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Global collision-risk hotspots of marine traffic and the world's largest fish, the whale shark

Global collision-risk hotspots of marine traffic and the world's largest fish, the whale shark
Global collision-risk hotspots of marine traffic and the world's largest fish, the whale shark
Marine traffic is increasing globally yet collisions with endangered megafauna such as whales, sea turtles, and planktivorous sharks go largely undetected or unreported. Collisions leading to mortality can have population-level consequences for endangered species. Hence, identifying simultaneous space use of megafauna and shipping throughout ranges may reveal as-yet-unknown spatial targets requiring conservation. However, global studies tracking megafauna and shipping occurrences are lacking. Here we combine satellite-tracked movements of the whale shark, Rhincodon typus, and vessel activity to show that 92% of sharks’ horizontal space use and nearly 50% of vertical space use overlap with persistent large vessel (>300 gross tons) traffic. Collision-risk estimates correlated with reported whale shark mortality from ship strikes, indicating higher mortality in areas with greatest overlap. Hotspots of potential collision risk were evident in all major oceans, predominantly from overlap with cargo and tanker vessels, and were concentrated in gulf regions, where dense traffic co-occurred with seasonal shark movements. Nearly a third of whale shark hotspots overlapped with the highest collision-risk areas, with the last known locations of tracked sharks coinciding with busier shipping routes more often than expected. Depth-recording tags provided evidence for sinking, likely dead, whale sharks, suggesting substantial “cryptic” lethal ship strikes are possible, which could explain why whale shark population declines continue despite international protection and low fishing-induced mortality. Mitigation measures to reduce ship-strike risk should be considered to conserve this species and other ocean giants that are likely experiencing similar impacts from growing global vessel traffic.
0027-8424
Womersley, Freya C.
bd2e3be2-2eb1-4d49-8b17-40f07367f9ff
Humphries, Nicolas E.
7eb196e4-95ec-4878-a26e-e96abd8accd6
Queiroz, Nuno
822695eb-684b-4e4b-b662-6435e7bf86d6
Sims, David W.
7234b444-25e2-4bd5-8348-a1c142d0cf81
et al.
Womersley, Freya C.
bd2e3be2-2eb1-4d49-8b17-40f07367f9ff
Humphries, Nicolas E.
7eb196e4-95ec-4878-a26e-e96abd8accd6
Queiroz, Nuno
822695eb-684b-4e4b-b662-6435e7bf86d6
Sims, David W.
7234b444-25e2-4bd5-8348-a1c142d0cf81

Womersley, Freya C., Humphries, Nicolas E. and Queiroz, Nuno , et al. (2022) Global collision-risk hotspots of marine traffic and the world's largest fish, the whale shark. Proceedings of the National Academy of Sciences, 119 (20), [e2117440119].

Record type: Article

Abstract

Marine traffic is increasing globally yet collisions with endangered megafauna such as whales, sea turtles, and planktivorous sharks go largely undetected or unreported. Collisions leading to mortality can have population-level consequences for endangered species. Hence, identifying simultaneous space use of megafauna and shipping throughout ranges may reveal as-yet-unknown spatial targets requiring conservation. However, global studies tracking megafauna and shipping occurrences are lacking. Here we combine satellite-tracked movements of the whale shark, Rhincodon typus, and vessel activity to show that 92% of sharks’ horizontal space use and nearly 50% of vertical space use overlap with persistent large vessel (>300 gross tons) traffic. Collision-risk estimates correlated with reported whale shark mortality from ship strikes, indicating higher mortality in areas with greatest overlap. Hotspots of potential collision risk were evident in all major oceans, predominantly from overlap with cargo and tanker vessels, and were concentrated in gulf regions, where dense traffic co-occurred with seasonal shark movements. Nearly a third of whale shark hotspots overlapped with the highest collision-risk areas, with the last known locations of tracked sharks coinciding with busier shipping routes more often than expected. Depth-recording tags provided evidence for sinking, likely dead, whale sharks, suggesting substantial “cryptic” lethal ship strikes are possible, which could explain why whale shark population declines continue despite international protection and low fishing-induced mortality. Mitigation measures to reduce ship-strike risk should be considered to conserve this species and other ocean giants that are likely experiencing similar impacts from growing global vessel traffic.

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womersley-et-al-2022-global-collision-risk-hotspots-of-marine-traffic-and-the-world-s-largest-fish-the-whale-shark - Version of Record
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Accepted/In Press date: 26 February 2022
e-pub ahead of print date: 9 May 2022
Published date: 17 May 2022

Identifiers

Local EPrints ID: 485285
URI: http://eprints.soton.ac.uk/id/eprint/485285
ISSN: 0027-8424
PURE UUID: 1e52fb8b-caa5-4dc4-ab79-aecbb30d4b49
ORCID for David W. Sims: ORCID iD orcid.org/0000-0002-0916-7363

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Date deposited: 04 Dec 2023 17:30
Last modified: 19 Jun 2024 01:45

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Contributors

Author: Nicolas E. Humphries
Author: Nuno Queiroz
Author: David W. Sims ORCID iD
Corporate Author: et al.

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