The proposed assessment will develop a life-stage demographic model to simulate population dynamics of Pacific Lamprey and evaluate threats to their population(s). This model will improve the effectiveness of RMU assessments by improving understanding of Pacific Lamprey population dynamics.  In addition, the model will address seven threats identified in the RIP, including stream and floodplain degradation, water quality, flow alterations, passage, predation, invasive species and climate change.  Through model simulations, we can evaluate the impacts of current threats on Pacific Lamprey life stages, and the efficacy of restoration actions to alleviate threats.  We will build upon existing knowledge of lamprey in the Willamette RMU and complement that with literature values as needed (e.g., Clemens et al. 2013; Porter et al. 2017; Goodman and Reid 2022; Hess et al. 2020, 2022). “The Willamette Basin is probably the most important production area for Pacific Lamprey in the Columbia Basin” (Kostow 2002). Further, Willamette Falls is the source of the largest tribal harvest in North America. Hence, the model will focus on the Willamette RMU; however, with the use of different vital rates (as appropriate), the basic model can be used for other RMUs.

Determination of the RMU status for Pacific Lamprey depends on understanding population dynamics, life-stage vital rates (e.g., survival, reproduction) and their responses to threats.  Life cycle models are an integrative approach to understand how threats or restoration actions may influence each lamprey life stage and interactions among stages. These models provide a level of sophistication in assessments that is not possible via other means of study.  For these reasons, such models are routinely applied in assessments of species such as Pacific salmon and trout but are currently not available for Pacific Lamprey.

We propose to develop a life cycle model for Pacific Lamprey, which have complex life cycles that pose challenges to evaluating conservation and restoration (Figure 1). Developing a life cycle model for this species will represent a major advance in tools to be applied to Pacific Lamprey conservation. It will provide a strong foundation for informing conservation actions and help to identify critical information gaps that are relevant to those actions.  The collective understanding of the life cycle of Pacific Lamprey are known well enough to develop a model that can be adapted across the species’ range and to numerous applications, including evaluation of habitat fragmentation and degradation, passage, water availability, translocation, climate, or interactions among different management scenarios.

To highlight the applied value of the Pacific Lamprey life cycle model, we will focus on applications in the Willamette RMU.  This RMU is relatively well-studied and supports populations that are productive enough to serve as a regionally important resource for tribal use of Pacific Lamprey for ceremonial and subsistence purposes.  Within the Willamette RMU we can explore several threats to Pacific Lamprey in the watershed, including predation on upstream migrating adults, survival in the river linked to environmental exposures (e.g., water temperature, available locations for refuge), questions regarding upstream passage, spawning and early rearing, survival of larval stages, and survival of downstream-migrating transformers.

Development and application of the model will occur in several steps:  1) conduct a literature review to identify key aspects of Pacific Lamprey life cycles, 2) assemble this information into a general model that allows for expression of alternative life histories or life cycles that are known, 3) populate the model with parameters from the literature on Pacific Lamprey or surrogates (i.e., studies of other, closely-related lamprey species), 4) evaluate model performance and identification of key behaviors and uncertainties, 5) application of a model that is adapted to address questions regarding threats or management scenarios identified in the Willamette RMU. The model will be coded in R or other suitable language, with code and a full model description provided in the form of a peer-reviewed publication.  If time and resources allow, we will also provide a version of the model that can be used or adapted by individuals who are not proficient in coding (e.g., an R Shiny).