SURVEY OF LAKE TAMBLEGAM. 45 



place during the fishing season no changes need be made, except to 

 provide small reserves upon each bed. 



It is very important that reserves should be laid down, upon 

 which diving should not be allowed even in the season. These 

 reserves need not be large, but they would be of great value as 

 spawning centres after the main beds have been depleted. This is 

 the only way of protecting the beds from being ruthlessly over-fished. 



Further knowledge is required regarding the age and rate of growth 

 of Placuna. Hornell agreed with Kelaart that the largest oysters, 

 measuring 7 inches by 6 inches, are about three years old, and do not 

 live to a greater age. On the other hand, Willey was of the opinion, 

 after three years' work, that the mature pearl-bearing oyster is from 

 three to six years old. Willey recognized seven stages, as follows :— 

 Sfat, the first sedentary stage, with a major diameter varying from 

 I inch to 2 inches ; placunet, from 2 to 3 inches ; yearling, from 

 3 to 4^ inches ; adolescent, up to 5| inches ; first adult, up to 6| 

 inches, about three years old ; second and third adult, up to 7 or 8 

 inches. 



Hornell recommended a size limit of 5| inches in the shortest 

 diameter. Willey has pointed out the difficulty of projiosing a size 

 limit, since most of the superficial growth takes place in the first 

 two years, after which the growth is mainly concerned with the 

 thickening of the shell. It is much more satisfactory to know the 

 age of a bed of oysters, which can be ascertained by making frequent 

 systematic inspections in the manner I have indicated. Willey has 

 shown that the mature oysters in the lake are probably all of the 

 same age. If this be the case, it is much safer to determine the age 

 of the bed of oysters, and to prohibit its being fished until the proper 

 time. In this way the need of a size limit is obviated. Willey 

 suggested that the number of oysters obtained at a fishery should 

 be limited, in order to prevent over-fishing. There appear to be 

 difficulties in the way of such a proposal, and a much more 

 satisfactory plan appears to be the estabhshment of reserves. 



The diving at Tamblegam is done by Moormen. After witnessing 

 the diving operations on the pearl banks or in Trincomalee harbour, 

 one is not impressed by the attainments of the Tamblegam diver. 

 They do not care to dive in more than 3 fathoms, and they can 

 only stay down for about eight seconds, even when diving in a depth 

 of 1 fathom. They do not, of course, use any rope or stone. They 

 simply turn a somersault in the water, and the last one sees of them 

 as they disappear is their feet. Owing to the abundance of soft mud 

 the water is never clear enough to see the bottom, even when the 

 depth is less than a fathom. In rough weather the water contains a 

 large amount of mud in suspension, which renders the work of the 

 divers very difficult, and they are reduced to feeling for the oysters. 

 Whenever diving operations are in progress, the boat is anchored by 

 a long pole being plunged into the mud from the bow of the boat. 



