Types Of Water

Fish live in an overwhelming number and type of aquatic communities throughout North America. The word community is a good description because it suggests they adapt to and function within their local neighborhoods. Life in distant yet similar communities might be pretty much the same, although if the circumstances were radically different, the fish would have no choice but to adapt as best they could.

Let’s look at the major classifications of waters in which fish live. Each could be broken down into many subdivisions, but we’ll try to keep things a straightforward as possible, at least to begin.

Natural Lakes—Natural lakes are what they sound like: waters created by Mother Nature, rather than by man. In many areas they are the result of glacial activity countless thousands of years ago, with glacial expansion first grinding out holes and valleys and depositing loose materials at the leading edge of glacial movement, later followed by meltwater from receding glaciers filling the pockmarked landscape. Over the intervening centuries, these waters have been further modified by erosion, siltation and other natural processes, along with experiencing the effects of man.

Lakes fall within the infertile-moderately fertile-overly fertile spectrum, depending upon their location. This recalls our Goldilocks principle of lakes being deep, rocky and cold at one end of the spectrum; shallow, fertile and warm at the extreme opposite end; with the rest lying somewhere in the middle. In general, the farther you proceed northward across the border between the upper U. S. and Canada, natural lakes become cooler and less fertile, although they often still host excellent fishing. Much farther south, they tend to be shallow and warm and often excessively fertile. In between, in a broad area often termed the natural lake belt, modestly fertile lakes predominate, offering a wide range of excellent fishing opportunities. Thus lakes of the far north tend to host coldwater fish like lake trout, those of the far south warmwater species like catfish, and in between, a wide range of others.

In each case, local habitat determines what species naturally occur. In lakes that are a bit cool, relatively clear, with plenty of rock and some weeds, species like pike and walleyes often predominate, along with bass. In lakes that tend to be shallower and weedier, perhaps a touch warmer and more fertile, bass tend to be the major predators. Yet there are many waters that host a varied population of major gamefish, largely because these species are so versatile and adaptable that they can make due in a wide range of waters, often prospering.

Natural lakes might be spring-fed, and be largely isolated fish communities. They might primarily be the result of regional drainage with small creeks or rivers flowing through them, with fish movement possible in or out of one lake into another. Or a combination of both. Some lakes are mostly natural widenings of river systems, with the effects of current subtle and subdued. Even the massive Great Lakes system separating the northeastern U. S. from southeastern Canada is, in effect, a network of huge natural lakes connected by rivers. Suffice it to say that the area where you live determines the types of lakes present, and all lakes are not equal.

Rivers—Where lakes tend to be rather localized environments, rivers are best viewed in stretches because, after all, they flow across vast distances, joining with other rivers to create mighty waterways on their relentless journey to the ocean. Rivers start out as numerous tiny creeks and streams, until the accumulation of flowing water becomes large enough to warrant the river designation. Thus the size and flow of a river changes the further along its path.

Each stretch of river tends to take on the characteristics of the local landform as well. Rivers flowing through rocky terrain often tend to be swift and rocky and cool, favoring species like trout or smallmouth bass or walleyes. Yet other sections of the same river flowing through slow-moving weedy areas might better host largemouth bass or catfish. Thus rivers tend to be very diverse fish communities, hosting many different species in various stretches.

For communication purposes, we tend to view rivers as moving from young on the cool and rocky end of the spectrum, more like creeks and streams, to old at the shallow, broad, fertile end of their journeys. Young meaning where they begin their lives (originate), and old meaning they’re drawing toward their eventual ends. In between lie stages like adult or middle-aged, whose landform generally reflects the types of fish you’ll find in those stretches. An adult river stretch might favor smallmouths or muskies, for example, while a middle-aged is great for walleyes, with some overlap of course.

Since we’ve mentioned age, we’ll risk tossing a couple more scientific terms at you, although once again you needn’t memorize them. Lakes are similarly viewed in this age scenario as well. Scientists refer to young, infertile lakes as oligotrophic; middle-aged, moderately fertile lakes as mesotrophic; and old, very fertile waters as eutrophic. The main difference between the aging processes in lake and rivers is that rivers age by both stretch and time, while lakes just plain get older over time. Those lying farther south have simply experienced many more years of erosion and siltation than northern waters that once lay beneath mile-thick canopies of glacial ice.

Farther-north lakes thus tend to be viewed as being geologically younger, while those lying more to the south are considered older. Really old lakes nearing the end of their lifespan often become swamplike in nature.

The wild card, of course, is man, and the aging affects of pollution, habitat destruction and the like. Unfortunately, man can drastically accelerate the aging process, triggering in decades changes that would otherwise take thousands of years. As habitats change, so do fish populations, and of course the fishing.

For the record, we classify reservoirs into several major designations according to their landform prior to flooding: lowland/swampland, flatland, hill-land, highland, plateau, and canyon. Hey, those names don’t sound like lakes, do they? Nope. They get their names from the type of terrain that was flooded. If you think of it in those terms, you’ll understand what’s beneath the surface, because you can usually see good examples of what the lake bottom looks like simply by viewing the surrounding shorelines. Points and ridges run out into deep water. Are they steep-sided or gradually sloping? Creek channels and gullies entering the lake extend out into the basin. Visualize the lake bottom in your mind’s eye, and you can begin predicting where fish might be as well.