/01 requests CPCs to gradually reduce supply vessels by 31 December 2022, which also affects the management of bigeye and skipjack tuna.

 SKIPJACK TUNA The annual skipjack tuna catch limit for the 2024–2026 period was established in IOTC Circular 2024-11 applying the skipjack tuna harvest control rule specified in Resolution 21/03, which has been amended by IOTCRes 24/07. The new management procedure will be used to establish the catch limits for the 2027–2029 period.

BIGEYE TUNA The only conservation measure established by the IOTC specifically for bigeye tuna is Resolution 23/04, which establishes catch limits by contracting parties or cooperating non-contracting parties (CPCs) as per the management procedure (Res. 22/03) and Resolution 01/06 concerning IOTC bigeye tuna statistical document programme. 

YELLOWFIN TUNA Resolution 21/01 establishes an interim plan for rebuilding the IO yellowfin tuna stock in the IOTC area of competence. This plan details yellowfin tuna catch limits and provisions, requiring that CPCs whose fleets exceed their catch limits will have that overcatch deducted from their annual limits in future years. Moreover, Resolution 21/01 requests CPCs to gradually reduce supply vessels by 31 December 2022, which also affects the management of bigeye and skipjack tuna.

 SKIPJACK TUNA The annual skipjack tuna catch limit for the 2024–2026 period was established in IOTC Circular 2024-11 applying the skipjack tuna harvest control rule specified in Resolution 21/03, which has been amended by IOTCRes 24/07. The new management procedure will be used to establish the catch limits for the 2027–2029 period.

TROPICAL TUNAS In addition to the species-specific management measures above, there are other IOTC resolutions affecting the three tropical tunas, which are described below: 

„ Resolution 24/06 establishes a ban on discards of bigeye, skipjack and yellowfin tuna by purse-seine vessels. 

„ Resolution 24/02 establishes procedures on a FAD management plan, including: 

■ An IOTC-wide FAD register effective as of 1 January 2026. 

■ A limit of 250 instrumented buoys at sea at any one time per vessel from 1 January 2026 (225 from 1 January 2028) and a limit of 400 instrumented buoys to be acquired annually by each fishing vessel. 

■ A requirement to report daily information on all active drifting fish aggregating devices (DFADs) to the IOTC with a time delay of 30 to 60 days. 

■ Ban, prevention and reporting measures for abandoned, lost or otherwise discarded DFADs. 

■ A requirement to use non-entangling FADs constructed without netting material and remove from the water all traditional FADs encountered (e.g. those made of entangling materials or designs). 

■ A stepwise timeline for a fleet-wide transition to the use of biodegradable FADs between 1 January 2026 and 1 January 2030. 

■ A DFAD marking scheme requires that the instrumented buoys attached to deployed DFADs are permanently marked with a unique reference number marking and the IOTC unique vessel identifier. 

■ A timeline to reduce supply vessels in tropical tuna purse-seine operations.