8;' U. S. BUREAU OF FISHERIES. 



sturgeons has been collected." There is evidence in both of these 

 species that sexual matiirit}^ is not r^ ached as early as in the case 

 of the " scaled " fishes, and that, unlike these fishes, the reproduc- 

 tive cycle is not an annual one. If these observations are corrob- 

 orated by future work it will explain to a considerable extent the 

 ease with which the sturgeon fishery has been depkted. A large 

 collection of dermal plates of both sj^ecies of sturgeon has been made, 

 together with data on weight, length, and the condition of. the sex 

 organs. 



The study of the natural history of the sheepshead has included 

 observations on their habits in Lake Pokegama, Minn., and the col- 

 lection of otoliths and scales (to be used in age determination), with 

 records of length, weight, and sexual condition. These data have 

 been supplemented by other data of similar character obtained from 

 fishes taken at Fairport, Iowa. 



Some observations have been made on the habits and natural his- 

 tory of the channel catfish. 



Tagging experiments have been conducted at several localities in 

 the Mississippi Basin for the purpose of obtaining information as 

 to the migrations of several of the more important fishes. Over 

 150 small hackleback sturgeon were tagged and liberated in the 

 Mississippi River. A great many sheepshead were tagged and lib- 

 erated at Lake Pokegama and at Fairport, Iowa. In cooperation 

 with the Louisiana State Conservation Commission some 300 small 

 paddlefish were tagged at Lucas, La. These fish were seined from a 

 large borrow pit outside the river levee, tagged, and transported to 

 the river. The fish were all of small size, presumably of the year, 

 none being longer than 12 inches. In Lake Pepin, a wide section 

 of the Mississippi River between Minnesota and Wisconsin, 1,660 

 fish were tagged and liberated. These tagged fish were distributed 

 among the various species as follows : Wall-eyed pike, 728 ; saugers, 

 771; sheepshead, 16; carp, 42; buffalo, 103. At the close of the 

 fiscal year comparatively few of the tagged fish had been recovered 

 and no significant results had been obtained. It is hoped and ex- 

 pected that future returns will be sufficient to give the information 

 desired. 



DESTRUCTION OF TROUT BY PELICANS IN YELLOWSTONE NATIONAL PARK. 



During the summer of 1922 the bureavi, in cooperation with the 

 National Park Service, began an investigation of the pelicans in 

 the Yellowstone National Park to determine their destructiveness in 

 relation to the trout, the supply of which the bureau helps to main- 

 tain by artificial propagation. The services of Dr. H. B. Ward, 

 of the University of Illinois, were secured for this work. The re- 

 sults of this investigation indicate that the pelican is a highly 

 specialized predatory bird, and that its breeding period in the park 

 is so precisely synchronized with that of the trout that its depreda- 

 tions effect maximum losses. 



The pelican colony on Yellowstone Lake in 1922 was found to 

 number between 500 and 600 birds, from which about 200 young 

 resulted. For the six weeks of their sojourn on the lake they sub- 

 sist almost entirely upon the black-spotted trout, the toll taken by 

 each pelican during the season amounting to about 350 fish, and in- 



