ANIMAL: Rainbow Darter Etheostoma caeruleum Type of Animal: Darter Habitat: Riffles in moderate to fast-flowing clear-water streams/gravel bottom streams/rocky bottom streams/small to medium-sized rivers/clear rocky river bottoms, creeks, benthic areas in small fast-moving streams/small to medium-sized rivers/creeks/reservoirs, pebble areas where streams meet pools, adults prefer faster water in deeper shallow water, younger fish prefer pools/slower shallower areas, not found deeper than 1.64 ft Location(s): Great Lakes, Ohio River Valley, Mississippi River/surrounding area, Potomac River, found as far W as Texas Appearance: Fairly small fish, 3 dark spots on back, males more colorful than females often w/ brighter orange & iridescent blue spots/stripes, faded rainbow coloration, females/nonbreeding males have brown striping, breeding males have blue striping separated by orange, males have more colorful fins than females, female fins smaller/clearer, females lighter in color than males, both sexes become brighter in breeding season especially males Food/Diet: Copepods, small crayfish, water fleas, larvae, caddisflies, midges, blackflies, mayflies, water mites, aquatic larvae, snails, eggs of other small fish, nematodes, lamprey eggs Status in Wild: Stable Conservation: Breeding in aquariums, zoos, & aquaculture Lifestyle: Small schools, breeding males defend small territories during breeding season Additional Info: Called: Male Female Young: Fry Group: School Weight: Male: 0.1 oz Female: 0.07 oz Gestation: 10-12 days Life Span: 2-3 years Body Length: Male: 1.88 in Female: 1.69 in Tail Length: Male: 0.25 in Female: 0.2 in Main predators are burbots, stonecats, smallmouth bass, spotted bass, creek chubs, bluegill, longear sunfish, crayfish, & herons. Multiple males often follow single female until she chooses one, usually the biggest brightest one. Prior to spawning, females buries fins/torso on bottom, burying/unburying herself several times until she signals to male. After this, female releases eggs & male fertilizes them. 7 eggs laid per clutch but females will mate w/ multiple males & can lay up to 1,500 eggs a season. Very few make it to maturity (reached around 1.5 months). Eggs buried along area where spawned, hatching 10-12 days later. Gets name from male breeding coloration & way it moves. Usually active at dusk & dawn (crepuscular). These fish are active swimmers. Spawning season occurs in spring. Spawning pairs very commonly disturbed by other males. Fun Fact(s): As aid to keep them from being swept downstream, they have reduced swim bladder. Have ability to sense chemical cues/behaviors from each other. If attacked by predator, it can release chemical cue alerting other fish to danger. Due to strong preference for clean water, they’re important biological indicators. If threatened, they’ll hide & stay motionless until danger passed.
