Thanks to Nathan for his suggestions! This week we're going to learn about three strange and interesting fish!

A northern snakehead:



A giant snakehead:



A Greenland shark, fish of mystery:



The upside-down catfish is indeed upside down a lot of the time (this is actually a picture of Synodontis nigriventris, closely related to the upside-down catfish we talk about in the episode):



An ancient Egyptian upside-down catfish pendant that ladies wore in their hair:



Show transcript:

Welcome to Strange Animals Podcast. I’m your host, Kate Shaw.

We haven’t done a fish episode in a while, so this week let’s learn about three weird fish. Thanks to Nathan for suggesting the first two fish, the snakehead and the Greenland shark.

The snakehead is a freshwater fish that gets its name because while it’s an ordinary-looking fish for the most part, it has a flattened head that looks a little bit like a snake’s. Different species of snakehead look different in other ways, of course, so let’s examine a couple of typical species.

The northern snakehead is native to Asia, but it’s been introduced into other parts of the world by accident or as a food fish. It’s one of the largest species, with reports of some specimens growing up to five feet long, or 1.5 meters. It’s usually no more than three feet long, though, or 1 meter. It’s brown with darker blotches and has sharp teeth that it uses to catch fish, frogs, and other small animals.

Like other snakeheads, the northern snakehead can breathe air and survive out of water for several days as long as it stays damp. Young snakeheads can even wriggle considerable distances on land to find water. It likes stagnant or slow-moving water.

Because it’s a fierce predator that can find its way to new waterways, introduced snakeheads are invasive species that can cause havoc to populations of native fish. The northern snakehead has been introduced into many waterways in the United States in the last twenty years, as a result of people releasing unwanted aquarium fish and accidental release of snakeheads in fish-farming operations. Since snakeheads reach mature age quickly and females can lay thousands of eggs at a time, snakeheads are illegal to own in many places now and release snakeheads into the wild is even more against the law.

The giant snakehead also grows up to five feet long, or 1.5 m, and is from parts of southeast Asia. Young giant snakeheads are red, but when they grow up they’re black and white with a thick black stripe down each side. It’s also been introduced into a lot of places as a food fish and a game fish, but since it’s a tropical species it can’t survive colder weather and isn’t as invasive as a result, at least not outside of tropical and subtropical areas.

The giant snakehead can be aggressive, though, especially when it’s guarding its nest. Both parents act as guards of the eggs and the newly hatched babies, which follow their mother around wherever she goes. That’s actually really cute.

Next let’s talk about the Greenland shark. We covered it briefly in episode 74, about colossal squid and the things that eat them, but mostly we talked about its close relative the sleeper shark. The Greenland shark is similar in some ways but it’s much bigger than the sleeper shark. It lives in the North Atlantic and Arctic Oceans where the water is barely warmer than the freezing point and it grows up to 24 feet long, or 7.3 meters, with females being larger than males.

But despite how enormous it is, it’s not a shark you need to worry about. First of all, what are you doing swimming in water that cold? Second, the Greenland shark is a slow swimmer, no more than about 1 ½ miles per hour, or 2.6 km/h. You can walk faster than that without even trying. You can probably dog-paddle faster than that.

And yet, the Greenland shark manages to eat seals and fish and other animals that move quickly.