92 U. S. BUREAU OF FISHERIES 



First spat was found on July 10 on shells beneath the wharf 

 at Doboy Island, about V/2 feet above mean low water. Setting 

 apparently continued throughout July and August, although the 

 number of umbo larvpe caught in plankton was very small (15 on 

 July 2 and 23 on August 4) . 



For a study of the distribution of setting, shells were taken at 

 various depths from different localities and examined at regular 

 intervals, and brush and wire bags filled with oyster shells were 

 planted on the flats and on the bottom in the vicinity of Doboy 

 Island and in Duplin River. 



Shells taken from below the low-tide mark on the north, south, 

 and west sides of Doboy Island and in Duplin River were found to 

 bear spat of varying sizes; the zone of the heaviest setting was, 

 however, above the low-water mark. On August 31 shells thrown 

 along the shore of Doboy Island were examined by Weatherby, who 

 reports that the heaviest setting (300 to 400 spat per square foot 

 of area covered with cultch) was between and 2 feet above 

 mean low-water mark. In the zone between 2 and 4 feet above low- 

 water mark there were from 200 to 300 spat per square foot. In 

 the zone between 4 and 6 feet above low water there were 50 spat 

 per square foot and no spat were found 6 feet above the low-water 

 mark. Mean low water was taken as the average low-water mark 

 for the period of the survey and corresponded to the 4-foot mark 

 on the tide gage set at the wharf of Doboy Island. 



Experiments witli wire-bag collectors were carried out at the dock 

 of Doboy Island. Thii-ty-six bags, 3 feet long, about 8 inches in 

 diameter, and eacli containing one-half bushel of shells, Avere used 

 to cover a vertical interval of approximately 5 feet. This was done 

 by first putting two bags on the bottom lying parallel and about 

 2 feet apart. On top of these two more bags Avere placed, also 

 parallel and the same distance apart, but at right angles to the first 

 two. Additional bags were added until the stack was of the height 

 mentioned aboA^e. The bottom bags were lying on shells and oysters 

 from 1 to 11/2 feet beloAv mean low water. The number of spat was 

 obtained by counting those attached to 10 shells picked at random 

 from each bag. Every bag used in the experiment was examined. 

 By September 1 there Averc, on the average, 15 spat per shell in the 

 zone of 1 to 3 feet above Ioav Avater; 10 spat per shell in the zone 

 from 1 foot below and 1 foot aliove low Avater; and 6 spat per shell 

 in tlie zone of betAveen 1 and 2 feet below low water. 



Oak and sassafras brush, approximately 1,000 bundles in all, Avere 

 distributed among three places. Four hundred bundles AA^ere placed 

 horizontally and extending from 1 foot beloAv mean Ioav water to 

 about 4 feet aboA^e mean Ioav water on the mud flat 100 to 150 feet 

 south of the dock at Doboy Island. These bundles were piled to a 

 thickness of about 3 feet. The entire lot was then anchored with 

 rocks and with stakes driven vertically tlirough <he l)undles. The 

 rocky shore on both sides of this brush and part of the mud flat 

 on which the lirusli was placed Averc covered Avith (toon oysters. 

 Approximately 300 bundles of bnisli Avere placed on the nnid flat 

 at the mouth of North River. These bundles Aveic stuck into i]\v. 

 bottom in a \ertical position and as close together as they could be 

 placed. Approximately 300 bundles of brush were put out in a layer 



