CEYLON PEARL OYSTER REPORT. 



are transferred by the Inspector to a final diagram or plan furnished with twelve 

 concentric circles. When this has been done, the distribution of old and of young 

 oysters is graphically shown for a circular area having a diameter of 1^ miles (fig. 1 

 represents two such inspection areas on the Muttuvaratu Paar in 1902). 



Fig. 1. Inspection charts of (A) northern and (B) southern parts of Muttuvaratu Paar in November, 

 1902. There are four concentric circles made by the divers' boats between the centre and the 

 J-mile buoy, four between that and the J-mile buoy, and four from that to the f-mile. Each 

 complete area is therefore 1| mile in diameter. The numbers enclosed in rings indicate depths 

 in fathoms. The numbers on the concentric circles give the quantities of oysters brought up at 

 a dive on that spot. The cones indicate dives on a rocky bottom with no oysters. The dotted 

 line therefore surrounds the oyster-bearing area. 



After calculating in square yards the area occupied by oysters, the approximate 

 number of oysters thereon may be estimated by taking the average number of 

 oysters per dive (ascertained by examining the divers' results) in conjunction with 

 the average amount of ground which a diver is credited with being able to clear 

 at one descent. Usually this area is considered, on normal ground, to be from 

 2^ square yards to 3 square yards. By assuming the area per dive to be 3 square 

 yards, the danger of an overestimate is avoided. Inspection estimates are usually 

 less than the total number of oysters obtained at the ensuing fishery. " Thus, at 

 the 1904 fishery, I estimated the number of mature oysters to be 35,000,000, whereas 

 the number actually fished from the area in question was roughly 37,000,000 

 (41,000,000 minus the amount of immature oysters fished on April 2nd)." 



The North and South Modragam Paars were examined on March 5th, and in 

 addition a series of diving and dredging traverses was made further north, in the 

 region of the Vankali Paar, in fruitless search for the oysters found there during our 



