XLII REPORT OF THE COMMISSIONER OF FISHERIES 



INVESTIGATION OF SHELLFISH AND TERRAPIN 



Shellfish investigations, aside from those on the oyster, include 

 studies of the Pacific coast clams, the scallops of North Carolina, 

 and the fresh-water mussels of the Mississippi River Basin. As a 

 result of the investigation of the life history and ecology of the 

 razor clam in Alaska, regulations have been framed that will tend 

 to overcome depletion from overfishing and restore the productive- 

 ness of the natural beds. The report on these investigations, pub- 

 lished in 1925, points out that the growth rate of the razor clam in 

 Alaska is approximately half that of clams of the Washington 

 coast, and on this account commercial extinction of the species here 

 is much more probable than on the southern beds. These studies 

 were continued during the past year and further information on the 

 growth and abundance of clams on the various beds in Oregon and 

 "Washington have been made, the results of which are being sum- 

 marized for publication. 



The scallops of North Carolina, although extremely localized, 

 occupy an important place in the fisheries of that State. The exist- 

 ence of the species was threatened in 1924 by an unusual flood of 

 fresh water late in that year, which resulted in the virtual failure 

 of the fishery the following season. At the request of the State 

 authorities the bureau began an investigation of the biology of this 

 mollusk, which resulted in specific recommendations being made for 

 the regulation of the fishery to permit the maximum take of scallops 

 without endangering the supply. It is reported that this season the 

 species returned to approximately its former abundance. 



Document No. 865 — The Fresh-Water Mussel and Mussel Indus- 

 tries of the United States — -which has proved so popular is being re- 

 vised. It appears that the mussel fishery of the Mississippi River 

 Basin is one of the largest of our fresh-water fisheries. The yield 

 during 1922 was approximately 52,000,000 pounds of shells, with a 

 value of over $1,000,000, while the manufactured products, which 

 consist of pearl buttons and novelties, were valued at nearly $8,000,- 

 000. Investigations of the mussel resources and of the biology of 

 the various commercially important species have played an important 

 part in the development of this industry, and the brilliant researches 

 of the early workers have been considered one of the notable achieve- 

 ments of the bureau. With the depletion of the more accessible beds, 

 attention was turned to the possibilities of artificial propagation, and 

 successful methods were developed at the Fairport laboratory. Dur- 

 ing the past year further experiments have been conducted in the 

 rearing of mussels in hatchery troughs, but these have been subor- 

 dinated to the researches in the elimination of the parasitic period 

 in the life of the glochidia. Careful studies on the acid alkali 

 balance in the blood of the fish have been an important link in the 

 effort to rear the larval mussels without host fishes. While the 

 methods have not been completed, prospects are extremely promising 

 and if successful will revolutionize methods of mussel propagation. 



Close cooperation with the various States has been maintained in 

 perfecting protective legislation. During the spring months an ex- 

 tensive survey of the mussel-producing areas in the White and Black 

 Rivers in Arkansas was conducted at the request of the State fish 



