BIOLOGICAL EFFECTS ON HARD CLAMS OF 

 HAND RAKING AND POWER DREDGING 



By 



John Bo Glude and Warren So Landers V 



Narragansett Bay, Rhode Island, has supported an intensive commercial 

 fishery for the hard-shell clam, Venus mercenaria , known locally as the 

 quahaug or quahog, for many years"! Hind diggers, using tongs or bull- 

 rakes, are allowed to fish in any unpolluted waters in the State. Power 

 dredgers have been restricted to the southern half of the Sakonnet River 

 except for a short time during World War II when additional areas were 

 opened to increase food production <> Locations of fishing areas are shown 

 in Figure 1, 



Controversies continually arise between fishermen using power methods 

 and those who harvest the clams by hand„ Rakers and tongers claim that 

 they are using the only methods which do not harm the bottom or destroy 

 young clams o They claim the dredges tear up the bottom, breaking many of 

 the clams which are caught as well as those which go through the bag of 

 the dredge and are left to die. They also believe the dredges bury the 

 small clams so deeply that they are smothered, and that the bottom is 

 sometimes plowed to such an extent that current action causes scouring 

 which prevents a new "set" from surviving., 



Dredgers claim that they are merely cultivating the bottom and pre- 

 venting it from becoming too compact for the clams to live.. Dredging, 

 they state, really improves the bottom, inducing new sets and increasing 

 the growth rate of those clams which are left« 



1/ Fishery Research Biologists, Clam Investigations, J] „ 3. Department of 

 ~ the Interior, Fish and Wildlife Service, 



Note, o , <, oThe authors wish to acknowledge the valuable assistance of 

 Dro Charles J.. Fish in planning the experiment, and the cooperation of the 

 Narragansett Marine Laboratory in providing equipment and laboratory- 

 space » David Wo Calhoun suggested methods for statistical analysis, 

 Dr, Geoffrey Beall reviewed the statistical analysis involving transforma- 

 tions and offered many helpful suggestions, Louis D, Stringer, Fishery 

 Research Biologist, U, S, Fish and Wildlife Service, prepared most of the 

 illustrations for this paper, Thomas F, Kane, Fishery Aid, U, S, Fish and 

 Wildlife Service, collected much of the field data. 



