Tiger shark population faces decline: Study
Recent studies by fisheries scientists of the
Kerala University of Fisheries and Ocean Studies
(Kufos) raised concerns about the dwindling populations of shark species in the Indian Ocean. The studies, which looked at the iconic tiger sharks (
Galeocerdo cuvier
), flagged concerns about global decline and called for
shark conservation
zones.The population of the tiger shark is in a state of global decline, with the species assessed as 'Near Threatened' on the
IUCN Red List
. Despite this, there is a lack of fundamental information required for regional management, such as those on life history and ecology."We
looked at the population dynamics of G. cuvier in the Arabian Sea, which is one of the world's most important shark fishing regions. Length-frequency data of G. cuvier landed at Cochin over 16 months in 2023–2024 revealed the dominance of the 180–240cm length class, with the largest individual measuring 405cm long.
Almost 95% of younger adults are caught and they are coming in as bycatch, contributing to 23% of the shark landings," said Rajeev Raghavan, aquatic biologist and faculty at the Kufos department of fisheries resource management.A total of 264 species of sharks and rays are known from the Western Indian Ocean (WIO), of which 43% are threatened. Some parts of the WIO are more significant for shark fisheries, such as the Arabian Sea, which harbours 15% of the described chondrichthyan species of the world, more than half of which are threatened. Close to 98% of the tiger sharks that landed at Cochin during the study period were the targets of commercial fishery using baited longline, while the remaining 2% were bycatch originating from gillnet and trawl fisheries."We need to bring in the tiger shark conservation zones. Unlike the Indian Ocean Tuna Commission, which looks at the entire tuna catches across the world, shark conservation does not have such a body. Some countries have banned tiger shark catches. Since it is not banned in India, our fishermen go to far-off deep-sea waters to catch them. The fact that they must go far to catch these species is an indication of dwindling numbers," Raghavan said.
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Dialogue Earth sent a freedom of information request to the European Commission requesting details of attendees of fishing agreement negotiations between the European Union and Madagascar (one of the Indian Ocean's coastal states), including for yellowfin tuna. Only redacted information that does not identify lobbyists was received. Callum Roberts, a professor of marine conservation at the University of Exeter, tells Dialogue Earth he is 'highly doubtful' the Indian Ocean's yellowfin tuna population has grown. 'I think we all deserve far more robust evidence of tuna stock recovery before any credibility can be given to this convenient result,' he says. Dialogue Earth spoke to Isabella Lövin, a Swedish member of the European parliament representing the Miljöpartiet (Green Party) and a member of the European Parliament's Committee on Fisheries. She says the yellowfin assessments must be scrutinised by independent experts: 'These shifting baselines have to be looked at.' The Global Tuna Alliance, a group of retailers and supply chain companies, issued a statement saying: 'engaging constructively with the IOTC and its partners to ensure the management of yellowfin tuna remains firmly grounded in science and precaution.' Kitakado tells Dialogue Earth that, as the chair of the scientific committee, he cannot comment on 'individual views or specific technical matters, which are either already addressed in the committee's reports or are expected to be considered in upcoming discussions within the relevant working parties and the committee itself'. He adds: 'I appreciate the interest in this issue and trust that the committee will continue to fulfil its role with the seriousness and diligence it requires.' The Indian Ocean Tuna Commission secretariat says it has no comment to make beyond the committee's existing report. A spokesperson for the European Commission's Directorate-General for Maritime Affairs and Fisheries says the European Union 'trusts' the 2024 Indian Ocean Tuna Commission stock assessment, adding it is 'based on the rigorous work of highly qualified, independent scientists'. On the presence of lobbyists in the European Union delegation, the spokesperson says: 'The EU follows a wide and transparent consultation process with all stakeholders.' Anne-France Mattlet is the director of Europêche, an industry body representing 45,000 fishing vessels, including the majority of the European Union vessels in the Indian Ocean. She says the Indian Ocean Tuna Commission's stock assessments are 'rigorous', and that Europêche continues 'to advocate for science-based conservation and management measures'.
