Mercury rising

Monster catfish, mercury and DDT: There’s no telling what you’ll catch in Sacramento’s waterways.

Modesto’s Eddie Cortez fishing in the Sacramento River by the Rio Vista bridge.

Modesto’s Eddie Cortez fishing in the Sacramento River by the Rio Vista bridge.

Photo By Larry Dalton

The mystery fish glides smoothly through the chemical-green darkness, a white catfish, Ictalurus catus, 40 inches long, weighing more than 15 pounds. A monster for these waters near the confluence of the Mokelumne and Sacramento rivers, where it has spent the last 10 years combing the muddy riverbed, sniffing and snuffling and sucking through the muck for amphipods and shrimp, mudsuckers and crawfish, any organism, dead or alive, that even remotely registers as food in its rudimentary brain.

Over the eons, it has evolved into nature’s version of the perfect garbage disposal, an opportunistic, carnivorous bottom feeder capable of devouring just about anything that will fit into its freakishly large mouth. There are stories of such fish breaking the surface and swallowing small ducks whole. A thick, bony skull and sharp spines on the leading edges of its pectoral and dorsal fins protect the mystery fish from aquatic predators as it slides onward through the submarine gloom, plucking crawfish off the bottom as if they were hors d’oeuvres as it enters the Walnut Grove Marina.

The murky medium in which it has lived its entire life is laced with pesticides, urban run-off, industrial waste and sewage. No one knows exactly how much of these pollutants are suspended in the water and imbedded in the riverbanks, or how they have affected the fish and the other organisms that live in the Delta. No one can say for certain that this particular fish, and others like it, are safe for human consumption.

That’s the mystery, and it’s only just now beginning to unravel.

Last September, the San Francisco Estuary Institute (SFEI) published the most complete study of toxic contamination of fish in the Sacramento-San Joaquin Delta to date. The preliminary study, which focused on largemouth bass and catfish, found that in more than half of the 30 fish examined, the level of methylmercury, an organic form of mercury that can cause neurological damage and even death in humans if consumed in high enough amounts, exceeded the advisory limits set for safe human consumption by the state Office of Environmental Health Hazard Assessment (OEHHA). In addition, levels of PCBs exceeded the state advisory limit in nearly a third of the fish, and 23 percent exceeded the limit for DDT.

OEHHA (pronounced “wee-ha!”), a division of CalEPA, works in conjunction with the California Department of Fish and Game (DFG) to ensure that the public is informed about the potential risks of eating specified sport fish. Each year, OEHHA’s consumption advisories are published in the DFG’s Sport Fishing Regulations booklet. For instance, there’s been a consumption advisory for sturgeon and striped bass caught in the San Francisco Bay Delta Region since 1996. OEHHA also has the option of issuing a one-time advisory at the county level, via local health departments, which then take over the responsibility of informing the public. But so far, OEHHA has not issued an advisory for catfish and largemouth bass in the Delta at any level.

Why no advisory has been issued is in itself a mystery, with answers that are hard to come by. OEHHA regulators swim in an area saturated with as many different public and private stakeholders as the water has pollutants: state and local water resource boards, county health departments, farmers, corporations, sport fishermen associations, small-town tourism boosters. It’s a balancing act as delicate as the environment itself, and if OEHHA and DFG favor any particular side, they tip their hands in the 2001 Sport Fishing Regulations: The consumption advisories, arguably the most important information for potential sport fish consumers in the 64-page booklet, are buried way back on the penultimate page.

That’s not a problem for Mike Rukstalis, a hulking, curly headed construction contractor from Benecia, who claimed he reads the booklet from cover to cover every year when he renews his fishing license. He’s familiar with the San Francisco Bay Delta Region advisory; he knows you’re not supposed to eat stripers or sturgeon once they grow beyond a certain size. He also knows that catfish aren’t on the advisory list. That’s one reason why he likes mooring his boat at the Walnut Grove Marina every summer. If the stripers aren’t hitting out on the river, he can always fish for monster cats under the dock.

“Catfish are attracted to things that smell stinky,” Rukstalis said, scrunching up his nose as he sliced off a hunk of rotten salami he’d been saving for bait. He imbedded a hook in the rotten hunk. “The stinkier the better.” He dropped the bait in the water, set his pole flat on the dock, and took a sip from a bottle of peach schnapps. “Now we wait.”

Most of the dozen or so anglers interviewed for this story weren’t anywhere near as studious as Rukstalis when it came to reading the fishing regulations. Dan Hairell, 56, a Modesto retiree interviewed minutes after pulling a 22-inch striper out of the Sacramento River near the Rio Vista bridge, was one of the few people who had read the advisory and could recite the parameters. He planned on eating the striper, which was within the safe limits set by OEHHA, when he returned home. “I wouldn’t do it very often, but once in a while is OK,” he said. “Besides, anything you eat nowadays is bad for you.” That wasn’t enough to persuade his wife Susan, fishing beside him, to join him for dinner.

“I just don’t eat fish,” she said. “I catch and cook ’em; he cleans and eats ’em.”

Nelson Lagmay learned about the advisory the way many anglers do: through word-of-mouth. Lagmay, 41, lives in Thornton and has been fishing the Mokelumne River for the past 20 years. He prefers fishing for stripers, and over the years, he’s landed bass ranging from 15 pounds to 27 pounds in size. A friend told him to eat no more than one meal of striper per week, which is approximately the amount of fish he thinks he actually consumes. It also happens to be double the striper consumption limit for adult males listed in the advisory. Lagmay was surprised, and said he would consider cutting down.

“I hardly eat catfish anymore,” he said. “It has a different taste than it had 10 to 15 years ago.” Often, he’s pulled in catfish mottled with red and yellow sores. He throws them back. But the 15-pound monster cat his teenage son caught at the mouth of the Mokelumne several weeks ago appeared to be healthy, so they kept it. “It was clean,” he said. “We ate it and we ate it and we ate it.”

Rukstalis had no problem with that, either. He eats catfish all the time. “I looked in the advisory; catfish aren’t in there,” he said, adding with a bit of false bravado, “besides, if it’s not enough mercury to tell the temperature by, I’m not worried.”

To eat the fish or not to eat the fish? That’s the question. But what’s the answer? The introduction to the DFG’s advisory section offers little help to those seeking to become informed:

“Sport fish may present a health hazard when eaten due to natural and industrial chemicals in their flesh, especially when they are consumed often,” it begins ominously. Yet by the second paragraph, the text becomes an exercise in equivocation: “These advisories are not intended to discourage you from eating fish. Fish are nutritious and an excellent source of low-fat protein. The advisories should be followed to make your sport fish eating safer.”

For 20 years, DeltaKeeper Bill Jennings has been prowling local waterways.

Photo By R.V. Scheide

DeltaKeeper Bill Jennings has a more direct answer: “A 15-pound catfish is the last thing I would eat out of the Delta,” he said.

For the past 20 years, Jennings, a former fly fishing shop owner who cut his activist teeth on the peace and civil rights movements of the 1960s, has been patrolling Delta waterways and filing a multitude of lawsuits to force local, state and federal government agencies to comply with Clean Water Act regulations. DeltaKeeper is affiliated with WaterKeeper, a watchdog organization for the nation’s major waterways. As the leading DeltaKeeper, Jennings commands three boats, a lab with the latest high-tech testing equipment, and a small staff of researchers and student volunteers from out of his home next to the levee in Stockton.

One of the nonprofit organization’s major victories was forcing the San Joaquin County Department of Health and Human Services to erect signs warning anglers not to eat fish caught in the deep water channel next to downtown Stockton. Jennings pushed for the signs after dangerously high levels of PCBs were detected in the popular fishing spot. They are among the few consumption advisory signs posted anywhere in Northern California. The message is clear and direct—“Don’t eat the fish caught here”—in English and six other languages.

“There’s a huge subsistence fishing community using the Delta area,” Jennings said. On any given day of the week, large numbers of Asians and Hispanics can be found fishing the banks of sloughs, waterways and rivers. Some are new immigrants or migratory workers who depend on fish caught in the river for a major source of protein. “These communities are clearly at an increased risk,” he said, puffing on his ever-present pipe. “We need to put up more signs. We need to do a consumption study. We need to do more monitoring.”

DeltaKeeper helped fund one of the few surveys of sport fish in the Delta, the aforementioned SFEI study.

“We really don’t know what [the public] is eating,” said SFEI’s Jay Davis, a biologist who co-wrote the institute’s report, who repeatedly stressed the need for more research. “We found high concentrations of methylmercury in the places where we’ve looked, but we’ve only looked at a small portion of the watershed.”

Methylmercury is more hazardous to humans and other organisms than the elemental form of mercury because it “bio-accumulates.” That means when the big fish eats the contaminated little fish, the big fish gets all the little fish’s contamination, added to its own. When an even bigger fish eats the big fish, the bigger fish gets all the big fish’s contamination added to its own … and so on, up the food chain. The mystery fish, Ictalurus catus, vacuuming the Delta floor for the past decade, gobbling up tainted crawfish and mudsuckers, which in turn have fed upon other contaminated organisms, is potentially a bio-accumulating methylmercury monster.

If methylmercury levels are high enough, the health effects can be devastating. The most serious poisoning incidents on record occurred in Japan in the 1960s. In one incident, 111 people died or became very ill after eating fish contaminated with levels of methylmercury ranging from 9 parts per million to 24 parts per million (ppm). The symptoms experienced by the victims ranged from numbness and tingling in the lips, fingers or toes to involuntary muscle tremors, coma and death in extreme poisoning cases.

Based on studies of the Japanese incidents, the U.S. Environmental Protection Agency set the methylmercury limit for freshwater sport fish at 1 ppm, approximately one-tenth the level at which the onset of negative health effects was observed in the Japanese incidents. The U.S. EPA issues a national consumption advisory for any species of fish found to consistently exceed this value in scientific studies. In California, the methylmercury limit set by OEHHA is set even lower, at .3 ppm.

When striped bass and sturgeon taken in the San Francisco Bay and the Delta were found to contain methylmercury in excess of the .3 ppm state limit in 1996, the following advisory was inserted in the DFG regulation booklet:

“Because of elevated levels of mercury, PCBs and other chemicals, the following interim advisory has been issued. A final advisory will be issued when the data has been completely evaluated. Adults should eat no more than two meals per month of San Francisco Bay sport fish, including sturgeon and striped bass caught in the Delta. (One meal is about eight ounces.) Adults should not eat any striped bass over 35 inches. Women who are pregnant or may become pregnant, nursing mothers and children under age 6 should not eat more than one fish meal per month. In addition, they should not eat any striped bass over 27 inches or any shark over 24 inches.”

The consumption limits are lower for pregnant women, nursing mothers and children under 6 because methylmercury can cause neurological damage to fetuses, babies and children at lower levels than it causes problems in adults. While most experts agree that federal and state consumption advisories such as this adequately protect the majority of adults who consume sport fish, considerable disagreement remains about how to best protect pregnant women, nursing mothers, developing children and other at-risk populations, such as communities who practice subsistence fishing.

In April, two nonprofit environmental organizations, the Environmental Working Group and U.S. Public Interest Research Group, released a report criticizing current federal methylmercury advisories because they might allow pregnant women, nursing mothers and developing children to consume amounts that potentially may cause serious birth and developmental defects. The groups recommended that the advisories be expanded to include more species of fish and smaller recommended portions for at-risk populations.

Interestingly, while U.S. EPA’s advisory threshold for methylmercury, 1 ppm, is three times higher than California’s .3, the federal agency currently advises consumers to eat no more than one serving of freshwater sport fish—of any species— per week. That goes considerably further than OEHHA, which continues to end the San Francisco Bay Delta Region advisory with the same sentence it’s used for the past six years: “This advisory does not apply to salmon, anchovies, herring and smelt caught in the Bay; other sport fish caught in the delta or ocean, or commercial fish.”

In other words, catfish and largemouth bass, the other sport fish caught in the Delta, are not included.

The SFEI study on catfish and largemouth bass, which was submitted to OEHHA last September, recommended that a long-term monitoring program be conducted to track contaminants in the Delta sport fish. But so far, no such program has been forthcoming.

“They analyzed the data, and their primary response was, ‘Who’s going to pay for the study?’ ” Jennings said. “They’ve been notably reluctant.”

Warning signs in downtown Stockton are among the few in Northern California.

Photo By R.V. Scheide

“In order to make an advisory, we have to conduct an adequate risk assessment, and that takes time,” said OEHHA spokesman Allan Hirsch.

“We’ve been dying to get a clear statement about how much data would be required before they would actually issue a study,” Jennings fumed. “The enormous fallacy is that people assume regulatory agencies are protecting them. The reality is that all of these organizations are subject to political influence.”

“I can’t think of a time that we had political pressure to not put an advisory out,” Hirsch countered. “Most of the times, the counties are willing to work with us.”

But Hirsch admits that keeping the public informed of potential methylmercury problems can be difficult. A local interim advisory issued for the Bear and Yuba rivers last September makes an excellent case in point. A U.S. Geologic Survey study of bass and catfish in the two rivers last year found methylmercury levels above the advisory limit. OEHHA contacted the health agencies in the involved counties, which held a joint press conference to issue the interim advisory. Articles appeared in newspapers. Fliers were posted in bait shops. But what if the stories weren’t seen or the fliers posted? OEHHA doesn’t have any sort of enforcement mechanisms, so all the parties concerned were on the honor system. The agency can’t even make bait shops ensure that everyone who purchases a fishing license receives a copy of the regulation booklet.

Not that receiving a copy of the booklet is going to help anyone figure out if it’s safe to fish in the Yuba and Bear rivers, because the interim advisory is not listed in the 2001 regulations or either of its two annual supplements. There’s no mention of it in the online version of the regulations at A search of the OEHHA Web site at came up empty. The only thing standing between those who weren’t in the area the day the advisory hit the paper and a potential above-advisory dose of methylmercury is the friendly neighborhood bait shop—not exactly the most reliable source for this kind of information.

“People don’t go out of their way to broadcast advisories,” Jennings noted. “It’s a disincentive for people to go to an area and fish.”

Interviews with various Delta bait shop clerks confirmed Jennings’ assessment. Asked point blank if there were any sort of health advisories for fish in the Delta, clerks at three separate locations responded with a poker-faced, “No.” In one case, the clerk was standing directly behind a stack of Fish and Game regulation pamphlets that contained the San Francisco Bay Delta Region advisory.

While OEHHA and Fish and Game’s methods for informing the public of potential health problems remain somewhat mysterious, there’s no secret surrounding the origins of methylmercury contamination in Northern California. Although mercury occurs naturally in the environment, most researchers agree that mining practices dating back to the Gold Rush account for most of the contamination.

Elemental mercury, or quicksilver, the metallic liquid most people think of when they think of mercury, was used to extract gold from ore in the environmentally brutal hydraulic mining process. In the process, gold ore, blasted from Sierra hillsides with high-pressure water, was mixed with mercury in wooden sluice boxes. The two elements formed an amalgam that could be separated from the ore and waste sediment and then later broken down. Once the gold was separated, the mercury was discarded with the rest of the waste products into streams and rivers, where it settled in the lakebeds and river bottoms of the North Central Valley watershed. UC Davis aquatic ecologist Darrel Slotton estimates that as much as 20 million pounds of elemental mercury may have been dispersed into the entire system.

To gain some geographic perspective on the dispersal of this mercury, imagine the North Central Valley, situated between the Coast Mountain Range and the Sierra Nevada, as a gently sloping funnel. The top of the funnel might be delineated by Highway 20, which connects Clear Lake and Grass Valley. Those two locations are historically important. The Sulfur Banks mercury mine in Clear Lake, which once supplied mercury to gold mines in the Foothills, is now an EPA Superfund site. In the mid-1980s, OEHHA issued a consumption advisory for fish caught in Clear Lake and Lake Berryessa, the site of yet another mercury mine.

When OEHHA issued its interim advisory for fish caught in the Bear and Yuba rivers, it completed the top of the funnel. This crisscross pattern was repeated up and down the valley as mercury mines in the Coastal Range raced to provide enough raw material to process gold ore in the Sierras. Mercury was often spilled in transit, adding to the pollution. Thus, the mercury contamination spread all the way to the bottom of the funnel: the Sacramento-San Joaquin Delta and San Francisco Bay.

Slotton, who has been researching mercury contamination in the North Central Valley watershed for more than a decade, admits that the Delta and the Bay’s precarious location at the bottom of the funnel was a cause of great concern when research in the area began during the 1990s. However, recent studies may have revealed a silver lining behind the dark cloud of potential methylmercury contamination. For reasons he and his colleagues have yet to fathom, elemental mercury in the Delta is not being converted into methylmercury at as high a rate as scientists had feared.

“We thought the Delta would be a complete disaster,” Slotton said. “But the levels aren’t as bad as we thought they’d be.”

Based on previous research conducted in the Eastern United States and Europe in areas that had been dramatically affected by methylmercury contamination, the levels were expected to be much higher, perhaps in excess of the EPA’s 1 ppm limit, a red flag that might have triggered immediate federal action. The lower-than-expected results have been heartening to researchers.

The bad news is that methylmercury continues to be the pollutant scientists studying the Delta remain most concerned about. Levels measured at individual sites and in individual sport fish in the northern Delta—the sloughs, rivers and waterways located nearest Sacramento—may be in excess of the state’s .3 ppm guideline, according to both Slotton and SFEI’s research. Traveling up the Sacramento River, the mercury rises, peaking near the confluences of the two other major river systems that drain into the northern Delta, the Cosumnes and the Mokelumne, where the mystery fish has spent most of its life, prowling the riverbed in its never-ending quest for food.

Not that methylmercury is the only problem.

“When someone says there’s mercury in the fish, that’s just the tip of the iceberg,” Jennings said. “We use these waterways for sewers to dump our waste in. They are polluted, and will become increasingly polluted, as we double the population of the Central Valley during the next 20 years. We’re fighting the good fight, but there’s an astounding number of pollutants entering the system.”

This 22-inch striper caught by Dan Hairell is OK to eat, according to state Fish and Game regulations.

Photo By Larry Dalton

If the mystery fish sensed all these pollutants, it gave no indication as it slipped smoothly into the Walnut Grove Marina, located at the mouth of the North Mokelumne. It drifted with the current, its white underbelly flattened against the muddy bottom, whiskers probing, oblivious to the pesticide residue, discharged houseboat sewage, and methylmercury coursing across its gills. Ahead in the darkness, it sensed the fragrant bouquet of decay, the smell of something rotten, yet sweet. It turned toward the rotten smell, moving gracefully beneath cabin cruisers, houseboats and dingies with a singular purpose. Beneath the dock at the far end of the marina, it found the source of the smell: a medallion of rotten salami resting on the bottom.

It did not sense the hook imbedded in the rotten meat; nor did it notice the strand of nylon monofilament fishing line leading to the surface, where, topside, Mike Rukstalis was reminiscing about marlin fishing in Cabo.

“The first day, I caught seven fish,” he said excitedly. It was catch and release, which was fine by him. “The first fish, when I finally landed it, I got one look at its big beautiful blue eyes, and I realized that there has to be a God.”

The pint of peach schnapps, full when he started fishing an hour ago, was nearly empty. The sun was just beginning to set; the eastern horizon had turned a smoggy, modulated lavender in color. In the sloughs and waterways, tiny smelt leapt out of the water toward the sky, like backward silver rain.

The tip of Rukstalis’ pole dipped toward the water. It dipped again. Casually, without standing up, he picked the pole up. When the dip came again, he yanked the pole.


The mystery fish did not jump and dance on its tail like a marlin; it simply dived for the bottom, taking Rukstalis’ line with it, the way a big monster cat will do.

“It’s like reeling in a log!” he exclaimed.

The fish broke the surface, and the small crowd that had gathered around Rukstalis gasped. It was the biggest catfish anyone had seen all summer. He netted the fish and placed it in the bottom of his boat. Before he could get in the boat to remove the hook and attach the stringer, the catfish came at him, using the spines in its pectoral fins like arms to pull itself forward. Rukstalis grabbed a club and rapped the creature on top of the skull, stunning it into submission.

He laid it out flat on the dock. It was unbelievably fat, as if its belly was about to burst. Rukstalis inserted a skinning knife into the fish’s anus, and in one quick motion, slit the fish’s belly clean up to the gills. Fifteen undigested crawfish, along with the fish’s entrails, schlupped out onto the dock.

“Ewwwwww!” said one of the teenaged girls in the crowd.

“What you gonna do with it?” a man asked Rukstalis.

“I’m gonna fillet it up and eat it,” Rukstalis answered.

“You can’t eat that fish,” the man said. “It’s been in the river too long.”


To eat the fish or to not eat the fish? That’s the question. Is there one, definitive answer? “A 15-pound catfish is the last thing I would eat out of the Delta,” said Bill Jennings. Scientists such as Darrell Slotton and Jay Davis would probably agree that eating such a big catfish might not be the wisest thing to do. But both are hesitant to answer when asked if it’s safe to eat any of the catfish caught in the Delta.

“From my perspective, it’s not that easy to get sick from methylmercury poisoning,” Slotton said. “It would kill me if everybody stopped fishing. … Still, I wouldn’t feed a bunch of it [catfish] to your kids.”

Davis concurs.

“Mercury is a very squirrelly type of chemical,” Davis said. “Nobody really knows what to expect. There are preliminary indications of a potential human health concern and the need for a more detailed study.” Until that study is conducted, Davis suggests that those who wish to play it totally safe apply the consumption advisory limits for striped bass and sturgeon to largemouth bass and catfish as well.

And Mike Rukstalis? Well, the big fella decided he might have a problem with eating a catfish potentially contaminated with methylmercury after all. He skinned and filleted the big fish, but couldn’t bring himself to eat it.

“I wish that guy at the dock had said something sooner,” he said. “I would have let it go.”