88 ALASKA FISHERIES AND FUR INDUSTRIES, 1911. 



to construct wire corrals about the mouths of the streams wherein 

 the young salmon have been released, in order to exclude the trout. 



In the absence of locahties suitable for fry planting it is desirable 

 to rear the fry until they have acquired a degree of activity and 

 strength which will better enable them to cope with their natural 

 enemies or other unfavorable conditions. 



The feeding of fry upon herring roe, canned salmon, uncooked fish, 

 and other animal foods has been practiced with varying degrees of 

 success for many years. Both hatching troughs and nursery ponds 

 have been employed for handling the fish. The capacity of the 

 troughs, however, is greatly reduced for young fish as compared with 

 eggs; hence if extensive rearing operations are contemplated it is 

 necessary to have a large number of additional fry troughs, or, better 

 still, a series of rearing or nursery ponds. To produce the best results, 

 nursery ponds should be of limited area, say, 20 feet by 40 feet, thus 

 permitting a control over the fish impossible m large ponds. At one 

 station there is a rearing pond nearly an acre in extent, but its efii- 

 ciency is much impaired for the reason that the fish do not get the 

 amount of food they require. The food is scattered about the edges, 

 but many of the fish toward the center of the pond obtain little or 

 none of it. In view of the unequal rate of growth considerable loss 

 from cannibahsm is bound to result in a pond of this character. 

 Smaller ponds permit of a control over the fish impossible ia larger 

 ponds. 



In the rearing of young salmon it would theoretically be of advan- 

 tage to create a growth of minute natural life in the water to afford a 

 supply of food. Taking into consideration, however, the large scale 

 upon which hatching is conducted in Alaska, the idea is of doubtful 

 value, because of the difficulty of producing enough of this food to 

 supply the needs of more than a few salmon. Starvation and camii- 

 bahsm menace the undertaking. As an aid to or in combination with 

 artificial foods such a plankton growth appears to be very desirable. 

 Further experimentation is necessary, however, before definite con- 

 clusions as to the practical value of plankton as food for salmon can 

 be determined. At the Fortmann hatchery of the Alaska Packers 

 Association some preliminary work has been accomplished ia this 

 field. 



It can not be too strongly urged upon all engaged in fish-cultural 

 operations that it is as highly essential to exercise caution and pursue 

 an intelHgent study of conditions in planting the fish as it is to devote 

 care to eggs and fry prior to the time of planting. 



