Evaluation of line transect method for estimating Mortonagrion hirosei Asahina abundance in a dense reed community (Zygoptera: Coenagrionidae)

The results of the mark and recapture method for estimating the number of M. hirosei adults were compared to those of census counts using the line transect method carried out in the same habitat, a dense reed community established in brackish water. The mark and recapture method gave a daily estimate of about 1000 and 800 individuals of each sex at the peak population in early July of 2003 and 2004, respectively. These results did not agree with the estimate from the census counts, giving 600 6 at that time in the same habitat. Some limitations of the line transect method were discussed for estimates of adults perching in the understory of the dense reed community. However, a relationship was observed with regard to daily population estimates of the line transect method and the mark and recapture method, indicating that the line transect method can be an effective tool for monitoring populations of the endangered damselflies inhabiting such a dense plant community.