Development of an environmental DNA assay and field validation for the detection of invasive pink salmon Oncorhynchus gorbuscha

Abstract

1. Pink salmon Oncorhynchus gorbuscha was introduced from its native range in the Pacific to Northwest Russia several times since the 1950s. While this species has been regularly observed in rivers in northern Norway since then, there has been an upsurge in the numbers of odd-year O. gorbuscha individuals observed in rivers, particularly in northern Norway in recent years, and particularly in 2017 and 2019. 2. In the present pilot study, an assay was developed to detect O. gorbuscha from eDNA water samples. Positive control water samples were taken at two locations of the River Signaldalselva in northern Norway during the summer of 2019, when adults were spawning in the river. Samples showed positive detection of this species in the river, while negative control samples collected upstream migration barriers in central and southern Norway confirmed the absence of the target species. 3. These findings reveal that eDNA-based methods can be used to track the ongoing O. gorbuscha invasion of northern Europe and other regions where it might be or become invasive. ddPCR, eDNA, invasion, Norway, Oncorhynchus gorbuscha, pink salmon, qPCR