The 1950 sampling included 100 grabs each in the bullraked, dredged 

 and control areas. Sampling was randomized by allowing the boat to drift 

 across the area with the wind or tide as samples were taken. This pro- 

 cess was repeated until the required number of samples had been obtained. 



We first planned to take only 50 samples from the control area in 

 I95O0 However, this series showed such a marked decrease in number of 

 clams compared to the 19U9 census (11.86 to 7 •03 per sample) that another 

 series of 50 samples was taken. The second series confirmed the results 

 of the first by showing an average of 7«71 clams per sample. (Appendix C) 



ANALYSIS OF RESULTS 



Breakage of Commercial-Sized Clams 



Breakage records for dredging shown in Table 2 are for clams above 

 60 mm, in length, whereas bullraking records include clams as small as 

 hS inm. 



Table 2 



nrfc.;kage of Commercial-Sized Clams by 

 Bullraking and by Dredginj^ in Test Plot 



19U9 1950 



Bullraking 0.1^ i/ 0.3^^/ 



Dredging 1.2^ 0.7/g 



1/ Most of breakage caused by handling. 



"2/ C,02$S gear breakage; balance from handling. 



The gear caused most of the breakage in the dredging operation, 

 whereas in raking the breakage was mostly from handling the catch. The 

 difference in size composition of the catches probably resulted in greater 

 breakage in handling for the hand-digging operation since the smaller 

 clams are more fragile. 



Narragansett Marine Laboratory conducted a population survey of hard- 

 shell clams in Narragansett Bay during the summers of 19U9 and 1950, using 

 an 8-tooth commercial dredge. Records of this survey show average break- 

 age of 1.0^ in bottoms without rocks and 2.9^ in bottoms with rocks. The 

 bottom in our test plot is uniformly sandy-mud without rocks; thus the 

 breakage there agrees closely with that reported by the Narragansett 

 Marine Laboratory, The maxixmim breakage reported in the survey of the Bay 



12 



