Physical and biological constraints on the capacity for life-history expression of anadromous salmonids: an Eel River, California, case study

Abstract

Recovery of anadromous salmonid populations is complicated by their complex life-histories. We examined the spatiotemporal interplay of stream temperature, geomorphic features, and a species’ thermal sensitivity mediated by biological interactions in a case study of steelhead trout (Oncorhynchus mykiss) and Chinook salmon (O. tshawytscha) in California’s Eel River watershed. We estimated habitat suitability and fish capacity for each salmonid run and freshwater life stage during average, cool, and warm years in each of the watershed’s subbasins, including a historically-occupied high-elevation subbasin upstream of an impassable dam. Our estimates varied depending on whether we accounted for exposure to the Sacramento pikeminnow (Ptychocheilus grandis), an introduced predator/competitor. Our results indicate that the dammed subbasin has substantial salmonid capacity relative to the rest of the watershed and could provide an important cool-water refuge during warm years and from pikeminnow, potentially improving the productivity and resilience of multiple anadromous salmonid populations. Our approach can be applied in any setting where spatially explicit habitat metrics can be estimated and population specific and life-stage specific habitat criteria can be specified.

A comparison of methods for estimating juvenile salmon habitat capacity to assist with restoration planning and evaluation

“…Like other models, additional validation is needed. The utility of the UCM appears to be in comparing different management scenarios within a basin (Cooper et al 2020; FitzGerald et al 2022).…”

“…Initial validation for the application of the UCM using steelhead throughout Oregon suggested that it provided reasonable estimates of capacity (Cramer and Ackerman 2009); however, like most capacity models, it needs additional validation for other species and systems (Roni et al 2018). It has been used in a variety of management scenarios to determine the impacts of instream flow and restoration and, most recently, barrier removal (Cooper et al 2020; Fitzgerald et al 2022). At least in the instance of the Mine Tailings Reach, the baseline UCM estimate of 3398 parr appears closer to the 2015 snorkel survey estimates.…”

North American River Otter Diet Includes Invasive Sacramento Pikeminnow and Herpetofauna on South Fork Eel River, Northern California

“…The Eel River contains invasive Sacramento Pikeminnow as well as native Pacific Lamprey ( Entosphenus tridentatus ), Chinook Salmon ( Oncorhynchus tshawytscha ), Coho Salmon ( Oncorhynchus kisutch ), summer and winter Steelhead (anadromous Oncorhynchus mykiss ), and Sacramento Suckers ( Catostomus occidentalis ), among other species of native and non-native fish (Brown and Moyle 1997; Kinziger and others 2014). Native salmon, trout, and lamprey species are anadromous, so their presence in the SF Eel River varies by season as they use the area for spawning: Chinook Salmon in the autumn, Pacific Lamprey from April to July (Brown and Moyle 1997; Fitzgerald and others 2022). Signal Crayfish ( Pacifastacus leniusculus ) are present, along with a variety of notable herpetofauna, including, for example, Foothill Yellow-legged Frog ( Rana boylii ), Rough-skinned Newt ( Taricha granulosa ), Northwestern Pond Turtle ( Actinemys marmorata ) and invasive American Bullfrog ( Lithobates catesbeinus ) (Kupferberg 1997; Finlay and others 2002; Peek and others 2021).…”

Integrating spatial stream network models and environmental DNA to estimate current and future distributions of nonnative Smallmouth Bass

“…Ultimately, natural resource managers and conservationists in the Pacific Northwest and beyond will need to continue to address issues from Smallmouth Bass and other nonnative predatory fish into the future with uncertain outcomes of chosen management actions. Therefore, it may be prudent to develop SDMs to predict where invasion-resistant refugia are most likely to occur into the future to aid in long-term conservation strategies (FitzGerald et al 2022;Isaak and Young 2023).…”