268 Modern Fuhculture in Fresh and Salt Water. 



will merely glance at such forms of life as prey on the 

 fish of rivers, lakes and streams. 



FISH. 



Large trout are usually cannibals, and in private 

 ponds should not be allowed to live. I have seen a 

 trout try to swallow one that was so near its own size 

 that it could not pouch it and it swam about all day 

 with a portion of the tail and caudal fin they are not 

 the same protruding from its jaws. Such fellows I 

 always netted out, or speared, for once they begin the 

 habit they never stop it, and they will devour many 

 times their own weight in a month. 



A small fish known as miller's thumb, blob, muffle 

 jaw, and star-gazer, belonging to the genus Cottus, or 

 Uranidea, for they shift the names occasionally, is 

 called bullhead in England. It is a homely, big-headed 

 little thing, and Jordan records nine species, from three 

 to five inches long, one species reaching seven inches. 

 They are found in the Great Lakes, rivers and streams 

 from Lake Superior to Georgia. They lie on the bot- 

 tom or under stones and move after the manner of the 

 darters. This fresh-water sculpin is one of the natural 

 checks on the overproduction of trout and salmon. It 

 eats the eggs and the young fish. It is found in all 

 trout waters as far as examined. It is very destructive. 

 At an experiment once made in the aquarium of the 

 United States Fish Commission, in Washington, a 

 miller's thumb about 4^ inches long ate at a single 

 meal, and all within a minute or two, twenty-two little 

 trout, each from three-quarters of an inch to an inch in 

 length. 



