Thermocline fishing guage

[Spider]

Last weekend I was fishing Lake Michigan for salmon and heard many reports on the radio about the depth and temperature of the thermocline. What kind of units work best? Can I lower it on my downrigger and bring it up for the reading? Are they wireless? portable? Any help, recommendations, price or websites would be appreciated. Thanks

[Thagstrom]

spider,
Yes there is a unit that will tell you the exact temp at the downrigger ball. A buddy of mine used to have one until it got caught on the bottom of Michigan. I have seen them around in a magazine or two. I will see if I can locate one for. I will be guiding though for the next week and will be tough for me to get back to you. Pester me so I don't forget.
esoxtacklebox@cs.com

Terry
Terry's Guide Service

[Ray]

Spider,
The unit I recommend, is the Fish Mate. It is made by a Rochester, NY engineer. It's an item that's not on the market. You have to talk to the guy and he will build one for you. I've had mine now for 11 years, and have had no problems. How this unit works, is through the downrigger cable you get with the unit. There is a thermister on the end of it. I will try and find the guy's name and address and I will e:mail you. There's another unit on the market, that is the same as the Fish Mate. It is made by Walker. This Walker is the same and works the same way. You can hook a downrigger release on it and have a continous readout. There is Fishhawk, an excellent unit, if you want to spend all that money. They have a portable one that you hook on to your downrigger cable and lower down and this will give you a reading. That kind of system is only good if you want to check the temperature on the spot. The thermocline changes from hour to hour if you have a wind that turns the water over.

[cisco]

I don't know if the FishHawk I own is still available, but it is a portable unit run by 9v batteries and spools 200 feet of rubber coated wire -- I lower it over the side with a pound ball attached and get both temp and light readings at any depth I want, simply by pressing a toggle switch right or left (temp or light). It is a great unit and one I've used for over 25 years.

If under power, I can run it down with a downrigger weight, but care has to be taken when doing so (you don't want a rubber coated wire wrapped around a wire cable).

Incidentally, I could care less about the thermocline -- I look for upper and lower avoidance temps for the species I'm seeking. FishHawk gives the info needed.

Good luck.

[Jenn- WI]

Hi...
Just curious....what is unique about the units you mention here? The thermocline is going to be the location where the significant temperature change occurs, so why not just use a temperature probe? I may be missing something I guess....but when I took some limnology and aquatic ecology field courses, I remember we'd locate the thermocline just by doing temperature readings in the water column at meter intervals until we graphed the significant change in water temp...
Thanks for the help/ info
Jenn

[cisco]

In Lake Michigan the search for a thermocline is largely meaningless in regard to fish location. Salmonids can and do live in two and three story lakes -- those with more than one thermocline. Also, the sheer size of the lake gives rise to thermobars, which, stated simply, are vertical thermoclines.

On inland lakes there is often insufficient oxygen below the thermocline for the popular sportfish. Not so on Lake Michigan. On that body of water it is more important to find the preferred temps for the species sought. Preferred temps fall between the so-called upper avoidance and lower-avoidance temps, or upper and lower limits. But, an important variable to toss in is the presence of forage. If the food is in 65 degree water, king salmon will go there even tho they prefer to stay in temps below 60 degrees.

By and large, the thermocline will be the lower limit for sport fish in Minnesota lakes that have them -- I say that have them, because a lake such as Mille Lacs, for example, will most often be too mixed by wind to stratify to the extent it has a thermocline. That does not mean there will be no temp difference between top and bottom, but the lake does not "layer" into a relatively stable configuration.