DEVELOPMENT OF AN OYSTER CULTCH MATERIAL FOR THREE DIMENSIONAL OYSTER AQUACULTURE

Off bottom oyster culture is clearly superior to any bottom oed techniques, however it sufferes from the lack of a satisfactory cultch material. The recent practice by a large scale commercial Dyster aquafarm of using hand punched scallop shells strung on a 1/8 " nylon cord has resulted in estimated losses of 25-30 % due to 3hell fracture and cord breakage. Drilling was investigated as a possible means of increasing useful shell processing and decreasing post-stringing losses. Based on laboratory experiments, a 1/8 " steel drill bit operated at 1328 rpm was found to be more efficient than either 1/4 " or 7/8 " drill bits operated at any speed. A net processing time of 20 shells per ninute with a processing loss of 6.3 % was possible using the 1/8" bit and drilling the shells one at a time. Group processing was considered, increasing successful output to 25.7 shells per minute with a processing loss of 18.9%. A polypropylene-crushed scallop shell composite was also con-sidered as a possible cultch and tests were made for abrasion and spat fall attraction. Abrasion was found to be of little importance, Spat fall was concluded to be a function of time after molding and surface texture. A commercially acceptable set was obtained in the laboratory by soaking the cultch in a 10 % solution of fresh oyster shell liquor for three hours prior to 24 hour exposure