Water Temps

[Big E]

I was able to read the water temp for the first time yesterday and it read between 43 and 45 degrees (at 18') throughout the day.  There is 5" of ice but in some places its bad ice.

Couple questions:

1.  What are normal temps for a lake that is frozen over and producing ice?
2.  What effects does water temp in the 40s have on ice production?
3.  Do water temps effect have an effect on how many fish are in the area?  What temps are optimal?

[TonyTheIceMan]

I was able to read the water temp for the first time yesterday and it read between 43 and 45 degrees (at 18') throughout the day.  There is 5" of ice but in some places its bad ice.

Couple questions:

1.  What are normal temps for a lake that is frozen over and producing ice?
2.  What effects does water temp in the 40s have on ice production?
3.  Do water temps effect have an effect on how many fish are in the area?  What temps are optimal?

1.  The temperature you measured does not seem reasonable.  The water temperature just below the ice should be about 32 F and should get warmer as you get closer to the bottom.  The bottom temperature should be 39 F which is the highest density for water.  Any water warmer or colder than 39 will tend to float toward the surface (bottom of the ice) and eventually become 32 F.  Could the location where you are measuring the water temperature be where there is a current from a stream? 
2.  As far as production of ice, you cannot get ice until the water temperature at the surface gets to 32 F. 
3.  Different species of fish like or tolerate different temperatures.  You should be able to look up which fish tolerate what temperatures.

Regards,
Tony

[edfalc]

excellent answer

[IceholeFisherman]

Fill a glass full of crushed ice and then fill it with water. Put you thermometer in it for a few minutes. The reading should be very close to 32 degrees. Sounds to me you gauge is wrong. This is the way they told us to calibrate temp gauges used in the automotive air conditioning servicing industry.

[rrfish]

I've checked H2O temps in my ice holes and the water is usually 34 degrees.  I know my thermometer is reliable.  I think your thermo might be a little wacky.  If I were on 5" of ice in 40 something degree water, I'd be off that ice faster than a.....

[scavengerj]

Tony is correct in his statements. Icehole has the correct way to calibrate a thermometer or at least check its accuracy.
Being 18' down and reading those temps it sounds as if you have current flowing, a seep, a spring where you measured the ice. If none of those are correct, I'd check out the thermometer as Icehole suggested.