Having persisted for at least 400 million years, elasmobranchs (sharks, skates and rays) are part of one of the oldest extant vertebrate groups and an essential part of every marine system. But many elasmobranch species are now globally subjected to harvesting rates that are widely deemed to be unsustainable. Relative to other fish, sharks grow slow, mature late and produce few young, leaving them particularly susceptible to overfishing.
The conservation of marine species, including elasmobranchs, relies heavily on our ability to detect and monitor species distribution and abundances. This poses a particular challenge to biologists and managers worldwide, due to the cost and effort associated with the assessment of elasmobranch biodiversity and habitat use.
Owing to recent advances in DNA sequencing and bioinformatics, the use of environmental DNA (eDNA) has developed into a cost-effective and rapid, non-invasive method for collecting and analyzing biological samples from large portions of the environment, without the necessity of capturing, or even seeing, the target organism.
All animals shed cellular material (skin cells, mucus, metabolic waste, sperm and blood) in their surrounding environment. This eDNA can be present in the water as free DNA, cellular debris and particle bound DNA which can be collected directly in the form of seawater samples for DNA extraction and subsequent targeted sequencing to determine species composition and abundances. eDNA is rapidly diffused from its source and eventually broken down by the action of UV radiation and microbial activity. The limited persistence of eDNA in aquatic environments underlies the principle of contemporary species detection, as the detection of eDNA from a specific species indicates its presence or very recent presence.
The e(lasmo) project addresses the development and application of an eDNA approach to be used for the qualitative and quantitative assessment of marine communities, with a special focus on elasmobranch species.
By comparing community differences detected through eDNA with existing knowledge gathered by using more traditional techniques, we aim to develop and apply this novel eDNA approach to investigate elasmobranch diversity in order to assess species richness in areas of special conservation concern and examine the influence of interacting factors such as habitat type and conservation regime in determining diversity and abundance. The potential implications of eDNA for elasmobranch, and larger scale marine community assessment and monitoring, spatial planning and fisheries management are significant. Stefano and Judith are supported for this project by the Pew Charitable Trusts and an Industrial Case Scholarship from the University of Salford.