34 U. S. BUREAU OF FISHERIES 
portant species, such as the whitefish, yellow perch, and the several 
species of chubs, are following the trail of the Lake Erie cisco and are 
definitely on their way to commercial extinction. 
SHELLFISH INVESTIGATIONS 
Dr. Paut 8. GALTSOFF, in charge 
The shellfish investigations during the year 1936 consisted in the 
continuation and completion of several projects initiated during the 
preceding year for the improvement of methods of oyster culture and 
the protection of the oyster against various pests. This work included 
studies on the metabolism and fattening of the oyster; sex changes 
in oysters and clams; the biology and control of such parasites of the 
oyster as starfish, drills (Urosalpinx), and borers (Z’hais) ; and the 
effect of pulp-mill pollution on oysters. These investigations were 
carried out at the Bureau’s stations and laboratories at Woods Hole, 
Mass.; Milford, Conn.; Washington, D. C.; Beaufort, N. C.; and 
Apalachicola, Fla. The laboratory at Olympia, Wash., was closed and 
all the work on the Pacific coast was discontinued in May, when the 
State Department of Fisheries found it impossible to continue its 
financial support of this work. Dr. A. E. Hopkins, in charge of the 
investigations at Olympia, Wash., was transferred to Apalachicola, 
Fla. An additional P. W. A. grant permitted the continuation of the 
studies of the effect of pulp-miil wastes on oysters in the York River, 
Va., which were begun in 1935. At the request of the War Depart- 
ment a detailed program was prepared for experimental and field 
studies of the effect of dredging operations on oysters in the vicinity 
of the Intercoastal Waterways in South Carolina. At the recom- 
mendation of the Bureau, the War Department appointed G. Robert 
Lunz, Jr., who worked according to plans prepared by Dr. Galtsoff 
and under his supervision. 
PHYSIOLOGY AND CULTIVATION OF OYSTERS 
The production of oysters of high nutritive value is at present 
the principal problem of oyster culture in the Northern States. Good 
oysters are characterized by the storage of a large amount of glycogen 
in their tissues and by the presence of sufficient quantities of metals, 
especially iron and copper which are essential for a balanced diet. In 
order to determine the seasonal fluctuations in the chemical composi- 
tion of oysters kept under known natural conditions, a large amount 
of material collected in 1934 and 1935 was analyzed for iron, copper, 
manganese, and zinc by Dr. Galtsoff and Charles D. Weber. 
The results of the analyses show considerable fluctuations in the 
amount of these metals. Thus, iron varied from 103 to 914 mg per 
kilo; copper, from 669 to 3,000 mg; manganese from 5.10 to 7.92 mg; 
and zine from 4,130 to 13,700 mg per kilo of dry weight. There were 
noticeable seasonal changes in the metal contents, especially in the 
manganese which was consistently higher during the summer months, 
probably owing to the accumulation of this metal by the ovaries, 
which showed a much greater manganese content than other tissues. 
In the ripe specimens there was from 51 to 59.6 mg per kilo of 
manganese in the ovaries as compared with 4.4 and 4.6 mg in the testes; 
