High?frequency and long?term observations of eDNA from imperiled salmonids in a coastal stream: Temporal dynamics, relationships with environmental factors, and comparisons with conventional observations

A greater understanding of eDNA behavior in the environment is needed before it can be employed for ecosystem monitoring applications. The objectives this study were to use autonomous sampling conduct long-term, high-frequency native salmonid species a Californian coastal stream, describe temporal variation on multiple scales and identify environmental factors that drive variation, evaluate ability datasets detect rare represent organismal abundance. Using high-throughput sample processors (ESPs) qPCR, we enumerated concentrations from 674 water samples collected at subdaily intervals over 360 days single site. We detected two imperiled salmonids (coho salmon Oncorhynchus kisutch steelhead/rainbow trout O. mykiss) most samples; was generally lower concentration more variable than mykiss eDNA. High-frequency (i.e., daily) variability showed occasional patchiness large differences between consecutive samples), while seasonal observed consistent with ecology Salmonid significantly associated creek discharge, photoperiod, whether mouth open or closed by sandbar. release hatchery-origin parr into stream significant increase remainder study. compared signals fish abundance data traps located Fish often trapping. Significant positive associations mykiss; however, no such kisutch. This adds our knowledge occurrence lotic systems informs future biomonitoring efforts using automated technology.