Using environmental DNA (edna) in water samples is an innovative monitoring approach that is less expensive, less invasive, and offers similar or higher detection probabilities than conventional…

Using environmental DNA (edna) in water samples is an innovative monitoring approach that is less expensive, less invasive, and offers similar or higher detection probabilities than conventional approaches used to monitor aquatic species (goldberg ET AL. 2011 taberlet ET AL. 2012 thomsen ET AL. 2012 goldberg ET AL. 2013 schmelzle and kinziger 2016 evans ET AL. 2017). Studies have shown that edna methods can be used to effectively determine site occupancy, and that estimates of edna concentration may be able to provide information on relative population densities under some circumstances (takahara ET AL. 2012 schmelzle and kinziger 2016 salter ET AL., 2019 stoekle ET AL. 2021 shelton ET AL. 2022). While edna has the potential to improve our ability to detect aquatic species and to conduct monitoring in large areas with high efficiency, minimal take, and lower cost (thomsen and willerslev 2015), standardized survey protocols are needed for edna data to be sufficiently characterized for regulatory decisions. This project is designed to provide first of its kind guidance for the standardized application of edna approaches for detecting and monitoring an aquatic species listed under the endangered species act of the united states of america. We propose to develop a standardized edna survey protocol for northern tidewater goby (eucyclogobius newberryi). The tidewater goby is a small (30-60 MM total length), benthic fish endemic to lagoons, bays, and estuaries along the entire coast of california (swenson, 1999). The number of sites occupied by tidewater goby has declined due to coastal developments, droughts, and exotic species introductions (swift ET AL. 1989). Tidewater goby were listed as endangered under the U.S. Endangered species act in 1994 (USFWS, 2005). The northern tidewater goby (e. Newberryi) is known from more than 70 sites between the palos verdes peninsula and the california-oregon border, and is the focal species for this study (swift ET AL., 2016). (the recently described southern tidewater goby (e. Kristinae) is known from only nine sites south of the palos verdes peninsula, LOS angeles county, to SAN diego county.) determining the number of sites occupied by northern tidewater goby is critical for management (USFWS 2005). However, determining site presence is challenging and the species can be easily overlooked using conventional monitoring approaches when abundance is low and when field observations are limited by water clarity, depth, and habitat size and complexity. Northern tidewater goby are an ideal candidate for development of standardized protocol because extensive previous research has established edna methods as effective monitoring tool for the species (schmelzle and kinziger 2016 sutter and kinziger 2019 martel ET AL. 2021). Comparison of detection probabilities between edna methods and standardized seining approaches revealed that edna methods have nearly double the detection rate as seining for northern tidewater goby (schmelzle and kinziger 2016). Further, edna monitoring has been effectively employed to generate accurate single-point-in-time estimates of the entire geographic distribution of tidewater goby (sutter and kinziger 2019), and rangewide characterizations of site extinction and colonization patterns from year to year (metapopulation dynamics martel ET AL. 2021).