6 DISTRIBUTION OF FISH AND FISH EGGS, 1915. 
changes, turbidity of the water after heavy rains, ravages of snakes 
and other enemies, and depletion of the stock through cannabalism, 
all of which conditions can be mitigated or controlled only in part. 
The harvest is therefore uncertain, and the output of one year can not 
be used as a standard on which to base estimates of succeeding 
seasons. 
For many years the Bureau has been doing a valuable work of con- 
servation by rescuing vast numbers of black bass and other native 
fishes from the temporary pools and bayous formed by the annual 
flooding of certain navigable interstate rivers, and at the same time 
has been able to secure considerable numbers of young pond fishes 
for general distribution. In the conduct of this work it has been the 
Bureau’s policy to remove fish only from such places as will dry up 
or freeze solidly before a recurring high-water stage, returning to the 
main rivers the bulk of the collections and utilizing any surplus to 
supplement its supplies for shipment to applicants. As in the pond 
fish-cultural work at its stations, the degree of success attending the 
seining operations depends largely upon climatic conditions, and 
occasionally the work proves a total failure because of the maccessi- 
bility of the spawning grounds, owing to the extremely high or low 
water stages prevailing. 
METHOD OF DISTRIBUTION. 
Almost the entire output of young fish of the commercial species 
handled by the Bureau is returned to the original sources of supply or 
liberated in other public waters where conditions are favorable to the 
establishment of new fisheries. Where eggs or fish for stock pur- 
poses are derived from interior waters especial care is taken to return 
to such waters a sufficient number of young fish of like species to 
insure the maintenance of the supply. The remainder of the stock 
available is then allotted on individual applications, bearing the 
indorsement of a United States Senator or Representative, such 
applications being submitted on a blank form furnished by the 
Bureau, which among other things calls for a detailed description of 
the waters for which fish are desired. In passing upon applications 
the preference of the applicants as to species assigned is taken into 
account, but the Bureau reserves the right of final decision of this 
question, taking into consideration not only the character of the 
waters, but the welfare of existing local fisheries, and selecting such 
species of fish as will not be likely to prove injurious to or be injured 
by those already established. 
In general the assignment of nonindigenous fishes is made only 
with the approval of the fisheries authorities of the States concerned. 
In this connection it may be stated that the Bureau has recently 
decided to refuse all requests for predaceous fishes for stocking waters 
