22 REPORT OF THE COMMISSIONER OF FISHERIES, 



During the year two rather extensive trips were made by the 

 assistant in charge of the investigation to various sections of the 

 Southeastern States for the purpose of inspecting malaria-control 

 I^rojects and to offer suggestions to local health officers concerning 

 the proper use of mosquito-destroying fish. The annual conferences 

 of the National Malaria Committee and the field men conducting 

 malaria-control work were attended. 



FOULING OF VESSEL BOTTOMS. 



In September, 1922, at the request of the Navy Department, the 

 bureau undertook direction of an investigation of the marine growths 

 on the bottoms of ships to determine, if possible, the conditions gov- 

 erning the amount and character of such growths and the possible 

 seasonal and regional factors affecting them, with a view of securing 

 data on the problem of preventing their attachment to ships' bot- 

 toms, as well as to determine the docking intervals for ships in 

 various kinds of service. 



The investigation has also indicated, rather conclusively, that most 

 of the fouling occurs while the ships are in harbors and that vessels 

 in commission that never stay more than six or seven days in any 

 port and that travel between ports a considerable distance apart do 

 not foul seriously, at least during August to March, in the North 

 Atlantic Ocean. On the other hand, it is found that vessels that lie 

 continuously at anchor in any one port for the five or six winter 

 months become heavily coated with hydroids but not with barnacles. 



Cooperation has been extended to the Navy Department in testing 

 the relative efficienc}' of various antifouling paints. 



MISCELLANEOUS IN\TiSTIGATIONS IN INTERIOR WATERS, 



Cooperation has been continued* with the Wisconsin Geological and 

 Natural History Survey in important investigations of the funda- 

 mental conditions of fish life in lakes. The aquatic plants, the 

 plankton, bottom fauna, and mussels of Green Lake were studied 

 during the past year with reference to quantity and distribution. 

 Arrangements have been made for the continuance of these investi- 

 gations during the fiscal year 1924. 



In cooperation with the Illinois Natural History Survey, the Chi- 

 cago Drainage District, and the U. S. Public Health Service, a 

 statistical survey of the Illinois River for 1921 was made by members 

 of the staff' of the Fairport Biological Station in connection with a 

 study of the effects of pollution and the reclamation of land along 

 the stream upon public health, recreation, agriculture, and the fish- 

 eries. 



During the summer of 1922, in cooperation with the National Park 

 Service, the bureau made an investigation of the pelicans in the Yel- 

 lowstone National Park to determine their destructiveness in rela- 

 tion to the trout, the supply of which the bureau helps to maintain 

 by artificial propagation. The results 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 witli that of 

 the trout that its depredations effect maximum losses. It was origi- 

 nally suggested that attention be directed rather definitely to the 

 problem presented by the parasites of the pelicans and of the trout 



