KEPORT OF THE OOMMISSIONEE OF FISHERIES. 109 



iting the bay received consideration, and that of the sessile or tixed 

 species can be accurately platted on the map. 



INVESTIGATIONS IN ARIZONA. 



Early in January Mr. Fred M. Chamberlain, naturalist of the 

 steamer Alhatross^ was detailed to study the physical and biological 

 features of the Gila River basin in Arizona. Observations were car- 

 ried on at Yuma during the last half of January and the month of 

 February, and during March and April visits were made to most of 

 the streams in the Gila basin. The physical characteristics of the 

 streams were determined and their suitability for iish -cultural work 

 fully considered, it being important that these streams be examined 

 before irrigation operations shall have seriously modified their charac- 

 ter. The results of these observations will be given in detail in a 

 report now in course of preparation. 



INVESTIGATION OF SMALL LAKES OF NORTHERN INDIANA. 



The examination of the small lakes of northern Indiana, begun some 

 years ago, was continued during a portion of the summer of 1903 and 

 for a few days in June, 1904. The investigations of the present fiscal 

 year, as heretofore, were under the general direction of Dr. Barton 

 W. Evermann and were carried on by Dr. J. T. Scovell, of Terre 

 Haute, Ind. The inquiries were directed chiefly toward securing data 

 concerning the food of the various food and game fishes occurring in 

 these lakes, and, second, toward determining the species and habits of 

 the aquatic plants and their relation to the animal life of the same 

 waters. The principal investigations were carried on at Lake Maxin- 

 kuckee, but more or less work was done at Bass Lake, Lake Manitau, 

 Tippecanoe Lake, and Twin Lakes. 



DISEASES AND PARASITES OF FISHES. 



The study of the diseases and parasites of fishes was continued by 

 Mr. M. C. Marsh, assistant assigned to the subject of fish pathology, 

 and a number of special investigations were made at difl'erent fish- 

 cultural stations of the Bureau. 



The gas-ljiibhle disease. — The mortality from this cause at Woods 

 Hole, Mass., and at Nashua, N, H., received attention in the summer of 

 1903. August and part of September were spent in investigations, 

 supplementing those already published, and, jointly with Prof. F. P. 

 Gorham, of Brown University, some important additions to the sub- 

 ject were made. Simple methods of de-aeration of water supercharged 

 with dissolved air were again effective at Woods Hole in preventing 

 symptoms of this disease, and, later in the j^ear, when the leaky suction 

 pipe supplying the aquaria and hatching tanks had been replaced by a 

 new, impervious one of iron, all trouble from gas disease disappeared. 



