The International Union for the Conservation of Nature (IUCN) is the body responsible for producing the famous Red List of Threatened Species. This list defines the conservation status of species by using criteria based on past and present population sizes, spatial distribution and the threats faced by the species. These criteria are used to put species into different categories of threat:
- Extinct – the species no longer exists
- Extinct in the Wild – the species only exists in captivity
- Critically Endangered – the species is at very high risk of becoming extinct
- Endangered – the species is at high risk of becoming extinct
- Vulnerable – the species is likely to become Endangered unless conservation action takes place
- Near Threatened – the species does not yet qualify for any of the Threatened categories, but it may do in the near future
- Least Concern – the species has been evaluated and does not meet any of the above criteria
- Data Deficient – the species has not yet been evaluated/there is not enough data to evaluate the species
Many sharks are slow growing, long lived and have relatively few offspring; a life strategy that is called k-selected. This life strategy means that they find is very hard to bounce back from fishing pressure, so their numbers fall easily and cannot rise again without conservation management intervention.
Sharks are assessed by the Species Survival Commission and IUCN Shark Specialist Group, and we’ve put together a list of the different threat categories and some of the sharks that fall under each one. All text within quotes is sourced from the IUCN Redlist description of each species. You may be surprised that it’s not always the most recognisable species that are under the greatest threat of extinction!
We all know about prehistoric shark species like the Megalodon that have become extinct, but here’s a more recent story. Until 2008, it was believed that the smalltooth blacktip shark (Carcharhinus leiodon) was no more – then it was found in a fish market. Without experts on the look out at every fish market across the world, it is difficult to record all the shark species present, especially if they look incredibly similar to other species!
Sadly, several shark species come under this heading. This includes the angelshark (Squatina squatina).
This shark is now locally extinct in parts of its range and has suffered massive population declines in the last fifty years due to overfishing; “…estimated and suspected past declines of at least 80% over three generations and the likelihood of continuing future declines resulting from fishing pressure”. The fantastic guys at the Angelshark Project are working hard to conserve these sharks in their last stronghold, the Canaries.
The daggernose shark (Isogomphodon oxyrhynchus) is only found around the coast of South America. We still know relatively little about this enigmatic shark, but it is known that they are in serious trouble due to incidental catch in artisanal fisheries. It doesn’t always take intensive commercial fishing fleets to wipe out shark species – because these sharks naturally occur over a small range, they are easily fished out by local fishers.
Great and Scalloped Hammerheads
Hammerhead sharks are easily recognised and much loved but did you know that both the great hammerhead (Sphyrna mokarran) and scalloped hammerhead (Sphyrna lewini) are listed as Endangered? Both species have undergone declines or at least 50% across their ranges and are still being overfished, partly as a result of being highly valued in the fin trade. These guys do not cope with being caught well, and very often die from capture stress, despite being released.
Two of the best recognised and most loved shark species are Vulnerable to the risk of extinction – the white shark (Carcharodon carcharias) and the whale shark (Rhincodon typus).
“Threats to the species include targeted commercial and sports fisheries for jaws, fins, game records and for aquarium display; protective beach meshing; media-fanned campaigns to kill Great White Sharks after a biting incident occurs; and degradation of inshore habitats used as pupping and nursery grounds.” The white shark has received legal protection in many countries across its range. Frustratingly though, when populations of white sharks are perceived to grow (note perceived), there are sometimes calls for a cull to reduce their numbers again, which somewhat defeats the point of protecting them in the first place.
Targeted and bycatch fishing are both threats faced by the whale shark, which already naturally existed at low abundance. Harassment through poorly managed “ecotourism” is an issue in some areas.
This group contains (among others) three famous species; tiger sharks (Galeocerdo cuvier), bull sharks (Carcharhinus leucas) and white tip reef sharks (Triaenodon obesus).
Tiger shark: “There is evidence of declines for several populations where they have been heavily fished, but in general they do not face a high risk of extinction. However, continued demand, especially for fins, may result in further declines in the future.”
Bull Shark: “It is caught in fisheries throughout its range, but it is rarely a target species. Its occurrence in estuarine and freshwater areas makes it more vulnerable to human impacts and habitat modification.”
White tip reef shark: “Formally it was abundant over coral reefs, these sharks’ numbers are at lower levels than those found prior to widespread expansion of fishing in the past 20 years. The species’ restricted habitat, depth range, small litter size and moderately late age at maturity suggest that with increasing fishing pressure this species may become threatened.”
This is sometimes one of the most alarming categories for a species to fall under as it can mean that there are just too few of the animals available to study for them to be formally classified! Upon classification, many Data Deficient species are immediately recognised as under threat of extinction.
Broadnose Sevengill Shark
The broadnose sevengill shark (Notorynchus cepedianus) is currently listed as Data Deficient due to lack of fisheries data. These sharks are generally considered as calm and peaceful and are commonly dived with in South Africa.
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