The Flowing Stream—One More World*
Shelby D. Gerking
Department of Zoology
Indiana University
Flowing streams literally teem with thousands of species of animals
and plants. In the broad sense, almost every animal group from the
microscopic protozoa to the mammals is represented, and man's habit of
eliminating wastes by introducing them into streams alters the natural
conditions in which these animals live. Since Dr. Ricker (1946) has
already discussed some aspects of the effect of pollution upon aquatic
life in general, this discussion is confined to a particular animal group
of interest to almost everyone—the fishes. Fishes are the most important
economic resource that is utilized from the streams of the Midwest,
rivaled only by the clam industry. Revenue from the sale of fishing
tackle, licenses, bait, boats, and the like runs into millions of dollars
annually; therefore fishes are usually given a prominent place in planning conservation measures.
The fish fauna of the Midwest is rich in species. An easy day's drive
in an east-west direction will cross streams in which at least 250 fish
species live. In Indiana alone there are 170 distinct kinds not including
forms of subspecific rank. Bizarre forms like the lampreys, gar, dogfish,
spoonbill catfish, and sturgeons have cartilaginous skeletons and from a
geological standpoint are the oldest fishes known in this part of the
country. Among the bony fishes, the sunfish, perch, bullhead, and pike
families command the greatest attention by the public and consequently
by aquatic biologists. The size range of these fishes varies tremendously
from the least darter, weighing about one fiftieth of an ounce, to the
blue catfish, which may weigh 150 pounds or more. Fishes living in
deeper water are drab, but the riffle-inhabiting darters and minnows
are beautifully colored and never fail to excite the curiosity of those
who see them.
The list of fishes interesting to both the layman and scientist could
be expanded many times, but of particular interest are the game fishes,
a group which can be defined simply as those fishes which are particularly prized by the public for recreation and food. The basses, sunfishes,
pikes, catfishes, and other game species are all present in our streams in
•Zoological Contribution No. 369.
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