MUSSEL CORRALS 



Enclosures were constructed to facilitate recapture of marked 

 mussels. Aluminum was used to make the enclosures strong, 



resistant to oxidation, and light enough to handle. Each was 



2 



square and enclosed an area of 1.5 m . They could be pushed 



approximately 13 cm into the substrate to reduce the likelihood of 

 mussels burrowing under them and extended approximately 8 cm above 

 the substrate to keep mussels from climbing out. 



Corrals were placed in groups of four or five. After the 

 diver pushed each corral into the substrate, he wired it to at 

 least one ground anchor. Accurate locations for each group of 

 corrals were determined by triangulation. 



COLLECTION AND MARKING OF MUSSELS 



To collect mussels, the boat was anchored approximately 10 m 

 upstream of the collection site. A diver entered the water and 

 was directed to the upstream edge of the collection area by the 

 crew on the surface. He then searched the substrate while moving 

 to his left or right and maintaining tension on the umbilical 

 line. This method allowed the diver to efficiently sample a 180° 

 arc a given distance downstream from the boat. When the surface 

 crew determined the diver was approximately perpendicular to the 

 current from the boat, they let out approximately 1 m of umbilical 



12 



