Abstract
Life-cycle models (LCMs) provide a quantitative framework that allows evaluation of how management actions targeting specific life stages can have population-level effects on a species. LCMs are particularly useful for species such as salmon that are highly migratory and use multiple aquatic ecosystems throughout their life. LCMs are lacking for threatened Central Valley spring-run Chinook (Oncorhynchus tshawytscha; CVSC), so the authors developed a CVSC LCM to describe the dynamics of Mill, Deer, and Butte creek CVSC populations. The authors propose a series of monitoring recommendations—such as the development of an enhanced juvenile-tracking monitoring program, and the implementation of juvenile-trapping efficiency methodology combined with genetic identification tools—to help fill highlighted data gaps.
Highlights
Life-cycle models (LCMs) are essential tools that are increasingly used in conservation and population management of vulnerable species (Honea et al 2009; Alldredge et al 2013; Merz et al 2013; Hendrix et al 2017; McGowan et al 2017)
Parameter Sensitivity Analysis During the pre-calibration sensitivity analysis, the highest sensitivity for Butte Creek dynamics was linked to the parameters of the temperaturedependent adult pre-spawning survival relationship (PRCC value greater than 0.4; Figure 5A)
The juvenile production estimate of fish entering the Bay could help with estimating the smolt-to-adult-return index, which is often used to tease apart the effect of freshwater versus ocean conditions on salmon population dynamics (Petrosky and Schaller 2010; Michel 2019)
Summary
Life-cycle models (LCMs) are essential tools that are increasingly used in conservation and population management of vulnerable species (Honea et al 2009; Alldredge et al 2013; Merz et al 2013; Hendrix et al 2017; McGowan et al 2017) They provide a quantitative framework across all life stages of a species that allows an understanding of how management actions (e.g., habitat restoration, harvest, hatcheries) can have population-level effects on species recovery. LCMs can be used to provide recommendations for modifying or implementing new management actions to better achieve conservation objectives, and predict the outcomes of such actions They can be used to support the implementation of an evidence-based adaptive management program—a methodology gaining support in the conservation and resource management community (Franklin et al 2007; Dahm et al 2009). Development of a LCM for the management of threatened salmon populations in the California Central Valley (CCV) is worthwhile and timely
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