THE WHITEFISH PRODUCTION OF THE GREAT LAKES. 649 
The condition of the fisheries is usually expressed by giving the annual 
catch, but as was pointed out by Rathbun and Wakeham (1893), ‘‘the best 
statistical test of a decrease is a comparison of the average catches per unit of 
apparatus for the several years for which statistics are available.’’ In com- 
paring the catches of different periods I have therefore reduced the average 
catch of each period to ‘“‘ pound-fathoms”’ by dividing the actual catch expressed 
in pounds by the length of gill and pound nets expressed in fathoms. I have 
thus obtained the catch in pounds per unit of net length. Unfortunately in 
making these calculations I have been unable to separate the gill and pound 
nets which have taken whitefish from those which have not, so that the values 
given in the tables in this paper are the lengths of all gill and pound nets used in 
the waters in question whether the nets have or have not taken whitefish. 
I have attempted, also, to consider the output of whitefish in its relation 
to the areas of the Great Lakes bottom occupied by them during that season 
of the year when they are not migrating. By dividing the number which ex- 
presses in pounds the catch of a lake or of any part of a lake by the number of 
square miles of lake bottom ordinarily occupied by the fish in question, I have 
obtained a pound-mile unit which is made use of in another part of this paper, 
where also the method of measuring the areas is described. By the device of 
the pound-mile it is hoped that in a measure errors have been avoided which 
arise from the comparison of the catches of different years when the areas fished 
over in those years have not been the same. 
The present paper then attempts to utilize the available statistics in an 
examination of the individual Great Lakes and of parts of lakes to see what 
lessons may be learned by a comparison of those areas which have been fished 
under one set of regulations with those that have been fished under a different 
set of regulations, and by a comparison of those areas which have been abun- 
dantly planted with those that have been less liberally treated. I am indebted 
to the United States Bureau of Fisheries for kindly obtaining information for 
me from the states of New York and Pennsylvania, to the Wisconsin Fish Com- 
mission for information furnished, to the Michigan Fish Commission for per- 
mission to make excerpts from the original records on file in their office and as 
yet unpublished, and to the Department of Marine and Fisheries of the Dominion 
of Canada for printed documents and excerpts from official records. 
NATURAL HISTORY OF THE WHITEFISH. 
SOURCES OF INFORMATION. 
In the report of the joint commissioners relative to the preservation of 
fisheries in waters contiguous to the United States and Canada, Messrs. Rathbun 
and Wakeham (1897) have collected a large amount of evidence concerning the 
