174 CALIFORNIA PISH AND GAME, 



A CASE OF DESTRUCTION OF PISMO CLAMS BY OIL.* 



By PROFESSOR FRANK WALTER WEYMOUTH, of Stanford University, 



California. 



That crude oil is harmful to marine and fresh Avater animals has 

 been so generally recognized that most states, including California, 

 have passed laws designed to protect their waters from oil by pro- 

 viding penalties for those who allow it to escape. Definite instances 

 proving its destructive effect though present, for instance in the case 

 of water birds, are not numerous, and for this and other reasons 

 convictions are not always easy to obtain. It is claimed by the clam 

 diggers at Pismo and Oceano that oil is chiefly responsible for the 

 decrease in the supply of Pismo clams. It is hoped that at another 



V-"??^?. 





rig. 55. Oil cakss on the beach near Pismo. The size may bs judged by comparison with the 

 cap. Photograph by W. E. Weymouth. 



time it Avill be possible to present an analysis of this claim and of 

 other factors influencing the abundance of this important food 

 mollusk, the data for which are not now available, but an instance of 

 the effect of oil which recently came under the writer's notice may 

 here be put on record. 



Sometimes oil reaches the beach from tanks on the shore near Avila, 

 but the most important source is from the water ballast discharged by 

 vessels coming to load oil at Port San Luis. This can not reach the 

 beach at Morro around the projecting "Pecho" coast against the 

 prevailing winds, but is blown on the beaches at Pismo and Oceano 

 at times in considerable quantities as bathers at these resorts are 



♦California State Fisheries Laboratory, Contribution No. 11. 



