THE ALLIES OF THE PERCH 327 



but three genera now in existence, one each in the rivers of 

 Queensland (in Australia), Brazil, and tropical Africa. 



Economic Importance of Fishes. The value to a people of 

 an abundant and cheap fish supply cannot be overestimated. 

 Recognizing its importance, the United States government 

 has long maintained a Bureau of Fisheries, which has been 

 active along both practical and scientific lines. A very ex- 

 tensive laboratory is maintained by the Bureau of Fisheries 

 at Woods Hole, Massachusetts, for the study of marine life. 

 Much of the work on problems of fresh-water life has been 

 carried on by the Bureau through its laboratory on the 

 Mississippi River, at Fairport, Iowa. Among the subjects 

 which are considered by the Bureau are the resources of our 

 inland and coastal waters, the geographical distribution of 

 the economically important fishes inhabiting them, and the 

 study of the natural history of fishes, their enemies, diseases, 

 and the remedies therefor. Perhaps most important of all, 

 it has carried on the artificial propagation and distribution 

 of valuable species. According to statistics for 1925 more 

 than 191,000 persons in the United States and Alaska are 

 engaged in fishing as a business. They receive close to 

 $98,000,000 annually for their products. 



Hatcheries have been established in many places for 

 rearing the young from fish eggs. In these hatcheries eggs 

 are gently pressed from the bodies of mature fishes, or 

 gathered from the nests where they are deposited in ponds 

 and streams. The fertilized eggs are placed in jars of water 

 through which a small water current is passed, or in wire- 

 bottom trays set into troughs of running water. The young 

 fishes after hatching are kept in troughs and ponds until they 

 are ready for transplanting to the lakes and rivers. Until 

 very recently fishes were liberated when but a few inches 

 long. The result was that many were destroyed by larger 

 fishes. A very recent plan of operation calls for fish nurs- 



