64 REPORT OF THE PISH AND GAME COMMISSION. 



these oysters are said by oyster men to be the equal of the better known 

 Olympia oyster, no very intelligent effort has been made to increase 

 the yield. Occasional trials have been made to obtain a better set by 

 placing out shells or other objects as collectors to which the young may 

 attach themselves. In these trials the collectors have mostly been put 

 out at the wrong time or in the wrong place. In response to requests 

 for aid, Dr. Heath was employed to conduct the present investiga- 

 tion. The work was mainly done on Tomales Bay for the reason that 

 assistance and co-operation could be had from the local oyster com- 

 panies. The knowledge gained, however, can be applied to any locality 

 where the conditions for oyster growing are favorable. Although the 

 work was in the nature of a preliminary investigation, and only a com- 

 paratively small amount of time was consumed, the work was done 

 with the immediate needs of the industry in view and resulted in 

 clearing up several points vital to the success of the industry. The 

 knowledge thus gained sliould result in the growing of California oys- 

 ters on a large commercial scale, not only on Tomales Bay but in several 

 of the other bays of the state. 



A preliminary report will soon be published giving the progress of 

 this work so that we will give here only very briefly some of the results. 

 It was found that in the immediate vicinity of the natural oyster beds 

 remarkable "sets" can be obtained on oyster shell collectors if these 

 collectors are put out at the right time. Collectors placed in the water 

 too soon accumulate a coat of slime and sediment which permits only a 

 very few of the embryo oysters to become attached. It is necessary, 

 therefore, to put out experimental collectors at intervals or to observe 

 the relative abundance of free swimming oyster larvae, in order to de- 

 termine the proper time for putting out the collectors. This work must 

 be done by an experienced person for it is necessary by means of the 

 microscope to distinguish the oyster larvae from the larvae of clams and 

 other mollusks. If this information is supplied each spatting season, it 

 will be possible for the industry to expand greatly. It is now quite 

 certain that the young oysters can be collected on oyster shells or other 

 collectors and later transplanted to prepared beds in places where no 

 oysters grow naturally, just as has been done in Puget Sound. In this 

 way large areas which are now unproductive can l)e made to maintain 

 beds of oysters. 



Work was carried on to determine the distribution of the free swim- 

 ming larvae in relation to water salinity, temperature and currents. 

 The rate of growth and character of food supply were also subjects of 

 study. Experiments were made in transplanting both young and 

 adults to different parts of the bay to determine how much of a change 

 in salinity or temperature they can withstand. 



