First detection of critically endangered scalloped hammerhead sharks (Sphyrna lewini) in Guam, Micronesia, in five decades using environmental DNA. (August 2021)

• Record Type: Journal Article
• Authors: Budd, Alyssa M.; Cooper, Madalyn K.; Port, Agnès Le; Schils, Tom; Mills, Matthew S.; Deinhart, Mari E.; Huerlimann, Roger; Strugnell, Jan M.
• Is Part Of: Ecological indicators. Volume 127(2021)
• Publication Date: 2021-08
• Subjects: Biomonitoring -- Chondrichthyes -- Conservation -- eDNA -- Elasmobranch -- Survey; Environmental monitoring -- Periodicals; Environmental management -- Periodicals; Environmental impact analysis -- Periodicals; Environmental risk assessment -- Periodicals; Sustainable development -- Periodicals; 333.71405
• DOI: 10.1016/j.ecolind.2021.107649
• Languages: English
• ISSNs: 1470-160X

Abstract

Highlights: Novel eDNA survey for detecting critically endangered scalloped hammerhead sharks. Enables the first detection of scalloped hammerheads in Guam since 1971. A single-day eDNA sampling effort outperforms five decades of visual surveys. The eDNA survey method is non-invasive, cost-effective, and user friendly. Survey application allows for rapid data generation for science-based conservation. Abstract: Among the hammerhead sharks, scalloped hammerheads ( Sphyrna lewini ) have undergone the steepest population declines worldwide. Due to their high susceptibility to exploitation, the species is now classified as 'critically endangered', the most threatened category listed by the International Union for Conservation of Nature. There is an urgent need for data on the distribution of S. lewini to inform the design and implementation of effective conservation management strategies, and mitigate the risk of global extinction. Environmental DNA (eDNA) is emerging as a powerful method to monitor the geographic distribution, population trends, and habitat usage of rare and endangered species. In comparison to traditional survey methods, eDNA methods offer lower cost, higher detection rates, and are non-invasive. At present, there is no targeted eDNA assay for the detection of S. lewini and existing methods to assess their distribution are either fisheries-dependent, leading to bias, or costly and laborious, leading to impracticality in regions of low or unknown abundance. Here we present an optimised workflow for the detection of S. lewini presence using eDNA methods, and apply these to successfully detect scalloped hammerhead sharks in Guam, of the western Pacific Ocean, where their presence has not been scientifically reported since the 1970s. The detection of S. lewini by eDNA survey methods was achieved from a single-day sampling effort, demonstrating the efficacy of the technique and workflow. If implemented, the eDNA survey methods developed here will enable the rapid generation of information on the distribution of scalloped hammerhead sharks in the western Pacific, and likely globally, and assist in the accurate placement of no-take reserves to best enable the species' recovery.