流水域におけるトウキョウサンショウウオの卵嚢分布状況およびその流失割合

概要

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The Tokyo salamander (Hynobius tokyoensis) indigenous in the Miura peninsula, is threatened with extirpation due to habitat loss from development. Artificial breeding sites in running water were introduced; however, many of the sites are not considered to be high quality breeding habitat. This species normally deposits its egg-sacs in still water, attached to a suitable twig, leaf or grass stem. We studied the retention of egg-sacs at two different types of running water sites. Our study showed that 48.7% of egg-sacs were washed away at natural stream sites, and 76.8% of egg-sacs were washed away by small streams created by erosion at abandoned rice paddy sites. We created still water sites in the abandoned rice paddies, and the results showed that only 5.3% of the egg-sacs were washed away. For conservation of this species, it may be necessary to protect a wide variety of riparian zones, groundwater systems, and forested areas.