What is the most endangered species of shark?
Show notes
Recent studies have shown that over a third of shark and ray species are threatened with extinction. But which species are the most threatened? And when a species is that rare, how do you know where to look? This week, we’re joined on the pod by rare shark expert Dr Dave Ebert, also known as ‘Lost Shark Guy’! Dave has travelled all over the world in search of sharks who are thought to have gone extinct and has contributed to many an IUCN red list assessment for sharks and rays. At Sharks International in Valencia, host Isla sat down with Dave to talk about Pondicherry sharks, lost sharks, sawfishes and guitarfishes; how to find sharks that haven’t been seen for 50 years and what it’s like to name a shark that’s brand new to science.
To kick things off, we chat about how nice it is to attend in-person conferences again, but also how much the landscape of conferences has changed (in many ways for the better) since the pandemic [6.02]. Many academic conferences are now ‘hybrid’ and have options to attend virtually, making them somewhat more accessible than they were before. We then move onto our topic of rare and endangered species, starting with how Dave began his career specialising in lesser-known species [14.02]. Dave talks about growing up in the ‘Jaws generation’ when the blockbuster film Jaws had just been released, and the field of shark science was pretty much non-existent. When he began his research career, studying sharks was the ‘road less travelled’ – even white sharks were poorly understood animals. At that time, if you thought of a question to answer, you could likely go and study it without much competition! While on fieldwork, Dave began to find species no one had ever seen or hadn’t been seen for decades. This ignited his passion for rare and ‘lost’ species, which is now the main focus of his work.
Speaking of rare species, we spend some time talking about ‘lost’ sharks, those species that have seemingly vanished from the ocean. One is even named the ‘lost shark’, or to give it its full scientific name, Carcharhinus obsolerus [17.22]. This shark is only known from three museum specimens, thought to have originally been obtained in 1934. Scientists re-discovered it and declared it ‘Possibly Extinct’ in 2019 – it was only then that the lost shark was named. As Dave says, there are several species, just like the lost shark, that could have disappeared without us even knowing. Without anyone looking for them, these animals could go extinct without a whisper. Or, they could come back from the dead. The tentacled butterfly ray is one such example [19.25]. It hadn’t been seen for a very long time and was about to be declared extinct until a colleague in Iran discovered a small remnant population off the country’s coastline. These smaller, lesser-known or rare species are important to know about, not only for curiosity’s sake but also for ecological reasons [20.48]. They are often an important food source for larger shark species and an integral part of the food web; if they go extinct, it could have severe consequences for animals further up the food chain.
A further problem is that many of the most endangered shark species exist in shallow, coastal waters where they are an easy target for fisheries [22.02]. However, they can also be an important source of nutrition and income for fishing communities. Critically endangered sawfishes, for example, are sought after for their valuable fins, meat and unusual rostrum [23.21]. Fishers can make a lot of money from catching a sawfish, which drove a lucrative trade and sadly resulted in these species almost disappearing altogether.
We discuss a few other species of ‘lost’ shark, like the Pondicherry [24.52] and honeycomb catshark [26.25], both of which have not been seen in the wild for decades.
So, how do you go about finding a species that is seemingly lost? Dave explains that he never looks for these species in particular – rather, they find him [28.00]. It often starts with a photograph sent in from a researcher or shark enthusiast who has found an unusual species at a fish market (pro tip: if you do find an odd-looking species of shark, take a picture from the lateral view, with something next to it to provide a reference of size!). Dave then works with local people – often fishermen – to determine the identifiable characteristics of the possible species. Sometimes, it’s the lost shark. Other times, it’s one that looks very similar. Or, it’s a species entirely new to science. In these cases, the species then has to be described and named, which is a much longer and more complicated process than you’d think…[32.48].
To wrap up, we come back to the central question of the episode: what is the most endangered species of shark [37.50]? It’s tricky to narrow it down to just one species. As Dave points out, over a third of sharks and rays fall under one of the three threatened categories identified by IUCN – Vulnerable (VU), Endangered (EN) and Critically Endangered (CR). But there are groups of sharks and rays that collectively are at a higher risk of going extinct than others. Perhaps the most threatened group is the giant guitarfishes. Almost all species in this group are classed as Critically Endangered.
We end our chat by discussing a new genus of skate that Dave has discovered in his own backyard in California [43.18].
About our guest
Dr Dave Ebert
Dr Dave Ebert has devoted his life to studying the ocean’s most elusive, dangerous and yet fascinating predator – the shark! His global explorations have led to the discovery of over 50 new shark species. Author of 30 books, including Sharks of the World, Dave is a popular television guest frequently appearing on various programs for the BBC, Discovery Channel, and National Geographic. As a regular on Shark Week, Dave has led expeditions searching for the rarest, most elusive sharks in the world. He has even discovered new shark species while filming on location. Whether he’s sharing anecdotes about dining with royalty or hanging with fishermen in remote villages, Dave brings the audience along on his own personal journey with vivid stories of exploration, discovery, and travel from his most recent adventures. He is the founder of the Lost Sharks project and co-host of the podcast Beyond Jaws!
