518 



BULLETIN OF THE BUREAU OF FISHERIES 



cutting edge. Pigment dots usually are grouped in bands around the free margins 

 of the scales, the bands showing best below the lateral line where the dusky hue 

 is absent. Above the lateral line and on the back there are often, especially in fish 

 over 300 millimeters in length, one or two or more well-defined dots of pigment 

 lying below each scale near the center of its exposed surface. There is no pigment 

 on the belly. The sides of the head are pigmented throughout, most heavily in the 

 preorbital area. The mandible is white. All fins are more or less smoky in color 

 throughout, but the ventrals are usually darkest and the pectorals are possibly 

 the palest. The fish caught off Port Washington, Milwaukee, and Michigan City 

 show comparatively very little pigment. The back is not smoky, there are no bands 

 around the free margins of the scales below the lateral line, and the abdominal 

 fins are usually immaculate. These unpigmented fish are among the smallest speci- 

 mens in the collection, and it is possible that pigmentation increases with age. 

 Specimens equally small, however, and which show decided pigmentation, were 

 taken in Grand Traverse Bay and around the South Manitou Island. 



Pearl organs very likely are developed in the breeding season by sexually 

 mature individuals, as in other lakes. Few specimens taken at that time have been 

 examined, but it is probable that the development of the pearls is not different 

 from that recorded for Lake Huron specimens. 



VARIATIONS 



Racial variations. — So few specimens have been collected from any one port 

 that nothing can be said of race differentiation. No conspicuous features are exhibited 

 by any of the fish collected from various localities, except that pointed out in the 

 preceding paragraph, namely, that specimens south of the island region are less 

 pigmented. 



Size variations. — In Table 82, 10 specimens of various sizes are compared in 

 detail. The collected specimens, divided into two size groups at 300 millimeters, 

 show, like specimens of the table, that changes with growth evidently concern 

 principally the relative size of the eye and to less extent that of the head. 



GEOGRAPHICAL DISTRIBUTION 



All records indicate that originally the whitefish occurred in abundance all 

 along the shores of Lake Michigan and around the islands to the north. At present 

 it has been so reduced in numbers that over most of the shore line it is commer- 

 cially insignificant, and only in the northern sector of the lake is it still the object of 

 special fisheries. 



Specimens have been collected by me from several ports. Complete data for 

 these are given in Table 81 and are platted on the chart in Figure 4. 



METHODS OF CAPTURE 



The principal methods of capturing whitefish are by means of pound nets and 

 gill nets, the latter of about 4j^-inch mesh. In the northern sector of the lake, 

 north of a line drawn through Frankfort and Escanaba, both pound and gill nets 

 are used, the latter chiefly on grounds in more than 10 fathoms and on the spawning 



