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 rcdthroat 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. Tne 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 the young remain for awhile 

 in the water where they were born and then run back to the lake at 

 the proper tune ? 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. Heavy losses 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 wnere 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 



