Downrigger Speed And Temperature
This is quite simple, if you are not using a speed/temp unit, you are either exceptionally good at fishing, or you are not catching as many fish as you could be. I am always amazed at the docks when someone who heard me on the radio, catching fish, comes up to me and says "I was using what you said, and I put it down at the depth you told me, but it did not work". My first question is always is "do you have speed and temp at the ball?" You can guess what the answer is! Without this tool, you just can't tell what the speed of your lure is. I do not think the temperature is as critical because you can see on your graph where the fish are.
However, it will give you a starting point if fish are scattered in different temps. Back to the lure speed. Lake Ontario has currents, sometimes very strong ones. You can be going 3.5 mph at the surface and 1.8mph at the ball, and vice versa. When pulling flashers for fall kings, speed is the most critical factor. Most flashers have a preferred speed, anything other than that and they just don't attract fish. With spoons and plugs this is also true, but it is not as critical as with flashers. The first thing to do is to get yourself a down speed/temp unit. I use a fishhawk 840, I am partial to that unit. It has worked well for me. There are other units on the market, though.
Next, learn what speed your setups work best at. Fish are picky, and knowing what speeds they want will help the cause. Usually for spoons, I run 1.8-3.5 mph, but this will change constantly. One day 1.8-2.2mph will work, and another day 2.5-3.0mph will work. You will need to figure this out. For flashers, usually a E-chip Pro-Troll, Hot Spot or Big Shooter I will run 1.6-2.5mph. Sometimes faster, but not often. Salmon slashers or Kingfishers work best from 1.5-3.5mph. They are probably the most forgiving. One last comment on speed, trust your unit. So many times I have been on other boats and I hear "Oh, that can't be right, no way." Well, it probably was, these units are very accurate. I have seen very large differences between surface and ball speed, especially when the wind is blowing and you have a slide going. So, to reiterate, trust your unit.
As far as temps, 54 degrees is a good starting point. Lakers like 38-44 degree water. Browns like warmer water, 54-57 degrees. Kings and Coho like 44-54 degree water, and Steelhead, well, I really can't say because I have caught them in cold water, 50 degrees, and I have seen them swimming on the surface when the water was in the low 60's. These temps are not always the case, so use your graph to locate fish, then get your speed right at the ball and you will start producing more fish.