1168 FISHERIES OF THE UNITED STATES. [14] 



cornplished by placing a dam across the river which prevents the fish 

 from proceeding further. The fish thus remain in the vicinity of the 

 dam until ripe, when they are secured by seines hauled by employes of 

 the hatchery. At the whitefish hatcheries on the Great Lakes pounds 

 have been constructed along the shore in which the fish have been re- 

 tained for a few days until ripe, so that the entire number of eggs, or a 

 large percentage of them, can be impregnated. The penning of fish, 

 especially in summer, often results in great loss, as some species are so 

 restless when in confinement that they soon kill themselves by rushing v 

 against the barriers, or become so bruised that they fall an easy prey 

 to fungus, which destroys great numbers of them. At one of the hatch- 

 eries in Canada the plan is adopted of penning the fish in salt water,, 

 which entirely does away with the danger from the fungus, as it never 

 makes its appearance in salt water. 



The spawning season of any particular species in a given locality 

 usually lasts but a few weeks, and for this reason a large force of men 

 has been required for a short time in taking and caring for the eggs and 

 distributing the fish, after which the hatchery is closed for want of 

 eggs. The plan of retarding eggs by means of refrigerators, in which 

 they can be stored, promises to give good results. Mr. F. N. Clark, the 

 superintendent of the Northville hatchery, informs me that his hatchery 

 will accommodate scarcely more than a hundred millions of eggs ; but as 

 it is found desirable to hatch out larger quantities, a refrigerator is beiug 

 erected, with an ice-chamber at the top and pipes running down to eou- 

 vey the air into the chamber beneath, which is to contain the eggs. 

 These are to be spread on trays, placed one above another, with air- 

 spaces between them. Here they will be kept until room occurs for 

 them in the hatchery, one lot being taken from the refrigerator and 

 hatched, while the rest remain to await their turn. He hopes to in- 

 crease the capacity of his hatchery in this way from one hundred to 

 five hundred millions, and believes that he will be enabled to distribute 

 fish during at least four months, and to extend the hatching x>eriod by 

 at least three months beyond its natural limit. 



In the early stages of fish-culture in this country considerable diffi- 

 culty was experienced in transporting fry from one locality to another, 

 and the expense of such transportation was a serious item. The fry 

 were usually placed in large cans, carried in the baggage-cars of pas- 

 senger trains, two assistants usually accompanying every shipment, to 

 change the water and keep it at a proper temperature. Cars constructed 

 expressly for the purpose, with hotel accommodations for the messen- 

 gers, are now employed by the United States Fish Commission. These 

 are fitted with refrigerators, tanks, and water-pipes. Their use greatly 

 reduces the difficulty and cost of transportation, as a car-load can now 

 be taken as easily as a half dozen cans by the old method. 



Fish-culture was for some years confined wholly to a few species, but 

 of late the number has been considerably extended. 



