490 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



In 1957, 76.7, and 82.7 percent of the annual 

 increment in height and length of raft -grown 

 Wareham River oysters occurred during the 

 months of July, August, and Septeml)er; whereas 

 in 1958, 77.7 and 84.3 percent of tlie annual growtli 

 in heigiit and length occurred during the months 

 of June, July, and August (figs. 11 and 12). For 

 the raft-grown oysters from Mill Creek, S3.7 and 

 90.4 percentage of the annual increment in height 

 and length occurred duiing the months of June, 

 July, and August, 1958 (fig. 12). 



WAREHAM SET "56" 



WAREHAM SET 56 TAYLORS POND SET "57" 



FiGUitE 11. — Monthly increase in lieislit and Ien«tli "f 

 o.vsters as percentage of total growth durins l!);")?. 

 Temperature curve based on records taken at time of 

 measurement. 



MAM JJASON MAMJJASO 



T'iGURE 12. — Jlonthly increase in height and length of 

 oysters as percentage of total growth during 19.jS. 

 Temperature curve based on records taken at time of 

 measurement. 



EFFECTS OF TEMPERATURE, FOULING, AND 

 SPAWNING ON GROWTH 



Temperature 



Shell growth did not occur when the water tem- 

 perature was below 10° C. Tliis observation is 

 in agreement with the findings of Loosanofi' and 

 Nomejko (1949) and Walne (1958). In general 

 the oysters in Oyster Pond River grew from April 

 to October inclusive (figs. 11 and 12) . During the 

 years 1957 and 1958, approximately 20 percent of 

 the total annual growth occurred when the water 

 temperature was between 10° C. and 15° C, but 

 more tlian 75 percent of the year's growth took 

 place when tiie water temperature was al)ove 

 15° C. 



Fouling 



Tlie question arose whether the monthly re- 

 moval of fouling organisms has any etl'ect on the 

 shell growth. On November 17, 1958, the heights 

 and lengths of oysters from two strings were com- 

 jjared; one sample was selected from a string that 

 had remained undisturbed, while the other sample 

 was selected from the string tluit had been cleaned 

 of fouling animals and plants each month. The 

 results of this comparison are as follows : the aver- 

 age height and length of oysters on the undis- 

 turbed string were 65.9 mm. and 48.9 mm., respec- 



