Salmon migration detour set for Georgiana Slough

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Young, impressionable salmon migrating from the Sacramento River to the Pacific Ocean this week will encounter something their parents probably never warned them about: the underwater equivalent of a Pink Floyd concert.

Strobe lights, deep sonic pulses and a wall of bubbles will greet salmon in the northern Sacramento-San Joaquin River Delta, but, in this case, the hydrological hubbub is an attempt to repel, not attract, the fish.

The California Department of Water Resources wants to deter the fish from entering the predator-infested waters of the Georgiana Slough, an offshoot waterway leading to the huge churning pumps that send water to 25 million Californians.

Over the next 45 days, engineers with the agency will finish fastening speakers, lights and air lines to steel pilings sunk into the river bottom. The experimental contraption, which biologists will build and study through April, is the latest bid by the state to stem the tide of Chinook salmon killed every year in the delta.

By the agency's estimate, 65 percent of the salmon that venture from the main stem of the Sacramento River and into the slough near the city of Walnut Grove are lost to the appetites of larger fish or the pumping equipment.

"The idea is to nudge the fish out to the Sacramento River so they can make a beeline to the ocean and don't go down this longer route," said Mark Holderman, project program manager. "The longer they're in the delta, they're more exposed to predators and water diversions."

Tag and track

Water resources officials plan to tag and track 1,500 juvenile salmon to determine whether the "bubble barrier" is working.

A similar but smaller 2009 project at the confluence of the San Joaquin and Old Rivers kept 81 percent of the fish from veering into dangerous waters, department research showed. The bubbly cacophony was used in the same place the next year but was only 23 percent successful. Holderman said faster, higher flows in 2010 washed more fish past the barrier.

Fishing advocates worry that the multimillion-dollar system will disorient and overwhelm the salmon, making them even more vulnerable to striped bass and other predators.

"This is like so many projects we've seen in this estuary," said Bill Jennings, executive director of the California Sportfishing Protection Alliance. "It's a plausible idea, a good idea, but it may have unintended consequences."

A precipitous, decadelong decline of delta smelt and salmon - resulting in two canceled commercial fishing seasons and one eight-day season - has become a rallying cry for environmentalists and fishing groups. It has also become a thorn in the side of agricultural interests that control most of the water exported from the delta and a major quandary for policymakers in the midst of crafting a management plan for the West Coast's most important estuary.

In the short term, California water managers are under order by federal regulators to curtail the death rate of a once-thriving fish species that must traverse the estuary on its way from breeding grounds upriver to the sea.

Working on a broader level, the state-mandated Delta Stewardship Council is trying to reconcile the freshwater needs of the fish with the economic and public health needs of the state's cities and farms.

Draft plan

A draft plan released this month by the stewardship council concluded that not all endangered fish species - delta smelt, in particular - may be saved from extinction in the wrenching battle to preserve the delta and provide a reliable water supply for California.

On Wednesday, a study by the influential Public Policy Institute of California went a step further, describing scenarios in which "biological triage" may be necessary.

"Listed species deemed the least likely to survive projected inevitable changes are taken off species-specific life support," the report said. "The purpose would be to ... protect the more resilient (but still declining) species" such as chinook salmon, green sturgeon and splittail in the delta.

Conservationists like Jennings, however, aren't ready to give up on any of the fish without a fight. And he's wary of whiz-bang fixes that don't address what he believes is the chief underlying problem in the delta: the export of too much water at the expense of fish.

"This is an overallocated watershed," Jennings said. "You simply can't give away more than you've got. If we don't address that question, this is all just building Potemkin villages on a hill."