movement and through hybridization. The 

 present distribution of species in these streams 

 and their tributaries is Madison River - brown 

 and rainbow trout, whitefish, and very few 

 grayling and brook trout; Firehole River - 

 brown and rainbow trout, and some brook trout 

 in certain sections; Gibbon River - grayling 

 and hybrid trout (rainbow x cutthroat) in Grebe 

 and Wolf Lakes and in smaller numbers down- 

 stream, brook trout and rainbow trout in the 

 middle section of the stream, ^and brown and 

 rainbow trout below Gibbon Falls . 



During the period from 1948 to 1952 

 the average annual plants in this system were: 



Madison River - 66,800 trout 



(brown fingerlings, 

 and rainbow adults) . 



Firehole River - 74,240 trout 



(brown and rainbow 

 fingerlings). 



Gibbon River - 11,000 brown trout 

 fingerlings . 



Management of these fish populations 

 began with few restrictions on the angler. In 

 1942 the fishing season extended from May 30 

 to October 15 in the Firehole and Gibbon Rivers, 

 and from May 30 to September 30 in the 

 Madison River . The daily limit of catch was 

 15 pounds plus one fish, not to exceed ten fish 

 per person. In 1946 the daily catch limit was 

 changed to five fish per person per day for the 

 Madison River, the Firehole River below 

 Kepler Cascades, and the Gibbon River below 

 Gibbon Falls. Subsequently, the entire 

 Gibbon River was placed under the same 

 restriction, as was the Firehole River above 

 Kepler Cascades. In 1949 the use of fish eggs 

 for bait was prohibited in the park. In 1950 

 a bait restriction was put into effect on the 

 Madison and Firehole Rivers; only artificial 

 flies with a single hook could be used by 

 fishermen, and no other lures . The Gibbon 

 River below Gibbon Falls was put under the 

 same restriction in 1951. No minimum size 

 limits exist on the Madison River system . 



DESCRIPTIONS OF STREAMS 



Firehole River 



The Firehole River originates in Madison 

 Lake, located about eight miles south of Old Faith- 

 ful, and flows northward for about 32 miles where 

 it joins the Gibbon River (fig. 1). The flow in 

 early September 1957 was about 35 cfs. at Old 

 Faithful and about 200 cfs . where it joins the 

 Gibbon. Many hot springs and geysers enter the 

 river along a 12 -mile section below Old Faithful . 

 The river falls about 700 feet from two miles 

 above Old Faithful to its mouth, an average gra- 

 dient of 28 .2 feet per mile. It varies in width from 

 40 to 100 feet and in depth from six inches to over 

 ten feet. Firehole Falls are 40 feet high and are 

 located about four miles above the stream mouth; 

 for the next two miles below the falls, the Firehole 

 flows through a gorge in a series of cascades. 

 The falls, together with the cascades, serves as a 

 barrier against upstream fish movement. 



The chemistry of the water in the Firehole 

 River is variable because it is influenced by peri- 

 odic eruptions of geysers . Water was collected 

 from Old Faithful and from above the mouth of 

 Nez Perce in 1958 and analyzed by the U.S. Geo- 

 logical Survey (table 1). Several ions, particu- 

 larly silica, bicarbonate, sodium, and chlorides, 

 increased greatly as a result of geyser activity. 



The temperature of the water In the Fire- 

 hole is influenced to some degree by geysers, but 

 only localized areas become too warm for brown 

 and rainbow trout. Simonian (1952) recorded the 

 Influence of Giant Geyser, the largest geyser in the 

 park, on the temperature of the Firehole River . 

 Water temperatures 200 yards downstream from 

 the eruption rose from 64° F. to 75° F. At the 

 point where the thermal water was entering the 

 stream, a temperature of 115°F.was recorded. 

 Giant Geyser erupts irregularly with a minimum 

 interval of 48 hours, and the temporary influence 

 of the warm water does not prevent brown and 

 rainbow trout from living under such conditions . 

 The distribution of the brook trout in the Firehole 

 was outside of the areas Influenced by thermal acti- 

 vity; they were principally confined to small trib- 

 utary streams and to areas above Old Faithful , 



