GREAT LAKES COREGONIDS 



465 



The data reviewed indicate that the bloater can be captured most abundantly 

 at depths of about 30 fathoms, though at times it may be relatively uncommon at 

 that depth. Numerous individuals often become entangled in large-meshed nets 

 at that depth, and occasional specimens are known from these nets between 10 and 

 100 fathoms. It appears that the abundance of the species decreases toward the 

 extremes of the zone of distribution. 



BREEDING HABITS 



Not even the hook fishermen know when the fish spawn. The same opinion as 

 to the spawning season is held for the bloaters as for the chubs, namely, that they 

 spawn all the year round. However, there is no evidence to support such a belief 

 except that eggs are found in the fish during most of the season; but these eggs are 

 not ripe when found. Specimens taken on December 3, 1919, in Colpoy Bay and 

 on December 9, 1917, at Harbor Beach were not yet ripe. On March 14, 1919, Mr. 

 Hollander wrote me from Harbor Beach that bloaters were then very scarce. Fish 

 of this species which he collected for me on March 15 were spent females and pearled 

 males. As the males are not found with pearls later in the year, it is certain that 

 these fish had been on the spawning grounds a short time previous to March 15 

 (probably in February), and that for this reason they are scarce in March in the 

 bait nets at 30 fathoms. At what depth and on what bottom they spawn is not 

 known. 



FOOD 



Doctor Hubbs has examined the contents of 26 stomachs of specimens taken off 

 Alpena, Mich., in September, 1917 and 1919, in 30 fathoms or less, and of 36 speci- 

 mens from 60 fathoms and deeper, of 42 stomachs from specimens taken off Che- 

 boygan, Mich., on October 15, 1919, and 1 taken in Georgian Bay on July 30, 

 1919. 



The shallow-water specimens from Alpena had eaten from 60 to 98 per cent 

 Pontoporeia. Almost all stomachs contained Pisidium more or less abundantly, 

 and also wood and seed fragments. Sand, cinders, adult-insect remains, and Mysis 

 were found occasionally. Stomachs of the deep-water fish from Alpena showed that 

 Mysis constituted almost the sole food. Six stomachs had Pontoporeia and nine 

 fragments of wood. Pisidium, insect larvae, sand, or pebbles were found in very 

 small quantities in occasional stomachs. The Georgian Bay fish (also from deep 

 water) had eaten only Mysis. 



The Cheboygan specimens from intermediate depths had eaten Mysis more 

 frequently than Pontoporeia. Some stomachs had predominantly the one, some the 

 other, but both forms occurred in most, indicating (in view of the rarity of Mysis 

 and the abundance of Pontoporeia in the stomachs of the Alpena fish from 30 fathoms 

 or less, and the reversed ratio in the stomachs of those from 60 fathoms or more) 

 that the zones of distribution of the two forms overlap at about 35 fathoms. Pisid- 

 ium and vegetable fragments are also frequent articles in the Cheboygan stomachs, 

 and the casually swallowed items are the same as those given in the previous para- 

 graph. In addition, Leucichthys eggs occurred in 10 of the stomachs, usually in 

 small numbers, except that they comprised 94 per cent of the contents of one stomach. 



