Rainbow Darter
Etheostoma caeruleum

Description:  The Rainbow Darter is a small freshwater fish.  The top of the fish is dark brown in color and contains 3 dark spots on the back.  There are between 6 and 10 vertical bars on each side of the fish.  (In males, these bars are blue and red, while females have dark brown and yellow bars.)  The fins are red in color with blue outlines.  The male fish’s colors are more pronounced during breeding season in the spring and become paler after the females have laid their eggs.  Females have coloring that is much more drab overall.
Size:  Rainbow Darters can grow to be up to 3 inches in length.

Individual animal information:  Cosley Zoo possesses one Rainbow Darter, which was obtained from Milwaukee County Zoo in 2008.

Adaptations: 

• The bright coloring of the Rainbow Darters may help them to attract mates.
• Darters use their long snouts to turn over rocks under which they find small invertebrates to eat.

Diet:  In the wild, Rainbow Darters consume insect larvae and other small invertebrates such as snails and crayfish.  They will also consume the eggs from other fish.  At Cosley Zoo, the Rainbow Darter is given fish flakes, bloodworms and glassworms (insect larvae), and brine shrimp.

Reproduction:  Females lay 3-7 eggs at a time in the gravel at the bottom of the river.  Males fertilize the eggs immediately, and the females bury them.  The eggs hatch 10-12 days later.  After laying the first group of eggs, the male and female travel a short distance and repeat the process numerous times. 

Shelter and space needs:  Rainbow Darters are bottom dwellers which are found in small to medium sized creeks and rivers.  They prefer areas with fast-moving currents. 

Life expectancy:  4 years.

Relationship with man:  Rainbow Darters are beautiful fish which can be found in many home aquariums.  In the wild, they are an important source of food for many larger fish.  They are very sensitive to pollution and will only be found in the cleanest water.  Because of this, they are good environmental indicators that can help to tell us how healthy an ecosystem is.

Fun facts:

• The Rainbow Darter is so named because of its habit of darting after prey travelling in the river’s current.
• A single pair of Rainbow Darters can produce 800-1000 fertilized eggs per year.