Littoral Zone #14 - How Lakes Work with Brian Chan and Phil Rowley

Wet Fly Swing Fly Fishing Podcast

#708 Show Notes: https://wetflyswing.com/708

Presented By: TroutRoutes, On DeMark Lodge, Stonefly Nets, Grand Teton Fly Fishing

If you want to have more success fly fishing lakes, you need a good understanding of how lakes work—knowing how lakes work helps you get to the right spot at the right time, no matter the season.

You’ve probably heard the saying that 90% of the fish live in 10% of the water, and it’s true for lakes just like rivers and streams!

In this two-part series on how lakes work, Phil Rowley and Brian Chan break down everything you need to know about fishing lakes effectively.

About our Guest

Brian has spent over 30 years as a fisheries biologist for the provincial government, specializing in managing trout lakes in the interior regions of British Columbia. Over the years, he worked on hundreds of lakes, managing them, stocking them, setting regulations, and carrying out habitat protection and enhancement work.

Brian is also an ambassador for several fly fishing and boating companies, including Scientific Anglers, Sage Fly Rods, Islander Reels, Marlin Boats, Semperfli Fly Tying Materials, and Daiichi Hooks.

He is a passionate fly fisher and fly designer, and together with Phil, they’ve put their expertise to good use through their online fly shop.

Check out Brian and Phil's Stillwater Fly Fishing Store.

Episode Chapters with Brian Chan on How Lakes Work

Lakes aren’t all the same, and knowing how they work is key to becoming a better stillwater angler. Here’s what you’ll learn in this episode:

Lake Productivity and pH

Three Lake Classifications

Different Zones in a Lake

Lake Productivity and pH

pH is a scale that measures how acidic or alkaline a lake is, with 1 being super acidic and 14 being super alkaline. The pH level affects the water chemistry, impacting how well the lake supports aquatic life, from insects to fish.

What’s the Ideal pH for Trout Lakes?

The best pH for trout lakes is between 8 and 9.2. This is the sweet spot for plant growth and lots of invertebrates, which are food for trout. If the pH exceeds 9.2, the water becomes too salty for trout, and it would not be easy for them to survive.

For example, lakes like Pyramid Lake have a pH above 9, which is perfect for Lahontan cutthroat trout but challenging for rainbow trout. The pH scale is logarithmic, meaning small changes in pH can make a big difference in fish survival.

Brian explains that pH levels in lakes aren’t always the same and can change over time due to several factors:

Spring snowmelt helps keep lakes balanced by flushing in nutrients, but the lake can get too salty without it.

Human activities like logging can change water flow and impact the lake’s chemistry.

Climate change is also a significant factor, as some areas aren’t getting the same snowmelt they used to, causing pH to rise.

Marl and Chara Shoal

How Lakes Work: Three Lake Classifications

Lakes can be divided into three categories: oligotrophic, mesotrophic, and eutrophic. These classifications help us understand which lakes are better for fishing and support healthy fish populations.

Knowing the type of lake helps anglers figure out why one lake might be an excellent spot for big trout, and another might not be as productive.

Oligotrophic Lakes

Oligotrophic lakes are big, deep, and well-oxygenated, with lots of water flowing in and out. The flushing rate in these lakes is high, meaning the water changes quickly, so there isn’t much shallow water for plants to grow.

Because of this, these lakes have limited food sources for trout. Fish here mostly survive by eating other fish, not just insects.

Mesotrophic Lakes

Mesotrophic lakes are a step up from oligotrophic lakes in terms of productivity. They’re still large but a bit shallower, and they often have small rivers or creeks flowing in and out. The lake has a bit more shoal areas or littoral zones, so some plant life grows in those shallow water areas.

Eutrophic Lakes

Eutrophic lakes are the gold standard when it comes to trout fishing. They’re shallow, nutrient-rich, and full of life. These lakes are often less than 50-60 feet deep and have lots of shallow areas for plants to grow.

These lakes' flushing rate is slow, so they stay nutrient-rich for longer. Chironomid fishing is also incredible here due to the muddy bottoms.

Different Zones in a Lake

Lakes have different zones, and understanding them helps anglers know where to fish at various times of the year.

Littoral Zone

The littoral zone, or shoal area, is the shallow water at the lake's edge. This is where sunlight can penetrate to the bottom to create photosynthesis. It’s usually 7 to 8 meters deep.

The littoral zone is where all the vegetation grows and where trout and other fish species feed, particularly in the spring to early summer and again in the fall, right until freeze-up.

This is the zone where we spend the bulk of our fishing time—whether it's 5 feet of water or 22, 23 feet of water—this is the prime area.

Limnetic Zone

The limnetic zone is the open water area in the middle of the lake, just beyond the littoral zone. Here, sunlight still penetrates, but it doesn’t reach the bottom. This means there’s no vegetation growing like in the shallows, but it’s still a prime habitat for zooplankton, which trout love to eat.

Although this zone has less food diversity, the zooplankton and deep-water hatches make it an essential spot for fish. In the warmer months, fish move out of the shallow water and into the limnetic zone, where the oxygen levels are better and the water is cooler. This is when fishing techniques like using blob patterns can be incredibly effective.

Thermocline

The thermocline is a transition layer between the warm upper water and cooler deeper water. It’s usually a narrow band, about a meter in depth, where there's a sudden drop in temperature.

The thermocline keeps the colder water from mixing with the warmer water, which is why the deeper parts of the lake stay cool and oxygenated. Fish often move from the shallow waters to sit just above the thermocline, where they find cooler water and better oxygen levels, especially during hot summer months.

Profundal Zone

Beneath the thermocline in deeper lakes, there’s another zone called the hypolimnion, the cold, deep water layer. It's the bottom part of the lake that remains cool and doesn’t mix with the warmer upper waters

Remember, all lakes are different, but understanding lake structure makes your fishing day more successful and enjoyable! Show Notes: https://wetflyswing.com/708