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COLUMN: Understanding fish behaviour for fishing success in Cariboo

Doug Porter’s regular Outdoors in the Cariboo column
Doug Porter has been fly fishing since he was 12. (Patrick Davies photo - 100 Mile Free Press)

Have you ever wondered why some anglers are more successful than others? I know it has always intrigued me. Decades of study have helped me to narrow down what successful anglers have learned to increase their chance of success on the waters.

As I mentioned in a previous column, different strains of rainbows have different food preferences, and knowing what strains are in a lake helps in understanding what chosen offerings might provide an advantage in taking a fish home for the table. In review, the Pennask and Fraser Valley Strains are mostly insect eaters, while the Blackwater and Horsefly Strains, when they reach a certain size, will turn to eating minnows (piscivorous).

Again, stocking information can be found at the Freshwater Fisheries Society of BC site at Having a knowledge of which strain of rainbows are in the lake to be fished, the presentations would vary; for instance, the first two strains would most likely take a trolled or cast fly representing an aquatic insect, while the last two would be more likely to take a lure, fly, or plug representing a minnow. Using this information would be a good starting point, but one must also be aware that there are often more variables to be considered.

One is that unlike humans, which are quite comfortable at 22 degrees C (70 degrees F), rainbow trout are not, and prefer water temperatures around 13 C (55 degrees F). So, in the spring and fall, when the water is cool, fish can be found in the shallows foraging on their favourite food; while in the summer months, they will head to deeper water seeking out ideal temperatures and oxygen levels. By this time most of the insect emergences will be over and the fish become semi-dormant, waiting for fall to cool the waters in the shallows when they can return there and begin foraging on available insects, crustaceans, and leeches, as well as water boatman and backswimmers.

For those observant anglers, I am sure they have noticed that most minnows can be seen in the shallows along the shoreline and in the weeds found there. Here they can live in relative safety, for if they ventured out into open water, they would soon fall prey to predatory fish.

The temperature and oxygen condition preferences would also apply to the other sport fish like kokanee and lake trout. They too will venture into the shallows in the spring taking advantage of cooler water and whatever food source is available. While kokanee feed mainly on zooplankton, they will forage on insects such as chironomids and mayflies when they are emerging or even on their larvae or nymph stages. Lake trout, until they reach a certain size, also feed on aquatic insects before becoming piscivorous.

Kokanee are basically landlocked Sockeye Salmon that have adapted to a freshwater environment. They do maintain some of the aggressive feeding characteristics of their kin and can be readily taken on a variety of lures, plugs and spinners, as well as a selection of fly patterns.

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Using a depth sounder to locate kokanee in early spring is almost impossible as they are close to the surface at this time of year and will spook away from a moving boat, making it almost impossible to see them on the screen. It is not until later in the spring that they can be seen on a sounder as they begin to seek out comfort zones in the deeper water. Lake trout will do the same as the surface water warms. When the larger lake trout are in deeper water, they can be taken on a variety of plugs, spoons, and lures.

While I have provided a very brief overview of how fish respond to water temperatures and oxygen, as well as available food sources, I will leave it up to the reader to do more research and observations throughout the fishing season. Since each body of water may differ slightly from one another, it is best to check with resorts and sporting goods outlets to see what the fish are biting on the best at any given time.

As Gary Cooper says at the end of many of his fishing videos “luck is an attitude”. I would like to add that if one relies on luck to put meat on the table I would suggest they develop a taste for potatoes and starches!