584 proceedings: biologicai. society 



After alluding to the origin of the fish life in the park, to the limited 

 number of native species (ten), and to the successful introduction of 

 five trouts of America and Europe, the speaker discussed the following: 



(i) The problem of keeping out obnoxious fishes. The introduction of 

 predatory fishes like the pikes, pike perches, and basses would be un- 

 wise and might be a calamity to the trouts and grayling. Two plant- 

 ings of black bass in 1 893 and 1 895 were, fortunately, unsuccessful, but 

 in waters where the black bass were said to have been deposited the 

 speaker found a great abundance of yellow perch (Perca flavescens), 

 whose introduction was apparently without official record or sanction. 

 (2) The problem of food for the native and introduced trouts. There is a 

 scarcity of food for adult trouts in Yellowstone, Lewis, and Shoshone 

 lakes; cannibalism prevails; and the fish are driven at times to a diet 

 consisting almost exclusively of caddisflies caught singly at the surface. 

 It is proposed to introduce small cyprinid and other non-predatory 

 fishes in the expectation that the lakes may support a more numerous 

 supply of trouts. (3) The problem of parasitism of the native trout. 

 The tapeworm parasite that, in its larval stage, infests a large propor- 

 tion of the redthroat trout {Salnio lewisi) in Yellowstone Lake, passes 

 its adult stage in the white pelican. The trout could be freed from the 

 parasite by the eradication of the pelican, and the intensity of the 

 parasitism might be reduced by diminishing the number of pelicans 

 and by providing other fish on which the pelicans and trout could in 

 part subsist. This problem merges into the next. (4) The problem of 

 the pelicans. The pelicans present a double problem: responsibility for 

 the parasitism of the trout and destruction of large numbers of trout. 

 The speaker's census of the pelicans in the park in 1919 indicated not 

 over 1,300 adult and young birds. The consumption of fish by peli- 

 cans was regarded as not inordinately large, in proportion to the size 

 of the waters and the abundance of the redthroat trout, which is the 

 chief food of the pelicans. The statement of Mr. Ernest T. Seton 

 before the Biological Society on January 24, 1920, that the Yellow- 

 stone Park pelicans eat only diseased trout and therefore do no harm 

 was controverted. The extermination of the pelicans was not advo- 

 cated by the speaker, who had recommended to the park authorities 

 that the birds be kept under close observation and their number be 

 reduced by destroying a part of their eggs, after it had developed that 

 they were taking an unduly large toll of trout and were counteracting 

 the government's fish-cultural work. (5) The problem of maintaining 

 the fish supply in the park. The fishes are the only wild vertebrates in 

 the park whose deliberate and general killing by visitors is allowed and 

 encom-aged. The maintenance of the fish supply in the smaller waters 

 against yearly increasing destruction constitutes a serious practical 

 problem. The restrictions on fishing now imposed — size and string 

 limits — may have to be extended, but, in the opinion of the speaker, 

 the situation for the present may best be met by increasing the abun- 

 dance of fish by artificial means rather than by further curtailing the 

 anglers. 



