Non‐native species limit stream restoration benefits for brook trout

Abstract

Success of stream restoration can be difficult to define because many interacting abiotic and biotic factors across spatio‐temporal scales can have measurable effects. Consequently, failure in habitat restoration to achieve targeted biological goals may reflect interactions of habitat restoration with unaccounted risks that have yet to be addressed on the landscape. This is particularly true within invaded landscapes, where habitat restoration can benefit non‐native competitors as much as the native fishes for which restoration is designed. We tested for interacting effects of a reach scale habitat restoration effort and non‐native trout competition on habitat use by a brook trout (Salvelinus fontinalis) metapopulation within a productive main stem corridor of the Shavers Fork watershed, West Virginia. We used a joint species occupancy model within a BACI sampling design to show that brook trout occupancy of main stem habitat was highest post‐restoration within restored sampling reaches, but this benefit to native brook trout was conditional on brown trout (Salmo trutta) not being present within the main stem habitat. Collectively these results indicate that habitat restoration was only beneficial for native brook trout when non‐native trout were absent from the restored sampling area. Proactive approaches to restoration will be integral for supporting resilient ecosystems in response to future anthropogenic threats (e.g. climate change), and we have shown that such actions will only be successful if non‐native competitors do not also benefit from the restoration actions.

Community ecology in a bottle: Leveraging eDNA metabarcoding data to predict occupancy of co‐occurring species

“…Coupled with the result that brown trout DNA occupancy increased with brook trout biomass, this could reflect the notion that quality habitat for native trout is also favorable for naturalized, non‐native trout. Brown trout have been documented to outcompete brook trout for resources (Hitt et al., 2016; Huntsman et al., 2022; Trego et al., 2019). Although our data were not collected with the intention of directly examining potential competition between these species, we found no evidence to suggest brook trout DNA occupancy was affected by brown trout biomass, suggesting this species is currently widespread, abundant, and minimally impacted by brown trout at our study site.…”

“…Very little is known about ecological correlates of occurrence for gill lice species due to their small size, cryptic nature, and reliance on capturing hosts to estimate distributions via techniques such as netting and electrofishing (Katz et al., 2023), which can compromise fish welfare (Reynolds & Dean, 2020). Salmincola edwardsii primarily infects salmonids in the genus Salvelinus (Ruiz et al., 2017), and brook trout in Canada and the midwestern and eastern United States have been documented with high prevalence of S. edwardsii infections, which may be exacerbated by stressors such as climate change and competition with non‐native trout (Fausch & White, 1981; Huntsman et al., 2022; Mitro, 2016; White et al., 2020). One such non‐native species is the brown trout, which was introduced globally from Europe, largely for enhanced angling opportunities (Crawford & Muir, 2008; Sax et al., 2022), and has been observed to outcompete brook trout for microhabitats suitable for thermoregulation and foraging (Hitt et al., 2016; Trego et al., 2019).…”

Multiscale population demographics and growth responses of trout in the upper Snoqualmie River watershed, Washington

“…First, detection efficiency of trout could have varied during or between snorkel surveys based on changing depths and other habitat conditions (Albanese et al 2011). In all cases except the lower main stem, we assumed complete coverage of the wetted width and depth of each main‐stem channel and accurate observations of all trout 100 mm TL and greater in each habitat unit (Huntsman et al 2022). To reduce observational errors, snorkelers frequently communicated about fish species, counts and sizes, and depths during and after surveys in each habitat unit.…”

Density effects on native and non‐native trout survival in streams

“…Consequently, significant effort has been dedicated to characterising and remedy the effects of non‐native salmonids on native cutthroat trout populations (Day et al, 2021; Fausch et al, 2009; Shepard et al, 2014). Studies of non‐native salmonids commonly address their impacts on native fish distributions as a valuable step towards the management of invaded landscapes (Bell et al, 2021; Huntsman et al, 2022; Wenger et al, 2011). However, estimates of demographic rates (e.g.…”