YELLOWSTONE Fishes of the Yellowstone National Park

The native fish life of the park was profoundly affected by the great lava flow which occurred over a large part of the park in Pliocene times. Whatever fishes were then present were necessarily killed, and, with the reestablishment of the watercourses after the cooling of the surface of the lava, fishes in outside waters were to a great extent prevented from reaching the lofty plateau, which comprises most of the area of the park, by the high and steep falls over which the streams leave the lava beds.

It thus follows that the native fish fauna of the park is very limited. Except in Yellowstone River and its tributaries practically no fishes occur naturally above the falls, and in the extensive basin of that river the few species that do exist gained access to the region above the falls because of the imperfect watershed separating the Yellowstone and the Snake River basins.

The original comparative barrenness of the park in fish life was due entirely to topographical conditions. The physical character of the waters is, in general, highly favorable for fishes, and an examination of the streams and lakes of the park by Prof. Forbes in 1890³ disclosed the presence in certain barren waters of an abundant insect and crustacean food well suited for sustaining certain kinds of fishes. The theory that would account for the original absence of fishes in particular park waters as due to the high temperature and chemical constituents of the great volumes of water flowing from the geysers and hot springs is entirely untenable for several reasons: First, native trout abound and flourish in various streams and lakes in close proximity to the outpourings of geysers and hot springs, and, secondly, both native and exotic trouts have been successfully planted in barren waters receiving the discharge of geysers and hot springs.

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³A preliminary report on the aquatic invertebrate fauna of the Yellowstone National Park, Wyo., and the Flathead region of Montana. By S. A. Forbes. Bulletin U. S. Fish Commission, vol. XI, for 1891, p. 207-258, pl. XXXVII-XLII. 1893.

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The fishes of natural occurrence in the park represent 10 species, as follows: Longnose sucker, rosyside sucker, chub, silverside minnow, longnose dace, dusky dace, Rocky Mountain whitefish, redthroat trout, Montana grayling, and blob . Of these only the trout and the grayling have generally been recognized as game fishes, although the whitefish might properly be so considered. While these were very abundant in certain waters, the annually increasing numbers of angler-tourists in the park made it desirable to augment the natural supply of game fishes by the introduction into barren waters of selected species of other game fishes.

In immediate response to the outcome of investigations to determine the suitability of fishless park waters for game fishes, the Bureau of Fisheries in 1889 inaugurated the planting of selected species in predetermined waters, and this work has been continued to the present time. The one species of native trout was soon supplemented by the very successful introduction of five other trouts, and in a short time the park became an angler's paradise, affording better and more varied trout fishing than could be found anywhere else in the country, if not in the world.

The nonindigenous trouts that have been introduced into park waters are the rainbow, Loch Leven brown, lake, and eastern brook trouts, all of which have become firmly established. The distribution of the native redthroat trout has been greatly extended into previously barren waters. The introduction of two other game fishes has been attempted, but apparently without positive results. One of these is the landlocked salmon (Salmo sebago), of which 7,000 fry were planted in Yellowstone Lake and 2,000 in Duck Lake in 1908, but not a vestige of these plants has ever been seen. The other species is the largemouth black bass (Micropterus salmoides), of which 500 fingerlings were planted in "lakes in Yellowstone National Park," according to the indefinite official record. These lakes are thought to have been Feather Lake and Goose Lake, in the Lower Geyser Basin. An earlier plant of 250 black bass was made in the Gibbon River, in 1893, but it is not known which of the two species of black bass composed this plant. There is no evidence of the survival of black bass anywhere in the park, and this may be regarded as a fortunate circumstance. In our opinion, there should be no further attempts to establish black bass in the park, as they do not harmonize with the trouts, and their predatory habits make them unsafe species to introduce among the soft-finned fishes which, with two minor exceptions, constitute the local fauna. The only other species of fish that has been introduced into park waters is the yellow perch, whose planting was unofficial and is apparently to be ascribed to the unauthorized act of a private individual. This fish now abounds in certain lakes in the Lower Geyser Basin.

The hundreds of thousands of visitors who have already been in the park and the millions of others who are destined to visit it owe to fish culture and fish acclimatization a debt whose value can hardly be estimated. Within a few years after experienced fish-culturists began to give attention to needs of the park the hitherto fishless waters began to produce desirable game fish in abundance, and this has continued up to the present time. The early work, as well as the efforts of the fish-culturists of late, has been directed mostly to maintaining the supply of fishes already established.

For many years the Bureau of Fisheries has conducted fish-hatching operations in the park. The first hatchery was located at the Thumb of Yellowstone Lake; the principal hatchery now is on the lake shore near the Lake Hotel. In 1921 a permanent hatchery was erected on Soda Butte Creek, which had been the site of a field hatchery for a number of years. The hatcheries are maintained, primarily, 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 running 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 the 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 mature'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 where 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 recently stocked with redthroat trout for the first time are various lakes in the southwest section of the park.