RAFT CULTURE OF OYSTERS IN MASSACHUSETTS 



483 



Oystermen, who are williiifj to utilize tiie State 

 seed resources, experienoe difiiciilty in oljtainin^ 

 new grants. At i)i-esent, eacii coastal coninumity 

 has jurisdiction over the shellfisheries of its tidal 

 water and restricts the issuing of grants to the 

 residents. Furthermore, tlie officers of coastal 

 nuuiicipalities are reluctant to make available any 

 new grounds to private individuals for oyster 

 cultivation. Finally, an oysterman has no as- 

 surance that his grant will l>e renewed at the 

 expiration of the lease. Slow gi-owth of oysters, 

 high mortality, and the difficulty of obtaining per- 

 manent grants discourage him from investing his 

 time and money in growing oyst-ers by the present 

 slow methods. 



GROWING OYSTERS OFF BOTTOM 



Experiments successfully tried in the United 

 States, Canada, Australia, and Japan have shown 

 that oysters grow faster when lifted off the bot- 

 tom. In Elkhorn Slough, Monterey Co., (\xlif.. 

 Bonnot (1935) obtained remarkably rapid growth 

 of Japanese seed oysters, frtis.tosfrfd- gigaa. which 

 reached market-size in only 8 months. Some 

 Eastern (U.S.) oysters in this experiment grew 

 well but at a slower rate than the Japanese species. 

 Similar studies were conducted at I^adysmith, 

 British Columbia, Canada. One-year-old Japa- 

 nese oysters were hung from rafts in March and 



by November were large enough to harvest. 

 Quayle (1!)5()) reports that by this nu'thod oysters 

 can be harvested in two years instead of thi-ee. 



In Jajjan and .Vustralia, oysters are cultured oft" 

 bottom on a commercial scale. In the lidaiul Sea 

 of Japan, 20 million poimds of oyster meats are 

 harve.sted annually using bamboo rafts (Wallace, 

 1959). Australian oystermen grow many of their 

 oysters in wooden trays kejit al)ove the bottom 

 (Kesteven, 1947). Despite the success of off-bot- 

 toni cultui-e in Ja))an and .Australia, this method 

 had not l>een adopted to any extent by commei'cial 

 growers in the T'nited States. 



PURPOSE OF THE STUDY 



To develop a method of oyster culture which 

 might be useful in revi\ing the Massachusetts 

 oyster industry, and at the same time utilize the 

 State seed resources, the U.S. Bureau of Com- 

 mercial Fisheries at Woods Hole began studies on 

 the growth and survival of oysters kept on rafts 

 in Oyster Pond and Oyster Pond River, at Chat- 

 ham (Mass.). The present paper summarizes the 

 observations made between 1956 and 1959. Par- 

 ticular attention was given to whether the benefits 

 obtained from the cultivation of raft-grown oys- 

 ters would justify the possible additional cost of 

 production. 



LOCALITY AND DESCRIPTION OF THE AREA 



Oyster P(md (fig. 3) is ai)proximately three- 

 fourths of a mile long and one-quarter of a mile 

 wide. Its bottom along the shore is hard sand 

 which changes to soft mud in deeper water. Rec- 

 ords show that natural oyster beds once existed in 

 the pond, but by 1877, all had disappeared (Beld- 

 ing, 1909). 



Oyster Pond River (fig. 3) begins at the outlet 

 of the pond where it runs SAV. for seven-eighths 

 of a mile and then l)ends to a SE. direction for an- 

 other three-quarters of a mile before emptying 

 into Stage Harbor. The width of the river is 

 fairly constant throughout its entire length, 

 avei-aging about l(i5 yards. The depth varies 

 from 1 to 9 feet at mean low water except for a 

 10-foot channel. Tidal currents re^-orded with a 

 (iurley current meter are about '2 feet per second 

 during fiood tide. The bottom is generally hard- 

 packed sand, l)ut in deeper water away from the 

 shore and in areas where tidal creeks flow into the 



rivei-, the bottom is soft with a high percentage 

 of silt and clay. High cliff's are found along the 

 entire length of the north side of the river, and 

 for the first seven-eighths of a mile on the south 

 side, but for the remaining three-quarters of a 

 mile only tidal flats appear. 



TEMPERATURE, SALINITY, OXYGEN CONTENT, 

 AND pH OF WATER 



S\irface water temperature in Oyster Pond 

 River was recorded during each visit to the site. 

 In addition, a thermograph was installed from 

 A])ril 1 to November 20, 195S. During I95S the 

 average monthly temperature fluctuated fi-om 1.2° 

 C. in February to a higli of 22.1)° C. in July, and 

 then to a low of 0.8° C. in December (fig. 4). The 

 water tempeiature was also fomul to vary during 

 the day. For exam))le, on April 24, 1958, a low of 

 11.8° C. was recorded at (i:00 a.m. By 12:00 noon 

 the temperature had climbed to 1(5.2° C. In the 



