Nippon Suisan Gakkaishi 67 (4), 687-695 (2001)

Sediment Environment and Macrobenthic Community in Surf Clam Bed off Shimamaki Coast, Hokkaido, Japan

Izumi Sakurai,1 Hiroyuki Hayashi,2 Hisami Kuwahara3

1Hokkaido Central Fisheries Experimental Station, Hokkaido 046-8555, 2Kushiro-Toubu Fisheries Extension Office, Hokkaido 088-1118, 3National Research Institude of Fisheries Engineering, Ibaraki 314-0421, Japan

Sedimentary condition, bottom disturbance and macrobenthic structure of the shallow sandy bottom off Shimamaki, west Hokkaido, Japan, were studied in relation to a surf clam Mactra chinensis bed. Surveys were conducted in July and October 1999, and February and April 2000. There was no seasonal change in the sedimentary condition; median diameter (Md), sorting coefficient (σ), total organic carbon and total nitrogen of sediment ranged from 0.18-0.33mm, 0.47-0.74, 0.35-1.30mg/gDW and 0.12-0.34mg/gDW, respectively. Bottom disturbance of calculating Shields number (Ψ) as an index fluctuated markedly with seasonal change of wave action. Four macrobenthic communities (A, B, C and D) were identified according to cluster analysis using the similarity index (Cπ) and were characterized as dominant presence of Glycera chirori and Scaphechinus mirabilis in A, Eohaustrius eous and Euzonus ezoensis in B, Umbonium costatum and E. ezoensis in C, and S. griseus in D, respectively. Distribution patterns of the dominant species in each community changed seasonally by their recruitments in deeper than 10m depth, although D community distributed in shallower than 10m depth through the year. The sedimentary condition and the bottom disturbance in the habitat of M. chinensis were similar to those in C community. The environmental characteristics such as the surf clam bed are discussed.


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