THE LAKE NEWS
Wednesday, December 7, 1988
Kokanee Salmon
By Ted Burns
It happened in the early evening of October 20, near the west end of Cowichan Lake about five kilometers beyond Caycuse. I noticed some gulls circling above the lake and stopped to see what was attracting them. Hundreds (perhaps thousands) of small fish were breaking the surface in splashy rolls. It sounded like the beginning of a big raindrop summer shower. Occasionally a fish would leap clear. They were Kokanee -landlocked sockeye salmon that inhabit the lake in millions but are seldom seen or caught.
Cowichan Lake Kokanee are very small. I’ve measured hundreds of their spawned out carcasses on pea gravel beaches around the lakeshore. They average little more than 15 cm (6 inches) - too small to spawn in the creeks flowing into the lake because creek gravel is too large for them to dig. They are a cool water fish and spend the summer in deep water 15-20 meters below the surface; well below the depth of most anglers’ lures. Aside from their spent bodies on the beaches, the only time they show themselves in numbers is in the fall when they indulge in some pre-spawning surface partying like that of October 20. They spawn in late November and early December.
Kokanee are a drain on Cowichan Lake’s meager plankton supply which is important food for young trout and coho. They are extremely efficient plankton feeders and gather it by straining the water with their gill rakers which are fine comb-like protrusions on their gill arches.
It seem that few kokanee are eaten by Cowichan Lake trout. The rainbows don’t generally grow large enough to prey on them and the cutthroats, some of which do, are usually restricted to shoal areas around the edge of the lake although they are sometimes seen chasing silvers well out in the lake. Kokanee roam the length and breadth of Cowichan Lake. If there were a way of utilizing the super abundant Kokanee resource without negatively influencing the other fishes Cowichan Lake, much benefit could result. Some people have suggested importing the giant Gerrard rainbow trout from Kootenay Lake which feed almost exclusively on Kokanee. These fish are the world’s premier trout, reaching weights of 16 kilograms (35 pounds). If a population of the big Kootenay rainbows could be established in Cowichan Lake, they would thin the Kokanee population and provide a huge new element of attraction to the Cowichan Lake sport fishery. Kokanee could even become a desirable fish because their size should increase. There are other races of fish eating rainbows that could be introduced including one from a small lake in the Walbran Creek drainage west of Cowichan Lake.
There is always a great deal of fear about introducing new species and with good reason. Many introductions have been disastrous. The main worry with Gerrard rainbows is how they might affect young. coho rearing in Cowichan Lake. What if they preyed heavily on them? Lake rearing coho are a significant part of the Cowichan population. I don’t think it will happen because Cowichan Lake coho are not large enough to attract the big rainbows until they reach the smolt stage (and that period is short) and they generally hug the shore. Could there also be an impact on Cowichan Lake cutthroats? These fish are currently not all that numerous but once provided very good fishing - the best on the Island for big cutthroats. Is there room for both? I doubt that Gerrard rainbows will ever become really numerous in Cowichan Lake. Is it a chance worth taking?