River were grossly underestimated. Cooper 

 (1952) recorded a 25 -percent rate of exploita- 

 tion in the Pigeon River, Michigan. Allen (1951) 

 found that anglers caught 27 percent of the 

 catchable-size fish present at the beginning of 

 the season in the Horokiwi, New Zealand. 

 Schuck found that anglers caught from 15 to 28 

 percent of the available crop in Crystal Creek, 

 New York. Hobbs (1948, as quoted from Allen, 

 1951) reviewed several papers on brown trout 

 and found that an average of 13 .8 percent were 

 harvested. Brown trout grow fast enough to 

 enter the catch by June in their second year, 

 and there were, at a minimum 40,000 young-of- 

 the-year brown trout present in September, 

 1957. Although overwintering mortality will 

 reduce this population considerably, there will 

 be adequate numbers to support a large fishery. 

 Allen (1951) found in the Horokiwi stream in 

 New Zealand that even under a relatively heavy 

 fishing pressure, angling mortality on brown 

 trout seldom accounted for more than one -third 

 of the natural mortality. Cooper (1953a) found 

 that angling never made up over 17 percent of 

 the total mortality from the first to the second 

 year of life for brown trout in the Pigeon River . 

 Needham (1949) found natural mortality in 

 brown trout populations much higher than ang- 

 ling mortality. 



The catch of wild rainbow in both the 

 Firehole and the Madison did not vary greatly 

 from 1954 to 1957. The range in the catch on 

 the Madison was from 1,040 to 1,301 fish while 

 the range on the Firehole was from 1,955 to 

 2,540. There is little doubt that it is possible 

 to overfish resident rainbow trout populations in 

 streams since so few large self-sustaining resi- 

 dent populations exist in the United States today 

 in spite of the large number of rainbows planted. 



There is evidence from our population 

 studies and creel census that overexploitation 

 of rainbow trout probably existed in both the 

 Madison and Firehole Rivers . The catch of 

 rainbows was predominantly Age Class I fish 

 which had not had a chance to spawn. Leach 

 (1939) stated that 15 to 20 percent of female 

 rainbow trout mature in their second year and 

 60 percent in the third year . Most males mature 

 in their second year. Our data from the Madi- 

 son and Firehole Rivers show a sex ratio in the 

 catch of Age II and older fish of 51 .4 percent 



males to 48.6 females during 1956 and 1957. 

 If we combine our age compositions of the catch 

 data with our total catch, we find that there were 

 240 Age Class II and 213 Age Class III rainbow 

 trout caught on the Madison in 1957. If 48.6 

 percent of these were females and only 15 to 25 

 percent of the Age Class II and 60 percent of 

 the Age Class III fish were sexually mature, 

 we can calculate that anglers caught about 79 

 female spawners . Our population data in 

 September, 1957, showed less than 50 females 

 left in Age Class II and III . Thus, our total 

 population of spawning females was less than an 

 estimated 129 fish. A comparable estimate of 

 the number of female brown trout spawners 

 would be over 2,000. In September, 1957, we 

 counted 900 Age Class browns and 509 Age 

 Class rainbows on the Madison River. Thus, 

 it appears that the survival rate in Age Class 

 fish up to September of the first year is higher 

 for rainbows than browns . The lower number 

 of older rainbows may be attributed to higher 

 exploitation of the spawning population rather 

 than a possible lower survival rate of rainbows. 



The whitefish catch increased during 

 periods of heavy fishing pressure, but there is 

 no evidence that whitefish were being fished 

 heavily. They are not considered as palatable 

 as trout during the summer and are not as popu- 

 lar to catch . They were also present in deeper 

 and more turbulent water than browns or rain- 

 bows which makes them more difficult to catch, 

 especially for the inexperienced angler . 



Brook trout were abundant in certain sec- 

 tions of the Firehole and Gibbon, but their small 

 size makes them unattractive to most anglers 

 and they are not fished heavily enough . Heavier 

 exploitation of this species mi^t increase their 

 average size. 



INFLUENCE OF PLANTING ON WILD FISH 



There has been some disagreement in the 

 literature on the subject of the influence of hatch- 

 ery fish on wild fish populations. Hazzard and 

 Shelter (1939) stated that the increased fishing 

 pressure commonly associated with planting 

 brook, brown, and rainbow trout increased the 

 harvest of wild fish. Chamberlain (1943) found 

 that planted fish served as a buffer and prevented 

 overexploitation of wild rainbows. Cooper (1952) 



23 



