Water Clarity and Temperature FYI

Here's my FYI again (every season about now) for the topic of water clarity and "where the fish are" at any particular place.

I'm a scuba diver and have dove the Lake in various places in May and June. The Western Basin has a thermocline up until around early-mid to late June, depending on the season and location. It moves down the water column as the surface waters warm and winds / currents mix the waters. Just because the water clarity is X at the surface doesn't mean it's like that all the way through the water column down to the bottom. The transition from the warmer water near the surface and the colder water near the bottom can be drastic, from 55-65 degrees at the surface to 45 degrees on the bottom. I've personally seen / felt this while diving. Once in mid June I was at a spot where the bottom 8-12 inches were much colder than above, way colder. I was hanging there 3-4 feet off the bottom in 60 degree water, and would reach my hand down to the bottom. As soon as my fingers / hand hit that colder water it was like sticking your hand in a cooler full of cold water to get a beverage. Really striking.

The point here is right now through sometime in June the water column is going to have significant temperature and clarity differences. I've seen three or four different water clarities in one column of water, top to bottom. I've seen both clear on the surface and murky near the bottom and murky at the surface and clear near the bottom. You can't truly judge the water clarity down the water column by looking at the surface 5-6 feet.

What you are really looking for is the combination of clarity and temperature. The big E-NE-N-NW blow we had last week probably played havoc with the thermoclines / water temperatures and clarities throughout the Western Basin, surface and below. The surface wave push forced a lot of warmer water to the bottom along the southern shoreline and pushed the responding opposite currents to move a lot of the lower water column around out in the Lake. A lot of mixing. I have little doubt over the next 4-5 days there are some places out there where you have 2-3-4 significantly different water temperatures in one column of water. The thermocline is probably about half way up in most places deeper than say 18-20 feet, no doubt in 25+ deep areas. You could see vertical lines of clarity difference in the satellite images the last few days - razor thin vertical lines between muddy and clear water zones.

I’ve seen this underwater horizontally, crisp definitive lines between clarities. Running a lure just one or two feet higher or lower can put you above or below that line.

This week and coming weekend I'd be looking for those transitions, but always keep in mind the water depth you are running lures at may not be the same clarity and/or temperature as the surface. Just because the surface is still murky or in the more murky area of the "stained" category doesn't mean there won't be walleye there, down in a clearer horizontal layer of water. This is especially possible in areas of significant currents and current transitions, which may not be visible or detectible at the surface.

Wow... thanks!

Great info. I think we have all felt the warm or cold spot at beach some time in life, just another similar situation

Thanks for that great info.Now I'm really confused on where to fish.All we can go by is what we see at the surface.So if too muddy to see your lure more than a few inches we move on.You say may be cleaner water down and catchable fish there.I know the walleye like the cloudy days.I wonder if the fish find some muddy water near surface to cut down the light and feed in cleaner water under it.I asked Pooh bear about locations to fish and he said could not catch anything in the clean water last month?Interesting.

I surprisingly am less confused where to fish in a certain sense. Makes it an easier decision to move on if one location isn't producing that you think should be or maybe slow down and cruise through some spots you might not think are great and check the finder. Also makes me wonder about underwater ice fishing cameras lol. Great info again.

Addition to the FYI - A few fish finding tips when water thermoclines and clarity are in play, now through mid-to-late June:

When the winds blow hard and/or lots of muddy river water flows in, the shallow areas near shore are probably at or near the same temperature and clarity, top to bottom. You will usually see the big muddy areas in these locations on the satellite photos. The colder, denser waters out in the deeper areas don’t mix easily with this warmer water. The warmer water will sometimes ride up over the colder water when currents push them together. They also begin to mix, bringing the water temperature closer together. Similar to slowly pouring warm water into a glass half filled with cold water; the middle of the glass mixes but the bottom stays pretty much cold.

All this current pushing and mixing causes the various areas of water to move and change. Sunlight also warms the water and drives temperature change.

Look for the clarity transitions, especially in areas near shallow to deep water transitions. Currents along these depth transitions can cause several different water clarities and temperatures down the water column. It is these areas that will usually provide the clarity and temperature the walleye prefer at the time. You have to trial and error to find that area and depth. Few fisherman do this anymore, but rig up a thermometer line. Weight at the bottom, then a (waterproof) thermometer tied off from a foot above the bottom every 5 feet up to a foot below the surface. When you pick your first fishing location, drop the line over adjusted for the depth and start fishing. Five minutes later pull up the line and quickly read the thermometer temperatures and write them down. If you see a significant temperature difference between two thermometers (say 55 degrees at 15 feet and 50 degrees at 20), try keeping your lure just above the cooler temperature, or just under the warmer one, and target that layer of water in the water column. You can also use one thermometer, just start at the bottom and read it every 3 minutes, dropping it back down 5 feet shallower each time (one thermometer takes longer but gives you the option to check any depth). If you have multiple temperature differences, try each layer in turn until you find the depth the walleye are at.

If you do this at several locations, you can start to build an area water column temperature map, which can give you an idea of where to move next if no locations so far are producing walleye.

Another thing to keep in mind is a walleye can swim a long way in a short time. A school of walleye can cover well over half the Western Basin (15 miles) in half a day. It doesn’t take that school long to find conditions they prefer at the moment. You may not be marking or catching any at spot A at 8am, but if the conditions change at that location by 3-4pm, it may now be holding walleye. If the fish stay in the water they prefer they will travel within it, moving with the current or circling/swimming around. If you catch them at spot A on Friday memorize the surface clarity and the temperature/depth at which you caught them. On Saturday (same time) look for the same surface clarity, or close, with the same depth temperature you caught them at on Friday. Start there, even if it’s miles away from the Friday spot. It usually takes walleye a few days to transition from one water preference to another when thermoclines are involved, so good water is usually good for multiple days.