Darren:
        I have developed a couple of degree-day functions for spawning of
marine fishes that I used in some models.  My experience was that the
best way to go about this was to find data on spawning times coincident
with temperature data.  Often spawning vs. temperature relationships are
not found, but you can find the information that you need to build those
relationships in the same report.  Generally, I, and my colleagues, had
to dig through gray literature to find the info that we needed to
construct a degree-day vs spawning function.  If there are agency
reports, they may well have what you need in them.
        I would also consider putting in a function that relates not just
to temperature, but to day length as well.  In building a spawning
fucntion for a model a degree-day function alone may cause you to predict
spawning that is driven by a short-term warming that may occur out of
season, say February.  If you link your spawning fucntion to day length
as well, you'll probably have fewer problems with short-term temperature
variation.

cheers,
Jeff Tyler


On Fri, 4 Apr 1997, Darran L. Crabtree wrote:

>         Hello, I have introduced myself before, but that was about 6
> months ago.  Quickly, I am a PhD candidate at the SUNY College of
> Environmental Science and Forestry in Syracuse, New York.  I am interested
> in the contributions of fish production from the nearshore areas
> (including coastal wetlands) of Lake Ontario to the open water system.
>
>         Presently I am employed as a research assistant evaluating the
> impacts of a flow control device on the Irondequoit Creek (Lake Ontario
> tributary).  I would like to give the operators of the flow control
> device (which would be in place only at high flow times) a model that
> would simulate critical "times" for fish passage based on temperature.
> The USGS has a gauging station on the creek so temperature data will
> "always" be available.
>
>         At first I was going to simply overlay known spawning "times" for
> species that utlilze this creek and wetland.  This would yield a static
> picture of fish utilization.  My collegue suggested using temperature as a
> forcing function so that the model could predict critical periods.  He
> pointed out that time has little meaning to fish and that temperature
> represent a "real" biological cue.  He then suggested the use of "degree
> days" which incorporates the temporal dimension into temperature.
> However, I cannot find useful references relating degree days to fish
> spawning.
>         Does anyone have any information/citations on degree days
> especially related to spawning in fishes?
>
> Thanks in advance
>
> Darran L. Crabtree
> State University of New York
> College of Environmental Science and Forestry
> Syracuse, New York 13210
> 315-470-6949
> [log in to unmask]
>

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Jeffrey A. Tyler, Ph.D
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