A marine biologist goes to the mountains

This past weekend I attended a family reunion at South Lake Tahoe. It had been several years since the previous reunion for this side of the family, and it was wonderful seeing almost all of my cousins and their various offspring, plus aunts and uncles, in a glorious setting. All good things must come to an end, though, and finally we all left Tahoe to return to our regular lives.

On our way back I stopped at the Taylor Creek Visitor Center and did a short hike. The Rainbow Trail is a 1/2-mile loop that winds through forest, meadow, and riparian habitats and includes the stream profile chamber, which shows a bit of the natural creek where kokanee salmon migrate in the fall. It’s a beautiful spot to walk around a bit and get a last nature fix before dealing with traffic and the drive home. Some day I’ll time a visit to coincide with the salmon run. “Salmon run? What salmon run?” you may wonder. Well, read on.

Taylor Creek flows northward about 3.5 km from Fallen Leaf Lake into Lake Tahoe. It forms part of the wetland that protects Tahoe from runoff and silt, helping to maintain the clarity of the lake. As with most of the land in the Tahoe basin, Taylor Creek has been modified by human activity:  the streambed itself has been altered by road development, and the introduction of non-native species such as bullfrogs threatens populations of native species. Still, it is a remarkably beautiful place.

Beavers are also continually changing the course of the creek. They fell trees and construct dams that redirect water flow and create still ponds upstream of the dam. In the summer it is not uncommon to see dams and other evidence of beaver activity. Of course, the dams impede the movement of most fish up and down the creek.

One of the more noteworthy fish living in Taylor Creek is the kokanee salmon, a landlocked version of the sockeye (Oncorhynchus nerka) that is one of five species of salmon in the northeastern Pacific Ocean. Whereas most eastern Pacific salmon are anadromous, living their adult lives at sea but returning to freshwater rivers to reproduce, the kokanee spend their entire lives in freshwater. Kokanee were introduced into Lake Tahoe in the 1940s and have since become a popular game fish. In the fall, they migrate from Lake Tahoe into Taylor Creek to spawn. Beaver dams would block the kokanee’s return to their spawning grounds, so every year the U.S. Fish and Wildlife Service demolishes the dams to allow the salmon access to the creek; this action also increases runoff into Lake Tahoe and decreases the total area of wetlands in the region, both of which have a detrimental effect on the lake’s clarity. The net result is spawning habitat for a non-native species, the kokanee, at the cost of decreased lake clarity and (arguably) damage to a native species, the beaver. We humans seem to be unrelentingly amenable to making such trade-offs. I wonder where that will get us in the long run.

For most visitors, the highlight of the Rainbow Trail is the stream profile chamber. This little chamber has displays about the life cycle of the kokanee salmon, the seasons of Taylor Creek, and a window into the stream itself. At this time of year the only fish inhabitants were Lahontan redsides (Richardsonius egregius), minnow-like fishes about the length of my hand or a bit shorter. The kokanee, wearing their brilliant mating costumes, will pass through the stream in October.

I did take some video footage of the redsides swimming in the chamber, bathed in the sunlight that filters through the upper layers of water. The bird and other animal sounds you hear are recordings that are played in the chamber.

Returning to the outdoors, I hiked through more meadows and forest, stopping frequently to look and listen for birds. This summer, despite drought conditions throughout California, the Tahoe region has gotten enough rain for wildflowers (and mosquitos) to persist; I walked through fields of goldenrod, blooming skunk cabbage, lupine, and Queen Anne’s lace. The aspen trees (Populus tremuloides) haven’t started changing color yet, but walking through them I could hear the rustle of their leaves, which is one of the characteristic sounds of northern California high-altitude Sierra Nevada forests.

In the autumn the aspens will change color and blanket the high Sierra in golds and oranges–yet another reason to return to the Tahoe area in the fall!