24 REPORTS OF THE DEPARTMENT OF COMMERCE. 



The first free-swimming larvae were found July 16, 1918; the period 

 of greatest abundance was from August 9 to 26, and none was observed 

 after August 30. As the larvae were found to be free-swimming for a 

 period of about 20 days, it is evident that the bulk of the spawning 

 occurred about August 1. Set was found during the last week in 

 August on most of the beds in water not over 4 or 5 fathoms deep, 

 but practically all of this set died except that which attached in the 

 very early part of the season. 



A tentative conclusion drawn from this investigation is that it is 

 of prime importance to secure an early setting, such as results from 

 the spawning of oysters in the shallow and warmer waters of harbors 

 and mouths of rivers. Since it is just such beds that are generally 

 most affected by pollution in the form of sewage and trade wastes, 

 which may be fatal to the life of the free-swimming larvae, it is evi- 

 dent that the matter of the possible effect of polution on the occur- 

 rence of oyster set demands serious consideration. With the coopera- 

 tion of the water laboratory of the Bureau of Chemistry studies 

 have, therefore, been undertaken with regard to the nature and the 

 effect of the pollutants introduced in the shallow waters. 



Further investigations relating to the natural propagation of 

 oysters have been conducted in Great South Bay, Long Island, and 

 Narragans'ett Bay, R. I. 



A very serious condition has manifested itself in oyster beds of a 

 large section of the York River in Virginia, where for several years 

 the oysters have been rendered virtually valueless for market. Exam- 

 inations of the oysters, begun in November, 1918, revealed the fact 

 that they were affected with a green coloration associated with 

 watery and lean meats. This condition is quite distinct from that 

 known as "green gill" and does not appear to be in all respects of 

 the character of greening which in other localities has been attrib- 

 uted to the storage of copper. No cause has yet been found for the 

 condition observed, which is, perhaps, a very indirect result of 

 disturbance of environmental conditions. The investigation is still 

 in progress, and the Bureau expects to continue it by regular periodic 

 observations for such period of time as may be necessary to arrive at 

 definite conclusions. Since chemical problems are involved, the 

 Bureau has enlisted the cooperation of the water laboratory of the 

 Bureau of Chemistry in the further prosecution of the study. 



A poor condition of oysters presented itself, likewise, in Apalachi- 

 cola Bay during the early winter. After careful investigations were 

 conducted by the Bureau, the condition was attributed to a de- 

 ficiency of rain in preceding months. At a later time, and after a 

 period of increased rainfall, it was learned that the oysters had 

 fattened and resumed a normal condition. 



Late in the fiscal year the Bureau was enabled to undertake at 

 slight expense, by cooperation with the New Jersey State Agricul- 

 tural Experimental Station, a study of the feeding, growth, and 

 propagation of oysters in the vicinity of Barnegat Bay. 



The service of the Bureau to the oyster industry has been rendered 

 more effective by the cooperation extended by several State depart- 

 ments, notably in Connecticut, Maryland, New Jersey, New York, 

 and Rhode Island. 



Sea rmissels. — The sea mussel is one of the largely unutilized 

 resources of the North Atlantic coast. Wliile it has not been difficult 



