514 U. S. BUEEAU OF FISHERIES 



coated tubes and partitions that were planted there on July 23. 

 The partitions were planted just above low- water mark on a natural 

 oyster bed and gathered from approximately 100 to 500 seed oysters 

 per collector. The cement-coated tubes are a new type of spat col- 

 lector that was developed here during the past summer for gathering 

 set on soft mud bottoms where shells and partitions can not be used! 

 Tubes 2 feet in length and 11/2 inches in diameter proved to be the 

 most satisfactory size and collected from 200 to 300 spat each. They 

 were planted vertically in the soft mud bottom surrounding the 

 oyster reefs and were most heavily covered with spat when set out 

 at low-water level. 



The heaviest setting of oysters in this region occurs in a narrow 

 1-foot zone just above low- water mark, and has been found to be 

 due to the higher copper content of the water at this stage of tide. 

 Chemical analysis of the water showed the presence of copper in 

 concentrations of 0.3 to 0.4 milligram per liter and a salinity of 15 to 

 18 parts per thousand during the tidal period when the setting of 

 oysters was most pronounced. At other stages of tide when setting 

 did not occur the salinity of the water was high (30 to 33 parts per 

 thousand) and the copper content less than 0.05 milligram per liter. 

 Therefore, in planting seed collectors of any kind in this region it is 

 obvious that particular care must be taken to select the zone in which 

 heaviest setting occurs. 



A study of oyster distribution along the shores of Core Creek 

 and canal revealed a new kind of brush that can be utilized for 

 gathering seed oysters on the adjacent mud bottoms. The branches 

 and trunk of the myrtle were found to be excellent for this purpose 

 and were densely covered with well-shaped, rapid-growing oysters 

 of different ages. Experiments with this brush will be made here 

 during the coming year. 



In Oyster Creek partition collectors were planted on June 17, by 

 Inspector Robert L. Willis, of the State fisheries department. They 

 were elevated a few inches above the bottom on stakes and gathered 

 a light set of approximately 200 seed per partition. Setting in this 

 locality is rarely heavy, which makes it a particularly valuable area 

 for the growing and maturing of large, well-shaped oysters for 

 market. 



The partitions and tubes planted on Cross Rock in Newport River 

 likewise collected during the latter part of July a light set similar 

 to that observed on the shells covering this oyster reef. This bed 

 produces a good grade of oyster, but is not as favorable a location 

 for seed collection, as the near-by coon oyster areas. 



At the fisheries laboratory the setting of oysters has been more 

 or less continuous from the first week in June up until the first of 

 October. Two plantings of partitions were made and collected a 

 crop of seed oysters ranging from 200 to 1,500 per collector. The 

 heaviest setting was found on partitions planted from low-water 

 mark to 2 feet above and is governed by the lower salinity and 

 higher copper content of the water during this stage of tide. Chemi- 

 cal analysis showed that at such times copper was present in con- 

 centrations of 0.15 to 0.20 milligram per liter and served as a 

 pronounced stimulus for the setting of the oyster larvae. 



