140 REPORT OF COMMISSIONER OP FISH AND FISHERIES. 



s])rin^ iunl ji'cysca- loniiatioii, Avitli juimerous Ktroniiis of liofc watfi- ciiiiitvinj; into 

 the l.ikc, and lar<;o springs of liot wator opeuiug iu the Jloor of the lake near shore. 

 Trout abound in the vicinity of these warm waters, jtresuniably on account of the 

 abundance of food there. Tlicy do not love the warm water, but carefully avoid it. 

 Several jhtsous with whom I talked on the subject while in the jiark assert that 

 diseased fish — that is to say, those wiiich are thin andafiected withlleshworms — are 

 more connnonly found near the Avai'm water; that they take the bait readily, but are 

 lazy. I freijuently saw pelicans swinuning near shore in the Aucinity of the warm 

 springs on the Avest arm of the lake. It would appear that the badly infested or 

 diseased fish, being less active and gamy than the healthy fish, would be more easily 

 taken by their natural enemies, who would learn to look for them in jilaces where 

 they most abound. But any circumstances which cause the pelican and trout to 

 occui)y the same neighborhood will multiply the chances of the parasites developing 

 iu both the intermediate and iinal host. The causes that make for the abuudance 

 of the trout jiarasito conspire to increase the number of adults. The two hosts 

 react on each other, and the parasite profits by the reaction. 



All -effective remedy miglit be found in tlie extermination of the peli- 

 cans, providing tliey are the only Iinal ho.sta of this parasitic Avorm. 

 The relief which might thereby be afforded, however, is not of sufHcient 

 importance to justify the destruction of so interesting a feature of the 

 park. The trout in that region is not important as a food supplj'-; the 

 diseased fishes are in most convenient places for capture, and with the 

 increase in fishing will be drawn upon more largely than the healthy 

 ones. The introduction of other species into the lake would, more- 

 over, tend to improve conditions by adding new varieties of food for 

 tlio trout, thereby probably diverting them more or less from the warm 

 waters and imparting to them a more vigorous cimstitution. The peli- 

 cans would also profit by this new source of food, the trout would 

 suft'er less from their attacks, and parasitism would be decreased in 

 jiroportion. 



Other fish parasites were obtained in the Yellowstone Parle by Prof. 

 Linton, who has presented three reports treating of these interesting 

 forms.* 



COLORADO ANT) UTAH, 



Investigations were conducted in Colorado and Utah during July 

 and August, l.SSl), by Dr. David S. Jordan, assisted by Prof. B. W. 

 Evermann, Mr. Bert Fesler, and Mr. Bradley M. Davis. The special 

 object of this inquiry was to determine the character of the streams 

 and lakes of tiie llocky Mountains and the Great Basin as represented 

 in this State and Territory, the variety and distribution of the lood- 

 tishes now inhabiting these waters, and their suitability for the intro- 



* On two species of larval Dibothria from the Yellowstone National l^irk. IWill. 

 U. S. Fish Comin., ix, for 1889, pp. G5-7i), pis. xxv-xxvii. 



A contribution to the life-history of Dihothrium cortliccps, a parasite infesting 

 the trout of Yellowstone Lake. Idem, ])p. 337-3r>8, jds. cxvii-cxix. 



On fisli entoz()a from the Yellowstone National Fai'k, (Apjiendix 5 to this vol- 

 ume.) 



