THE WHITEFISH PRODUCTION OF THE GREAT LAKES. 673 
TABLE 16.—SHOWING THE AVERAGE CATCHES AND PLANTS OF WHITEFISH IN MICHIGAN WATERS OF 
LAKE MICHIGAN FROM MANISTEE TO FRANKFORT, INCLUSIVE, FOR THE THREE FIVE-YEAR PERIODS 
1892 TO 1906, INCLUSIVE. 
Whitefish area, 90 square miles. 
Catch. Plant. Nets. 
Years. Total Pounds per Laer per | Fry per Fry per Total Fathoms 
odnds | square net- Total fry. | square | pound erehnnie per square 
Pp mile. fathom. mile. caught. = mile. 
1892—-1896______-_ 128,000 I, 422 0.80 7,900, 000 87,777 62 156,900 I, 743 
1897-1901 - z 152,000 1, 688 1.16 5,300,000 58, 888 35 138,900 1,543 
I902—-1906_______ | 211,000 2,344 Oh) of poten Sane By ete ey (ina ae tata (habe a oem 242,900 2,498 
PRODUCTION COMPARED WITH INTENSITY OF PLANT. 
The data that have been presented seem to show that wherever, whether 
in American or Canadian waters, there has been a large plant of whitefish fry 
per unit area (20,000 in at least one period) this is correlated with a considerably 
increased average yield of adult fish per unit area in one or another period (Man- 
istee and Frankfort and southeast Michigan areas of Lake Michigan, Canadian 
waters of Lake Erie); wherever there has been a moderate plant of fry per unit 
area (5,000 to 10,000 per square mile) this is correlated with a moderately 
increased yield of adult fish per unit area in one or another period or by a practically 
stationary yield (north shore of Lake Michigan, Michigan waters of Lake Huron 
from Port Huron to Mackinaw City, Michigan waters of Lake Superior) ; wher- 
ever there has been a small plant of whitefish fry per unit area (less than about 
3,500) or no plant, this is correlated with a diminished yield of adult fish per 
unit area (Canadian waters of Lakes Superior, Ontario, and Huron and Georgian 
Bay, except for a slight increase in Lake Huron from second to third period). 
CONCLUSIONS AS TO EFFECT OF PROPAGATION. 
The result reached in this section is expressed in another form in tables 17 
and 17a, in which the whitefish areas already discussed are arranged in the 
order of the intensity of the plant made on them per unit area. Arranged in 
this way the series falls into three groups. The first, including the Manistee 
and Frankfort area, the southeast Michigan shore, and the Canadian waters 
of Lake Erie, comprises areas which have in at least one of the three periods 
received plants of at least 20,000 per square mile. The increase or decrease 
in the catch of each area of this group is shown for the second and third 
periods in the right-hand column in percentages of the catch compared with 
that of the preceding period. Positive values indicate an increase in catch, 
negative values a decrease. These percentages are of considerable amount and 
are positive in every case but one; the catch for the southeast Michigan shore is 
less for the second period than for the first (43 per cent), but it increases again 
enormously in passing from the second period to the third (350 per cent). 
B. B. F. 1908—43 
