PROGRESS IN BIOLOGICAL INQUIRIES, 1923, 13 



greatly improved, in so far as pollution is concerned, the general 

 planting of inshore lots with oysters (where this will not result in 

 loss from storms, etc.) is to be urged as the most hopeful method in 

 sight for the improvement of oyster sets in the sound. 



In September there came to the attention of Dr. P. S. Galtsoff, 

 in the course of his hydrographic surveys, the matter of the death 

 of large numbers of " set, " especially in the neighborhood of New 

 Haven. He found that in addition to those being killed by the drill, 

 many were dying from some unknown cause. Attempts, by histolog- 

 ical methods, to connect this mortality with some parasite were un- 

 successful. When, in October, he again visited this region he 

 found that although the drill was still active the mortality from the 

 unknown cause or causes had ceased. 



CLAMS AND CRABS OF ALASKA. 



In connection with the administration of fishery reservations in 

 Alaska, an investigation of the clams and crabs has been undertaken. 

 The utilization of these shellfish has only just begun in Alaska, and 

 wliile there is no immediate danger of depletion it is desired to obtain 

 all the information that may be needed later to properly control the 

 utilization of the resource. For this work the bureau has obtained 

 the services of Dr. F. W. Weymouth, of Stanford University, who 

 has made extensive studies of the life histories of both clams and 

 crabs in California and British Columbia. Some preliminary work 

 has been done in the way of compiling information as to the present 

 state of the industry and active field work will be begun soon after 

 the close of the present fiscal year. 



FRESH- WATER MUSSELS. 



Investigations of the factors affecting the survival and growth of 

 juvenile mussels conducted at Fairport and at Lake Pepin have been 

 characterized by important results, which have appeared sufficiently 

 favorable to warrant the establishment of a small rearing system at 

 Fairport. This system consists of 140 metal troughs fed by a gravity 

 supply of water, twice sedimented in ponds before reaching the 

 troughs. The elasticity of this system, and its apparent efficiency, 

 mark it as a distinct step toward the conservation of fresh-water 

 mussels. One of the main features of the system is the exclusion of 

 light from the troughs. Experiments have prove'd that the dark 

 trough, probably because it simulates natural conditions on the 

 bottom of mussel-bearing streams, will produce about 25 times as 

 many mussels as the open trough. 



Similar noteworthy results have been produced experimentally at 

 Lake Pepin, Minn., by the use of a totally different apparatus. There 

 a floating basket with wooden floor approximately 8 feet below the 

 surface was used. A second smaller basket, in which the infected 

 fish are held until the mussel embryos are liberated, was suspended 

 within the larger inclosure. This style of pen and bottom was used 

 in an effort to avoid losses caused by enemy organisms living on the 

 lake bottom. Its value is evidenced this year by the fact that on 

 the bottom of one experimental float 10 feet square more than 23,700 

 young mussels, all at least half an inch long, and many longer, were 



