22 



COMMERCIAL FISHERIES REVIEW 



Vol. 28, No. 10 



oysters and scatter them more evenly over the 

 ground. The cultivation was during the second 

 summer after planting of seed, and during the 

 following year if oyster growth and thickness 

 of the planting appeared to warrant it. This 

 procedure has virtually eliminated breaking 

 and scattering by hand during low tide and has 

 saved the grower considerable expense. The 

 harrow is dragged from an "A" frame mounted 

 on either an oyster scow or a tow boat and 

 raised and lowered by winch, powered or un- 

 powered. Only one person, the boat operator, 

 is usually needed for either arrangement, since 

 the harrow may be dragged continuously ex- 

 cept when beds are heavily covered with eel 

 grass or moss. At such times, an additional 

 man is needed to raise the harrow frequently 

 for cleaning (fig. 3). 



Fig. 2 - A two-section English pasture harrow hanging 

 frame on a 10- by 30 -foot oyster barge. (Photo by 



from an "A" 

 Co S. Sayce) 



Two methods of dragging permit com- 

 plete coverage of an oyster bed without ex- 

 cessive dragging over some parts and none 

 over others. One method is to circle the bed 

 continuously, reducing the radius one width 

 of the harrow at each circuit. The other is 

 to begin at one corner and drag forth and back 

 along the oyster bed moving over one harrow 

 width each time. This system of dragging 

 requires a small, tight turning circle at the 

 end of the oyster bed or off the end (if space 

 is available) or lifting the harrow at the end 

 of each crossing. This disadvantage, as com- 

 pared with continuously circling the oyster 

 bed, is compensated by the advantage of more 

 precise control of the amount of harrowing 

 any given portion leceives; additionally, it is 

 easy to harrow on a line perpendicular to the 

 first one. The ground type, its position in 



reference to prevailing winds and tides, and amount of harrowing needed should be considered 



when a decision is made about the procedure. 



Fig. 3 - A single -section English pasture harrow suspended from a 

 dredge boom showing eel grass dragged from an oyster bed. 



(Photo by C. S. Sayce) 



Oysters that are partially buried may be pulled out of the ground to the surface without 

 excessive damage to them. This action is desirable to raise buried oysters following storms 

 or just prior to harvest to loosen them in preparation for pickup by an oyster dredge. In ac- 

 tion, the harrow digs out and tumbles oysters cleaning them of mud and fouling organisms. 

 It is used, therefore, to clean shell cultch just before an impending spatfall. 



OBJECTIVE 



Use of the harrow in oyster farming has increased during the past few years, but its ef- 

 fect upon oysters has not been investigated. This paper describes an experiment in Willapa, 

 Bay, Wash., conducted between July 8, 1964 and March 13, 1965, by the staff of the Washington 

 Department of Fisheries, Willapa Bay Shellfish Laboratory, to evaluate the use of the pasture 

 harrow upon Pacific oysters. 



METHODS 



A natural bed on Long Island State Oyster Reserve in southern Willapa Bay was chosen 

 for this experiment (fig. 4). The ground, composed of a mixture of soft mud and old, native 



