inSTREAM

Individual-based stream trout research and environmental assessment model

What is inSTREAM?

inSTREAM's software provides a variety of graphical outputs that make it easier to control, test, and understand the model. The “RiverWorld” window is a top-down view of the virtual stream, showing the habitat cells and each individual trout. Mouse clicks can open windows displaying the state of each cell or trout.

inSTREAM is an individual-based model (IBM) of trout in a stream environment; it predicts how trout populations respond to many kinds of environmental and biological change. The simulated environment includes spatially and temporally varying in hydraulic conditions (depth, velocity, cover providing velocity shelter), temperature, turbidity, and food availability. The model trout adapt to changing conditions mainly by selecting which habitat to use, making a tradeoff between growth rate and mortality risk. Trout feed and grow, experience various kinds of mortality, and reproduce.

What can inSTREAM be used for?

inSTREAM was originally designed as an instream flow assessment tool: a model for predicting how fish populations respond to changes in stream flow and temperature, as occur downstream of dams. IBMs have many potential advantages over conventional, habitat-based tools for instream flow assessment (e.g., PHABSIM). In particular, inSTREAM can predict the effects of variable flows (not just minimum flows), and the cumulative effects of changes in flow, temperature, and other variables often affected by dams.

inSTREAM is also useful for assessing the effects of environmental processes other than instream flow and temperature. For example, the model can predict population-level effects of changes in turbidity, physical habitat and channel shape (including habitat restoration), food production, and species introductions.

We also use inSTREAM as a tool for basic ecological research. Many questions and theories of ecology are very difficult to test rigorously in the field, but are easily tested in inSTREAM. We have used simulation experiments to examine such questions as: (1) What is the relation between animal density and habitat quality—is the habitat where animals are most often found really the best habitat? (2) What controls negative power-law self-thinning in stream trout—is it the allometric metabolic relationship, as theorized? (3) How do animals make tradeoffs between mortality risk and growth?

Who can use inSTREAM? What does it cost?

inSTREAM is a public domain product distributed free of charge. See links below to download the current release and supporting documentation. We appreciate potential users contacting us so we know who is trying to do what. inSTREAM requires installation of the Swarm simulation system, which is also freely available from The Swarm Development Group but we encourage users to support SDG by becoming members.

Sponsors of inSTREAM's development include the Electric Power Research Institute, USDA Forest Service, US Environmental Protection Agency, Pacific Gas and Electric, and Southern California Edison.

Is inSTREAM new?

Current versions of inSTREAM are the offspring of a long line of models and research programs.

• Version 1 (1999) was based on the rainbow and brown trout IBM of Van Winkle et al. (1998, Ecological Modelling 110 :175-207), but the model was substantially revised and implemented in completely new software. The software allows the user to choose how many, and which, trout species to simulate; separate parameters (and even different behaviors) can be provided for each species.
• Version 2 (2000) was applied to the cutthroat trout population of Little Jones Creek, but still allows simulation of multiple trout species. An Experiment Manager was added: this tool automatically generates and executes multiple model runs representing scenarios (in which inputs are altered) and replicates of each scenario. This version was documented in: Railsback and Harvey 2001 (PSW-GTR-182, Pacific Southwest Research Station); and used in: Railsback and Harvey 2002 (Ecology 83: 1817-1830).
• Version 2.2 (2002) adds the capability to simulate multiple stream reaches. The user can control how reaches are linked, and whether trout can move among reaches in one, both, or neither direction.
• Version 3 (2003) includes two major changes to address the problem of how sub-daily changes in flow affect fish and their populations. First, trout decide whether to feed or hide, whereas previous versions assumed trout all feed during the day and hide at night. Second, the trout repeat their choice of whether to feed or hide, and which habitat to use, several times per day: at any time flow changes significantly, and every switch from night to day or day to night. Version 3 was described and used in: Railsback et al. 2005 (Ecology 86:947-959).
• Versions 4.x are updates and modifications of Version 2.2 designed specifically for public release and routine use in environmental impact assessment.

Use these links to learn more:

Download version 4 software, example input, and documentation

Summary description

Tests and validation

Example applications

If you are interested in inSTREAM:

Please contact Steve Railsback or Rollie Lamberson. Additional information is available on our Who We Are page.