Abernathy Fish Technology Center
Pacific Region

Applied Research Program in Modeling and Decision Support

Capability/Technical Service - Empirical and simulation modeling.

Definition. Conserving populations of sensitive aquatic species often requires a better understanding of the anthropogenic and natural factors (ecological context) that affect persistence. Often, basic empirical data are lacking or existing empirical data must be applied or extrapolated to address important management questions. We use complementary approaches to address these needs. First, in the absence of empirical data we attempt to fill the information need by estimation of important landscape-level patterns in occurrence or population parameters (empirical modeling). Second, given sufficient data and an appropriate conceptual or ecological framework, we can probabilistically model processes for which empirical data are lacking and evaluate different management strategies (simulation modeling).

Sample Projects

1) Modeling occurrence of cutthroat trout in isolated stream networks as a function of habitat size and time since isolation
Our objective is to use a combination of found and new data to develop a predictive model for presence of westslope cutthroat trout in isolated stream networks in the northern Rocky Mountains as a function of time since isolation and patch (habitat) size. The intent is to produce an empirically-based tool for managers to refine evaluations of barriers and isolation management options for the species.

Westslope Cutthroat Trout

Preliminary results were presented at the 2008 Annual Meeting of the Western Division of the American Fisheries Society, in Portland, OR. Final analysis of the dataset is ongoing with an expected completion date of summer 2011.

Perched culvert at road crossing

Partners: US Forest Service, Rocky Mountain Research Station; US Forest Service, Region 1

2) Modeling the potential effects of redd trampling by cattle on cutthroat trout
High estimated rates of cattle trampling on artificial redds (clay targets, e.g., Gregory and Gamett 2008) within federal grazing allotments in southwestern Montana has raised concern that direct mortality from trampling may contribute to imperilment of native westslope cutthroat trout (Oncorhynchus clarkii lewisi). Our goal was to estimate and model the effects of trampling by cattle on egg-to-fry mortality for stream-resident cutthroat trout and to explore the demographic implications of that mortality. We used results of a study of angler trampling by Roberts and White (1992) to estimate the mortality caused by cattle trampling, and incorporated these estimates into a temperature-driven model of egg-to-fry mortality representative of the developmental stages during which resident cutthroat trout populations in central and southwestern Montana would be vulnerable to the effects of trampling. The egg-to-fry model was used to characterize the effects of trampling by cattle in streams under two thermal regimes and across a range of empirically-estimated trampling rates from typical cattle grazing scenarios. We linked the egg-to-fry model to a matrix population model to evaluate how trampling affects population growth rates, then considered how trampling may influence persistence in demographically isolated populations.

Modeling indicated the effect on mortality not as dramatic as observed trampling rates might suggest, but these trampling rates were most likely to contribute to declines where the population is marginally stable without the additional impact of trampling.

Conceptual depiction of egg-to-fry mortality

The models and results are intended to serve as guidance for federal biologists evaluating the potential environmental impacts of livestock permits (e.g., under the National Environmental Policy Act, or NEPA).

Partners: U.S. Forest Service, Rocky Mountain Research Station; US Forest Service, Beaverhead-Deerlodge National Forest; US Forest Service, Region 1

Publication: Peterson, D.P., B.E. Rieman, M.K. Young, and J. Brammer.  2010.  Modeling predicts that redd trampling by cattle may contribute to population declines of native trout.  Ecological Applications 20(4):954-966. (pdf)

Related references:
Gregory, J. S., and B. L. Gamett. 2009. Cattle trampling of simulated bull trout redds. North American Journal of Fisheries Management 29:361–366.

Roberts, B. C. and R. G. White. 1992. Effects of angler wading on survival of trout eggs and pre-emergent fry. North American Journal of Fisheries Management 12:450–459.

3) Modeling suppression of nonnative brook trout to benefit native cutthroat trout.
Nonnative trout species are among the most significant threats to persistence of native inland salmonids, such as cutthroat trout (Oncorhynchus clarkii spp.). Early detection of nonnative trout invasions and subsequent eradication is the preferred management alternative to deal with this threat, but sometimes eradication is not possible for technical or socio-political reasons. In such cases, maintenance control or suppression of nonnative species using mechanical methods (e.g., electrofishing) becomes a frequent alternative where the risk of inaction is unacceptable.

Colorado River cutthroat trout

Brook Trout

We conducted population modeling to help biologists design and implement effective electrofishing suppression programs. To do this we built stage-based, stochastic matrix models describing sympatric populations of stream-resident brook trout (Salvelinus fontinalis) and cutthroat trout and used the models to show the demographic differences between the species and compare the efficacy of various electrofishing treatments for suppressing brook trout. The models were used to assess the population response of cutthroat trout to brook trout suppression as a function of the frequency and temporal distribution of annual suppression visits, electrofishing intensity (number of passes) during individual suppression events, electrofishing capture efficiency, and immigration by brook trout.

Stream Electroshocking

Partners: Colorado State University; Canadian Rivers Institute, University of New Brunswick; Department of Mathematics, University of New Brunswick

Publication: Peterson, D. P., K. D. Fausch, J. Watmough, and R. A. Cunjak. 2008. When eradication is not an option: modeling strategies for electrofishing suppression of nonnative brook trout to foster persistence of sympatric native cutthroat trout in small streams. North American Journal of Fisheries Management 28:1847-1867.
Last updated: March 19, 2014
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