Feature - A Cutthroat Murder Mystery: 

The Fish of Alta Lake

I arrived in Whistler in the fall of 1981 and was immediately intrigued by the fact that Alta Lake was once considered fishermen's Mecca. But my first experience on the lake only produced a few 10", worm-infested fish. As someone who grew up catching rainbow trout in the 3 to 15-pound range on the Great Lakes, I found it amazing this lake could once have supported four lodges and attracted so many fishermen. I knew things had changed a lot but found it confusing; given very little modern angling pressure, the lake's mature fish were so small.

This was a mystery. What had changed in the lake? I asked around and several explanations surfaced.

According to some people, there was possibly a sewage problem from lakeside septic fields. That problem cuts both ways though, often providing abundant growth and large fish.

Others pointed to many spawning tributaries that had been changed and altered. But usually, when natural recruitment diminishes, fish become larger. Not the case in present day Alta Lake, where 12-inch fish would be considered large.

Another theory related to an over-abundance of sticklebacks. Maybe these small, minnow-like fish were out-competing the rainbows for food as well as predating on their eggs.

In 1999, this problem was addressed when sterile cutthroat trout were introduced into Alta Lake. The slim, muscular cutthroats, with their oversized mouths and vicious teeth, are very effective at devouring various small fish, including the three-pronged stickleback. It was hoped the cutthroats would reduce the number of sticklebacks and give the advantage back to the rainbows. Since the cutts were sterile, they would only live five years and pass without reproducing.

It didn't take long for the cutthroat to prove themselves. Introduced as 6" to 8" fish they quickly doubled in size and by the summer of 2001 were averaging 15" to 19" in length. For the first time in many years, fisherman began appearing on Alta Lake.

Still another theory was the lack of kokanee salmon in Alta Lake. When I arrived in Whistler there were still some spectacular runs of these scarlet spawners. In lakes where rainbow trout are able to grow over two pounds, they forage on kokanee and can grow astonishingly large. It was hoped that habitat improvements might re-established the kokanee and provide rainbows with a valuable protein source.

Some people were concerned the introduced cutthroats might have a negative effect on the remnant kokanee population. The unexpected return of kokanee migrating up from Green Lake last September to spawn in the River of Golden Dreams heightened concerns. There was speculation the kokanee were not native to the Whistler area.


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