Whale sharks caught in Indian Ocean tuna fisheries should be released, not kept, according to a new scientific paper. A conditional ban was agreed in 2025, and the paper sets out the evidence needed to put it into effect.
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A whale shark swims beneath snorkelers.
A ban waiting for scientific advice
In 2025, the Indian Ocean Tuna Commission, which manages tuna fishing across the Indian Ocean, adopted a measure that conditionally banned keeping whale sharks (Rhincodon typus) caught by its fisheries. For whale sharks, the ban only takes effect once the Commission’s scientific advisers, its Scientific Committee, “explicitly and unambiguously” recommend it. The committee has agreed that whale sharks are a species “of the greatest biological vulnerability and conservation concern”, but has not yet made that recommendation.
James Bell of the UK’s Centre for Environment, Fisheries and Aquaculture Science (Cefas) led the new paper. It was submitted for the 2026 meeting of the Commission’s working group on bycatch, the animals caught unintentionally in fisheries. His co-authors include colleagues at Cefas, South Africa’s Department of Forestry, Fisheries and the Environment, and Australia’s national science agency, CSIRO, along with MMF Co-Founder and Executive Director Dr. Simon Pierce. The paper asks the working group to endorse the ban, and the Scientific Committee to advise the Commission that it is an appropriate measure.
What the evidence shows
Whale sharks have been listed as Endangered on the IUCN Red List, which assesses species’ extinction risk, since 2016. The population across the Indian and Pacific oceans makes up around 75% of all whale sharks. It is estimated to have declined by more than 65% since 1900. Whale sharks are slow to recover from losses. Males are thought to start maturing at around 25 years old and females at 30 to 40, and whale sharks are thought to live for at least 50 years.
Official catch reports to the Commission record only three whale shark catches between 1950 and 2024. Yet trained observers aboard fishing boats record regular encounters between whale sharks and tuna fleets in the western Indian Ocean, especially in Seychelles waters and the international waters just to the north. These fleets use purse-seine nets, which encircle a school of fish and then close underneath it. The authors conclude that the official records are almost certainly incomplete.
How release helps
A ban on keeping whale sharks won’t stop them from being caught, but the authors expect it to reduce how many die. Studies estimate that only 0 to 4% of whale sharks die soon after release from purse-seine nets, as long as crews follow safe handling practices. Less is known about longer-term effects. Whale sharks also have little commercial value in most of these fisheries and are already released in most recorded cases, so the authors expect a ban to cost very little. Tuna commissions in the western Pacific and the Atlantic already prohibit keeping whale sharks.
The paper also calls for the existing rule against deliberately setting nets around whale sharks to be kept and, where possible, strengthened. It proposes letting trained observers take small tissue samples from live whale sharks before release, without harming them. This would happen only as part of approved research, and only where it is safe and does not compromise the shark’s release. Those samples support DNA studies that estimate how many whale sharks remain and whether their numbers are changing.
Read the full paper. To learn more about the species, visit our whale shark page, or adopt a whale shark to support new research on whale sharks.