PROGRESS IN BIOLOGICAL INQUIRIES, 19 31 521 



the low-tide level. The salinity of the bay is affected by local rain- 

 fall and is very low in winter and spring. 



Observations on imported Japanese seed oysters planted in Elk- 

 horn Slough, Calif., show that this species grows very rapidly. 

 Seed oysters were received from Japan and planted on March G; 

 they were ready for the market in eight months. 



ALASKA RAZOR-CLAM INVESTIGATION 



Observations on the razor-clam beds in the Prince William Sound, 

 Copper River, and Bering River areas were made during the season 

 of 1931, under the direction of Seton H. Thompson, by the temporary 

 emplo3^ees detailed to enforce the regulations in regard to the clam 

 fishery. 



Sampling to determine the age composition of the commercial 

 catch was continued. The clams taken were from 5 to 12 years old. 

 It has been pointed out in a previous report that 36.5 per cent of the 

 clams mature in their fourth year, 80 per cent in their fifth year, 

 and all are mature at 6 years of age. Approximately 50 per cent of 

 all clams taken in the commercial fishery in 1931 were older than 6 

 years, and 80 per cent were mature. More than 55 per cent had 

 spawned more than once. 



Other observations included a determination of the time and dura- 

 tion of spawning, and the abundance of clams 1, 2, and 3 years old 

 on the bars. The large number of young clams observed on the 

 bars reflects the present healthy condition of the beds. 



The razor-clam fishery in this locality in 1931 was more intensive 

 than in any year since 1927, and the pack was considerably larger 

 than any since 1925. The larger pack was partly due to an exten- 

 sion of 15 days to the fishing season, and partly due to the exploita- 

 tion of new bars as well as to the increase in the number of clam 

 diggers. 



It now appears that with the beds in their present satisfactory 

 condition, the regulations which limit the size of razor clams that 

 can be taken for commercial purposes and provide a closed season 

 of six weeks will afford adequate protection for this fishery. 



MUSSEL INVESTIGATIONS AND POLLUTION STUDIES 



Investigations of the fresh-water mussel fauna of the interior 

 waters have been continued by Dr. M. M. Ellis, professor of phys- 

 iology at the University of Missouri, assisted by several investi- 

 gators. These, together with several professors of the university who 

 collaborate and advise and graduate students who work independ- 

 ently on related problems, constitute the " Columbia (Mo.) unit " of 

 the division in interior waters. Commodious and well equipped 

 laboratory quarters are furnished to the bureau's staff free of charge 

 by the University of Missouri in a new wing of the medical building, 

 acknowledgment of which is hereby gratefully made. 



During the spring of 1931 field parties visited the Lake Keokuk 

 district several times to continue observations made during the 1930 

 survey. Other parties studied streams in northeastern Arkansas, 

 eastern Kansas, and north central Texas. After reoutfitting the 

 U. S. Quarterboat 3Jf8 as a floating laboratory at Keokuk, Iowa, a 



