Individual-based stream trout research and environmental assessment model
provides a variety of graphical outputs that make it easier to control,
test, and understand the model. The animation windows are
top-down views of the virtual stream reaches, 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.
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 alternative flow regimes (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?
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 is programmed using 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, Southern California Edison,
and the US Bureau of Reclamation.
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. Most importantly, the software provides
graphical interfaces to observe and test habitat conditions and trout
- 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
- Version 5 (2012) provides a major update in software usability.
Its Windows version is packaged in a new graphical user
interface that eliminates the need to install Swarm. Version 5 also separates
inSTREAM from specific hydraulic models: users can simulate cell depths and
velocities using any one- or two-dimensional hydraulic model, process habitat
variables using GIS, and provide these inputs to inSTREAM in a generic format.
This is also the first version that supports multiple stream reaches that
are fully two-dimensional (as in the above graphic).
Download inSTREAM version 5 software,
example input, and documentation
See a summary description of inSTREAM
Read about our tests and validation
See example applications
Access our archive of older
versions of inSTREAM
Steve Railsback or Bret Harvey.
Additional information is available on our Who We Are page.