Every spring, some of the water that might have gone to farms instead flows down the Tuolumne River to help young salmon get to sea.
And every spring, officials with the Modesto Irrigation District say, striped bass gobble up many of these fish as they swim through the Sacramento-San Joaquin Delta.
The MID is trying to get state and federal officials to control the bass population rather than seek increased releases from Don Pedro Reservoir.
The district contends that the bass, introduced to California in 1879, have come to dominate the delta at the expense of salmon and other struggling native fish.
"What's written on the wall, from my perspective, is one word: predation," said Tim O'Laughlin, the district's general counsel, during a Nov. 17 presentation to its board.
MID General Manager Allen Short said the argument has gained little traction with people who insist that the best solution for salmon is increased flows.
But water is just what is needed, said Zeke Grader, executive director of the Pacific Coast Federation of Fishermen's Associations.
"MID is just in big-time denial," he said. "They and others have got to acknowledge that a certain amount of water has to be left for the estuary and the fish."
Grader said salmon and bass co-existed for most of the past 140 years and they can do so again if river flows increase.
Salmon counts ebb and flow on the Merced, Stanislaus and Tuolumne rivers, peaking most recently in 2000 with nearly 42,000 fish but plummeting to fewer than 2,000 last year. Officials expect low numbers this year because of drought in the mountains and warming ocean temperatures.
The stakes are high: The MID and Turlock Irrigation District supply about 210,000 acres of farmland with Tuolumne River water, which also is part of the city of Modesto's drinking water supply.
The farm products bring income to growers and employ tens of thousands of people at processing plants in and near Stanislaus County.
The districts already maintain certain water levels in the Tuolumne to help state and federal efforts to protect salmon.
They could be required to boost the flows in coming years as the federal government renews the license for Don Pedro and officials try to fix the beleaguered delta.
Other water suppliers are involved in salmon efforts, including the Oakdale and South San Joaquin irrigation districts on the Stanislaus River.
Pumping action harmful
Parts of the western and southern San Joaquin Valley have had especially sharp water cutbacks because they rely on fish-damaging pumps in the delta.
The stakes are high, as well, for commercial salmon fishermen, represented by Grader's group. He said about 2,000 anglers are out of work because of the shutdown of the 2008 and 2009 chinook salmon seasons off the California coast, resulting from the spawning decline on Central Valley streams.
Patrick Koepele, deputy executive director of the Tuolumne River Trust, said high flows have several benefits for young salmon: They speed their passage to the ocean. They dilute contaminants. They tend to be colder than low-flowing rivers.
"The warmer the water, the better those predators do," Koepele said.
The trust has worked with the MID, TID and other partners to monitor and enhance river conditions.
O'Laughlin, the MID lawyer, said the task is complicated because an estimated 95 percent of the plant and animal matter in the delta is non-native.
"The fishery has been drastically, drastically changed," agreed Doug Demko, a private consultant to the MID on fish issues.
The district backed state legislation that would have relaxed restrictions on bass fishing so their numbers could be reduced.
The bill, by Assemblywoman Jean Fuller, R-Bakersfield, was later amended to simply require a study on the predation problem. It passed the Assembly in June and awaits action by the Senate Appropriations Committee.
U.S. Rep. Jim Costa, D-Fresno, held a hearing last week that aimed to show that increasing river flows cannot be the only tool for protecting salmon.
The main issue was the effect of water pollution on the fish, but Costa said predation by striped bass must be considered, too.
"There are multiple factors that are causing the decline of fisheries in the delta," the congressman said.
Bee staff writer John Holland can be reached at email@example.com or 578-2385.