I had a bit of trouble when I first saw this fish’s name — I wasn’t quite sure how to read the ‘redear’ part of the name. Every time I look at it I read it as ‘re-dear’, when it’s quite clearly supposed to be ‘red-ear’. I think the people who named this fish should have just disposed of any ambiguity and gone with red ear sunfish. One extra space won’t kill anybody.

The native range of redear sunfish is in the southeastern and central US, though they have been introduced to other parts of the United States, as well as Panama, Puerto Rico, Morocco and South Africa. These fish have been introduced for the very simple reason that people like to fish for them. Redear sunfish like warm, still, waters, and so are generally found in ponds, lakes, rivers and reservoirs.

See the bright red gill cover? It does kind of look like an ear.
Image by Ltshears, Public domain, via Wikimedia Commons

Redear sunfish range in colour from green to grey or black, with lighter undersides. They have thick vertical stripes down the length of their bodies. The name ‘redear’ comes from the bright red colour that male redear sunfish have on their operculums. Females also have colourful operculums, but they are orange not red. And since the operculum isn’t actually an ear, but is instead a bony protective covering over the gills, these guys are really poorly named. They should be called ‘red-operculed sunfish’, or something like that. Though I guess it isn’t nearly as catchy. They can reach up to 43 cm, but sizes between 20 and 24 cm are more common.

Redear sunfish are known for eating molluscs and crustaceans, and are especially fond of snails. They have very strong teeth that enable them to crush the shells of snails and other creatures, such as clams. This strange diet allows redear sunfish to feed without much competition, something that should reduce the harm redear sunfish do to native fish in their introduced habitats. In fact, some think introducing these guys could be helpful to control quagga mussels, an invasive species in freshwater areas. Whether or not this is actually true I suppose we’ll find out, but based on past records of introduced species, I’m a little wary…

A male sunfish guarding the nest he has painstakingly made.  Image source: Wikipedia
A male sunfish guarding the nest he has painstakingly made.
Image by I, Ianare, CC BY 2.5, via Wikimedia Commons

Reproduction in redear sunfish is triggered by water temperature, with mating occurring between 21 and 24 degrees celsius. Males build nests out of sand and mud, near plants so the eggs have some protection. They then set about trying to attract females, which they do by snapping their teeth together, to make a popping sound. If the female is impressed by the noise, as well as his colouring, she will lay some eggs in his nest. He can then fertilize the eggs and protect them from harm.

Despite the claims that redear sunfish don’t really hurt native fish populations, there have been declines of local fish in areas where sunfish have been introduced. I think a quick look at humanity’s track record of making smart ecological decisions should give us a bit of a warning. I don’t think the fact that the fish are fun to catch makes up for any damage they might do to local ecosystems.

Cover image by Ltshears, CC BY-SA 3.0, via Wikimedia Commons