Species‐specific patterns in spatio‐temporal dynamics of juvenile chum salmon and their zooplankton prey in Otsuchi Bay, Japan, revealed by simultaneous eDNA quantification of diverse taxa from the same water samples

To understand the spatio-temporal dynamics of juvenile chum salmon Oncorhynchus keta and their zooplankton prey, neritic Pseudocalanus newmani, oceanic Eucalanus bungii, Themisto japonica, we developed species-specific environmental DNA (eDNA) quantification methods. First, confirmed that collected in Otsuchi Bay preyed on target by stomach contents analyses using assays. Size-fraction water bay showed P. newmani E. bungii were derived mostly from nauplii early copepodids. We then investigated distribution abundance eDNA same samples January to June 2018 2019. Chum was found end mid-June. appeared across throughout season most abundant February May, while other two species only spots, lower quantities, March May. The timings quantities became greater corresponded well Oyashio intrusion into bay. In addition, data indicates possibly transported also Coastal present study successfully revealed patterns salmon, reflecting ecological characteristics oceanographic conditions, effectiveness simultaneous quantifications for diverse taxa samples.