GREAT LAKES COREGONIDS 



531 



shallow lakes, which must become fairly warm in summer, show the same peculiar 

 features. 



Size variations. — The same kind of variation of proportions with size is exhibited 

 by Superior specimens as has been recorded for those of Michigan. In Table 88 are 

 compared in detail 10 individuals of varied sizes. Separating the specimens of the 

 collection into two groups, according as they are more or less than 300 millimeters in 

 length, the only character that appears to be different in the two groups is the H/E 

 ratio. The figures for the smaller fish are (3.8) 4.2-4.4 (4.7); for the larger ones 

 (4.1) 4.4-4.6 (5), indicating that the eye becomes smaller with growth, relative to the 

 head. Of course, all the fish in the collection are fairly uniform as to size, the length 

 of most of them falling within 50 millimeters of the dividing point of the two groups; 

 and if there were greater disparity in size between the groups compared, the differences 

 in this ratio would become much more conspicuous and other ratios also might be 

 found to differ. 



METHOD OF CAPTURE 



Whitefish are taken chiefly by means of pounds and gill nets, as in Lake Michigan, 

 but a few are taken by other apparatus. The pound nets are located chiefly on the 

 north shore, but there are a few on the southern and eastern shores, most of which 

 yield whitefish. Gill nets, too, are used for whitefish in these areas, but the catches 

 are mixed with trout, for the most part, and here, as in the other lakes, the gill-net 

 industry would long since have perished if it had been dependent on the whitefish 

 alone. 



GEOGRAPHICAL DISTRIBUTION 



Table 87 shows data for specimens collected from various points along the north, 

 east, and south shores. The records are shown platted on the lake chart in Figure 3. 

 Whitefish are known to exist at all ports on the lake, but they are rare in many sec- 

 tions, particularly on the west shore, where only occasional specimens are taken. 

 They occur around Isle Royale and Michipicoten Island, also, and Will Parker says 

 he has taken stray specimens on Stannard Rock Reef (separated from the mainland 

 by a 30-mile stretch of water, which in most places is from 50 to 100 fathoms in depth). 



Lake Superior does not offer particularly favorable conditions for littoral fishes, 

 and the whitefish, therefore, has never been more than locally common. Excepting 

 the bays and the south shore, there is elsewhere only a narrow zone along shore, in 

 many sectors barely a mile wide, in which bathymetric conditions are favorable, to 

 say nothing of bottom conditions. Many of the bays even are too deep over most of 

 their extent, and along the south shore there is only a strip not more than 5 miles 

 wide over which there is water of suitable depth. The bottom, except on the south 

 shore and in the bays, is largely rocky, where the whitefish probably find little food ; 

 and the low temperature of the lake's waters also probably retards the development 

 of food organisms, even where conditions are otherwise favorable. 



SEASONAL MOVEMENTS 



The whitefish behave in Lake Superior as in the other lakes, moving to and away 

 from the shoals during the season. 



Data from the pound nets. — Lake Superior often is still covered with ice by May 

 1, so that the driving of the pound nets may not be completed before the 1st of June. 



