Trolling for salmon (and trout) is a complex game. Currents, temperatures, depths, speeds, colors....they all play a factor in having a great day or stinking up the box.
A common thread amongst salmon and walleye trollers particularly on the Great Lakes is a fixation on down speed and down temperature as a be-all-end-all key to success.
There are a number of probe type devices that can attach to your lines or lures that can transmit this information in real time to the boat. Those devices DO help provide valuable information, but in our opinion are far too heavily relied upon and often to the detriment of fishing success.
Let's first talk about speed. Trolling speed is a funny thing, and while it can make or break a fishing trip (it's the most important factor in our opinion outside of fishing where the fish are), it's an often misunderstood variable.
First, Speed Over Ground (SOG) as measured by your GPS device mounted to your boat (Chartplotter, etc). This measures your exact speed as you move over ground...as if there were no water between you and the ground. Think of the MPH gauge on your car or truck.
Down speed, as measured by a probe device deployed on a downrigger or your fishing line, is the measurement of the speed your lure is moving through the water. The includes your speed over ground and any currents. Remember, currents flow in a direction, and that direction could be "cross cutting" your direction of troll, or you could be trolling directly into the current, or trolling directly with the current. These currents, when present, and particularly when FAST, can dictate the action of your lure.
Example, if you are going too slow...i.e. slower than the current, and you are trolling in the same direction as the current, your lures are actually doing nothing in terms of action. They are barely moving...you are going to slow.
The thing about current however, is that it ALSO has an impact on your boats movement through the water. Have you ever noticed when driving back to port that you sometimes have to constantly correct your steering to get where you want to go? That is because the current is "pushing" or sliding your boat in the direction of which it is flowing. This is particularly noticeable when you are set on autopilot and heading out or back to port. Your chartplotter is saying you should be taking let's say a 270 degree "bearing" back to port, but your bow is "heading" on a 290 degree angle. You still make it back to port, but your autopilot is compensating for the current "pushing" you 20 degrees one way or another from your true heading back to port.
This concept can also be applied to trolling speed. We as a personal note ALWAYS and ONLY measure our trolling speed by Speed Over Ground (SOG) on our chartplotter. We don't care what the current is doing down below, we just adjust our throttles to always make sure that our Speed Over Ground is where we want it to be. For the most part it is 2.7 mph (we will get into that shortly). So again, you may have noticed if you do this (trying to maintain a particular speed over ground) that when you change trolling directions you often have to adjust the throttle to maintain that particular speed. Why? Because the current is either pushing you (throttle back) or you are trolling into the current (throttle up).
We notice this frequently when trolling in a certain direction (with the current) we have to almost adjust the throttle to idle speed just to get slow enough. And then we turn around (into the current) we have to increase the throttle dramatically in order to maintain our speed over ground..because the current is pushing against us.
Knowing this tells us how strong the current is. If we REALLY have to back off the throttle, or REALLY increase the throttle in a particular direction, that tells us that there is strong current.
Back to why we almost always and exclusively troll 2.7 GPS Speed Over Ground. Rarely anywhere in the Great Lakes (where we fish) does the current flow faster than 2.5 mph or so in normal fishable conditions. Sure, during storms the current is raging and the water could be moving 3-6 knots. But in calmer fishable conditions, the current rarely if ever flows that fast, and is typically in the low 2 knot or mph range. Thats just the way it is...we have measured it in neutral with a down speed probe and have rarely ever seen a reading over that level.
Knowing this, we found that if we trolled at least 2.7 mph Speed Over Ground...we (not the current) always dictated the speed. Whether we are going with the current, or into the current, whichever direction...as long as we did 2.7 Speed Over Ground we would always be going faster than the current, therefore we had a consistent trolling speed of which we could base our trolling program off of.
So..what does that mean? We call it "speeds and leads". Your average trolling speed for your program should always be consistent. You can't be a "slow guy" and then a "fast guy" and then a "slow guy" again. You need to pick one and stick with it...this will dictate the length of your leads off your downriggers, your diver leaders, and your fly and meat rig leaders. Doing this will maintain consistency in your trolling program and production.
We chose to be "fast guys" for reasons stated above. We always want to be in control of our speed, regardless of the current. As long as we go 2.7 or faster, it doesn't matter what the current is doing..we are still going 2.7 mph. If the down current is 2 mph, our lures are still moving at 2.7. If the down current is .5 mph, we are still moving at 2.7. If the down current is 2.6, we are still moving at 2.7.
Based off this, we have dialed in our downrigger and diver leader lengths, as well as our fly and meat rig leader lengths to perform optimally at that speed (2.7). Over years of testing, certain leader lengths produce the best at this speed, and everything we tie is the same length...we mean everything. There is no "eyeballing it" when it comes to downrigger and diver leads, or fly leaders....its always the exact same on the dot every time.
This allows us to be extremely consistent day after day, we know our program is optimum and completely dialed in for our particular speed. Now, the program still works at speeds up to and slightly over 3 mph, and it will still pull fish slightly slower, but it works best at 2.7 mph.
Circling back to the first statement in this article...speed is a funny thing. You can talk to five guys out fishing and get five different "speed" measurements. Some guy is talking GPS speed, some guy is talking probe speed, some guy is going with the current, some guy is going into the current. To make it worse, some guys units (Chartplotters and probes) measure differently. We have trolled right next to a guy with a different chartplotter and he says his GPS speed is 3 tenths faster or slower than our unit says.
So....DON'T EVER ASK ANYONE ELSE WHAT SPEED THEY ARE GOING. There are WAY too many variables as discussed above, and you could be trying to duplicate a program that is being measured in a completely different way than what your boat is doing. Point here...figure out your speed, always troll it regardless of direction, and set your "leads" to match your "speed". Again...we like 2.7 (and alot of other tournament/charter capts do too!)
There is ONE exception to our 2.7 Speed over Ground rule...and that is when there is NO current. You know the days...flat calm, nobody is catching shit, just slow as hell. In that particular situation we go slow as hell! We are talking like 1.8 Speed over Ground, for salmon (kings and coho). This water is stagnant, very little to zero oxygenation...just bad water. If there are fish still here (and sometimes there is, particularly coho as they don't seem to mind it) we just flat out crawl. If you are a walleye troller, you will love it. For the rest of us it's like slitting our wrists with a plastic knife, but it can and does produce. You may have to adjust your "leads" in this situation, tighter to the downrigger ball works well.
And as for Lake Trout, the faster the better. 2.7 is where it starts, 3.0 crushes the big boys. In fact, the fastest we have ever trolled on the great lakes was 4.5 Speed Over Ground, we caught 15 Lake Trout. Suspended to be sure, it would be too hard to bounce bottom with our balls. We cranked our heavy divers as tight as we could, the rods were PINNED back with the drags cranked. We knew the fish were about 30' down, so we ran 400' coppers which of course at that speed were WAY higher than they would be at normal speeds. This was an all spoon program, Michigan Stingers flattened with no bend. We were trying for steelhead that day (and all we caught were Lake Trout). The Lake Trout would just not bite at slower 2.5-3.5 speeds. We covered 20+ miles that day trolling...great day. But on a "regular" lake trout day, it's 2.7 to 3.0 Speed Over Ground. And we aren't running spoons, or metal dodgers, and certainly not cowbells!
Temperature. Temp is an easy one. In the spring, down temp is worthless. It's all cold...very cold. 90% of your fish will be in the top 30 feet of the water column feeding. Put every rod you have in that zone and work on finding fish in the lake, forget about down temp. Surface temp breaks are nice to find, but often rare to find. We look more at water color differences in the spring, rather than temperature differences. Though you will often find water color changes line up with temperature breaks.
In the mid summer, you can make a case for down temp. The lake has finally set up with a thermocline and there is a fairly distinct difference in temperature. No secret that fish and baitfish like to hang here...but not always. The bait likes it warm (higher above the thermocline), the fish like to digest colder (below the thermocline). So if you only fish at the thermocline, you are only targeting fish moving from below the thermocline to above the thermocline to feed. Why would you want to do that?
Always run a couple rods higher up in the water column to keep fish honest. The bait lives here, and predators will come here to feed..so run something higher up always.
Always run a couple rods lower in the water column. Fish spend the least amount of time feeding and the most amount of time digesting...in cold water. Even though fish are done "feeding" on the bait up high in the water column, it doesn't mean they won't take a snack swimming by in the cold water much lower than the thermocline.
So this goes back to blowing up the "ideal target temperature". There isn't one, its completely useless. Fish feed all over the water column, just at different times during the day. Make sure you adjust and cover the entire water column and you will pick up more fish than you think.
You need a probe to tell you where the thermocline is? Why? You can probably see it on your depth sounder if its dramatic enough...it looks like a fuzzy line. Or, just put your spread out covering the entire water column and let the fish tell you where they are currently feeding. If your high stuff (out of temp) rods are going, put more up there. If they shut down, take them out and put more low stuff down. Let the fish tell you where they are feeding, don't ever just assume it's at a particular temperature or at the thermocline.
Later summer and temperature. Okay, let's talk about staging kings. All bets are off, and they can be caught in 75 degree water, and 45 degree water....depending on their stage of maturity.
Kings will come in waves as they get ready to run the rivers. Some are early (late July) some are late (into September). So...and early runner starting in late July is thinking about the river. He or She is mature, they have the urge, they know the river they are about to run is about 75 degrees (not exactly, but they know it's going to be warm).
Kings begin to warm themselves up and acclimate themselves to warmer temps as they get ready to run. We catch MORE kings out of temperature (60 degrees plus) during late summer and fall...then at any other temperature throughout the year. The majority of the kings we catch in August in September are caught out of 63 degree plus water. But..there's a catch.
We are targeting the staging fish. We are not way offshore fishing deep cold water kings that have no inclination to run the river until late September. They aren't ready yet. Sure you can catch these cold water immature dwellers, but why? The big staging feeders are closer to shore and aggressive in the warmer water.
Now these stagers may run the river, and the "not ready yet" fish are still not ready yet, and we may charge offshore and fish deep and cold until they start to look for warm water. But you have to pay attention to fish migration, and coloration of fish, and realize when they are gone, they are gone. Time to back out deep and find the next wave waiting to come in.
And we say staging, we aren't talking about trolling in front of the pierheads, we are talking about catching mature "sun tan" kings on 100 and 150 coppers over 140-200 feet of water. WAY out of temperature.
And the great thing about these stagers, is once they come into the warm water, they like to stay in it. They may not all feed all the time, but they don't go back down and hang out in the ice water. They are committed to acclimating themselves to the warmer water because they know its time to run.
So...tell us again why you need to know exactly what your down speed is and what the temp at the ball is? It just doesn't make sense to us. Nice information to have? Sure... Critical can't leave the dock without it kind of information? Not a chance..
The next time you stroll the dock and check out the charter fleet you will notice a few (not all, not even the majority) of captains don't have a probe attached to a downrigger before they are going out. Sure, they could be storing it and putting it out later...but many times it never comes out at all. It's alot of times a lemming mentality "he's got it, I got to have it". Learn to fish without it and you WILL catch more fish.