When we read the tourney recaps like Mark Rose's win this past weekend on Pickwick, we see he won fishing 25 foot of water. A couple weeks previous, Lloyd Pickett, Jr. won the EverStart event on the same body of water fishing 35 foot deep. Read all the recommendations on the major fishing sites at the moment and you'll see stories about ledge fishing. Naturally, with all this talk, the first inclination for many is to go out and try and find deep fish here in Indiana. That's not always the best move for many of our lakes.
In Part I, we covered the biology around what is happening in our lakes during the summertime. Let's take a little closer look now at what is happening, and why going shallower and not deeper is frequently the right move as the summer heat sets in for both the bass and the bass angler.
If you go to the Army Corp of Engineers website and check out the water temperature and oxygen profiles for our major reservoirs, you'll see something very similar to the one at left (Cataract - 7/26/11). One of the first things you'll notice is that there is no oxygen in the water column below 15', which obviously becomes a big problem if you're looking to find bass in deep water. What's going on?
Our reservoirs are just starting to set up thermoclines. You combine this with high nutrient loads, stained to murky water made even more so by algal blooms (remember the self shading concept?), and high water temps., and you end up with shallow light penetration that means deep water respiration and decomposition "sucking up" all the available oxygen.
Another difference between say, the TVA reservoirs and ourselves is that those reservoirs are primarily used for power generation, and so you have a steady pull of water through the primary and bypass gates which helps keep the whole water column mixed up and stable, stable in this sense being less likely to thermocline and set up into stratified layers. It's along the same principle as to why river systems so rarely develop thermoclines.
So lack of oxygen in the depths is the first significant hurdle - in many cases our fish simply can't go that deep and live for any length of time. But there's another factor going on that contributes to this shallow bite phenomena. Remember the graph to the right from Part I? This was taken from an incoming river to one of my local reservoirs. What you'll see is that during the day when the sun is out and the heat is on, the algae in the water are actually cranking out tons of O2, raising the oxygen level as high as 10-14 ppm. The same basic thing is also happening in the reservoir in the form of supersaturation, where the surface (shallowest) layer has the highest oxygen in the lake, and dropping as you move down through the water column.
Additionally, the main lake has all the pleasure boat traffic and wind/wave action which is helping to create more oxygen infusion into the water where the air/water surface interface is the greatest. It also sets up for very strong currents in the top 5'-10' of water, again helping to keep everything mixed up. In essence it creates an artificial current situation.
So bass being the adaptable creatures they are, and not having a particular issue with warm water temperatures in and of themselves, will find that in many cases, the shallower they go, the more conducive conditions actually are for their survival. Lots of their food base is still shallow in the form of young-of-the-year fish, and in many cases there is also shade or cover to utilize for resting or foraging. Note also in the first graph that water temps are basically uniform from the surface down to about 12' of water and again, there is no real benefit to be gained by moving deeper.
In Part III, we'll cover what the best available options are for catching bass in the shallows (there is still a method to this madness), as well as look at some recent fishing reports I've received to demonstrate what some anglers are finding right now out on the water.
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