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
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
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.
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