Assessment of lake environment using dragonfly assemblage: A case study at Lake Takkobu, Kushiro Marsh, northern Japan

UBUKATA Hidenori, KURAUCHI Yohei

doi:10.3739/rikusui.68.131

A periodical census of mature dragonflies (Odonata) was conducted at 11 investigation sites along the shore of Lake Takkobu, Kushiro Marsh, Hokkaido in 2004, resulting in a record of 2,572 individuals of 18 species belonging to six families. Dragonfly abundance is analyzed in relation with the following five environmental factors: i.e., width of reed bed, water depth, coverage of aquatic macrophytes, ratios of gravels(≥2mm) and silt(≤0.075mm). The two-dimensional pattern in the dispositions of investigation sites observed on a detrended correspondence analysis (DCA) diagram of dragonflies broadly coincided with that of an actual pattern on the map, whereas this was not the case for that of a DCA diagram of the environmental factors. As the result of a canonical correspondence analysis (CCA) using both dragonfly and environmental data, the investigation sites were separated into four clusters: i.e., deep sites with rich aquatic macrophytes and wide reed beds; deep sites scarce in macrophytes; shallow sites with poor macrophytes and narrow reed beds; and shallower sites with an abundance of macrophytes. Based on the results of the CCA, most dragonfly species are selected as possible indicators of the environmental conditions of the lake: e.g., Cercion calamorum (Ris), Enallagma circulatum Selys and six other species as those preferring sites rich in aquatic macrophytes, E. circulatum, Epitheca bimaculata sibirica and five others as those favoring wider reed beds and deeper water; Sympetrum striolatum imitoides Bartenef, Trigomphus melampus (Selys) and three others as those preferring sites scarce in macrophytes; Orthetrum albistylum speciosum (Uhler) preferring the shallowest water with the fewest macrophytes and reed beds; and T. melampus and Sympetrum croceolum (Selys) favoring deeper water. Finally, some other factors that may influence the microdistribution of dragonflies in the lake are discussed.

Assessment of lake environment using dragonfly assemblage: A case study at Lake Takkobu, Kushiro Marsh, northern Japan

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