666 BULLETIN OF THE BUREAU OF FISHERIES. 
An examination of any one of these tables shows great fluctuation in the 
annual catch of whitefish, which may increase or diminish nearly 50 per cent 
between one season and the next, and in some cases varies 300 per cent between 
successive years. The cause of these annual fluctuations is to be found, no doubt, 
in part in the weather conditions, which permit almost continuous fishing in one 
season while they may greatly interfere with the fishing in the succeeding season. 
But these fluctuations may also be due in part to some feature of the habits of the 
whitefish themselves which we do not at all understand. It would be possible, by 
terminating almost any one of these tables at a suitable point, to convey the 
impression that there has been a very great falling off in the catch of whitefish in 
any one of the lakes. Thus if table 2 should terminate with the year 1902 it 
would show apparently a steady decrease in the catch of whitefish in the Canadian 
waters of Lake Superior and a like impression may be gained with respect to any 
other one of the lakes by terminating the table at the appropriate year. 
DISCUSSION OF AVERAGE CATCH AND PLANT FOR CERTAIN AREAS. 
It is evident from an examination of tables 1 to 10 that no conclusion of value 
is to be reached by comparing the whitefish production of the Great Lakes for 
individual years. The annual fluctuations, whatever may be their cause, 
vitiate any conclusions that may be drawn from such comparisons. It is further 
evident that any comparisons should take into account the relative whitefish 
areas of the lakes compared, and should consider both the catch and the plant 
with reference to these areas. 
In tables 11 to 18 an attempt has been made to avoid the errors just men- 
tioned by comparing the average catch for the three five-year periods from 1892 
to 1906, inclusive. In the first column is entered the average annual catch in 
pounds for each of these five-year periods. In the second column is given the 
average catch per square mile of whitefish area, while in the third column is 
stated the average catch per fathom of net used. In the same tables are given 
the plants of whitefish; the annual average for each five-year period, the average 
per square mile of whitefish area, and the average per pound of whitefish caught. 
The same tables give the average annual number of fathoms of nets used for each 
period and the fathoms of nets per square mile. By nets is to be here again under- 
stood all nets used in the areas in question, not merely nets in which whitefish 
were taken. Not much value can therefore be attached to that part of the table 
which deals with nets. 
Canadian and Michigan waters of Lake Superior —In table 11 the data for 
the Canadian and Michigan waters of Lake Superior are brought together for 
comparison. The Michigan whitefish area of 2,400 square miles extends from 
the St. Marys River westward to the Wisconsin boundary line, as indicated on 
the map of Lake Superior. It does not include Isle Royal for the reason that 
