What's In a Name?
Etheostoma (ee-thee-os´-toe-mah) taken from etheo, which means "to
filter" and from stoma, which means "mouth" in Greek
nigrum (nie´-grum) meaning "black" in Latin
Where Do They Live?
The Johnny darter is the most common darter in the state. It lives in most of our
lakes, streams, and rivers from the Boundary Waters to the southern prairie. Johnny
darters are among the first fishes to move into new aquatic habitats or to
recolonize a stream after a catastrophe. They prefer clear water with sandy or
gravely bottoms and slow or still waters, but they do very well in moderately turbid
(cloudy), moving water. They seem to tolerate many kinds of water pollution, more so
then other darters species. They often found living with the American brook lamprey,
white suckers, bigmouth shiners, central stonerollers, blacknose dace, and other
species of darters.
How Big Do They Get?
How Long Do They Live?
Like most other darters, Johnny darters are small fish. Males grow faster and reach
a larger size than the females do. A large male may reach 65 mm (2.5 in) and a
little over 2 g (0.07 oz). Females rarely get bigger than about 60 mm (2.3 in) and
1.6 g (0.05 oz). Their normal lifespan is 3 years.
What Do They Eat?
Young Johnny darters eat mostly small copepods and waterfleas. As they grow, they
add larger waterfleas, midge larvae, mayfly larvae, caddisfly larvae and sometimes
sideswimmers to their diet.
What Eats Them?
The Johnny darters are eaten by many of the predatory fish that share their habitat.
Some examples are burbot, lake trout, smallmouth bass, walleyes, and yellow perch.
Since they are common in shallow areas, it is very likely that fish-eating birds,
such as herons, also prey upon them.
How Do They Reproduce?
Most Johnny darters probably reach sexual maturity at one year old. Their spawning
season covers all of May and most of June, when water temperatures are 12-24° C
(53-75° F). The males arrive at the spawning grounds before females to establish
their territories. The spawning sites commonly occur in pools, slow runs, or shallow
lake waters, where there are large rocks, tin cans, logs, mussel shells, or any
other types of debris. Eggs are laid on the underside of these items. Once the
territories are established, males clear a space under the rock or other nesting
item and clean the underside of it. When a female approaches the nest, the male
darts out and chases her out of the territory. The male goes back to the nest and
rests underneath it. When the female enters the nest upside down, the male usually
will accept her. They both turn upside down and the male lies along side of the
female. She lays her eggs one at a time until she has laid 30-200 eggs. One or more
times during the spawning the male releases sperm to fertilize the eggs. The female
will spawn with other males, and the male will spawn with other females. A single
female may spawn several hundred eggs in a season (we do not know exactly how many).
A single nest may end up with over 1000 developing eggs (embryos really) attached to
it. The male guards the eggs until they hatch. While he guards them, he keeps the
eggs well oxygenated and eats the ones that develop fungus. The embryos hatch in
6-10 days depending on water temperature.
Conservation and Management
Johnny darters have no special conservation status in Minnesota, but are protected
by special Minnesota law. They make a very good aquarium fish and will spawn if fed
well and exposed to proper temperatures. They may be collected and kept only with a
special permit in Minnesota.
Natural History of Minnesota Fishes
Photographs by Konrad P. Schmidt and Donald Biemborn
Text by Nicole Paulson & Jay T. Hatch in cooperation with
the Minnesota Department of Natural Resources' MinnAqua Aquatic Program