6 U. S. BUREAU OF FISHERIES. 
hatchery for a number of years. The hatcheries are maintained, pri- 
marily, for the purpose of keeping up the supply of redthroat trout. 
The redthroat trout is the only local trout which spawns during 
the season when the park is easily accessible and when it is possible 
without unwarranted effort and expense to obtain a supply of run- 
ning water for hatching purposes. The adult fish begin to ascend 
the streams that are put into flood by the melting snows and they 
continue to run until the latter part of July. Some fish, however, 
doubtless spawn also in Yellowstone Lake and other large lakes. 
The principal supply of eggs for hatching purposes comes from 
creeks on the eastern side of Yellowstone Lake. Into these creeks 
the trout run at spawning time and across them the fish-culturists 
erect intercepting barricades or racks. These racks are provided 
with narrow passageways that lead into traps in which the fish 
congregate. The trout are transferred to live cars, where they are 
held pending the ripening of their eggs. At the proper time the eggs 
are stripped from the fish and held at improvised field hatcheries 
pending shipment to the central station. The adult fish are released 
alive. 
The questions naturally arise, Why not let the trout run up the 
creeks and spawn naturally? Why not permit the eggs to hatch in 
the manner intended by nature and let éhie young remain for awhile 
in the water where they were born and then run back to the lake at 
the proper time? These questions, which will, no doubt, be asked 
by many thoughtful park visitors, afford an opportunity to indicate . 
one way in which it is possible to improve on nature and to point out 
why in the Yellowstone National Park, as elsewhere, it is desirable 
or necessary for the fish-culturist to go to nature’s assistance. 
The streams in which the redthroat trout spawn are usually much 
swollen at the time of the run. Pushing upstream energetically, 
the fish often go far from the lake and deposit their spawn during 
high water in places which later, with the complete melting of the 
snow, may become exposed to the air. oat ee of eggs occur 
in this way. If conditions are favorable for the laying and hatching 
of the eggs in streams that may be raging torrents in spring and 
early summer, it frequently happens that by July and August such 
streams become almost dry, are cut off from the lake and reduced 
to disconnected pools, and the young fish necessarily perish sooner 
’ or later. 
The adverse conditions occurring in nature make it probable 
that at best only 5 or 10 per cent of the eggs produce fry that reach 
the feeding stage at which the hatchery turns the fish loose. On 
the other hand, fully 90 per cent of the eggs taken by artificial 
methods are safely incubated and yield fry that are liberated in 
selected places—along the lake shore or near the mouths of open 
creeks se re there is a good prospect of survival. 
There are still a few fishless waters in the park, but each season 
additional lakes and streams are stocked and ultimately all waters 
suitable for fish will have received attention. In 1919 Mallard 
Lake, a beautiful mountain gem not far from Old Faithful Inn, was 
found to be fishless and was planted with eastern brook trout. This 
seems destined to become a favorite angler’s resort. Other waters 
