Population Studies on the Kelp Ecklonia cava and Eisenia bicyclis in Dokdo, Korea

Abstract

The vertical distribution, density and biomass, population composition, and morphometric parameters of the kelp Ecklonia cava and Eisenia bicyclis were investigated in the subtidal zone of Dokdo during the summer of 2000. In most area, Ecklonia cava occurred in the depth range from 2 m to 10 m, and showed the highest density and biomass at 5 m. Ecklonia cava also occurred from 2 m, but its vertical limit was extended to deeper than 25 m. In addition, E. cava formed the conspicuous belt in depth range from 10 to 25 m, with the highest density and biomass between 15 and 20 m. The density and biomass of E. cava in its vertical distribution range were 3.0 to 372.2 inds m super(-2) and 1.2 to 21.6 kg wwt m super(-2), whereas those of Eisenia bicyclis were 6.6 to 117.5 inds m super(-2) and 7.6 to 29.0 kg wwt m super(-2). The average length and wet weight of E. cava were 26.0 ± 32.7 cm and 64.0 ± 160.8 g, and those of E. bicyclis were 34.2 ± 41.4 cm and 226.8 ± 465.7 g. Total biomass of E. bicyclis in Dokdo was as high as 1,686.7 M/T wet weight, and that of E. bicyclis was 570.4 M/T wet weight. The length frequency distributions of two species were positively skewed due to the massively recruited juveniles and their subsequent growth. This means that the populations of these two species could be well maintained. Both species exhibited the significant direct regressions of stipe length, branch legth, blade length, blade width and body weight to frond length (r super(2) > 0.91, p < 0.001). This result indicates that frond length would be a good parameter for describing morphology and classifying age groups.