RAFT CULTURE OF OYSTERS IN MASSACHUSETTS 



493 



The development of raft culture in Cape Cod 

 watei-s would not eliminate the need for suitable 

 planting grounds. As mentioned earlier the shells 

 of the raft oysters are thin and fi-agile because their 

 growth is rapid. It is, therefore, necessary to 

 plant them on the bottom to thicken their shells. 

 Since most oysters grown in Massaciiusetts are 

 purchased to be sen-ed on the lialf-shell, restau- 

 rants and fish markets require an oyster with a 

 reasonably thick shell. From our obsevations, it 

 appeai-s that such an oyster can be obtained by 

 planting the raft -grown oysters on the bottom for 

 one year. 



It .should not be forgotten tliat the oystermen of 

 Cape Cod are almost entirely dependent on out- 

 of-State bedding stock. With the present decline 

 of oysters more and more Bay State growers are 

 going out of business. To date the seed resources 

 of Massachusetts are not being utilized. By de- 

 veloping the setting areas, the oyster industry of 

 the State could become self-sustaining and in- 

 dependent of out-of-State bedding stock. The in- 

 troduction of raft culture in local waters would 

 be one way of utilizing the State's seed resources. 



In conclusion, it must be realized that the study 

 was conducted in Cape Cod waters where more 

 than 75 percent of the annual increment of shell- 

 growth occui-s during three summer months and 

 where no growth takes place during the winter. 

 Other areas might give different results, especially 

 in the South where shell growth is not interrupted 

 by hibernation. It would be of interest to repeat 

 the raft experiments in the more southern waters. 



SUMMARY 



1. The harvest of oystere in Massachusetts has 

 dropped 83.3 percent in the last 50 years. In 

 1958, only 113 thousand pounds of oyster meats 

 where havested, an all-time low for the State. 



•2. The objective of the experiment was to de- 

 termine whether raft oyster culture is commer- 

 cially feasible in Cape Cod waters. 



3. A log raft was moored in Oyster Pond in 

 tlie winter and in Oyster Pond River during the 

 summer. Atttaclied to the logs were wire strings 

 containing shells with oysters from Wareham 

 River and Mill Creek. The mean height for raft 

 oysters in successive years was as follows: Ware- 

 ham River stock, 11, 49, 72 mm. ; Mill Creek stock, 

 29, 67, and 88 mm. 



4. Oysters attached to the raft had a faster 

 growth rate than those on the bottom; by the end 

 of the first year the raft-grown oysters from 

 A\'areham River were 13 nun. greater in mean 

 height than those growing on the bottom. The 

 difference increased to 20 mm. by the end of the 

 second j'ear. 



5. No measurable shell growth was observed 

 when the water temperature was below 10° C. 

 Seventy-five percent of the year's growth took 

 place when the water temperature was above 

 15° C. 



6. Greatest shell growth occurred when the 

 oysters were in spawning condition. 



7. Both fouled and cleaned oysters had the 

 same growth rates. 



8. Survival of raft oysters was about fi times 

 greater than for oystei-s growing on the bottom. 

 The high losses of bottom oysters is believed to 

 be due to predation by whelks and drills. 



9. The experiment demonstrated that oysters 

 can be grown from seed to market-size in 2Vo 

 years. Wild oysters take from 4 to 5 years to reach 

 market-size in Cape Cod watei'S. 



10. Thirty-two bushels of raft-grown oysters 

 were harvested. Of these, 25 bushels Avere sold and 

 7 bushels were replanted. A gross profit of $120 

 or $3.75 a bushel was earned from the two-log 

 raft. It is likely that costs for materials and labor 

 would be reduced and profits correspondingly in- 

 creased if raft culture were conducted on a larger 

 scale. 



11. The development of raft oyster culture in 

 Cape Cod waters appeai-s to be commercially 

 feasible. It is recommended tliat raft culture on 

 a larger scale be conducted for the purpose of 

 ascertaining the true commercial value of this 

 method. 



LITERATURE CITED 

 .\bbott, R. Tucker. 



19.54. .\merican seasheUs. P. van NVmstrantl Co., 

 Princeton. X..T., .141 ji. 

 Belding, David I.. 



1900. X report upon tlie niollusk fisheries of Massji- 

 c-husetts. Wright and Potter Printing Co., Boston. 

 JIass., 243 p. 

 Bon .vox, Paitl. 



193.">. The California oj-ster industry. California 

 Fish and Game. vol. 21. Xo. 1. j). O.VSO. 

 Bvti.er, PlIII.IP .\. 



19.")4. Sunnnary of our knowledge of (he oyster in the 

 Gnlf of Mexico. U.S. Fish and Wildlife Servii-e, 

 Fishery Bulletin. Xo. 89, vol. 59, p. 479-489. 



