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Slight Temperature Variances Influence Fish Movement

In late August and early September, many areas were blessed with substantial rain that brought relief from sweltering, summer temperatures. When recalling your joy, be assured fish also celebrated the welcome change, demonstrated by fish movement.

During prolonged 100-degree days, surface water temperatures can reach 85 to 90-degrees. We seek shade and air conditioning. Fish find comfort in depth and shade from various cover. If such features don’t exist, water temps in shallow lakes may not vary much from surface to bottom.  Such conditions resemble a desert-like environment to aquatic critters. Let’s consider a bass’ reaction.  When water temps reach mid to upper 80’s, they approach what you and I consider a heat stroke.  Add diminished dissolved oxygen rates and fish start to experience symptoms of an ICU patient.

Like us, they explore every nook and cranny looking for a cool spot.  Here’s a great example.  The owner of a large East Texas lake supports cutting-edge research with a leading fisheries biology school in the mid-West.  Graduate students put tracking devices on bass to study movement and general behavior.  Summer studies revealed fascinating discoveries about bass efforts tobeat the heat.  Everyone’s familiar with the thermocline.  For those who aren’t, during warm season months, lake’s stratify.  Somewhere about mid-depth, the upper zone is warmer and contains oxygen.  Below that line, it’s cooler and void of oxygen.  If the lake is 15-feet deep, anticipate the thermocline will occur around

fish movement

Despite low oxygen levels, bass will hold on the thermocline for cooler water temps.

7 to 8-feet (see adjacent illustration).  Of all places, researchers consistently found bass suspended at the thermocline.  Why would they go there?  There’s not much oxygen.  Despite marginal oxygen at the stratification zone, bass adjusted justfor the opportunity to enjoy cooler body temperature. Often, two or three degrees makes a difference.  Remember swimming in a farm pond?  When entering deeper water, you felt noticeably colder temperatures.  That was the thermocline.  Now you know what the bass experienced.

We conduct monthly maintenance for numerous customers.  Service includes monitoring water quality, filling feeders, and related tasks.  September field notes from one lake logged two distinct patterns from feed-trained bass. When investigating, the biologist learned water temperature was 88-degrees in front of a feeder with slow activity.  The site with aggressive feeding was near a drop-off and recorded 85-degrees.  It was only 3-dgreees, but that made a big difference to the fish.  They could suspend in the nearby cooler, deeper pocket until the feeder tossed the next treat.  Like most events, little things make a big difference.  Always flip baits under docks—they provide shade and slightly cooler temperature.

Hopefully, we’re transitioning to Fall.  Through Thanksgiving, observe weekly changes in not only fish behavior, but vegetation, and other areas.  Please enjoy this treasured time.  Walk the shoreline.  Sit on the dock.  Take notes. Those memorable moments with Mother Nature will speak to you if you take a minute to listen.  Fall is time to assess progress or shortcomings of the 2018 season.  One small finding could provide a big dividend in 2019.

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