Yellowfin tuna in the Indian Ocean has faced significant overfishing over the past ten years. However, a recent stock assessment undertaken by the Working Party on Tropical Tuna held in October 2024, was presented to the Scientific Committee of the Indian Ocean Tuna Commission (IOTC) at their December 2024 meeting held in Durban. The new stock assessment has determined that the yellowfin tuna stock is now in the green, a notable improvement after years of being in the red due to overfishing. Using new modeling approaches and updated data, the assessment highlights notable improvements in stock health and fishing sustainability.
When it comes to population health, the assessment shows that in 2023, the spawning biomass was estimated at 1,063,000 tonnes, which is 132% of the level required for Maximum Sustainable Yield (SBMSY). This indicates that the stock is above the minimum sustainability target. The recent recovery is supported by strong recruitment, with significant numbers of young fish joining the population since 2021. However, it is important to note that the spawning biomass is still only 44% of its initial level in 1950, reflecting long-term declines.
In regards to fishing pressure, the assessment indicates that the level of fishing mortality in 2023 was about 25% lower than the level of Maximum Sustainable Fishing Pressure (FMSY). Additionally, while the average catches from 2021 to 2023 were 413,000 tonnes, the total catch for 2023 was 400,950 tonnes, all below the Maximum Sustainable Yield (MSY) estimate for the Indian Ocean stock which is 421,000 tonnes (with a range of 413,000 to 432,000 tonnes estimated over the past 20 years).
The new green status indicates that yellowfin tuna stocks in the Indian Ocean are under sustainable exploitation. The stock is now classified as not overfished and not subject to overfishing.
The Head of Department for Fisheries Management at the Seychelles Fisheries Mr. Vincent Lucas highlighted several factors that contributed to this positive outcome. “We didn’t expand our fleet, we’ve remained within the quota that was allocated to us, so that relieved the pressure on the stock.” Mr. Lucas also noted other factors including a favourable environment for good recruitment which resulted in the increase in the spawning stock biomass as well.
The Chief executive officer of the SFA, Dr. Jan Robinson underscored the significance of this change in status, emphasizing that effective fisheries management is possible. “The assessment was done according to best practices within the tuna commission and the result of that stock assessment clearly demonstrates that fisheries management can work at the regional level,” he said.
Dr. Robinson emphasized the importance of the country’s contribution. “Seychelles should be very proud of what it did and the sacrifices it made in complying with the catch limits over most of the time that the stock was in red. We would like to thank all our partners and stakeholders, who have contributed to that success.”
Furthermore, Dr. Robinson also noted the importance of remaining conservative, so that the stock does not go back to the red status. He said that there is now an opportunity to move towards adopting harvest strategies for other species within the IOTC, namely Skipjack and Bigeye Tuna.
The stock assessment report for Yellowfin Tuna will be presented to the Indian Ocean Tuna Commission during its meeting scheduled for April, where future management decisions will be discussed.
The summary report can be found on this link: https://iotc.org/sites/default/files/content/Stock_status/2024/Engish/IOTC-2024-SC27-ES04_YFTE.pdf