Distribution And Ecological Function Of Pacific Lamprey In The San Luis Obispo Creek Watershed

Pacific lamprey (Entosphenus tridentatus) is an endemic species to coastal watersheds along the Pacific Rim in North America and Asia. The species\u27 geographic distribution is retracting and has not been mapped precisely, and the ability for the species to provide ecosystem services, such as water filtration, for supporting watershed management has not been tested. The San Luis Obispo Creek watershed, California, USA is at the southern end of Pacific lamprey’s retracting distribution, and the San Luis Obispo watershed is impacted by degraded water quality, making investigation of Pacific lamprey in the San Luis Obispo Creek watershed of direct local conservation importance. This thesis is presented as two manuscripts formatted for submission to scientific journals. The first manuscript features a study that estimates Pacific lamprey presence/absence throughout the San Luis Obispo Creek watershed using Environmental DNA. We compare our estimate to previous estimates of Pacific lamprey population distribution using established eFishing and redd survey methods. We found our estimate of distribution based on Environmental DNA to match the previous estimates throughout San Luis Obispo Creek, as well as indicate a location with Pacific lamprey presence that was previously unsurveyed. In this manuscript, we also discuss advantages and disadvantages to using Environmental DNA as a cost-effective and non-invasive method to survey Pacific lamprey in the wild. The second manuscript is a laboratory study focused on the larval (ammocoete) stage of Pacific lamprey. We tested the ability for an ammocoete population to reduce the concentration of harmful bacteria in water through filter-feeding. We found an increased decline of bacteria in experimental aquaria treated with ammocoetes than in control tanks or tanks containing non-filter feeding Pacific lamprey, indicating that ammocoetes can indeed significantly reduce bacterial loads in a contained environment. The laboratory study was conducted using water from San Luis Obispo Creek that was naturally inoculated with bacteria, generating broader applicability of the study in suggesting that Pacific lamprey have the potential to provide a water filtration ecosystem service in the wild for supporting high water quality watershed management objectives. These two studies contribute to knowledge on how to efficiently survey Pacific lamprey distribution in the wild and benefits the species may provide to ecosystems and human welfare. Collectively, they help us better understand the status and value of this often-forsaken anadromous species