Learning from Dead Stuff--1 May 2009

One thing that most wildlife biologists really like to do is find dead stuff. Dead stuff falls into many categories including fresh, too old to stink, and "Holy cow, what is that burning in my nose?". Not that there are only three categories--it's more of a continuum. This piece of carrion fell somewhere closer to "too old to stink" than "Holy cow!" so I decided to examine it a little more closely.

I realize when most people think of minnows, they typically picture a small, silvery fish ranging in size from pizza topping to bait. Minnows in California, however, tend to be especially large, with many species greater than two feet in length. This dead fish, a common carp (not native to California), was a tad over 24 inches. It is in the minnow family.

As one of the most successful fish families in California, minnows here have evolved to fill all sorts of niches that we don't ordinarily expect them to occupy. For example, the Sacramento pikeminnow is a large, predatory species that feeds almost exclusively on fish and grows to three feet in length. The Sacramento blackfish, which can be found at Kokopelli Wildlife Area, is like the whale shark of California's fresh water, cruising through still backwaters and filtering tiny particles of food from the water.

One interesting thing about minnows is that they don't have any teeth in their jaws. So all you swimmers who got out of the water when I wrote about the pikeminnow can get back in. They do have teeth, but they are located back in their throat and they are called pharyngeal teeth. And, like other animals, you can usually get a pretty good idea of what they eat by looking at their teeth. The pikeminnow has sharp, knifelike teeth for gripping and shredding live fish. This is what the teeth of the dead carp looked like (this picture is taken from the bottom side of the fish looking just behind the gills):

I'll post some pictures of the grinding surfaces of these teeth another time, but you can see they look sort of like molars. Carp use these to grind plant materials against the bony plate above. I hope to clean this specimen up and create a clean skeleton from lips to the back of the throat to show kids how minnows eat.

For more information about California fish, I highly recommend Peter Moyle's landmark text: Inland Fishes of California. It's really, really, really, really........great.