Although many darter species are endangered or threatened, the rainbow darter is one of the most abundant of all the darter species (IUCN, 2002; Kuehne and Barbour, 1983).
US Migratory Bird Act: no special status
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
The primay predators of the rainbow darter are larger freshwater fish (Paulson and Hatch, 2002).
Known Predators:
A small fish, the rainbow darter only grows to be 3 inches or 5 to 7 centimeters long (Williams and Gilbert, 2002). It can be a very brightly colored fish depending on the sex and whether it is breeding season. The base color is olive green and it is mottled with 6-10 brown saddles down the length of the body (Kuehne and Barbour, 1983). It also has up to 14 vertical stripes down the body, which are perhaps more clearly visible than the saddles. Females have brown stripes, while males usually have blue stripes that are separated by orange coloring. The first dorsal fins usually have red coloring close to the body with a blue fringe (Page, 1983). However, in female rainbow darters, this coloring is not very well developed and may simply appear as thin lines (Kuehne and Barbour, 1983). In fact, many of the fins on the rainbow darter are colored differently depending on the gender of the fish. For example, the second dorsal fins on male rainbow darters are usually blue with a red stripe running laterally down the middle, while females have thin black lines running laterally across the second dorsal fins. In addition, the pelvic fins of males are usually blue while female pelvic fins are usually clear. Finally, males may also have a red spot on the center of their blue anal fins. All other fins of the rainbow darter are usually clear with no coloring (Page, 1983). Rainbow darters have pointed snouts, and the greatest depth of their body usually occurs at the origin of the first dorsal fin (Williams and Gilbert, 2002).
Average length: 5-7 cm.
Other Physical Features: bilateral symmetry
Rainbow darters can live for up to four years (Williams and Gilbert, 2002).
Typical lifespan
Status: wild: 4 (high) years.
Average lifespan
Status: captivity: 3 years.
Rainbow darters prefer the fast-moving currents of shallow riffles in creeks and small rivers. They also have a preference for gravel or rocky-bottom streams (Williams and Gilbert, 2002). Typically, adult fish are found in faster and deeper running waters while younger rainbow darters are more common in slower, more shallow areas and pools (Page, 1983).
Habitat Regions: temperate ; freshwater
Aquatic Biomes: rivers and streams
The rainbow darter is found in North America, throughout the Great Lakes region and the Ohio River valley extending into northern Alabama and as far west as Missouri and Arkansas (Kuehne and Barbour, 1983). Distinct populations of rainbow darters have also been discovered in the tributaries of the lower Mississippi river in southwest Mississippi and eastern Louisiana (Page, 1983). They are now also extending beyond their native range, invading areas like the Genesee river system of New York State; the means of this introduction remains unknown (Fuller, 1999).
Biogeographic Regions: nearctic (Introduced , Native )
Rainbow darters feed on a variety of aquatic insect larvae, small snails, and crayfish. They will also feed on various fish eggs, typically either minnow or lamprey eggs (Kuehne and Barbour, 1983). Rainbow darters are known to have a special preference for caddis fly larvae. However, it is important to note that the feeding habits of rainbow darters differ according to the time of day and also the time of year (Kuehne and Barbour, 1983).
Animal Foods: eggs; insects; terrestrial non-insect arthropods
Primary Diet: carnivore (Eats eggs, Insectivore , Eats non-insect arthropods)
Due to their low tolerance for poor quality water, the rainbow darter is used as an indicator species of stream health. (Paulson and Hatch, 2002). They act as a link in the food chain between low and higher trophic levels in stream ecosystems.
The rainbow darter does not appear to have any adverse impact on humans.
The eggs of rainbow darters are usually 1.6-1.9 mm in diameter, and typically hatch between 10-12 days after fertilization (Page, 1983).
The different coloration of males and females and changes in coloration during the reproductive season may serve as visual signals to other darters and likely play a role in sexual selection. Recent studies have suggested that rainbow darters show a decrease in activity levels when exposed to macerated skin from either other rainbow darters or a conspecific such as the yoke darter, Etheostoma juliae. The decrease in activity is a behavioral response to the threat of predation and most likely results from an alarm pheromone released through the skin of the macerated darter (Commens and Mathis, 1999).
Communication Channels: visual ; tactile ; chemical
Other Communication Modes: pheromones ; vibrations
Perception Channels: tactile ; chemical
Rainbow darters prefer to breed in water temperatures between 17-18°C (Kuehne and Barbour, 1983). Thus, depending on their regional location, these ideal-breeding conditions will occur at different times in the year (Page, 1983). Male fish are more brightly colored during the breeding season (Kuehne and Barbour, 1983). In addition, males exhibit territorial behavior in shallow riffles (25-55 cm deep) during the breeding season, scaring off other males through various intimidation tactics (Kuehne and Barbour, 1983). The larger the male, the more successful he is at intimidating his counterparts (Page, 1983). Females swim into a male territory from pools downstream (Kuehne and Barbour, 1983). Once in the riffle, the female buries the ventral half of her body into the gravel substrate and the male fish promptly mounts her. The two fish vibrate together; the male deposits his sperm and the female deposits 3-7 eggs in the gravel. The two fish then swim upstream a short distance and repeat the process over and over again for several days until the female lays about 800 eggs (Kuehne and Barbour, 1983).
Breeding season: When waters are 17-18°C
Range number of offspring: 800 eggs (high) .
Range gestation period: 10 to 11.5 days.
Key Reproductive Features: iteroparous ; seasonal breeding ; sexual ; fertilization (External ); oviparous
Parental Investment: no parental involvement
The rainbow darter (Etheostoma caeruleum) is a small species of freshwater ray-finned fish, a darter from the subfamily Etheostomatinae, part of the family Percidae, which also contains the perches, ruffes and pikeperches. It is native to North America where it is found in small, fast-moving streams and small to medium-sized rivers. It grows to 2 to 3 inches (51 to 76 mm) in length.[1] The species is very sensitive to pollution and silt, staying in clean, pollution-free water. The rainbow darter is easily identified by three dark spots on the back, and blue and orange in the dorsal and anal fins.
The rainbow darter lives in clean, rocky riffles from March through June. It has a lifespan of about 4 years. The males can grow up to 48 mm long, while the largest female reaches just under 43 mm. The male form is resplendent in bright oranges and iridescent blue spots, stripes, and checks.
The rainbow darter is a small, benthic freshwater fish found in many creeks and small to medium-sized rivers throughout North America. In particular, it is common throughout the eastern United States, specifically throughout the Great Lakes and Ohio River Valley regions. Its distribution extends south to northern parts of Alabama and as far west as Missouri and Arkansas.[2] This distribution has been suggested to be due to once existing glaciers and to its intolerance of brackish water. One study to examine the phylogeography of E. caeruleum and its colonization patterns found its distribution is greatly due to historic glaciations, and furthermore, due to distributions from drainages which have since then resulted in the current morphological diversity of the rainbow darter.[3] Geographically, the rainbow darter is one of the most abundant and common Darter species. Current distribution shown may be outdated and should be verified with state agencies. Particularly Texas where the species exists in limited number.
The rainbow darter is classified as insectivorous, feeding on small invertebrates such as insects and crayfish, but it has also been known to feed on some fly larvae. In Four-Mile Creek in Ohio, the rainbow darter lives primarily on trichopterans (i.e. caddisflies), having two feeding peaks: one in the morning and a second in the late afternoon or early evening.[4] The primary predators of the rainbow darter are larger freshwater fish, such as burbots (Lota lota), stonecats (Noturus flavus), and smallmouth bass (Micropterus dolomieu).[2] Like many other darter species, it has the ability to maintain position on the substrate in flowing water.[5] This unique characteristic plays a key role in its microhabitat preference. E. caeruleum has been shown to prefer creeks and rivers with rocky substrates and swift-moving riffles.[6] This microhabitat preference has been suggested to be due to oxygen levels in the water during season changes or other factors, such as feeding or shelter-related habitat preferences.[6] Because E. caeruleum has such a low tolerance for brackish water, human-induced changes such as pollution or sewer drainage has the potential to cause a significant negative impact on its abundance.
Darters have a wide range of life histories, but size correlates with most life history characteristics. For example, larger darters grow faster, live longer, produce bigger clutches, and have longer reproductive spans.[7] Mate selection by female darters is assumed to be common.[8] When examining the rainbow darter, life history traits were: average size 45 mm, growth 32 mm, maximum age four years, and clutch size 82.[7] E. caeruleum mates during the spring, typically when water temperature is between 17 and 18 °C, and they will leave their normal microhabitat in the rapids to congregate on pebbles, where the stream leaves a pool, to mate.[2] Once mates are selected, the fish mate repeatedly for several days until the female lays about 800 eggs.[2] This darter also displays group spawning, and the males tend to exhibit territorial behavior during the breeding season.[8]
Currently, the largest threat to E. caeruleum is run-off and pollution due to urbanization. One study found the development of an interstate highway negatively affected the abundance of several fish species, including E. caeruleum, because of decreasing quality of water of the nearby creek.[9] Currently, management plans consist of reducing nutrient, pesticide, and sediment loadings within such streams.[10] This same study suggests conservation practices should be a combination of both physical habitat monitoring and water chemistry monitoring, because it would benefit fish communities within headwater streams more than just implementing one conservation practice or the other.[10] Although broad management plans are in place for many rivers and streams and their fish communities as a whole, no current management plans in place are specifically designed for E. caeruleum.
The rainbow darter (Etheostoma caeruleum) is a small species of freshwater ray-finned fish, a darter from the subfamily Etheostomatinae, part of the family Percidae, which also contains the perches, ruffes and pikeperches. It is native to North America where it is found in small, fast-moving streams and small to medium-sized rivers. It grows to 2 to 3 inches (51 to 76 mm) in length. The species is very sensitive to pollution and silt, staying in clean, pollution-free water. The rainbow darter is easily identified by three dark spots on the back, and blue and orange in the dorsal and anal fins.
