Flooding Is Bad News Even for Fish

While Northern California’s raging waters have wreaked havoc on its human inhabitants, from the perspective of a fish, they have brought both salvation and ruin.

For decades, sea-running fish such as chinook, steelhead and coho have had little freshwater to spawn in, so their numbers have dwindled close to extinction. But the past three years of abundant rains and runoff have started a revival.

But for the past week, it has been a case of too much of a good thing. The flooding has been so extreme--even for fish--that eggs and newly hatched salmon have probably perished in the rough, swift currents in the Sacramento-San Joaquin Delta and San Francisco Bay ecosystem.

For endangered species such as the chinook salmon, a single bad spawning season this year could have severe repercussions for generations to come. The young fish, if they had survived, would have returned to California streams to spawn in three years.

“This year, there’s probably too much water,� said Jim Lecky, Southwest regional salmon coordinator of the National Marine Fisheries Service, the agency responsible for protecting endangered salmon and steelhead. “It’s not a total disaster, but depending on where they are in their life cycle, they could be adversely affected. Those that had eggs in the gravel, the high flows have probably destroyed them.�

Since the winter of 1994-95, ample rain and melted snow from the Sierra Nevada have flowed into the salty San Francisco Bay, and the fresh water has drawn fish inland to deposit their eggs. Streams that had been near-dry have been revived, and some wayward salmon and steelhead trout have shunned their traditional routes and reinhabited them, in a cycle of renewal that the fish have repeated for thousands of years.

In the northwest corner of California, along the Klamath, Trinity, Smith and Eel rivers, some salmon and steelhead populations are the healthiest they have been in a decade. And for the first time in years, salmon are spawning in some Bay Area streams such as Alameda Creek.

“When we have a lot of outflow through the delta and through the Golden Gate Bridge, then survival of salmon and steelhead juvenile fish is better,� said Steve Taylor, a senior fisheries biologist at the state Department of Fish and Game.

“But the flows that we had recently, over the past two weeks, were way more than the fish need,� he said.

Winter-run chinook, declared an endangered species in 1989, might be severely depleted this season because they hatched in December, and the strong flow probably forced them into the ocean before they were hearty enough to survive, Lecky said.

In the long run, though, an occasional scouring helps renew rivers for future generations. Flood waters clean out pools, import new gravel for spawning grounds, spread seeds for new trees and remove timber debris and other material that clogs rivers.