FISH-CULTURAL PRACTICES IN THE BUREAU OF FISHERIES. 719 



The Operations at this hatchery, fully described in the Manual of Fish 

 Culture published by the Bureau of Fisheries in 1900, have undergone slight 

 change of method and need not be dwelt upon here. The source of egg supply 

 is the catch of the fishermen's weirs usually during the month of June, the fish 

 being purchased and towed in live cars to the station, where they are trans- 

 ferred to inclosures and there retained until the spawning season, in October 

 and November. When ripe they are stripped and the eggs placed upon wire 

 trays, which are stacked in troughs and carefully tended until the early spring, 

 when the eggs hatch. The young fish are distributed for the most part as fry, 

 but a considerable number are reared to the fingerling stage. 



POND CULTURE. 



Pond culture in the United States is applied only to nest-building fishes, 

 such as the basses, sunfishes, and the common catfish {Ameiurus nebulosus). 

 These species do not submit to manipulation for taking and fertilizing their eggs, 

 but fortunately a very large percentage of the eggs are fertilized when the 

 spawning functions are permitted to occur naturally, and the parent fish care 

 for and protect the young until the latter are free swimmers. The cultivation 

 of these fishes, therefore, consists in providing ponds which shall give to the 

 maximum number of breeding fish and their young all the essential conditions 

 of a natural environment, while at the same time protecting them from their 

 enemies and holding them under control. 



THE PONDS. 



Economy in construction usually dictates the shape and area of the ponds, 

 but an independent" water supply and drainage to each is desirable. For con- 

 venience of the fish culturist the area usually ranges from one-fourth to one acre, 

 although some ponds of larger size are desirable. It was formerly considered 

 essential to have at least one-fourth the area of the breeding pond not exceeding 

 I foot in depth, but it has been found that the deepening of the shallower por- 

 tions to a minimum depth of from i foot to i ^ feet has largely increased the 

 productive area. 



The presence of aquatic plants in fish ponds is a prime essential. The 

 young of the nest-building fishes do not accept artificial food, and must there- 

 fore have their natural diet of minute animal life, the abundance of which is 

 dependent to a large extent upon the character and abundance of plant growth. 

 Plants are also important as oxygenators of the water and afford shelter and 

 shade for the fish. The selection and control of aquatic vegetation, therefore, 

 is a matter to which the fish culturist must give much attention, and experience 

 at the various stations indicates that it offers a direct means by which the output 



