Experimental study on the possibility of a suspended culture of the Japanese littleneck clam Ruditapes philippinarum in Suttsu fishing port, Hokkaido

With a decrease in the domestic catches of Ruditapes philippinarum , suspended culture is a potential approach to increase its production. We investigated the establishment of suspended clam culture in Suttsu fishing port, Hokkaido. Cages accommodating 100 clams (mean shell length 28 mm) were suspended in the “stocking area” at the back of the port and the “fairway area” at the center of the port. Rearing periods were November 2017–October 2018 in the former and November 2018–October 2019 in the latter. Shell length was measured every month; water temperature, chlorophyll- a concentration, and flow velocity around cages were measured regularly. The mean shell length at the end of the experiments was 34 mm in the stocking area and 41 mm in the fairway. Although the water temperature, chlorophyll- a concentration, and advective components of flow velocity did not differ between the sites, the fluctuating component of flow velocity was higher in the fairway than in the stocking area. This suggests the former is more suitable for clam growth than the latter in terms of food supply. Therefore, the introduction of suspended culture in the fairway area of Suttsu fishing port is expected to improve the production efficiency of clam fishery.