11 
ing. According to Hile (1949), in the period 1895-1939, the United States trout 
catch in Lake Huron averaged 1,685,000 pounds annually. In 1949 the catch in 
this lake was 1,000 pounds, and in 1950 it was only 65 pounds (Hile 1951). For 
Lake Michigan the average annual take in the years 1940-1944 was 6.5 million 
pounds. In 1949 it had dropped to 342,000 pounds, and in 1950 to 54,000 pounds. 
For Lake Superior the catch has been more stable. In the United States waters 
of this lake the average annual take for more than 20 years before 1949 was a 
little over 3 million pounds. In 1949 the annual vield was just under 3 million 
pounds, and in 1950 it was nearly 3.2 million pounds. 
Lampreys have some characteristics which cast some doubt on a direct 
cause-and-effect relationship. They show preferences, attacking most readily 
the dogfish. They will attack a dozen other species commonly, however, includ- 
ing the lake trout, but other species have varied in numbers without regard to 
the lamprey. These predators are seasonally selective, too. In the fall they 
seem to prefer yellow perch and walleyed pike. Furthermore, the attacks are 
not necessarily fatal to trout. 
In the face of all of this information, we are led to wonder if the sea lam- 
prey, despite the great notoriety which it has received in the past few years, is 
but one of the decimating factors instead of the decimating factor, as we are 
sometimes led to believe. ao 
Now, if we consider only the three introduced species which we have dis- 
cussed, we find that we are in doubt at every point as to the cause-and-effect 
relationships which may be involved. The picture is far from clear. 
I hope that the above sketchy discussion will demonstrate that the aquatic 
environment of the Great Lakes is a complex one. That the governing factors 
are as yet poorly understood may be due in part to the fact that these conditions 
are constantly changing, even now, and other than a statistical base line is dif- 
ficult to attain. We do not know what the pristine conditions were. And we have 
a woefully small group of specialists assigned to the role of cause-and-effect- 
unravellers. 
SHORE LINE PROBLEMS 
Finally, in this discussion of the conservation problems of these inland 
waters, I should like to refer quickly to another matter. Heretofore all of the 
discussion has been pointed toward the aquatic environment. Let us look at the 
shore line. There are important conservation problems here, 
Now and then we read in the press, or in more formal publications, of 
questionnaires, which have been circulated among holders of lake frontage, 
seeking basic data on losses caused by high waters. These questionnaires, and 
the resulting compilations, leave me particularly unimpressed. Changes in wa- 
ter levels, and the resulting damage which they cause, are not acts of God. We 
can predict that they will occur, and in advance we know approximately the 
heights which they may reach. It is only common sense that certain strategic 
