Hello and welcome back to another spooktacular edition of Finn Friday! Today we are going to dive deep into the depths of the ocean to learn about an ancient species of shark, the Sixgill shark. The reason I think they are so cool is because they are so ancient! In fact, they are more closely related to species only found in fossils than any species that still swim in our oceans today. Isn’t that insane?! So grab a blanket (because it’s really cold at the bottom of the ocean) and let’s learn all about the Sixgill shark!
Where do they live?
Sixgill sharks have a relatively expansive range. They can be found all over the world in temperate and tropical waters. As I mentioned earlier, they are a deep ocean species. During the day they typically remain around 6,500 feet below the surface. During the night, however, they tend to migrate toward the surface and more shallow waters to feed. Juvenile Sixgill sharks have also been observed living in more shallow waters than their adult counterparts.
How long do they live?
Scientists believe that Sixgill sharks, on average, can reach ages around 80 years old in the wild. This means that Sixgill sharks are a relatively long-living species, however, scientists believe that many of them don’t get the chance to age past the juvenile stage. When sixgill sharks give birth, they have extremely large litter sizes for a shark (usually around 22-108 pups). Because of these enormous litter sizes, scientists believe that there is an extremely high mortality rate for the pups, so most don’t make it to maturity.
What do they eat?
Like the majority of other shark species, the Sixgill is an apex predator. Some of their favorite snacks include cephalopods (things like squid and octopus), crustaceans (things like crab and lobster), rays, other sharks, and even a marine mammal (like seals) here and there.
What do they like to do?
Due to the fact that they spend the majority of their time at such great depths, not much is known about Sixgill behavior. We do know a few things, though. They seem to pose no threat to humans unless provoked (the only known cases of a Sixgill attacking a human have occurred when the human first provoked the shark). There has also only been one reported incident since the 1500s. The few times when humans do interact (when approached by divers or caught by fishermen), Sixgill sharks seem to dislike being touched or near humans. They are known to swim away when approached and snap at humans when touched.
Now let’s get into some fun facts. There are a few things that set the Sixgill apart from other sharks. One of the biggest differences is how they got their name. The majority of shark species have 5 gill slits, but the Sixgill has six! They also only have one dorsal fin (the fin located on the back of the shark) which is located towards the tail of the shark, while the majority of shark species have two (one toward the middle of their body and the second toward their tail). Sixgill sharks also have bright green eyes! These guys are pretty ancient, so it makes sense that they would have some characteristics not found in other shark species. Many of their closest relatives date back over 200 million years! Their closest living relatives include the Greenland shark, Dogfish, and the Frilled shark.
Conservation status:
The IUCN Red List has the Sixgill shark listed as near threatened, but there is a definite lack of sufficient data. Many scientists believe that their populations are even more unstable and at risk than we think. Sixgill sharks are often caught as bycatch by industrial fishers as well as being prized sport fish. Due to their low reproductive rate, they are extremely vulnerable to overfishing, which is why scientists believe that their populations are likely more unstable than predicted.
Thank you for learning with me! I remember back when I was working in an aquarium during the summer as an undergrad, I had a guest ask me what the oldest shark species was. At the time, I had no idea. I even did a quick google search to try and find out and came up empty handed. Now I know that if I am ever faced with that question again, I can answer that it is the Sixgill shark! What was your favorite thing you learned today about the Sixgill? I thought it was really cool that they have green eyes. Let me know if you have any other questions about the Sixgill shark below!
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