GREAT LAKES COREGONIDS 



425 



occurs in lifts from 60 to 100 fathoms. The proportion is highest in those lifts from 

 Lake Huron that were made in 1917 in the center of the lake east of Alpena and in 

 1923, 17 to 20 miles northeasterly from Thunder Bay Island, and in these lifts it 

 may be as high as 90 per cent. In Georgian Bay the only lift in which blackfins 

 were abundant was made from 70 fathoms. The blackfin thus seems to reach its 

 maximum density at depths of 60 fathoms and more. This conclusion agrees with 

 accounts of its habits in Lake Michigan. 



BREEDING HABITS 



It is not known that anyone has taken the fish on their spawning grounds in 

 Lake Huron or Georgian Bay. From the condition of the ovaries of females examined 

 as late as the middle of October, and from the occurrence of faint pearls on the row of 

 scales below the lateral line in a single male taken at Lions Head, Ontario, on October 

 6, 1919, and one at Alpena on October 17, 1917, it appears that spawning does not 

 take place before November. It may be deferred even until the last of December, as 

 in the Lake Michigan form. 



As in johannx, some females often are taken which show undeveloped ovaries 

 while the ova in the majority of the females of the species are approaching maturity. 

 On September 21, 1917, out of 37 females examined 13 were nonspawning. (See 

 p. 361.) These nonspawners ranged from 26 to 29 centimeters in length, the 24 

 spawners from 23 to 33 centimeters. On October 17, 1917, out of 43 females 12 were 

 nonspawning and ranged from 25 to 29 centimeters in length; the remainder from 

 21.5 to 34 centimeters in length. On October 20, 1917, out of 41 females 11 were 

 nonspawners of 26 to 31 centimeters and 30 were spawners 22.5 to 35 centimeters. 

 The percentage of such sexually immature fish is too high to class the phenomenon as 

 an abnormality, but an understanding of its significance must wait on knowledge of 

 the rate of growth and age at maturity of the species. 



FOOD 



Stomachs have been examined from 56 individuals collected off Alpena, Mich., 

 in September and October, 1917, and from two taken in Georgian Bay off Lions Head 

 on October 6, 1919, all from depths of more than 60 fathoms. Mysis comprised 

 almost the sole food of all specimens. In one or two stomachs a trace of plant frag- 

 ments and of adult insects or a fish scale was found. 



Leucichthys nigripinnis cyanopterus Jordan and Evermann, of Lake Superior 



The Bluefin (Fig. 20) 



The nigripinnis of Superior differs in many tehnical characters from the typical 

 form, but the description of the body and its parts given for the type is applicable 

 except as noted hereafter. The numerical expressions of the chief characters of the 

 two forms are summarized for comparison chiefly from the data given in Tables & 

 to 11. 



