| Johnny Darter | |
|---|---|
| Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Perciformes |
| Family: | Percidae |
| Genus: | Etheostoma |
| Species: | 'E. nigrum' |
| Binomial name | |
| Etheostoma nigrum (Rafinesque, 1820) |
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The Johnny Darter, Etheostoma nigrum, is a species of ray-finned fish that are found in shallow water throughout eastern North America. It's name comes from the Greek and Latin root words of etheo meaning to filter, stoma meaning mouth, nigrum meaning black in Latin.[1] They are important members of their aquatic ecosystems as predators and prey do not normally cause problems or have negative effects to their habitats.[2] Their lifespan is about three years and they reach sexual maturity at the age of a year.[1] They are generally small, solitary fish that live in benthic habitats in freshwater and are active during the day.
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The Johnny Darter is found throughout eastern North America, from Wyoming and Colorado to the Atlantic seaboard as far south as North Carolina. They are the most common darter in Minnesota[1] and Ohio.[3]
The Johnny Darter have an average length of between 1.5 and 2.5 inches.[2] The males are generally longer than the females where males can reach up to 3 inches and the females do not get much bigger then 2.3 inches.[1] They weigh very little with the males weighing in at a little over 2 grams and the females weigh about 1.6 grams.[1]
These small, slender fish have brown to yellow scales, paler sides, and whitish bellies.[2] They have no bright colors and generally just have brown or black markings on a lighter tan background. These markings are usually a series of black "w" or "x" shapes along their sides running along their lateral line.[3]
On the fish, the opercles (or bony are forming the gill cover) have scales, whereas the preopercle (bone at the start of the cheek), nape, and breast are scaleless. The Johnny Darter has two dorsal fins, the first has hard rays which are called spinous rays, while the second fin is soft-rayed, which are flexible. The pectoral and pelvic fins are close to each other behind the gills. The pectorals are large and fanlike and are situated on the lower sides of the fish. The pelvic fins, or ventrals, are small and round and situated in the ventral side of the fish.[4] They have a rounded tail fin on the ventral side as well.
Johnny Darters prefer clear water with sandy and gravely bottoms. They like slow moving water, but can be found in moderately cloudy, moving water as well.[1] They are bottom-dwellers and stay on rocks at the bottoms of small ponds and streams with their heads facing into the current.[3] Of all the darter species, the Johnny Darter is the most tolerant of diverse conditions.[5] Since these darters are benthic, freshwater fish[2], their mouth is a subterminal where the nose is only slightly beyond the mouth and is situated in an inferior position that makes it easy for them to eat and catch their food. They eat lots of different things, but as young fish, they tend to eat copepods, or small crustaceans, and waterfleas. As they grow, the fish start eating larger waterfleas, differing types of larvae including midge, mayfly, and caddisfly, and they also eat the occasional sideswimmer.[1] These darters are generally eaten by predatory fish in their regular habitat. These predators are fish like burbot, lake trout, smallmouth bass, walleyes, and yellow perch.[1]
The spawning season for Johnny Darters is all of May and most of June when the water temperatures are between 12 and 24°C. Males arrive first to establish territories throughout the pond, lake, or stream. Spawning occurs throughout the shallow water or in pools and slow runs where there are large rocks, logs, cans, shells, or other debris. When a female approaches the nest, the male darts at her and chases her out of the territory. However, when she approaches the nest upside down and tries to enter, the male will accept her. They then both turn upside down and the female will lay between 30 and 200 eggs on the underside of the debris. Johnny Darters are not monogamous and the female and male will spawn with other fish. A single nest may hold up to 1000 developing eggs. The male will guard the nest and keep them oxygenated and will eat the ones that develop fungus until the embryos hatch which is about 6-10 days.[2]
These fish are not considered threatened throughout most of their range. They are considered vulnerable only in these following states: Arkansas, Kentucky, Oklahoma, Kansas, and Nebraska.[2] In Minnesota, they have no special conservation status, but are protected by state law.[1]