Interactions
A Johnny Darter is a small benthic fish, therefore it has
many interactions with different types of predators because it
is very small in size. Two of the many predators include
crayfish (Orconectes rusticus) and small mouth bass (Micropterus
dolomieni). In a study by
Rahel and Stein,
1988, Johnny Darter
interactions where measured under different conditions. The
control was the shelter use and activity of the Darters without
any predatory influence. That control was then used to compare
the activity after crayfish and small mouth bass were introduced
both separately and together.
When just a crayfish was present the shelter use and activity levels were very similar to that of the control.
When only a small mouth bass was present the darters had a 6% reduced activity rate.
However when both the small mouth bass and the crayfish were
present an interesting interaction occurred between the three
species. There was a 19% increase in the activity level of the
Johnny Darter. The crayfish would displace the darters and as that
was happening the small mouth bass would then in turn force the
darters under another shelter causing the activity level to increase
by that large percentage
(Rahel, Stein, 1988).
Johnny Darters are an aggressive fish who exhibit this behavior when other animals such as the crayfish enter their nest sites. This aggressive behavior reduces the amount of predators likely to prey of them and increases the likelihood of finding a mate (Rahel, 1989).
When larger fish, like northern pike for example, are near by Johnny Darters will release chemicals through their secretion cells in the skin. This provides another mild form of protection other than inactivity and shelter use (Smith 1979).