XVIII HEPOnX TO THE SECRETARY OF COMMERCE 



serious difficulties in fish culture of the region is due to the rank 

 growth of aciuatic vegetation. Chemical treatments have been 

 devised which will destroy the coarser plants without injury to the 

 fish or interference with the food sui)ply. Such treatments are being 

 applied to the ponds in the refuge and will have practical application 

 to pondfish culture throughout the country. 



The bureau's pathologist has continued his studies on the dise'ases 

 of trout and has rendered invaluable service not only to the bureau's 

 hatchery superintendents through the diagnosis and treatment of 

 disease in hatcheries, but to many State and private fish-culturists. 

 This line of work is so productive that plans are laid for its expan- 

 sion as rapidly as funds will permit. 



FISHERIES OF THE ATLANTIC AND GULF COASTS 



Fundamental studies on the factors that affect the abundance of 

 fish in the great commercial fisheries of the Atlantic seaboard have 

 been undertaken during the past two years with the aid of the fish- 

 eries steamer Albatross II and a staff of shore observers. Studies of 

 the chemical and physical condition of the water and its contained 

 floating life have been made at various seasons of the past year in 

 order to judge the success of spawning of various important species and 

 the influences that control their migrations. A comprehensive report 

 on the migrations and biology of the cod of southern New England is 

 now in press, and rapid progress has been made on studies of the 

 stock of mackerel. The erratic appearance and disappearance of 

 huge stocks of mackerel in Atlantic waters is now known to be due 

 to variations in actual abundance resulting from the occurrence of 

 successful spawning at fairh^ infrequent intervals, and it has been 

 possible to predict with increasing accuracy the commercial runs of 

 the following season. 



Investigations of the shore fisheries of southern New England and 

 the Middle Atlantic States, begun two ^^ears ago, indicate that 

 similar causes control the abundance of other important species and 

 that the decline in productivity of the squeteague, or weakfish, in 

 recent years is the result of natural rather than artificial causes. 



Much of the understanding of the biology of these food fishes 

 depends upon a knowledge of their early life history. A deliberate 

 attack upon this problem has been made in connection with the ocean- 

 ography of the North Atlantic region by extensive collection and 

 study of the eggs and larvae obtained in the surface waters and in a 

 program of collections in the South Atlantic region at the Beaufort 

 biological station. 



On the Gulf coast, studies of the fauna have been continued with 

 the aim of eventually producing a manual of the marine fishes that 

 will give descriptions of the species and the pertinent facts in their 

 life history, habits, and economics. 



FISHERIES OF THE PACIFIC COAST AND ALASKA 



Investigation of the commercial fisheries of the Pacific coast and 

 Alaska have been restricted to the salmon runs of Alaska, to the 

 completion of salmon-tagging experiments on the Columbia River, 

 and continuation of the Alaska herring studies. New investigations 



