2001 Volume 49 Issue 4 Pages 431-438
Missing blades of Laminarian algae, Eisenia bicyclis, Ecklonia cava, and E. kurome, have been observed in the marine forests along the coast of Nagasaki Prefecture, since 1998. In many cases, characteristic marks thought to be caused by fish grazing were left on the edge of remaining blades. To obtain further evidence for this, we observed the grazing behavior of seven species of fish common in this area, and analyzed the characteristics of bite marks on E. kurome in experimental tanks.
In the observations of grazing behavior, six species of fish grazed on E. kurome. Three species, Calotomus japonicus, Signanus fuscescens, and Kyphosus lembus grazed on E. kurome more actively than the other species, and left characteristic bite marks on the blades. The shape and size of bite marks on the blades were useful for identifying the species that caused the lost blades. In natural marine Ecklonia beds, as in Eisenia beds, large schools of these three herbivore species might cause the lost blade phenomenon on a large scale along the coast in this area.