THE WHITEFISH PRODUCTION OF THE GREAT LAKES. 659 
limit of the whitefish area had been taken as 30 or 4o fathoms the area would 
become more nearly continuous. In selecting 20 fathoms as the deeper limit 
of this area in Lake Michigan I have been guided by the statements of Ward 
(1896), which seem to merit every confidence. On the map of Lake Michigan I 
have, however, indicated also the 40-fathom limit by a dotted line. The area 
between the dotted line and the black area shows the region which contains 
longjaws in commercial quantities, especially along its shoreward margin. The 
blackfins rarely enter this area, but remain in deeper water. ‘This area is one 
into which the whitefish doubtless wander to a greater or less extent, but accord- 
ing to the statements of Professor Ward, not in commercial quantities. 
The map shows that if this area between the dotted line and the black area be 
included within the range of the true whitefish, that range is even then not con- 
aA 
5 CONNEAUT 
Fic. 4— LAKE ERIE. 
Whitefish area (shown in black), 12 to 30 fathoms. (Reduced from U.S. Hydrographic Office chart no. 1477. Scale: 
r in. = about 50 miles.) 
tinuous along the eastern shore of Lake Michigan. It is interrupted north of 
Big Point Au Sable and in a number of places still farther north. In handling 
the statistics of these fisheries we have attempted to study discreet areas within 
individual lakes. The extent of these is indicated in another place. 
Within the whole whitefish area of the Great Lakes the production of mar- 
ketable whitefish has greatly declined since the first statistics were taken in 1880. 
This is evident from a glance at the table given by Alexander (1905, p. 650), 
where is given the whitefish production for each lake for the years 1880, 
1885, 1890, 1893, 1899, 1903. As to the cause of this decrease there is no 
difference of opinion among those who have investigated it. Investigators from 
Milner in 1871 to Rathbun and Wakeham in 1893 to 1896 have reached but one 
conclusion, namely, that the decrease is due to overfishing. Ward (1896) 
