Great white sharks are an endangered top oceanic predator. Low reproductive and growth rates make the species vulnerable to overfishing and population depletion. Despite becoming a protected species in Aotearoa New Zealand in 2007, many great white sharks are bycatch each year because of accidental capture in set nets and other fishing gear.
Knowing the location and movements of great white sharks can inform fisheries management approaches to protect this species by telling fishers what areas to avoid and when. In Aotearoa New Zealand, a number of high-tech electronic tagging approaches have been used to understand great white shark movements to reduce fisheries bycatch. These tagging approaches rely on first capturing the sharks and then implanting a tagging device in order to track the movements. Non-invasive genetic techniques such as eDNA may provide a complementary or alternative method to track the whereabouts of great white sharks to protect this species.
A recent study in California illustrated the potential for this eDNA approach to inform fisheries management of great white sharks in real time. Rather than waiting and having the sample sequenced in a lab, the fishing vessel had a portable sequencing machine on-board so that samples could be processed immediately and have results turned around in 48 hours. This meant that the presence of great white shark DNA could rapidly inform management strategies by telling fishers that the protected species was either in the area – and therefore fishing should not occur – or was not present and therefore fishing could proceed.
This non-invasive genetic approach has the potential to rapidly survey for threatened or rare species in remote ocean regions to inform conservation efforts and fisheries management. It is important that sequencing is previously validated in a lab to ensure results are robust. Other knowledge about current and movement patterns are a prerequisite to ensure accurate sampling is taken to effectively inform management. The application of such technology is also limited by the reference databases of genetic material. Great white sharks have already been sequenced, so there are barcodes and reference genome to match the DNA samples to.
This non-invasive genetic approach has the potential to rapidly survey for threatened or rare species in remote ocean regions to inform conservation efforts and fisheries management.
In the future, fishers could use similar approaches to understand more about the habitats, movement and migratory patterns of other endangered, threatened or taonga marine species to support conservation efforts. Ongoing advances in sequencing technology will likely make a big difference to the application of real-time genetic information by increasing the capacity of these machines and improving turnaround times.
References and footnotes
 Truelove, N. K. et al. (2019) A rapid environmental DNA method for detecting white sharks in the open ocean, Methods in Ecology and Evolution, pp. 1128-1135.