Everyone knows water temp is a big factor in fishing. I was wondering, why do people measure the water's surface temp and not measure the water deeper down? I mean the fish aren't that close to the surface, so why not see the temp at the depth they are at...

What you are saying makes sense, but would require different types of equipment to get those readings. Surface temp is just a reference, and is rarely the actual temp our lure is sitting in.

I have one of these. I just hook a weight on the end and sink it down. I have the cord marked at every foot and it really helps. It also helps me match the temperature in my livewell to the temperature at the depth where the fish were.

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Surface temp is easy to build into a transducer or add to a transom so I guess it is just convient but it will help get you to the best water temp to fish. I take the temp at 5 feet and 10 feet and the surface.

Like Shane says, when you watch the water temperature you are gaging a reference only. However, it's a pretty decent piece of information to have and predict, fairly accurately, the mood of the fish.

Most anglers are shallow water anglers so they tend to worry about surface temp more. I have a hand held temp gage that I use myself that I can drop down to whatever depth I choose. Also have the wire marked off every 2 ft so I know what depth I am marking.

Back in the dark ages (about 40 years ago) temperature probes on a 50' weighted cable with 5' markers (Dark Industries) were commonly used to measure water tempatures at various depths. We did this for a few reasons; determine the thermocline depth and to locate springs; warmer winter water or cooler summer water. Place the cylinder probe in the basses throat to determine the water temperature where the bass was located when caught; how deep was the bass holding.

Today we have very accurate sonar units that can determine the thermocline depth without a temperature probe and return fish signals close to the bottom or in cover; we can see the bass and bait fish.

The bass haven't changed, they are still cold blooded animals that have a preferred temperature range. Today very accurate digital temperature probes are available with weighted cables and I use them and measure bass body temps on occasion to determine preferred locations.

Tom