algal foods. Marketable size is reached in 1/3 the time required for wild 

 stocks in Delaware Bay. Increasing demand for clams, limited supply, 

 sedentary habits, and the fact that they obtain their own food at no 

 additional cost, make clam aquaculture attractive. A major problem is how 

 to rear juveniles until they are large enough to be planted on intertidal 

 or subtidal beds (e.g., until they are resistant to predators). Most NOAA 

 programs on hard clams have been terminated. In 197 6 clam programs included 

 occasional pathological studies and development of processing techniques. 

 Sea Grant was supporting studies of intensive culture methods in Del. Future 

 NOAA programs should include expansion of pathology and genetics studies 

 and research on biology and technology of aquaculture. Funding for all 

 clam species should be increased from present level of about $100,000/yr to 

 $800,000/yr by 1985. Plans for multispecies programs are discussed and 

 NOAA aquaculture programs in fiscal year 1976 are listed. - J.L.M. 



673 



Glude, John B., and Warren S. Landers. 1953. 



Biological effects of bullraking vs. power dredging on a population of hard 

 shell clams, Venus mereenaria. Natl. Shellf. Assn., Convention Addresses 

 1951: 47-69. 



In Narragansett Bay, R.I., an intensive hard clam fishery has operated for 

 many years. Digging with tongs or bullrakes is permitted in any unpolluted 

 waters. Power dredges are restricted to a much smaller area, except that 

 for a short time during WWII other areas were opened to dredges to increase 

 food production. A long-standing controversy exists between the 2 segments 

 of industry. Hand diggers claim that dredges tear up the bottom and break 

 clams, bury small clams so deeply that they smother, and sometimes overplow 

 the bottom causing currents to scour and prevent new set from surviving. 

 Dredgers claim that they are cultivating the bottom and preventing it from 

 compacting, that they improve the bottom, inducing new sets and increasing 

 growth rates. Fishing methods are described in detail. A 3-acre test area 

 was closed to commercial clamming. Four bullraking areas were laid out at 

 one end, a control area in the center and 4 dredging areas at the other end. 

 These 3 were separated by 25-ft corridors, and similar corridors separated 

 the plots from the perimeter of the 3-acre plot. Two bullrakers were hired 

 to harvest appropriate areas and dredge boats were chartered for the others. 

 Rakers worked a plot until the catch reached a pre-established minimum 

 value, then moved to another. Dredging in a plot continued until the same 

 quantity of clams over 60 mm lona had been obtained from the corresponding 

 quarter of the bullrake area. The minimum size taken efficiently by the 

 dredge was about 60 mm. Underwater photos were taken of the bottom. Size 

 distribution of clams in the area was determined before the experiment. 

 After fishing, bottom samples were taken with a clamshell bucket which 

 sampled 5 ft^ to a depth sufficient to get all clams. Dredging caused 

 slightly more breakage: 1.2% in 1949, 0.7% in 1950. Bullraking breakage 

 was: 0.1% in 1949, 0.3% in 1950. Gear caused most breakage in dredging, 

 handling caused most damage in raking. On the bottom, dredging broke 2.9% 

 when rocks were present, 1.0% when not. No evidence of important breakage 

 of undersized clams or clams less than 60 mm long was found on any plot. 

 No evidence of significant smothering appeared. Virtually no setting took 

 place in 1949 or 1950, thus effects on setting could not be determined. 

 The surface of the bottom was almost identical in control and test plots 



1 to 3 mo after the experiment. Both test areas showed reductions in 

 number of other living forms as compared with the control. Size composition 

 of remaining clams on the dredged and tonged areas differed because raking 

 takes a larger number of clams below 60 mm. The implications of this for 

 recruitment are not known. Before the experiment the 3-acre plot contained 



2 size groups of clam, one peaking at less than 40 mm, the other at about 

 60 mm. The group of larger clams disappeared from the control area from 

 1949 to 1950 even though no clams were removed in the experiment. This 

 unexplained difference was not caused by sampling error. The same group 

 almost disappeared from the raked area also. Illegal clamming was 

 suspected. It is clear that no significant biological effects on hard 

 clam populations came about from the direct operation of one gear as 

 compared to the other. The biological effects of size selection by the 

 two harvesting methods were not determined. - J.L.M. 



188 



