The number of native fish present in a marine ecosystem is increasingly affected by multiple factors, including invasive species and overfishing. In a new study led by Okayama University, researchers have used eDNA to survey the population of the bitterling fish in the Ashida river basin in Japan.
The bitterling fish, Rhodeus atremius suigensis, was once abundant but is now threatened with extinction in this region. According to the researchers, this is concerning because the bitterling fish is recognized as an indicator species for the conservation of fish diversity in freshwater ecosystems.
“Rhodeus atremius suigensis is an extremely endangered bitterling fish, designated as one of the Nationally Endangered Species of Wild Fauna and Flora by the Ministry of Environment of Japan,” wrote the study authors.
“To prevent its extinction, effective ecological survey methods are necessary in order to guide habitat management. Recently, environmental DNA (eDNA) analysis has proven useful for detection and censusing of endangered aquatic species that are difficult to locate and capture.”
Environmental DNA (eDNA) holds information about which species were recently present in an area. The experts developed a system using eDNA to investigate the distribution and population density of bitterling fish in the Ashida river basin.
“We first confirmed the utility of this analysis in aquarium experiments, before performing field surveys.” said Professor Kazuyoshi Nakata from Okayama University, who led the study. “We set fish traps at 48 points in an agricultural channel in the Ashida river basin and examined the relationship between fish presence and eDNA concentration.”
The study revealed that eDNA concentrations were greater in areas where bitterling fish had been captured, and lower downstream. “Our results serve as a reference to how far and how much downstream eDNA can be detected, which will be useful to guide future conservation surveys,” said Professor Nakata.
The eDNA analysis technique used for this study could be used in larger areas to track other species. Ultimately, the finding of this research could help in the conservation of endangered species.
“These results not only demonstrate the reliability of this method, but also suggest its feasibility for conservation measures,” wrote the study authors.
The research is published in the journal Landscape and Ecological Engineering.
Image Credit: Kazuyoshi Nakata
Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.