I remember as a child being very impressed by the sturgeons at the Vancouver Aquarium. You see, they were bigger than all the other fish in the tank. Which to a kid, means they are the most important fish in the tank, and really the only ones worth looking at. Today, while pondering what animal to blog about, the memory of those sturgeons came to me, and I realized I know very little about them. So I looked them up, and have decided to share what I learned with you, my dearest readers.
Sturgeons are very ancient fish — after their first appearance in the Cretaceous period, they have changed very little. They are part of the family Acipenseridae, which contains around 25 species. Accurate classification of sturgeon species is difficult due to variations in appearance that can occur between the same species at different ages and in different locations. Another complicating factor is the sturgeon’s ability to hybridize between species of sturgeon. It just makes me glad I’m not a sturgeon taxonomist.
Sturgeons can be found pretty much all over the Northern Hemisphere, from the west coast of North America to the Yangtze river in China. Most species live in fresh water, inhabiting rivers, lakes and estuaries. Some sturgeons spawn in fresh water but move to salt water coastlines for their adult lives, while others spend their entire lives in freshwater, either because they evolved that way, or humans have forced them into that existence.
I wasn’t wrong to be impressed when I was a kid. Sturgeons can get big. Really big. The beluga sturgeon in the Caspian Sea can reach lengths of 5.5 metres, and weights of 2000 kilograms. Of course, the ones at the aquarium weren’t that big, but they were certainly large enough to make an impression on a young me. Sturgeons have some notable features that make them easily recognizable. They have four barbels on their face, which the sturgeon uses to feel its way around the often muddy waters in which it lives. Another distinct feature of sturgeons is that they have a number of bony plates on their body called scutes, instead of scales. It is thought that the lack of natural sturgeon predators (due to their large size and scutes) and their extremely long lifespan (over a hundred years!) have contributed to the extremely slow evolution of the sturgeon.
Sturgeons are bottom feeders, and use their barbels to find prey. When prey is found, the sturgeon uses its mouth to suck its meal up. Most sturgeons feed on small prey, like crabs, shells and small fish. They do not have any teeth, so they have to swallow their food whole. Some species can do this to quite large creatures, like whole salmon. You’d have to be pretty large to swallow a salmon whole. It’s a little scary to think about. Have they made a Mega Shark vs Giant Sturgeon movie yet?
Unfortunately for sturgeons, their long lifespan and slow reproductive rate make them particularly vulnerable to overfishing. They are also the source of caviar, which makes fishing sturgeon quite profitable. Caviar, of course, is fish eggs, which means the product is harvested from females with reproductive capabilities, further increasing the stress on sturgeon populations. All of these factors bode poorly for sturgeon conservation, and have made sturgeon the most critically endangered group of species in the world, according to the IUCN. So if you’re going to buy caviar, make sure it’s from a sustainable source!
Cover image source: http://www.biomar.com/en/BioMar-France/Species-and-products/Sturgeon/