'Electrofishing' for predators in the Delta
J.D. Richey cut the throttle, bringing his 20-foot jet sled to a sudden halt in the gentle flows of the lower Feather River. Richey, a Sacramento-based fishing guide, had spotted what river anglers call a “boil,” a school of small bait fish under attack by larger predators. During the feeding frenzy, the predator fish splash the surface as they swoop up from below to attack.
With the boat drifting within casting distance of the splashes, Richey’s two clients grabbed their rods and let fly lures designed to mimic a struggling bait fish. Seconds later, they leaned back, grinning widely as they reeled in fish a foot and a half long.
For Richey and the anglers, it was a successful weekday outing, resulting in a bounty of fish dinners to come. More broadly, the scene put them smack in the center of yet another Central Valley river conflict, one that pits “good” fish against “bad” fish, farmers against anglers, and without enough fresh water to allow them all to thrive.
The “bait fish,” in this case, were among 1 million baby fall-run Chinook salmon that state officials recently had released into the river from an upstream hatchery. While the fall run isn’t endangered, its population is in sharp decline. The winter run, meanwhile, is perilously close to extinction; and the spring run only marginally stronger. Compelled both by endangered species law and California’s struggling salmon-fishing industry, state and federal regulators have gone to painstaking lengths to try to bolster their numbers.
And the predatory fish? Those were mostly striped bass, an East Coast species introduced to California in 1879, just 14 years after the Civil War. Tens of thousands of anglers now fish for them each year in Central Valley bays, rivers and lakes, generating millions of dollars in fishing-related purchases and fees.
What role the non-native bass – called “stripers” by anglers – have played in the overall decline in Central Valley native fish populations, including Chinook, is an ongoing debate in Washington D.C., and Sacramento. Last month, an Obama administration official voiced sympathy for a bill sponsored by Rep. Jeff Denham, a Turlock Republican, that seeks to reduce the number of striped bass in and around the Sacramento-San Joaquin Delta. State lawmakers considered a similar bill that stalled last year.
The primary advocates for these bills and others are powerful agricultural interests that have spent more than a decade blaming striped bass and other non-native predators for playing a significant role in the decline of native fish species in the Central Valley, including Chinook, steelhead and Delta smelt.
Their concern is less about the fish and more about how the population declines affect their water supply and livelihoods. Court rulings empower the federal fisheries agencies that monitor species to govern water flows in the Delta, and their decisions often translate into pumping limits to keep fish from being harmed.
As salmon and other native fish species have declined, regulators have responded by cutting back exports at the two huge government pumping stations at the bottom of the Delta. The pumps supply water to millions of acres of farmland in the San Joaquin Valley and 19 million Southern Californians. Instead of regularly throttling back pumping, groups dependent on exported Delta water say, regulators ought to reduce the numbers of striped bass and other non-native fish preying on salmon and smelt.
A chief complaint is the decision to label the striped bass a game fish protected by laws that set strict catch limits. In most of California, recreational anglers can be cited if they catch more than two stripers a day or if they keep any bass smaller than 18 inches. Commercial fishing for stripers is prohibited. Central Valley farm interests would like to see the limits on striped bass and other non-native predators raised or removed.
“This is one of the (solutions) that we think falls into the low-cost, no-brainer category,” said Michael Boccadoro, a political strategist who serves as spokesman for the Coalition for a Sustainable Delta. The coalition is funded largely by Kern County agricultural interests that rely on imported Delta water.
In 2008, Boccadoro’s group sued California fisheries officials to pressure them to remove stripers from sport-fishing protections. As part of a settlement, state wildlife officials agreed to ask the independent commission that sets fishing regulations to let anglers catch and keep more stripers.
The Fish and Game Commission in 2012 rejected the proposal on a 4-0 vote – after getting a less-than enthusiastic endorsement of the proposal from the fisheries officials.
“There’s too little known right now,” said Stafford Lehr, an acting deputy director of the Department of Fish and Wildlife. “The consensus of the research is there’s more going on (with native fish declines) than predation. That’s the department’s position.”
Peter Moyle, a veteran fisheries scientist at UC Davis, is among the researchers who say striped bass are unfairly blamed for the declines in native fish. He described the striper as a “scapefish,” whose numbers have suffered marked declines in recent decades, alongside native fish. The real issue, he said, is what humans have done to the environment by over-allocating water to competing interests.
“There’s always something else – other than the way water’s managed – that’s causing the declines of fish,” Moyle said.
When you’ve got all your species trending downward, the common denominator is water.
J.D. Richey, Sacramento-based fishing guide
Scientists also are skeptical that a systematic removal of striped bass would have the intended effect. The Delta ecosystem has been so altered by humans, they argue, and invaded by so many non-native species that singling out an established species such as stripers may actually put more stress on the estuary. Of the nearly 46 fish species spotted in the Delta over the years, 27 were not native to the estuary.
Sean Hayes, a federal fisheries scientist who has studied predation in the San Joaquin River, said other non-native fish may move in to fill the niche that striped bass and other predators hold in the food web if they are aggressively singled out for removal.
“They’re certainly eating salmon,” he said. “But the reality is they’re eating each other far more.”
Lehr expressed more practical concerns: Cutting the striped bass population through fishing alone is likely a futile proposition given they inhabit such a vast area, he said. At various times of year, the stripers inhabit a range that stretches from the Pacific Coast near Monterey to just below the major dams on the Sacramento and San Joaquin river system.
Health officials have raised yet another objection: California’s striped bass, though prized by anglers for their flaky sweet meat, contain so much mercury that public health officials advise against children and women of childbearing age from eating them. Higher catch limits could increase mercury poisoning among impoverished groups who disproportionately eat fish caught for subsistence, Lehr said.
For now, state officials are experimenting with alternative solutions that offer something to appease the various interest groups, carving out safe space for salmon without decimating the striper population.
Hayes said one effort involves a search for predator hot spots, where river conditions make it easy for predators to gang up and gobble native fish. The hope is their research can suggest ways of altering the habitat to make it easier for the smaller fish to escape.
Other research is looking at the viability of removing predators from a known hot spot, and relocating them to areas where they don’t pose such a risk. That study is underway at the Clifton Court Forebay, a barren 2-mile-wide man-made holding pond that feeds the massive pumping plant near Tracy. The state uses the plant to ship water south from the Delta.
Small fish are drawn into the forebay when they follow the powerful currents generated by the plant’s 11 huge pumps. A fish screening facility sits at the opposite end of the pond at the canal that leads to the pumps. It’s designed to catch the wayward fish so they can be hauled away for release elsewhere in the Delta.
Studies have found between 60 percent and 99 percent of small fish are eaten by the predators that lurk in the forebay before they ever get to the screens.
For the last few weeks, the state has sent scientists into the forebay to see if they can change those odds. They periodically release specially tagged baby salmon at the forebay’s intake gates. And, three days a week, teams of researchers zap the predators waiting to eat them.
On Tuesday, more than a dozen researchers crowded into boats, netting dozens of predator fish that floated to the surface after being stunned by electrically charged cables dangling from two of the vessels. The haul – 11 white catfish, 59 largemouth bass and 150 striped bass – were relocated to a nearby lake where the fish posed no risk to juvenile steelhead, salmon or Delta smelt.
The researchers want to see whether, by regularly removing predators, significantly more salmon will make it through to the fish screens, so they, too, can be relocated.
Far upstream from the Delta, in his boat on the Feather River, Richey remembers boom years not so long ago when his clients hauled in salmon, steelhead and stripers. He views efforts to eradicate striped bass as “a diversionary tactic” that deflects attention from the unrelenting demand for exported water.
“When you’ve got all your species trending downward,” he said, “the common denominator is water.”
Striped bass, he said, have coexisted with salmon almost as long as California has been a state. And they certainly weren’t the only predator having a field day picking off salmon on the Feather River that recent morning.
Herons and egrets lined the banks, nabbing fish as they swam past. Terns and other birds dive-bombed from above. The anglers in Richey’s boat also caught largemouth and smallmouth bass that had been gorging in the boils.
“I’ll never deny that stripers eat salmon,” Richey said. “But so do everything else.”