PS 70-130
Monitoring upstream migration of fish using environmental DNA: Towards a more efficient method for assessing habitat connectivity
Habitat connectivity is a key property of an ecosystem representing the degree of free movement of animal species between habitats. In a river system, artificial obstructions such as dams could inhibit the upstream migration of fish requiring proper assessment of their impact. However, most assessments are lacking sufficient time and money to effectively and efficiently monitor fish migration. To mitigate this obstacle, we applied an environmental DNA (eDNA) analysis technique to evaluate habitat connectivity in a river by detecting fish DNA from water samples as an indicator of the presence of fish. eDNA is the DNA fragments shed from animals into the surrounding environment which could be used as the fingerprint of species of interest. We sampled water bimonthly from August 2012 to June 2013 at 12 sites along the mainstream of the Yodo River from the sea up to its source, Lake Biwa in Japan. Extracted eDNA were processed using Taqman real-time PCR allowing the identification of the two target species, temperate seabass Lateolabrax japonicas and flathead gray mullet Mugil cephalus. The overall objective of this study is to ascertain whether three major man-made barriers that prevent the upstream migration of these fish.
Results/Conclusions
DNA of the two species were successfully amplified and detected from the Yodo River. Based on DNA detection by PCR, it was determined that temperate seabass and flathead gray mullet could migrated up the river to a site 34 km from the sea during warm season using a fish way, equipped to a dam, located 12 km from the sea. In winter, both species disappeared from the freshwater section of the river, upstream of the fish way. Staying in the river during warm months and going down to the sea during cold months is a well-known behavior for these species and our eDNA analysis results were consistent with the existing knowledge. Furthermore, the two species were never detected at any time of the year in waters upstream of the other two dams 59 km and 70 km from the sea, respectively, because these two dams were not equipped with fish way for migrating fish. These results suggest that eDNA analysis is a practical and effective assessment tool for detecting the presence of target species and is useful for investigating habitat connectivity in river systems.