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Naturespeak

Fish local or imports?

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By Betty Rebellato

Whistler Naturalists

Anglers and nature lovers alike get satisfaction from seeing healthy populations of fish in our lakes and streams. Whistler’s waterways support populations of kokanee, rainbow trout, bull trout, sculpins, threespine stickleback, and, more recently in Alta Lake, cutthroat trout. But do the same fish exist in the Whistler area as were here historically?

For some species, the answer is likely no. The increasingly rare bull trout is indigenous to the Whistler area, as are sculpin and, likely, stickleback. Rainbow trout and kokanee likely exist here solely as a result of stocking. Both rainbow trout and kokanee have been stocked in Whistler-area lakes since the early 1920s as part of a nationwide (and continent-wide) effort to enhance angling opportunities. Remnants of these populations have become naturalized in the area and reproduce in the wild, continuing their existence in the Whistler Valley.

So how might the introduction of rainbow trout and kokanee have affected the local ecology of the area? Little historic information is available to determine what existed here prior to the intervention of man. However, many of the Lower Mainland and B.C. coastal lakes that have been left unaltered support populations of wild coastal cutthroat trout, which leads one to assume they would also have existed in Whistler-area lakes. Coastal cutthroat trout hybridize easily with rainbow trout, and the introduction of rainbow trout over the years has likely caused the disappearance of cutthroat trout from our waters.

Unlike most strains of rainbow trout, which feed primarily on insects and plankton, cutthroat trout are piscivorous (fish eating) and would have subsisted on stickleback in the area. If cutthroat trout truly did exist historically in the area, then their disappearance from our lakes would have allowed the stickleback population to grow to unnatural proportions, allowing them to expand into more niches and consume more plankton (their main food source) than before. In an effort to reduce the stickleback population back to what is believed to be more natural levels, the Province of B.C. in conjunction with the Whistler Angling Club introduced sterile cutthroat trout into Alta Lake on a trial basis beginning in 2003.

In addition to affecting the stickleback population, fish stocking practices may have also caused a decline in amphibian populations in the Whistler area. Research has shown that the presence of rainbow trout and other trout species causes a decrease in both the number and size of many species of amphibians, especially in those water bodies with little habitat complexity in which amphibians can hide. The practice of stocking fish into a lake can affect amphibian populations both through predation of palatable species, such as long-toed salamanders, northwestern salamanders, and pacific chorus frogs, and through the introduction of disease to other species of amphibians, such as the western toad.

Long-time local resident and fish historian Eric Crowe has been researching the origins and changes to British Columbia’s fish populations since the start of major fish stocking practices in the early 1870s. The Whistler Naturalists invite you to join us on Thursday, Jan. 18 at 7:30 p.m. at Millennium Place to hear Eric’s take on how stocking has affected cutthroat trout, steelhead, and other populations of fish in Whistler.

 

Upcoming Events

Eric Crowe––The Fish Detective. Thursday, Jan. 18, 7:30 p.m. at Millennium Place: After years of detective work, Eric has sleuthed some surprising conclusions about the history of fish in our local lakes and rivers. Come find out what secrets he’s uncovered. Admission by donation. Call 604-932-8900 for more details.

Monthly bird walk. Saturday, Feb. 3, 8 a.m. at the base of Lorimer Road. For details, call Michael Thompson at 604-932-5010.

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