Effects of Lake Rotation on Fishing

lake turnover it is an interesting phenomenon typical of most lakes that experience icy conditions in winter. The best fly fishing lakes in the Kamloops area are no exception.

There are two times during the year that small lakes experience “rotation”, in the spring and in the fall. In most cases, it is the spring rotation that’s of most interest to fly anglers dying to start their season.

So what is Lake Turnover?

Lake turnover typically occurs 1 to 2 weeks after ice breaks off the lake in the spring. The sun melts the ice and heats the surface water until it eventually reaches its densest state st 4C (39F). This denser or heavier water now follows the laws of physics and wants to sink to the bottom. As it begins to sink, it displaces the less dense water below, causing a complete change in the water column in the lake.

In the fall, the lake’s turnover occurs before it freezes over. The air cools the top layer until it reaches its densest state and then falls to the bottom. The lake then continues to lose heat, and as temperature dictates, the lake eventually freezes over.

Why is this worrying?

In both cases “rotation”, combined with the wind, is the natural way of reoxygenating the water. Both winter and summer induce layers of water that create temperature bands (called thermoclines). This lack of oxygen can be decisive for the fish and in many cases causes the winter or summer death of the fish. The mixing of the water created by the rotation and the welcome winds of spring and fall re-oxygenates the water to healthy levels critical for fish survival.

The rotation is quite an event for the body of water in which it occurs. It churns up the bottom of the lake creating floating decaying plant debris and dramatically increases the turbidity of the water. Oxygen levels drop for a short period and fish generally stop feeding. This event usually lasts 1-2 weeks, depending on the wind. When the spin ends, the oxygen levels rise rapidly and the fish, God bless them, are hungry and start feeding again.

So if you come across a lake in the spring that looks dirty and littered with debris, take note and get out of there because you are most likely wasting your time. Get back there in a couple of weeks and you can enjoy some of the best fishing of the season.