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Marine Ecology Progress Series

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MEPS 183:87-94 (1999)  -  doi:10.3354/meps183087

Effects of changes in seagrass shoot density and leaf height on abundances and distribution patterns of juveniles of three gobiid fishes in a Zostera marina bed

Masahiro Horinouchi*, Mitsuhiko Sano

Department of Global Agricultural Sciences, Graduate School of Agricultural and Life Sciences, University of Tokyo, Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan

ABSTRACT: The effects of changes in the structural complexity of a seagrass Zostera marina habitat on the densities of juveniles of 3 gobiid fishes, Pterogobius zonoleucus, Chaenogobius heptacanthus and Chasmichthys gulosus, were investigated by field experimentation at Moroiso and Aburatsubo Bays, Miura Peninsula, Japan. Following seagrass manipulation, involving reduction of leaf heights and shoot densities as well as complete removal of seagrass, juvenile densities of all 3 gobiids were found to be higher in those quadrats with sparser or shorter seagrass, the abundance in the seagrass-cleared quadrat always being greater than that in the control. In the quadrat with the lowest shoot density, juveniles resided among the shoots, and were evenly distributed over a horizontal plane. In the quadrat with the shortest seagrass, juveniles appeared above the canopy, and were positioned as in the seagrass-cleared quadrat, i.e. near the surrounding walls of untreated seagrass. By contrast, in the experimental patches lacking surrounding walls of unmanipulated seagrass, no juveniles appeared. The results indicated that water column-distributed juveniles of the 3 gobiid species prefer sparser seagrass and open areas close to the wall of untreated seagrass.

KEY WORDS: Habitat complexity · Seagrass bed · Gobiid juveniles

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