Illinois Natural History Survey - University of Illinois

Species Spotlight: Orangethroat Darter

The Family Percidae contains both darters and perches. While the larger members of the order--walleye, sauger, and yellow perch--are familiar, the majority of the species, the darters, are too small to be known by many people. Most darters are less than four inches long. Among North American freshwater fishes, however, the darters are second only to minnows in numbers of species and abundance. Due to the loss of the swim or gas bladder, darters dart about the stream bottom; hence, their name. Many species (especially the males) are brightly colored. The orangethroat darter, Etheostoma spectabile, is perhaps one of Illinois' most notable examples.

The orangethroat darter is approximately three inches in length. The breeding male has alternating brick red and metallic blue-green bars on the side of the body, bright blue and orange-red bands through the first dorsal fin, and a bright blue-green anal fin. Its bright orange throat provides the common name. The female is a dull, neutral olive with tinges of blue and orange.

Riffles and pools of small streams that have mixed sand and gravel bottoms are the preferred habitat of the orangethroat darter. This darter occurs throughout the state and is often a pioneering species. It soon reoccupies formerly dry streambeds and will ascend well into the headwaters. Larval insects such as blackflies and caddis-flies, bloodworms, and fish eggs make up the majority of its diet.

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The orangethroat darter, Etheostoma spectabile.

Spawning usually occurs in March and April. The colorful male migrates to the shallow gravel riffles (breeding riffles) in late March. The female spends most of her time in pools at the base of the riffles. The female swims into a riffle, where she is followed by several males. One male attempts to keep the others away by making short dashes at them with its fins erect. The female is closely followed by the male until she wiggles into the gravel. This is the signal that the female is ready to lay her eggs. The female forces her head into the gravel while in an almost vertical position and then moves into a horizontal position with the lower half of her body buried. This stimulates the male to mount. The pair then vibrates rapidly. Three to seven eggs are released, fertilized by the male, and buried in the gravel. The female moves forward on the riffle and spawns several more times, either with this male or another one.

Once the adults have spawned, they leave the fine gravel riffles for deeper rocky pools. The eggs hatch in about 10 days and the young grow quickly. They are usually found scattered over gravel near the adults and are almost adult size by fall.

Susan Post, Center for Economic Entomology



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