Biology Reference
In-Depth Information
MIGRATIONS: TWO SALMON TRAVEL BUTTE CREEK
Stream restoration has produced the most visible results for migrating fish at
Butte Creek. This creek originates in the mountains of Lassen National Forest, 15
miles northeast of the town of Chico. From its headwaters in a volcanic canyon
7,000 feet above sea level, it flows through mountain meadows into flats planted
with fruit trees and rice, then empties via the Sutter Bypass and a slough into the
Sacramento River. Efforts to restore fish habitat on this creek have vastly improved
conditions for migrating Chinook Salmon, whether they are adults headed up-
stream to spawn or juveniles moving downstream to a new life in the ocean.
What are these journeys like? Imagine it is late February. A 20-pound,
30-inch-long male salmon chasing sardines out in the Gulf of the Farallones
catches a whiff of something. That something—a smell, a taste, a specific chemical
signature—has arrived in the ocean via the winter outflows of his natal stream. All
of his senses now tell him it's time to return to the place of his birth and spawn.
He begins swimming purposefully toward the Golden Gate, and doesn't stop to
eat or rest on his way through San Francisco Bay. At the confluence of the Sacra-
mento and San Joaquin rivers he chooses the former. For 100 river miles he fol-
lows the thread of outflow that seems to grow ever stronger until he enters a ditch
near the Sutter Bypass. The ditch is thick with other salmon—spring run numbers
have more than doubled here due to restoration in upstream stretches. A few
weeks after leaving the Pacific, he arrives in Butte Creek, the stream of his birth.
Before 2000, the going would have gotten rough here. Along the 90 miles of
creek ahead, he'd have had to find his way over or around more than a dozen
small dams and diversions, each one delaying his progress for days or weeks. If he
got stuck, state fish and game trucks might have given him a ride upstream. But
since 1998, four dams have been demolished and removed from his path. And on
this day in early March, as he pumps his powerful tail against the surge of water
going the other way, the only thing that disturbs him is a Red-breasted Merganser
diving for a meal.
At Willow Slough he encounters the first of 11 new fish ladders, each tailored
to site-specific flow and elevation conditions. Willow Slough's ladder isn't made of
rungs climbing over a dam or weir. It's what's known as a “pool and chute,” offering
fish a chute-style passage through a hole in a step up in the river into a resting
pool. Today, most ladders are designed to move fish under and through obstacles,
rather than over them. The only thing going over the dam these days is what biolo-
gists call “attractant” flow.
Past the Parrot-Phelan Dam, before 1996, this male might have ended up
short on water or sidetracked into the M&T Chico Ranch water intake. Today, how-
ever, M&T diverts less water here than its rights allow, leaving more water in the
creek October to June when the spring run salmon need it most. Buoyed by these
waters and barred from entering the intake by one of seven new exclusion barriers,
this salmon moves safely upstream.
