46 Report of the Board of Shell Fish Commissioners 



APPLICATION TO GROUND EXAMINED. 



j 



Knowing the area of each grab and the number of grabs 

 made by a tongman at a given station, the number of square 

 yards actually covered may be easily calculated and, knowing 

 the number of oysters taken from this area, it is a simple 

 matter to calculate the number of oysters removed per square 

 yard. 



EXAMPLE. 



Let us suppose that twenty-four grabs are made by a tong- 

 man on a bottom covered by twelve feet of water and that 

 forty-six marketable oysters are caught. The area of a grab 

 at this depth is 2.93 square feet. 15 During the entire examina- 

 tion the area covered by twenty-four "grabs" is s'eventy square 

 feet of 7.7 square yards. Forty-six oysters having been re- 

 moved from this area, it follows that six marketable oysters 

 per square yard were taken. 



PATENT TONGS AND DREDGE. 



The factor which made it difficult to calculate the area 

 covered at a station with ordinary tongs (that of the variability 

 in the area of the grab with the depth of water) is entirely 

 absent from calculations of the areas examined with patent 

 tongs or dredge. 



With patent tongs the area of the grab remains constant, 

 one square yard, in all depths of water. The heads of patent 

 tongs are three feet in length and are separated and set to a dis- 

 tance of three feet before the tongs are lowered upon the bot- 

 tom. The number of oysters taken at each grab is therefore the 

 number which the ground will yield per square yard. 



With a dredge also the width of the toothed bar remains con- 

 stant and the area covered during an examination is found by 

 multiplying this width (2 1-3 feet in the dredge used by the Com- 

 mission) by the distance the dredge is towed on the bottom. 

 In making an examination the dredge is placed upon the bot- 



table, page 66. 



