EXAMINATIONS ON SPATIAL RANGE WHERE FISH BIOMASS CAN BE GRASPED BY ENVIRONMENTAL DNA CONCENTRATIONS BASED ON FLUVIAL MATERIAL DYNAMIC SIMULATIONS

Abstract

 The aim of this study is to clarify the limits to the downstream transport distance of environmental DNA (eDNA) containing materials in rivers and the upstream range suitable for grasping biomass of the target species with the eDNA concentrations at a certain point. The study area was the lower reaches of the Takatsu River, western Japan. We simulated one-dimensional dynamics of fish feces and mucus, the primary sources for eDNA containing materials, in several discharge patterns. The downstream transport distance of eDNA varied greatly depending on the discharge; 800 m at the lowest discharge and 1900 m at the highest discharge settings, respectively. The upstream distance suitable for grasping fish biomass in a river varied depending on the longitudinal distribution of the target species and discharge, ranging from 200 to 700 m for Plecoglossus altivelis altivelis and from 50 to 950 m for Candidia temminckii + Opsariichthys platypus. It was also suggested that eDNA can be used to predict the longtitudinal distribution of fish biomass at a higher resolution when the discharge is low.