define a "zone" or -Dearl oyster fjroimd suitable for eroloitation v;hen a sample of 1,000 

 kllograras (2,20U lbs.) of oysters yield more than one gram (5 coxats) of -oearls for each 50 

 kilograms of oysters. Thiis, a miniin\in pearl production is that of 90 carats per short ton 

 of live oysters. The lav/ is based exclusively on the content of pearls in the oysters, but 

 not on the abundance of oysters on the bottom. From the point of viev.' of management of the 

 pearl res-urce, the density of the oyster population is fully as important as the number of 

 pearls per oyster. 



Fo detailed biological data are available at present concerning the abundance 

 of oysters on different grounds and their rate of groirth. Since these data would be of great 

 value for the development of the oyster resources, I hope that eventually the necessary ob- 

 servations will be made by the government. The data on the fluctuations of the yield of 

 pearls per sack of oysters In different years are, however, available (table 6). 



Teible 6 



Yield of Pearls Per Sack of Oysters 



Each sack contains from 35 'to H5 kilograms of oysters. Since there are from 

 25 to 30 oysters to each kilogram, or from 875 *o 1»350 oysters per sack, and the average 

 yield (for three years, 13^5-^'''7). is 1^.5 carats per sack, we may conclude that one should 

 expect to open from 200 to 3OO oysters to find 1 carat of pearls. 



In recent years, the greatest portion of the oyster catch has been obtained 

 "by dredges (table 7). This, hov/ever, was not true in the previous years. Thus, during the 

 season of I939-I9U0 the total yield of pearls was almost eo_uslly divided between the dredges 

 and scaphanders. Lopez (19^) states that during this year the scaphander divers obtained 

 ^96,^-00 carats, while the dredgers contributed U.56,800 carats of pearls. Unfortunately, 

 the number of sacks of oysters gathered by each group is not given in the paper from which 

 these figures are a_uoted. It is, ho\/ever, interesting that the present yield of pearls in 

 the oysters obtained by divers is almost twice the yield in oysters gathered by dredgers. 

 This probably was not the case in previous years. 



The present relatively higher yield obtained by divers may be purely accidental, 

 or it may be attributed to their ability to select better stock. The problem req^uires further 

 study. 



BIOLOGY Aim CONSERVATION OP PEARL OYSTERS 



Knowledge of the biolosr of the pearl oyster is essential for the effective 

 conservation and exploitation of the STjecies. Unfortunately, biological data concerning 

 the time of spawning, setting, and growth of Venezuelan pearl oysters are scarce. Jos^ M. 

 Mosoueira Kanso, who for several years observed the oyster population around Margarita 

 Island, states (19U3, p. 36) that spavming of oysters in these waters begins at the end of 

 April and terminates during the last days of August. According to Mosoueira (p. Ul), about 

 10 nercent of the xiearl oysters around Margarita Island spawn by the middle of May. The 

 percentage of spavming molliisks increases to 20 by the middle of Jxme, and to 55 "by the 

 middle of July. A.bout 5 percent of the oysters may be found spawning in September. During 



19 



