How Does Water Clarity Affect Fish?

two guys holding walleye
The water was definitely clear that year!

At first I thought this was an odd question for so many anglers to be asking, but the more I thought about it the more I realized just how many memories I had directly tired to the clarity or muddiness of water. Sometimes the water was so clear you could see exactly where the large fish were hovering whether in the trout stream or bass sunning themselves in the shallows of the lake. 

Yet those fish weren’t going to bite. Yet there are plenty of fish that old-timer anglers will tell you that you only find in clean clear water.

On the other side we’ve had success fishing dirty and algae choked waters, but although we’ve bragged about our 2019 Lake Erie Walleye Fishing Trip and our 2018 Lake Erie Walleye Fishing Trip (with more to come), however there was one year where in three days we couldn’t catch 10 walleye total over three days – and that was after a Northeaster slammed into the lake and muddied the waters badly.

So water clarity definitely matters! While effects can vary, the clarity of the water can affect how eager fish are to feed, what type of bait or lures will work for fishing, what depth they go to, and even what type of species can be found (or not) locally. Long-term debris can cut down on oxygen levels and heat the water, further driving certain fish away or limiting food supplies.

In other words, water clarity matters a lot for most species of fish. In some cases certain species will straight out refuse to stay in an area where the water clarity isn’t high enough.

While to some degree it just made common sense, the more I really looked into it the more I realized just how much the clarity, aka “turbidity” really does make a difference in how the fish act, and as a result how you have to fish certain bodies of water or certain conditions.

Fish & Turbidity Explained

So here we’re all about making the science simple. A term like “turbidity” can be intimidating for some of us, but referring to it as “science of water clarity” is a lot easier to understand. If you see the term turbidity you’re looking at something having to do with measuring local water clarity.

Basically a good layman’s definition of turbidity is it’s the measurement of how cloudy the water is.

The most important thing to understand about turbidity whether you’re a guide, an angler, or an environmentalist are the following.

#1: Turbid water blocks sunlight

This is the main thing to understand about water being especially turbid is that the sunlight can’t go as far into the water. While some degree of turbidity must exist in most ecosystems, and a little bit isn’t bad, having far too much is when major issues can occur.

#2: Less sunlight means less plant growth

Less plant growth has a sort of domino effect in the water. Less plants mean less oxygen. Less oxygen means even fewer plants and plant life, and a lower ability to provide enough needed oxygen for any fish and other aquatic creatures in the area. 

Less food for the fry, less food for the bait fish, less food for the larger fish.

#3: Less plants means less oxygen

When the water’s clarity levels becomes extremely unbalanced, that can lead to a deadly drop in oxygen in the water. In those extreme situations this can mean mass kill offs of fish either directly from suffocation or from the side effects that come with heavily clouded water that doesn’t clear up or can’t be cleared up.

#4: Water clarity or turbidity affect fish feeding habits

There are some fish that are evolved to be able to search out prey in really muddy waters but most will change their feeding habits based on how clear (or not) the water is. Many fish still use sight as one of the main ways to find food and when a storm comes in and muddies up the water badly or pollution brings a semi-permanent cloud, they have a much harder time feeding.

Being more aggressive doesn’t help the angler if the fish can’t see the lure or bait! Others, notably like black bass, have no problem being aggressive and still thriving in less than ideal water conditions. Check out this fantastic Mythic Lures guide to muddy bass fishing for a really great resource on that topic.

The main point is that the overall measurements of turbidity in water makes a big difference. There are many factors that can affect this measurement and while the numbers will naturally shift as things like heavy boat traffic, a major storm, or seasonal flooding will all change things temporarily, the problems come when the overall water clarity is changed over long periods of time or shifts permanently due to outside influences.

Factors That Affect Water Clarity

These are some of the most common factors that will affect the overall clarity of the water and their turbidity scores. Almost every potential factor will be directly listed here, or it will be caused by one of these specific factors. 

Suspended Sediments

Just like it sounds like, this is chunks of dirt, mud, dust, that sort of earthen debris that gets into the water and just sort of muddies up everything. This can be caused by everything from farm run off to erosion to a large population of carp going on a feeding frenzy from the lake bottom. In other words – anything that drops mud, dirt, and other sediment in the water or kicks it up big time from the bottom.

One major example of this we experienced with this was a trip to Lake Erie four years ago. A Northeaster storm came in (a really, REALLY rare occurrence because of the geography and timing) and the waves and winds stirred up the mud big time and the fishing was horrific for that weekend. You were hard pressed to find anything much

Algae Count

Algae is a natural part of the ecosystem, and in areas that are heavy with fish like white amur or grass carp that eat mostly plant life, they are a very necessary part of the local waters. However, things like phosphorus and nitrogen, elements that are found in common fertilizers and thus end up in the water a lot, can cause absolute explosions of algae.

Too much algae, especially when they are exploding in large unnaturally fueled blooms, can absolutely choke out the environment and block the sunlight from getting down into the water where it’s needed. That can be a serious issue to local fishing areas.

As for large algae blooms that are above the average but not ecosystem threatening, anglers can often attest to how much harder it often is to get the fish to see, and therefore strike, you lure or bait rig.

Natural Color of Water

Some water is naturally greenish in color, some is naturally blue, some tends to be a bit darker or more brackish. In some areas the natural water color is even brown because of local plant life and bogs which can stain the water. Think of the way tea is made and how the steeped leaves in water turns the water a darker color. 

Same basic concept when it comes to the coloration of water. Obviously the darker the natural color, the less sunlight cuts through and the worse the visibility.

Power of Natural Currents

Natural currents not only move things on the surface but they can push up dirt, mud, and sentiment from the bottom of the body of water, as well. A sudden flash flood, long-term flooding, or even a major storm that really pushes the waves can cause currents to strengthen and kick up more muck and more sentiment than normal.

Natural currents are a major part of a water’s natural levels of turbidity.

Man Made Influences

There are plenty of different things that fall under this category, but there is no denying that man has a major impact on the water quality in any given area and that includes how the water looks and how clear (or not) it is. 

Some of these are obvious and big issues like pollution. You dump sewage into the water, that causes plenty of problems. On the other hand even things like a massive swim competition or major use of heavy motorboat traffic can do the same. There’s a reason many bodies of water are much muddier than usual right after July 4th in the U.S.

Just a short list of man-made factors that can change water clarity include:

  • Pollution
  • Fertilizer and/or farm run-off
  • Heavy motorboat traffic
  • Water movement resulting from activity (dams, dikes, irrigation, etc)

Specific Fish Heavily Influenced by Water Clarity

While water clarity is going to have a major effect on a local area’s fishing, keep in mind that there are species of fish designed to thrive in water with low clarity while on the other side of things there are certain species of fish that utterly disdain muddy or sediment heavy water.

Lake trout, for example, tend to be found in cold deep water in part because they despite muddy water. There are multiple game fish where the clarity and the cleanliness makes a huge difference in being able to find where they are and adjust your fishing strategies to reel them in.

Black bass in particular are known for not caring and for being one of the fish where adjusting tactics can lead to good results.

On the other extreme, you have carp that can be found thriving everywhere and will simply feast on the overabundance of plant life and catfish who evolved with the whiskers, which allows them to sense and live (and thrive) in incredibly murky non-clear water.

Depending on what exactly you’re fishing for, the clarity of water might have a huge effect while for others it will have very little. 

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