The Earth’s deep oceans constitute the last refuge of biodiversity protected from human activities. However, research has shown that even at extreme depths, deep-sea sharks and rays are extremely sensitive to overexploitation and take a long time to recover. These sharks in the dark require immediate regulation of international trade and fishing to prevent irreversible defaunation.

Nick Dulvy is Professor Emeritus of Marine Biodiversity and Conservation at Simon Fraser University (SFU) and was recently elected a Fellow of the Royal Society of Canada, Canada’s highest academic honor. He is a leading marine ecologist and collaborates with scientists around the world to address global environmental challenges such as the effects of climate change and overfishing on marine biodiversity. His research articles regularly appear in SFU’s Altmetric top 10, and he has attracted much media attention for his compelling work, particularly on sharks and rays.

For a recent study, Dulvy worked with a team of more than 300 experts from around the world to complete an eight-year analysis of 521 species of sharks, rays and chimaeras (a small group of mainly deep-sea species). . The study found that a third of deep-sea sharks are targets of the growing international liver oil trade, and half of them are threatened with extinction.

The paper, Oil and meat fishing leads to irreversible defaunation of deep-sea sharks and raysmade the cover of Nature when it is published in the spring. (Full article link, more information here). The researchers recommend implementing international laws on deep-sea fishing, where no regulations currently exist. Even a global ban on fishing below 800 meters would provide an important refuge for threatened deep-sea sharks and rays.

The Greenland shark, which moves slowly and lives in deep waters, can live up to hundreds of years. Its biggest threats are fishing, climate change and habitat loss. (Photo by Nick Caloyianis, National Geographic)

We spoke to Professor Dulvy about his research.

Can you explain what makes deep-sea sharks and rays so vulnerable to human exploitation?

The sharks of the deep are the century-old trees of the oceans. Even at extreme depths, deep-sea sharks and rays – species that spend most of their lives at depths greater than 200 meters – are among the marine vertebrates most susceptible to overexploitation due to their long life span. of life and their low reproduction rates. Deep-sea sharks have biological characteristics similar to marine mammals, once exploited for their oils and now highly protected.

The Greenland shark and gulper shark, for example, have population growth rates comparable to those of the sperm whale and walrus, respectively. Many deep-sea sharks and rays can only withstand very little fishing pressure. Some species can take 30 years or more to reach maturity, or up to 150 years in the case of the Greenland shark. Some only produce 12 young in their lifetime. Deep-sea sharks and rays require immediate trade and fishing regulations to prevent irreversible defaunation and promote the recovery of this threatened megafauna group.

Tell us about your research methods. How do you count the number of sharks and rays to determine their range and numbers?

We organized 17 workshops involving 353 participants from 71 countries over 8 years and trained scientists in the use of International Union for Conservation of Nature Red List evaluation methodology. This takes into account the rate of population reduction, threats and conservation actions and is used to classify species into one of nine categories, ranging from least concern to extinct. The deep-sea shark assessment took place in Vancouver in November 2019.

Your research has generated a lot of attention and helped shape some protections for marine biodiversity: what more should be done to protect deep-sea sharks and other deep-sea marine species?

Our results highlight that it is time to regulate the liver oil trade. Regulation of the shark fin trade has been hugely successful, but there are currently no trade or fishing regulations specific to deep-sea sharks and rays. We recommend depth and spatial limits on fishing activity implemented alongside catch regulation, bycatch mitigation, and international trade regulation. This could include national protections, regulations on deep-sea fishing, as well as listing species on Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). .

What is special about sharks that makes them so interesting? Why do people like sharks?

Children love dinosaurs and sharks; they are impressive and iconic examples of the wonders of nature. They appeared on our planet before the evolution of trees and long before Saturn got its rings. Today, their future is threatened by the rapid expansion of overfishing across the oceans.

To find out more: watch this video about sharks, see item webpage SharksInTheDark – Marine biodiversity and conservation and read the Conversation Canada article Fished for their meat and liver oil, many remarkable deep-sea sharks and rays are now threatened with extinction. by study co-authors Brittany Finnuci and Cassandra Rigby.