616 U. S. BUREAU OF FISHERIES 



pathological condition of the muscle tissue in oysters from several 

 different localities, but that death of the oysters occurred chiefly on 

 the areas where bottom conditions were least favorable. Since the 

 muscle of the oyster requires a f^reater oxygen supply than any other 

 tissue, it is apparent that the oysters on poor bottom would be the 

 first to weaken and die because of an insufficient amount of oxygen 

 for normal functioning of the muscle and closure of the shell. 



EFFECT OF AVASTE PULP-MILL LIQUOR ON THE OYSTERS 



A study was made by Dr. A. E, Hopkins of the effect of waste 

 liquor from a sulphite pulp mill on the Olympia oyster. Experi- 

 ments carried out at the temporary laboratory established by the 

 bureau near Olympia, Wash., demonstrated that the waste liquor 

 was highly toxic to oysters in concentrations as low as 1 part to 2,000 

 parts water. All oysters treated with these solutions for a sufficient 

 length of time either died within about 30 days, or did not remain 

 open to feed as much of the time as did control specimens in pre- 

 sumably uncontaminated sea water. The death time of oysters in 

 solutions of sulphite liquor varied in an inverse manner with the 

 concentration. Specimens which reacted to the liquor by remaining 

 closed a large portion of the time were able to live longer in the solu- 

 tions than oysters which remained open during most of the period of 

 treatment. In no case was new shell growth observed in oysters 

 in liquor solutions, although control specimens showed considerable 

 new growth. These effects were not due to acidity of the liquor 

 for they were observed as well when neutralized liquor was employed. 



Kymograph records of the shell movements of Olympia oysters at 

 different temperatures were found to show a striking effect of 

 changes in temperature on the relative length of time the shells re- 

 main open. Since feeding can occur only when the shells are open, 

 the significance of these observations is obvious. In tlie laboratory 

 the water showed an average diurnal fluctuation of about 2° C. 

 l)etween the minimum (about 6 a. m.) and the maximum (3 to 4 

 p. m.). At low temperatures, 4° to 7° C, this fluctuation produced 

 a great difference in shell movements, while at higher tempera- 

 tures, 14° to 17° C, the same temperature change caused almost no 

 change. While at low temperatures a small drop in temperature 

 causes the oyster to close, at high temperatures the same drop is 

 almost without effect. A report on this work will be published in 

 the near future. 



Experiments have been made to determine the relative sensory 

 effect on the oyster of certain salts which are in solution in sea water. 

 The oyster is highly sensitive to these salts and can detect them in 

 very dilute concentrations, as shown by the retraction of the tentacles 

 and contraction of the adductor muscle, which closes the shells. The 

 order of stimulating efficiency of the ions is as follows : Cations, K, 

 NH4, Na, Li ; anions, I, Br, NO3, CI. A report on these observations 

 is in press. 



Field work on the investigation of oyster mortality near Shelton, 

 Wash., conducted by H. C. McMillin was completed early in Janu- 

 ary. It was found that the death rate of oysters in Oakland Bay 

 was very high. On the lower ground only occasional oysters were 



