What's In a Name?
Rainbow darter: named from the range of colors on the male during the spawning season

Etheostoma (ee-thee-ah´-stoe-mah) taken from the word etheo meaning to filter, and stoma meaning mouth in Greek
caeruleum (sair-rule´-ee-um) means blue in Latin

Where Do They Live?
In southeastern Minnesota streams and small rivers, like the Cannon, Zumbro, Root, and Cedar rivers, rainbow darters are one of the more common darters. They are much less common in the lower St. Croix River and in the tributaries of the Minnesota River. They also live in the Red River drainage, but only in the Otter Tail River, where they are fairly common. Rainbow darters prefer waters that are clear with moderate to fast current and a bottom made up of gravel and boulders over sand.

Rainbow darters are often used as biological indicators because they do not tolerate most forms of water pollution. They share their habitat with a variety of fish, including northern brook lamprey, white suckers, northern hogsuckers, stonerollers, blacknose dace, and other species of darters.

"Cool Fact": Lake Phalen in Ramsey County is the only Lake in the world where rainbow darters have been found.

How Big Do They Get?
How Long Do They Live?
Rainbow darters are tiny relatives of the walleye. They typically grow to about 55-60 mm (2.2-2.4 in) and usually weight less than 3 g (about 0.1 oz). Rainbow darters commonly live for 2 to 3 years and in some rare cases 4 years.

What Eats Them?
We have rarely found rainbow darters in the stomachs of other fishes. They may be eaten by young burbot, large stonecats, and smallmouth bass. Fish-eating birds like great blue herons may also eat them. Humans do not eat them, and they are illegal to use as bait.

How Do They Reproduce?
Spawning season for the rainbow darter here in Minnesota is May to early June when water temperatures stay above 15° C (59° F). The brightly colored males set up their loose territories around rocks or depressions in the gravel of a riffle with medium current. Males chase all other rainbow darter males from their territories. When a female enters a territory, the male swims to her and pokes her sides with his snout. If she is ready to spawn, she buries herself partially under the gravel. The male lies upon her, she vibrates and deposits her eggs while the male fertilizes them. The female moves from underneath the male to spawn again with the same male or with another partner. Only about 3 to 7 eggs are laid with each spawning act, but a single large female may lay over a 1000 eggs in a single season. The fertilized eggs (embryos really) settle between the spaces in the gravel and receive no parental care. They hatch in 10-12 days depending on temperatures.

Conservation and Management
Rainbow darters have no special conservation status in Minnesota, but are protected by state laws sa part of the perch family. They do well in an aquarium if provided with a modest current, but you must have a special permit to collect and keep them.