Annual net production of the five Sargassaceae species in Yoro, western Wakasa Bay, Sea of Japan

Abstract

Annual net production of the five Sargassaceae species was investigated in Yoro, western Wakasa Bay, Sea of Japan. The Sargassaceae species were collected at a depth of 2.0–2.5 m and subjected to stratified clipping for 13 months. Annual net production was estimated at 2407 g dry wt/m2 for Sargassum patens, 2132 g dry wt/m2 for Sargassum macrocarpum, 1458 g dry wt/m2 for Sargassum siliquastrum. 1197 g dry wt/m2 for Myagropsis myagroides, and 1471 g dry wt/m2 for Sargassum piluliferum. The ratio of annual net production to maximum biomass (P/Bmax) for these species ranged between 1.3 and 1.7, being higher than in previous studies which used the same method. Winter storms with strong wave exposure and relatively calm condition in Yoro were considered to augment P/Bmax. The total losses estimated from the different units of stratified clipping were compared. If larger and less segregated units were applied, the total loss would decrease. It was suggested that a 50 cm stratum would be applicable to the larger species (3 m or longer) and a stratum of 20 cm or less would be applicable to mid-sized or smaller species (less than 3 m).