240 



A STUDY OF VERTEBRATES 



breeding places in the Connecticut River, and the salmon have been 

 exterminated along our eastern coast within the past few decades. 

 It is only a matter of a few years when the Western salmon will 

 be extinct if fishing is continued at the present rate. More fish 

 must be allowed to reach their breeding places. To do this a 

 closed season on the rivers of two or three days out of each seven 

 while the shad or the salmon run would do much good. 



The sturgeon, the eggs of which are used in the manufacture of 

 the delicacy known as caviar, is an example of a fish that is almost 

 extinct in this part of the world. Other food fish taken at the 

 breeding season are also in danger. 



Artificial Propagation of Fishes. — Fortunately, the govern- 

 ment through the Bureau of Fisheries, and various states by wise 

 protective laws and by artificial propagation of fishes, are be- 

 ginning to turn the tide. Certain days of the week the salmon 

 are allowed to pass up the Columbia unmolested. Closed breed- 

 ing seasons protect our trout, bass, and other game fish, also the 



catching of fish under 



a certain size is pro- 

 hibited. 



Many fish hatcheries, 

 both government and 

 state, are engaged in 

 artificially fertilizing 

 millions of fish eggs of 

 various species and pro- 

 tecting the young fry 

 until they are of such 

 size that they can take 

 care of themselves, when they are placed in ponds or streams. 

 This artificial fertilization is usually accomplished by first squeezing 

 out the ripe eggs from a female into a pan of water ; in a similar 

 mamier the milt or sperm cells are obtained, and poured over the 

 eggs. The eggs are thus fertilized. They are then placed in re- 

 ceptacles supplied with running water and left to develop under 

 favorable conditions. Shortly after the egg has segmented (divided 

 into many cells) the embryo may be seen developing on one side 



Artificial fertilization of fish eggs. 



