esshup - "Bill C. Lusk says that we have the same optimal growing days for LMB up here (north central Indiana) as in Texas, I wonder if the same applies to BG?'
esshup - maybe you missunderstood what Lusk was saying?????
I strongly disagree as a 'doubting thomas' with Lusk on this. I would like to hear his rationale on this topic. How can there be same temperature degree growing days for fish and plants in Ohio as Texas? Water warms up faster in Spring in TX than in Ohio thus more days in TX with water above 55F-60F for fish growth in TX than Ohio. His comment does not make common sense to me.
In a nutshell and put into numbers, growing degree days (GDDs) accumulate anytime the average temperature for the day is more than 50 F. Commonly used terms for thermal time are Growing Degree Days (GDDs), Growing Degree Units (GDUs), or heat units (HUs).
Fish are cold blooded and their body temperature is closely related to the air/water temperature similar to plant growth. Body growth occurs in many types of plants and warm water fish when the water temperature reaches 50F. As the temperature increases generaly the growth increases until a upper optimum temperature is reached and then growth tends to slow or decrease depending on the species.
To calculate GDD see this example, if the high for the day was 70 F and the low was 40 F, the average temperature was 55, and so 5 GDDs accumulated. The GDDs for each day are added to the previous total. (When the average temperature for the day is below 50 F, it is ignored. It is not subtracted from the total.)
For those who prefer formulas, it looks like this:
Max Temp. + Min. Temp. / 2 minus 50F = Daily GDD
In my experience with water temperature the average daily temperature is often close to the water temperature.
It stands to my reasoning that when an area or region has more GGDs or time when average temps are above 50F, this will equate to more days per year when that organism (bass, BG, many other fish and plants) will be actively absorbing nutrition and growing.
As an example the GDDs for Dallas TX area are normally around 5986 GDDs per year that bass can have adequate temperature (50F+) for growth. However in Northwest OH the GDDs are around 2910 GDDs /yr when bass growth could occur in Ave. air/water temp of 50F+. Dallas area has slightly over twice the GDDs than those of NW OH. I do not understand how Lusk thinks two similar LMbass each with unlimited food and in similar conditions will have the same optimal growing days when one has twice the GDDs as the other that has one half the GDDs. What am I missing here?
FYI Reference Reading:
http://agron-www.agron.iastate.edu/Courses/agron212/Calculations/GDD.htmGIS Interactive GDDsMaps to see what the normal and current GDDs are for your area of the country.
http://pnwpest.org/US/When choosing a map and location make sure you choose the map set that has the proper base temperature or lower temperature threshold. For fish growth use the 50F lower temp threshold map choice not the 32F nor 41F maps.
