There are many lakes, and many different kinds of lakes in British Columbia. We have so many lakes that they are almost uncountable: the number is somewhere in the tens of thousands. Some lakes are large, very deep and very cold all year round. Some are small and shallow, and make great places to swim on hot summer days. And others, although they are small are very deep, with almost no beaches or shorelines.

The type of lake, where it is located and what rivers drain them will dictate what type of fish live there. The first step in understanding fish and fishing is to understand the water they live in. To do that, there are several things you need to learn about:

• some basics about freshwater ecosystems: the relationships between living things and the rivers, lakes and streams that we all depend on
• the geology of a lake tells you where lakes come from
• the anatomy of a lake looks at the different parts of a lake, and helps you find the fish
• the seasons of a lake show how a lake changes over a single year
• the life span of a lake is about the changes in a lake over centuries and millennia

Freshwater Ecosystems

An ecosystem is a community of living things and their physical environment, the place they live in. Humans are part of an ecosystem. Unless you live in the salty ocean or a perfect desert, you live in a freshwater ecosystem - just one of a huge variety of plants, animals, insects, fungi and microorganisms that depend on fresh water to drink, breathe, grow, move, eat and generally survive.

Food for Thought... If you could be an animal, what kind of animal would you be? Answer: You already are an animal!

Fresh water is what binds a community of plants and animals together. It is the most important nonliving element of the ecosystem that we all share.

Fresh water ecosystems exist in watersheds. A watershed is an area of land in which all the water flows downhill to the same common destination. The watershed of a small stream includes all the land that drains its rainwater, meltwater and groundwater into that stream. The watershed of a great river, like the Fraser, may be huge, including many mountain valleys, lakes, and smaller watersheds that drain into it for hundreds of miles.

Food for Thought... What watershed do you live in?

The Freshwater “Eating System”

Ecosystems are all about complex relationships between living things, but most of those relationships are about eating. One of the basic questions about every ecosystem is, “Who is eating who?” You could call almost call an ecosystem an eating system.

A food web shows who eats who in an ecosystem. Look at the diagram below: a line drawn between a frog and a fly means that the frog eats the fly. As you can see, almost everyone is eating everyone else!

This good web shows just water creatures. As you can also see, fish are at the center. In the water, the only things that eat fish are bigger fish. And if you're a big fish, like a five hundred pound sturgeon in Okanagan Lake, nobody eats you! Except maybe Ogopogo.

Outside the water are other predators, however. Birds, bears and humans all eat fish.

Food for Thought... Where would you put people in the food Web?

Lakes are the physical center of freshwater ecosystems. Understanding all the life in and around a lake - even just one specific lake - can be a lifetime challenge. But you have already begun.

Geology of a Lake

Where does a lake come from? There are several different ways to make a lake. Lakes are filled by springs, direct snow melt and rain, ground seepage, in-flowing streams or combinations of all of these.

Not all lakes have fish! Many lakes in British Columbia are inaccessible to fish because of their geological history and their place in the landscape.

Kettle lakes have no connection to the rest of a watershed, and so they can't naturally have fish in them. They are isolated pools of meltwater - literally the puddle left behind when a great chunk of ice was left behind by a glacier. Chunks of ice like this were so heavy that they literally crushed a pit into the landscape, and then filled it with water when they melted. There are thousands of kettle lakes in this part of the world

Many alpine lakes are simply too high for fish to get into. They form high above the valleys, where no fish can swim. However, fish are amazingly good at swimming uphill - and they will find a way to naturally populate just about any lake that is connected to the rest of the watershed by a stream.

Lakes fed and drained by springs and groundwater are very common in British Columbia as well, especially in the North. Some of these are even warmer than their neighbours, because the spring is a hot spring! If such a lake is drained by a stream, there might be native fish it in. But if the water drains just by seeping back through the ground and into the water table, obviously the fish cannot reach it.

So how can you tell which lakes have fish and which don't? Actually, it's not easy. If you see an inlet or outlet stream, there is a good chance that the lake has fish in it. But even if you could tell at a glance that there was no way for fish to get in or out of a lake, that doesn't mean there are no fish in it. When Europeans were first settling in British Columbia, they brought several fish species with them from Europe and Eastern Canada. Many of the lakes they stocked were the lakes that had no native fish. Today, almost every lake that humans have access to has fish in it - even if the fish can't swim in or out.

Anatomy of a Lake

Did you know that a lake has parts? You will find variations on the same set of lake parts in every lake you study: the shoreline, the shoal, the drop off zone and the deep zone. Each zone has a role to play in the biology of a lake.

The Shoreline

The shoreline is a shallow area near the edge of the lake. It is generally less than half a meter deep. It is a very important area for a number of water and land creatures because it offers quick access to both land and water.

The shoreline is of particular interest to amphibians, which live in both land and water by definition: therefore, they are most likely to be found right near the barrier between the two.

If you're thinking of a lake, you're thinking of what is in the water. But what happens on land at the shoreline is also important. Is it a muddy shoreline full of grasses? A clear, sandy shore? Or a steep, rocky cliff? This will determine what kind of land life will approach the water, and what kind of aquatic life will approach the land.

Food for Thought... What creatures do you think like this area?

The Shoal

The shoal is the area of a lake from the shoreline to six meters deep. In many ways, this is the most biologically interesting part of a lake: it is where you will find most of the lake's plants growing. Because the plants offer habitat and shelter, it is also an area very rich in insects, small animals and small birds. Small fish also like to spend time here because they can catch an easy meal.

Every lake has a shoreline, of course, but not all lakes have much of a shoal. There is likely to be some extended shoal, somewhere in the lake: but in a steep, deep valley lake like Quesnel Lake, the shoal is just a thin ribbon near the shore. Other lakes, like lakes in the Kamloops area, are fairly shallow and have huge shoal areas, covering several acres.

Food for Thought... Why would the fish in lakes with lots of shoal areas grow very big very quickly?

Drop off Zone

At the edge of the shoal is a place where the water becomes deeper, often very quickly. This is called the drop off zone, and it is usually 6 to 8 metres in depth. As the water becomes deeper, less sunlight can get to the bottom, and this is often where you will see the plants stop growing.

Food for Thought... Often the best fishing is right along the drop off zone. Why is that?

Deep Water

Once you pass the drop off zone, you are into deep water. Not a lot happens in the deep water of the lake. Light cannot penetrate enough for good plant growth, and fish stick to areas where there are plants, because that's where the insects are. Fish may pause in the deep, cold sections of lakes for a rest, but not for long.

Depth Charts (Bathymetric maps)

You can find out where the shoals, drop offs, and deep water of a lake are by looking at a depth chart. You can get detailed information and depth charts for many lakes in BC and Alberta very easily. There are a couple of FREE information rich websites that you can explore and find these types of charts.

www.fishwizard.com is very detailed, but complex, site and is recommended for advanced users. Fish Wizard is also best viewed with a high-speed Internet connection.

www.anglersatlas.com is geared for fishermen and contains excellent data. Registration is required but is free. Registration also ensures that you get fishing news and updates.

Seasons of a Lake

Most of our favourite lakes in British Columbia change with the seasons, just as the weather outside our warm living rooms does. The only difference of course, is that we cannot see the changes as they occur under water. Understanding these changes is very important to understanding our environment, the insects and fish that live in the lakes and how to catch fish. We will start by looking at a lake once the ice is starting to form on its surface.

Food for Thought... Right after "ice-off" - the fish very actively feed and spend their time near the surface. Why?

Winter

By now, we have had many cold days and nights, the days are getting shorter and the leaves have fallen off the trees. In the lake, the plants are either dying or becoming dormant (sleeping through the cold winter). This means that no more oxygen will get into the water until spring. It also means that the rotting plants will use up oxygen that is so important to the fish. Throughout winter, the plants (and dead animals) rot and the fish use up the oxygen.

Spring and Summer

By spring there may be very little "good air" (oxygen dissolved in water) left in the lake for the fish to survive. Trout probably look forward to the end of winter even more than you do! In the spring the air starts to warm and melt the ice, and warm winds start to stir the water with air, getting more oxygen into the lake.

All of the water in a lake may get mixed up at this time, and go through something called "turnover.” The water will become murky and may take about two weeks to get clear. Soon plants and algae will begin to grow in the lake again, and make oxygen through photosynthesis. As the water becomes warmer in summer, more plants will grow and more oxygen will be added to the lake. But because the sun can only penetrate a little way into the water, only the top layer of water will be warm with lots of oxygen. Fish are forced to live nearer to the surface in the summer because they need the extra oxygen and food.

Fall

In the fall, the lake begins to cool, winds begin to blow and a second "turnover" can take place. Oxygen will be mixed into all the water and the fish can live throughout the lake. The fish are feeding a lot, building up reserves for the long, cold winter ahead. This is one of the best times for fly fishing, because the hungry fish will take a real interest in your fly!

Food for Thought... What causes the oxygen in the water to disappear? What restores the oxygen to the water?

Life Span of a Lake

Lakes, like all things, change over time. Even a lake has a life span like people do - there are young lakes, middle-aged lakes and old lakes. Many of the lakes in British Columbia are still quite young because they were formed by the last ice age that carved our northern landscape.

As our lakes age, many of them will slowly shrink. Land naturally takes over at the edge of a lake. It's very slow, but it happens. This is called “lake succession,” and this is how it works.

Each year trees and shrubs along the edge of a lake shed leaves and debris into the water that then settle to the bottom. This debris slowly decays to form new habitat for grasses, rushes and sedges. The grasses take root quickly and stabilize the new ground for dry land species. Some day shrubs and small trees will grow where lily pads once floated.

As the lake becomes smaller and smaller, it may not be able to provide enough oxygen or food for some fish. But this happens so slowly that they have plenty of time to move on to other lakes, if the lake is connected to the rest of the watershed by a stream.

Not all lakes are subject to succession, of course. If a lake has a steep, rocky shore, there is no way for the shore to creep into the lake, short of dynamite. You can tell where a lake is disappearing by the plant-life: wherever you see grasses, rushes, reeds and sedges along wet, indistinct and muddy shorelines, you know that the lake is being taken over, ever so slowly.

Food for Thought... How does man sometimes contribute to speeding up lake succession?