556 U. S. BUREAU OF FISHERIES 
geared to the egg supply, and a depleted species is its own limiting 
factor upon the scope of artificial replenishment measures. 
i Fish-cultural technology extends from the production of an entirely 
synthetic”’ fish, such as game trout, to a process of byproduct recov- 
ery as exemplified in the propagation of shad. A brook trout may be 
hatched from an egg obtained from a domesticated brood stock held 
at a private commercial hatchery and may be reared to a size per- 
mitting its capture by the angler immediately after its release from 
the hatchery. This is a synthetic but definite increment of a recre- 
ational resource. 
On the other hand, migrating shad, when caught for market, may 
be carrying over 30,000 mature eggs which can be incubated in a 
hatchery and released as fry. The survival ratio of these fry cannot 
now be accurately determined, but it is known that without the inter- 
vention of the hatchery, the reproductive contribution of the parent 
fish would be zero. 
Hatcheries have failed to stem the depletion of certain species, 
such as the whitefish, but their role as an elemental factor in con- 
serving the majority of the food and game species is widely conceded. 
The administration of this activity requires attention to the methods 
and technique of hatching, rearing, feeding, and transporting fish; to 
the maintenance and upkeep of the physical plant and equipment; 
and to the construction of new facilities. The year under review 
has shown tangible progress in all these aspects. While it has been 
possible to continue the services rendered to the general public by the 
stocking of public waters, much of the increased production attaimed 
in recent years has been diverted to maintaining the stock of fish in 
areas under direct Federal ownership or control. 
Complete transition to this type of activity is not anticipated, 
however, as long as the present unbalanced ratio between fishing 
demand and fish populations in State waters exists. The succeeding 
tabulations and comments are presented with the purpose of clarifying 
the significance of the various types of fish-cultural functions carried 
on by the Bureau. 
SPECIES PROPAGATED 
During 1939 there were handled at the hatcheries and rescue 
stations 47 species, the majority of which are fresh-water types. No 
attempt has been made to propagate a dozen or more important food 
fishes which are found in the coastal waters. No practicable methods 
for propagating certain of these forms have been developed, and there 
is further doubt as to whether results would be sufficiently valuable 
to warrant the effort. 
In addition to the varieties listed in the table, there are propagated 
forage fishes comprising some half dozen species of minnows and 
shiners. These are utilized as food for bass, etc., at the hatcheries 
and are not available for general distribution or listed in the pro- 
duction records. 
No carp, humpback salmon, or Atlantic salmon were handled during 
the year although these forms were propagated previously. The carp 
were dropped because of the desire to devote available funds to the 
propagation of more valuable forms. The “‘off year’’ for humpback 
salmon made it impracticable to obtain eggs of this species and no 
Atlantic salmon eggs were available from any source. 
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