Fish from the Local Official Perspective (4-D Temporal)

In InterWET, the fish from the local official perspective gives a four dimensional view or temporal view of fish using maps and the GAP and GWLF Models.
This fish calculator predicts change in overall brown trout populations in the Spring Creek Watershed. The calculator does not attempt to determine brown trout populations for a particular stream section or location.
A three factor approach is used to predict if brown trout populations increase, decrease, have no change, or have localized decrease. The three factor used are fish harvesting, in-stream temperature, and in-stream sediment.
The paper
Carline, R. F.; Beard, T., and B.A. Hollender. 1991. Response of wild brown trout to elimination of stocking and to no-harvest regulations. North American Journal of Fisheries Management 11:253-266.
showed that changes in fish harvest regulations can drastically affect fish populations. The fish calculator includes the effects of stocking and no harvest regulations.

The fish from the researcher perspective showed the influence of temperature on fish populations. In general, increased stream temperatures will decrease populations and vice versa.

The Aquatic GAP web site shows the impact of increased sediment levels on fish populations. In general, increased sediment will decrease fish populations.
Additional details can be found at the on-line dissertation on InterWET.

Click the button below to load the Fish Calculator.

The calculator can be resized for your screen.
This calculator requires as input eight different local policy choices and two fish commission policies. Explanation of the local policy choices is given in the runoff from a local official perspective web page. Select a set of values and click the calculate button.
First, notice the four outputs: the overall population change and the population change caused by each of the three factors. Note that the harvest factor, caused by the fish commission policies, overrules all other factors. When the fish commission policies do not impact the populations, then sediment and temperature has an effect. Note that the policies which increase sediment cause a population decrease in the sediment factor and likewise with the temperature.
The waste water policies are a special case. The water from sewage treatment plants impact the temperature of streams immediately downstream from the plant. The fish calculator calls this "Localized Decrease", because there will only be a decrease for some distance downstream. Eventually, the diluting effect of the stream will negate the impact of the warm water.

More Details?
Check out the on-line dissertation on InterWET for more information behind the theory and techniques used to make this web page.

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Questions or Problems? Let me know at parson@andassoc.com.
Last revision 9/9/01.
Created by Shane Parson, Copyright 1999.


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