The Rise And Decline Of The Olympia Oyster 



tion to 70 per cent in the lowest, while two controls 

 showed death of oysters amounting to 52 and 53 per cent 

 respectively. Statistical analysis of these results indic- 

 ated an undeniable correlation between the mortality of 

 the oysters and concentration of S. W. L. even at these 

 low concentrations; concentrations at least as low as 13.0 

 ppm. are inimical to continue Olympia oyster culture. 



4. Tidal current studies showed that fresh mill wastes 

 from Oakland Bay could reach any of the oystering areas 

 in lower Puget Sound within a period of a few days. 



5. It is concluded that pulp mill wastes originating 

 at Shelton, Washington, were the most probable cause 

 of the alarming decline in oyster production noted above 

 for the following reasons: 



A. All other possible factors were investigated and 

 were found not to have constituted sufficient cause for 

 the depletion of the fishery. 



B. The time of pulp mill operation is correlated with 

 the period of decline: the shut-down of the pulp mill was 

 followed by definite improvement in oyster sets and fat- 

 ness of mature oysters. 



C. Concentration of S. W. L. as low as 13.0 ppm. were 

 experimentally demonstrated to have indisputable de- 

 leterious and lethal effects on Olympia oysters. 



D. Tidal currents showed that pulp mill pollution 

 from Oakland Bay could reach Oyster Bay on one tide 

 and other oystering areas within a few days. It is obvious 

 that Oakland Bay itself would b)ecome polluted. 



6. A modification of the Pearl-Benson test is present- 

 ed, consisting essentially in the application of photo- 

 electric calorimetry to the reading of the treated samples 



(125) 



