A temporary cool down in air temperatures brought surface water temperatures down several degrees in most lakes. Warmer air temperatures returned late this week, so surface water temperatures are on the rise again.

It has been difficult to find a consistent pattern for walleyes in most lakes. The best presentations have been something that moves quickly, has several triggers for the fish and has to be fished in the right areas at the right depth.

Electronics are important for anglers’ success at any time of the year in all conditions. The old days of making long drifts or just trolling the edge of the weed beds will usually catch a few fish, but to be consistent, anglers have to be able to use their electronics effectively.

Most guides with good electronics and an advanced ability to use them, will look at the area with sonar before they start fishing. It is hard for most guides to have any confidence in a spot without seeing fish on sonar first.

Most guides want to see something on sonar before stopping the boat, unless they have fished the area recently and have things dialed in enough to be comfortable starting to fish without looking.

Seeing fish isn’t the end of the process. It is possible to see fish on sonar that won’t bite or are very difficult to catch. Most of the inactive or neutral fish have been located off of the sides of structure, while most active fish have been in shallower water in areas with weeds or rocks.

The temporary drop in surface water temperatures should help make the fish a little more comfortable during the day and set back the clocks a little bit for the fish. There is still plenty of time for another spike in water temperatures, so stay tuned.

There are lots of factors that can negatively affect the cold water species in the lakes. It is not just maximum water temperatures that can cause a summer-kill. The temperatures don’t have to exceed 80 degrees to kill fish, although that is certainly one way it can happen.

There can also be a summer-kill when water temperatures stay in the mid-70s for an unusually long period of time, which is the most likely scenario most years.

It it is a complicated and inexact combination of factors that are causing both short and long range problems for the cold water species living in the local lakes.

There are different types of lakes in the Bemidji area that act differently during periods of high water temperatures. The differences are based on the amount of deep water in the lake.

Lakes with only small amounts of water deeper than 40 feet with enough surface area will periodically turn-over the entire water column during extended periods of high winds.

The deep lakes act differently during the summer and will stratify by temperature and form a thermocline. A thermocline is simply the narrow band of water that separates the warm water from the cold water in the lakes.

The water above and below the thermocline stop mixing by definition, so water below the thermocline can eventually run low on oxygen to the point where most fish have to move above the thermocline to survive.

Water above the thermocline still has oxygen added to the water from wave action, springs and weed growth that creates oxygen. The problem for cold water species is the water above the thermocline may be too warm for them.

Large bays can act just like individual lakes. Big Traverse Bay on Lake of the Woods and Upper Red Lake are prime examples of large shallow bodies of water with no thermocline.

Lake of the Woods and Upper Red Lake have the hottest walleye bites in the area and have had the hottest bites most of the summer. Many walleyes are in the deeper parts of the lakes, with walleyes looking for the coolest water possible.

Most anglers have been using bottom bouncers and spinners with nightcrawlers or crankbaits trolled at the proper depths for walleyes.

Paul A. Nelson runs the Bemidji Area Lakes Guide Service. He can be contacted by calling or texting 218-760-7751 or by email at panelsonbemidji@gmail.com