19 



are the oysters thus dependent on the currents for their food but 

 also for air, and for the removal of waste products. 



The existence of currents fitted to perform all these functions is 

 not within human control, but the presence of spawning oysters 

 and suitable cultch, are controllable and such control is an imper- 

 ative necessity wherever oyster beds are undergoing depletion at 

 the hands of dredgers and tong men. 



Only in localities where the oyster beds have been almost ex- 

 terminated, or where such beds have never existed, is it necessary 

 to introduce adult spawners. In every locality, however, where 

 the number of oysters fished annually exceeds the number that 

 find room for attachment, there is an urgent need for cultch.' The 

 most important attribute which such cultch should have is clean- 

 ness. The importance of this is shown by the fact that 70 per cent, 

 of the new growth in Calcasieu Pass is attached to the inner sur- 

 faces of the old shells. A still clearer demonstration of the value 

 of clean shells as spat collectors is given in the results of the 

 following experiment : 



EXPERIMENT I. 



TO DETERMINE WHETHER A SET CAN BE SECURED IN CALCASIEU PASS 



On July 28th, two plantings each of 15 bushels of clean shells 

 were made in the lower end of Calcasieu Pass south of the Light- 

 house Reef (see map). Planting A was made in a ridge perpen- 

 dicular to the current ; planting B. in a ridge parallel with the cur- 

 rent. On Septernber ist, 100 shells were taken at random from 

 each of these ridges and the living as well as the dead young oys- 

 ters on both sides of the shells were counted. These counts are 

 ofiven in Tables III and IV. 



