Evidence of Recent Climate Change within the Historic Range of Rio Grande Cutthroat Trout: Implications for Management and Future Persistence

Abstract

Evidence of anthropogenically influenced climate change has motivated natural resource managers to incorporate adaptive measures to minimize risks to sensitive and threatened species. Detecting trends in climate variables (i.e., air temperature and hydrology) can serve as a valuable management tool for protecting vulnerable species by increasing our understanding of localized conditions and trends. The Rio Grande cutthroat trout Oncorhynchus clarkii virginalis has suffered a severe decline in its historical distribution, with the majority of current populations persisting in isolated headwater streams. To evaluate recent climate change within the subspecies’ historical range, we examined trends in average air temperatures, biologically important hydrological variables (timing of snowmelt and seasonal flows), and the April 1 snow water equivalent over the last 45 years (1963–2007). While rates of change in all three metrics were variable across sites, rangewide patterns were evident. Across the subspecies’ historical range, average annual air temperatures increased (0.29°C per decade) and the timing of snowmelt shifted 10.6 d earlier in the year (2.3 d/decade). Flows increased during biologically important periods, including winter (January 1–March 31; 6.6% increase per decade), prespawning (April 1–May 14; 6.9% increase per decade), and spawning (May 15–June 15; 4.2% increase per decade) and decreased in summer (June 16–September 15; 1.9% decrease per decade). Evidence of decreasing April 1 snow water equivalent (5.3% per decade) was also observed. While the impacts of these changes at the population level are equivocal, it is likely that negative effects would influence the subspecies by altering its distribution, decreasing available habitat, and altering the timing of important life history components. Continued monitoring and proactive management will be required to increase the resiliency of remaining populations to ensure long‐term persistence and protection in a changing climate.

Seasonal weather patterns drive population vital rates and persistence in a stream fish

“…Climate change impacts on wild animal populations have been most commonly examined using annual or single‐season temperature values (e.g., Roland & Matter, ; Wenger et al ., ; Dueri et al ., ). For example, potential changes in geographic distributions of coldwater salmonids have been projected based on alterations in annual mean temperature (Flebbe et al ., ; Zeiger et al ., ) and summer mean temperature (Roberts et al ., ; Wenger et al ., ). Although summer weather is important for a coldwater species such as brook trout and the omission of summer weather patterns is a potential caveat in our study, we found that changes in winter precipitation can also drive local populations to extirpation.…”

The Past as Prelude to the Future for Understanding 21st‐Century Climate Effects on Rocky Mountain Trout

“…Many of the climate-related threats described for Rio Grande cutthroat trout are similar to those for CRCT because both subspecies are restricted to small, isolated stream fragments (mean = 7.6 km for Rio Grande populations; Pritchard and Cowley 2006;Zeigler et al 2012) but recent natural disturbances associated with extreme climatic conditions also highlight the extirpation risks for some of these populations. An extreme drought in 2002 reduced trout abundance in several conservation populations, and anecdotal evidence suggests that a few populations may have been extirpated (Japhet et al 2007;Patten et al 2007).…”

Overview of different aspects of climate change effects on soils

“…Release of potential contaminants in surface waters as a result of accelerated weathering (Todd et al 2012) and other climate-change related effects [e.g., the effect of warming temperatures on nitrate concentration of streams (Baron et al 2009), and the hydrochemical effect of drought during hydrological episodes in streams (Laudon et al 2004)], and the increase in surface water temperature [e.g., the increase in Columbia River water temperatures in response to climate change (Caldwell et al 2013)] may significantly or even dramatically change elemental balances; affect microbially mediated reactions and processes occurring in rivers, lakes, and oceans; and/or affect aquatic life [e.g., may contribute to reduced fish survival and lower population productivity (Isaak, Wollrab, et al 2012;Isaak, Muhlfeld, et al 2012;Zeigler et al 2012).…”