Formation of fishing ground of the short-necked clam Ruditapes philippinarum in Hokuto, Hakodate Bay, Hokkaido
2015
Ito, S. (Hokkaido University (Japan). Graduate School of Fisheries Sciences, Laboratory of Marine Biology) | Tamura, R. | Morimoto, S. | Goshima, S.
Histological observation on adult gonads of the short-necked clam Ruditapes philippinarum, field surveys about distribution of adults, and settling site of juveniles were investigated to examine formation process of fishing ground of the clam at Hokuto, Hakodate Bay, Hokkaido, Japan. Gametogenesis was observed from April to September, and gonadal maturation occurred between June and September, with peak period from July to August in this survey year. Number of juveniles was the highest in October, and they settled from shore area to offshore area of the sampling site. In December, number of individuals in shore area was more than that of offshore area. On the other hand, adults were distributed over shore area in all research months. From the above results, we can suggest that this fishing ground is formed through the following steps. Larvae settle and recruit in the whole fishing area, and metamorphose into juveniles. Juveniles in the offshore area are transported, move or dead by some factor, and number of juveniles increase relatively in the shore area. Finally, when clams remained in the shore area grow to a fishable size of 32 mm in shell length, they become a target for the clam fishing.
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