140 



BULLETIN OF THE BUREAU OF FISHERIES. 



The epidemic itself was spread over large areas, which, in some cases, were many- 

 miles distant from one another. Lynnhaven Bay, with the two large creeks that com- 

 bine to form it, was the seat of the most serious outbreak at the time of this study. The 

 same location had been reported to have suffered in a like manner in 1912. From testi- 

 mony taken from various oystermen of Hampton and Phoebus, greengill had appeared 

 at different dates, but all who were interviewed agreed that the last general epidemic 

 occurred in 191 2. At that time the greengill was distributed the entire length of Hamp- 

 ton Bar and Flats from Newport News to Phoebus and Mill Creek, and both the north- 

 west and southwest branches of Back River also suffered. The present outbreak again 

 affected Mill Creek and both branches of Back River. Farther north and more on the open 

 coast greengill was found in considerable quantity on Drum Island Flats, but Hampton 

 Bar and Flats at the time of this investigation were free of the epidemic. It was learned, 

 however, that oyster beds from Cobbs Island down to Goodwins Island had suffered in 

 various years and at various locations from greengill. 



An effort was made in taking these data to get general information from those inter- 

 viewed in regard to weather conditions, temperature, depth of water, and general loca- 

 tions of outbreaks with their relationship to the greening, but with little success. The 

 theory offered by one individual would be contradicted by the next person interviewed, 

 so that no facts or ideas common to all observers were obtained from those most closely 

 connected with the oyster industry. 



Not being able to gain specific knowledge of the general relationships of greengill with 

 weather, temperature, sahnity, etc., from interviews, and at the same time trying to 

 find some connection between the true Marennes green-gilled oyster and the greengill at 

 hand, it was decided to take water samples from locations where the epidemic was preva- 

 lent and observe the temperature, salinity, and the vegetable fife in the water. Sam- 

 ples thus studied were taken on January 4, 5, and 6, 1916. The weather of these days 

 was rainy or cloudy, with the temperature varying from the freezing point to about 

 15° C. The water samples were taken from places where the water was not more than 

 6 inches deep and which, therefore, was open to a considerable change of temperature 

 during the day and night. No doubt the temperature of the water during the night 

 lowered to within 2 or 3° C. of freezing, while during the day it increased to perhaps 12 

 or 13° C. For about a week before these samples were collected, there had been a heavy 

 storm blowing from the southeast, and the bottoms of Lynnhaven Bay and the coves, 

 which up to the time of the storm were reported to be covered with a green carpet of 

 vegetable life, showed nothing but the typical gray clayey mud with the water very 

 much roiled. Samples were taken, however, and in five of the six samples obtained in 

 various parts of Lynnhaven Bay diatoms were found that exactly answered the descrip- 

 tion of the Navicula ostrearia as set forth by Lankester. The temperature of the water 

 ranged from 10 and 11° C. in shallow places to 5 and 6° C. in the deeper water. The 

 specific gravity of the samples varied from 1.018 to i.oig. The results of this collection 

 were as follows: 



