RAFT CULTURE OF OYSTERS IN MASSACHUSETTS 



485 



of wlielks, Iluxt/ron cdricd and H. r/i»tib'ri/ftifii)ti. 

 All four occur on the oy.ster fjrounds throiifihouf 

 the year and inflict a considerable amount of 

 daniape. Xoficeahly absent in the river is the 

 starfish, Ax/crlas forhesi. Only a few si)eciniens 

 were found in the lower stretches of the rivei- 

 dui-iufr the three years of invest ijrat ion. 



It is of interest to mention the fluctuation in 

 the abundance of the preen crab, Carcinides 

 tniiciiiis. In the spring of 11)57, the ci-abs were 

 found in such great inimbers that they were 

 caught by commei'cial fishermen for bait. By 

 1!).">8 the population of crabs had so declined that 

 commercial fisiiing became unprofitable and was 

 terminated after the fii-st day. In l!);")!), oidy an 

 occasional green crab was observed in the river. 



Two species of algae were conspicuous. Gra- 



eihtna confervoidex was found on the oyster shells 

 on the bottom, and Kntcromorphd sp. was the 

 principal fouling plant on the oy.sters attached 

 to the I'aft. Other major fouling oi-ganisms in- 

 cluded the compound ascidian, liotn/lhis xrlilos- 

 scri, the simple ascidian, Molgulu mnnhatteiv<lii, 

 and the barnacle, Bahnius hdhinoidcx. The most 

 abundant br\-ozoan was Schizoporella unicorniH. 

 Second in abundance were the peculiar nodular 

 colonies of Pdnismift'nui frispitiosd found in soft 

 mud in tiie channel and oyster bottom. 



Throughout the tidal flats wild oystei*s grow 

 attached to the stems of marsh grass, and often 

 are found on exposed rocks; some set on ribbed 

 mussels, Modiohix d(^?)ii.s.sa.<<; also many oysters are 

 fountl on muddy bottom. 



Figure 5. 



MATERIALS AND METHODS 

 CONSTRUCTION OF RAFT 



The raft (fig. 5) used in the work was con- 

 structed of "io-foot cedar logs joined together by 

 wooden crossbai-s wiiich held it together and kept 



6193600—62 2 



Raft used in tlie study. 



the logs sufficient ly apart to ])ermit free circula- 

 tion of water. Logs were selected as floats be- 

 cause they were readily available and inexpensive. 

 Each log was floated in the water and notched 

 on the top with an axe. A row of 4() staples (3 



