The Rise And Decline Of The Olympia Oyster 



the beds. His contention was that a gas automatic explo- 

 sion, blasting every fifteen minutes, attached to piling 

 over the oyster beds, would keep the ducks away. A De- 

 partment regulation to that effect was issued. It was 

 tried out. For the first few days the ducks flew away. 

 When they found it was harmless they became more bold, 

 and in a month they paid no attention to it. So the patrol- 

 man began shooting again. He was arrested, but never 

 tried. 



Since then, ducks have diminished in number, but are 

 still considered as predators. 



CRAWFISH 



Crawfish do not eat oysters. Their damage to oysters 

 is indirect. They live in the ground, and are found in the 

 tide flats where the bottom is sandy. They dig in and by 

 5^ome mechanism, apparently the motion of the fins on 

 the side of the body and the tail, they push the sand 

 back as they advance. This accumulates in a little pile 

 where the crawfish entered the ground. The tunnel, about 

 one inch in diameter, extends sometimes ten or twelve 

 feet. The crawfish lines the tunnel, as it digs, with some 

 hard substance. 



Crawfish are harmful to oysters in two ways. First, 

 after a dike has been constructed, a crawfish may go 

 down and under the dike. The ground outside the dike 

 being lower, the crawfish, probably to its own surprise, 

 comes to ground surface on the lower side of the dike. 

 The upper dike being filled with water, it begins to flow 

 through the crawfish tunnel. At first it looks like a bub- 

 bling spring, but soon the force of the water breaks 



(75) 



