ACIPENSER THE STURGEONS 25 



or tubercle-like ossifications;* sides of upper caudal lobe sheathed with small 

 rhombic plates. 



This species, which is confined to inland waters, was for- 

 merly abundant throughout the Great Lake region and the 

 Mississippi Valley. Lake sturgeon have of late years been 

 steadily decreasing, and are now only rarely taken in the Missis- 

 sippi on our own borders, and are seldom caught in the Illinois. 

 Fishermen at Alton now see but five or six in a year that weigh 

 over 10 Ib, whereas fifteen years ago forty or fifty large ones, 

 weighing from 50 to 100 Ib, were taken each season. 



The lake sturgeon is said to inhabit comparatively shoal 

 waters in the lakes, ascending streams in the spring to spawn. 

 The most extensive study of their habits has been made by 

 Milner, who found their food, in the Great Lakes, to consist 

 almost entirely of fresh-water snails (Gasteropoda). Craw- 

 fishes and insect larvae are also eaten by them, and the eggs of 

 fishes have been occasionally found in their stomachs, though 

 not in quantity sufficient to justify the charge of destructive 

 spawn-eating sometimes made. Lake sturgeon taken in the 

 vicinity of grain elevators have been found with stomachs well 

 filled with corn or wheat. They spawn early in June, generally 

 preferring rocky ledges near the shores. While their spawn is 

 probably subject to the depredations of other fishes, the young 

 are well protected, after reaching two or three inches in length, 

 by their spine-tipped bucklers. Adult sturgeons are much sub- 

 ject to attack by lampreys. 



Previous to 1870 the flesh of the lake sturgeon was scarcely 

 used. Fishermen generally made no use of them at all, and by 

 many they were considered a nuisance and ruthlessly destroyed. 

 In the following decade, however, several firms began the busi- 

 ness of smoking lake sturgeon and manufacturing caviar, isin- 

 glass, and oil from the eggs, air-bladders, and viscera. Smoked 

 lake sturgeon is now considered a superior article, and lake 

 caviar is ranked as the best produced in the United States- 

 selling (in 1898) for eighty cents a pound, while the Delaware 

 product brought only sixty cents, and the South Atlantic fifty 

 cents (GiLL). 



* Younger specimens are much rougher than adults; in a young sturgeon 10 inches long 

 taken at Ottawa, 111., each lateral scute has a peculiar flexuose keel or ridge in place of the charac- 

 teristic central spine, and the ventral plates are similarly keeled. We have small specimens in 

 addition which are perfectly normal in the character mentioned. 



11 F 



