REPORT OF THE COMMISSIONER OF FISHERIES. 109 
iting the bay received consideration, and that of the sessile or fixed 
species can be accurately platted on the map. 
INVESTIGATIONS IN ARIZONA. 
Early in January Mr. Fred M. Chamberlain, naturalist of the 
steamer Albatross, 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 fish-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 ina 
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 different fish- 
cultural stations of the Bureau. 
The gas-bubble 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 year, 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. 
