660 U. S. BUREAU OF FISHERIES 
obtained. Newly collected drills gave the same results. Migration experiments 
will be conducted to determine whether the drills are inactive in the field. 
Some work was done also on the phototropism of the organism, but no 
results were obtained. That is the extent of the work at the present time. 
I hope that as it becomes warmer more work will be done and more results 
will be obtained. 
FISHERIES OF THE GREAT LAKES 
GENERAL REVIEW 
By Dr. WALTER KOELZ 
The Great Lakes are a unique series of water bodies that have been formed 
by the blocking of ancient valleys. They have a very complicated history— 
now they were separated, now intimately joined. They have emptied through 
the Mississippi, the St. Lawrence, the Mohawk; they have even been flooded, in 
part, by the ocean, and all within relatively recent geological ages—that is, some 
25,000 years. 
The total area of the five lakes is in the neighborhood of 100,000 square miles. 
Lake Superior is the largest and deepest. The greatest depth is about 1,000 
feet. Lake Ontario is the smallest and Lake Erie the shallowest, being less 
than 100 feet deep over most of its area. The lakes are what limnologists call 
first-class lakes. Their waters are very deep, very pure, and very cold, and 
few plants, except alge, grow in them. Their economy is probably so different 
from that of small and shallow lakes that principles derived from a study of the 
smaller lakes may not be applied to the culture of the Great Lakes. In spite of 
the apparent sterility of their waters, the fish production has been high. The 
total annual yield of the commercial fisheries has averaged around 150,000,000 
pounds. The productivity of the individual lakes, however, is not equal, due to 
the varied conditions that obtain in them. Lake Superior and Lake Ontario 
are the poorest, averaging 500 and 650 pounds per square mile per year; Huron 
comes next, with 800; Michigan has 1,100; and Lake Erie has far exceeded the 
others combined, with about 6,000. These relative figures do not reflect the 
effects of depletion (it is assumed that depletion has been relatively equal in 
all), and the inequality of the figures undoubtedly is a reflection of the unequal 
productive capacity of the various bodies of water. Favorable conditions for 
fish do not depend alone on humidity, as many people, including scientists, seem 
to think, but on bottom conditions, temperatures, etc.; and the fishermen know 
well that there are hundreds of square miles in the lakes that produce nothing. 
Of the grand total of 150,000,000 pounds, about one-half consists of species of 
Coregoninze—the whitefishes and lake herrings. These fish occur throughout 
the boreal regions and are among the werld’s most important fresh-water fishes. 
Wherever they occur, however, it has been very difficult to define the limits of 
a species, so that it is not known, even approximately, how many species there 
are in the world, or, in fact, in any region. This has been no less true in the 
Great Lakes. Where other fishes are separable by color, number of fin rays, 
vertebra, scales, proportions, ete., the various species of these fish are alike in 
all these characters. 
It is necessary obviously to determine what forms occur and to define these 
forms before anything can be done to conserve the fisheries that they sustain. 
This uninteresting undertaking of describing the physical differences of species 
is what the average worker understands as systematics. Systematic workers 
are in more or less disrepute among the workers in practical science, and it is 
more or less just that they should be. Too many of our systematists have 
failed to realize that describing and naming species or subspecies or races is 
not an end, but only a beginning, and that no one should or may safely name 
or describe any form until he is acquainted with the important facts of its life 
history and that of its relatives. 
My work on the Great Lakes, then, has of necessity attempted to correlate 
differences in structure with differences in habits. It is of no biological sig- 
nificance that a human being should find that a fish is very unlike another fish, 
if the fish feel intimately acquainted with each other and are able to spawn 
together; nor does it alter matters if fish and fish are exactly alike, so far as 
I can see, if they have totally different physiological reactions and neyer spawn 
together. The Great Lakes whitefishes illustrate, abundantly, both kinds of 
phenomena. The lake herring in most of the lakes exist in two forms—one 
