Sea lions along Sacramento River blamed for salmon decline
By: Matt Weiser

Ask a Sacramento angler for reasons why Central Valley salmon populations have crashed over the past two years, and this is likely to be high on the list:

"Dozens of sea lions that live between Rio Vista and Verona year-round," said Sacramento fisherman Terry Horst. "That's a major problem because they eat tons of fish a day."

Scientific brain power has been applied in thick doses to many aspects of the alarming fish declines in the Sacramento-San Joaquin Delta – from weather patterns to water pollution. No one with a science degree, however, has had anything to say about sea lions.

Now Mark Dendy, a professor of biology and natural resources at American River College, has produced a survey of the Delta sea lion population. And, yes, there are resident sea lions, though not nearly as many as fishermen think.

According to Dendy, five individual California sea lions live most of the year in the Sacramento River. They account for most sightings between Isleton and Colusa.

These five spend much of their time in the river near downtown Sacramento, at the confluence with the American River. Dendy has seen them eating catfish and striped bass. But their favorite appears to be chinook salmon – as many as one every 45 minutes.

Dendy identified the five individuals through unique markings on each animal in photos and video gathered during 132 hours of boat observation between September 2007 and January 2008. They are not harbor seals but California sea lions, distinguished by small external ear flaps.

He published his findings as his master's thesis for a degree in life sciences from the University of Maryland, and presented results at a Delta science conference in October.

"I don't think it's the cause of the collapse of the salmon fishery by any means," said Dendy, 54, who lives in Elk Grove. However, he said, "This has become a problem in the Sacramento Delta."

Since 1972, the Marine Mammal Protection Act has made killing and harassing sea lions a crime. The law followed steep population declines caused by hunting for fur and blubber, and it was a success.

The population of California sea lions is not endangered and now could be as high as 300,000, with an annual growth rate near 6 percent, according to 2007 federal data.

It's likely that declining fish populations and habitats have forced this growing population to travel farther for food. Sea lions are known to be smart, adaptable feeders.

Dendy said sea lions have always visited the Delta but were a rare sight until about five years ago. Now they frequent areas as far inland as the Feather River and Colusa – more than 100 miles from the Golden Gate.

More sea lions are likely to follow, Dendy said.

Marty Gingras, supervising biologist at the California Department of Fish and Game Bay-Delta Office, said his agency knows little about the local sea lions. But employees have seen the animals seize sturgeon, striped bass and salmon out of nets during fish population surveys.

"We know that every fish that a sea lion takes is a fish that's not available to spawn naturally," Gingras said.

There is fear that Delta sea lion numbers could grow to rival those in the Columbia River. Hundreds of Stellar and California sea lions have taken up residence there and are blamed for consuming as much as 4 percent of the spring chinook salmon run.

State officials in Oregon, Washington and Idaho obtained federal approval in March to kill up to 85 sea lions. The Humane Society of the United States recently lost a federal lawsuit to prevent the killing, but it plans to appeal.

"All it's going to take," Dendy said, "is this continued uncontrolled growth of the population of sea lions and the destruction of habitats for fisheries, and you're going to see a huge problem like they have up on the Columbia River, and there won't be any more salmon. I believe the potential could be explosive."

Sacramento's five resident sea lions are males. Four leave in spring to visit breeding areas on the Southern California coast.

The fifth is a very large, senior male who stays near the American River confluence year-round. Dendy named him "Brutus," after the Popeye cartoon character. Brutus can be identified by his prominent forehead bulge.

On a recent cold winter morning, Brutus was found swimming calmly at the mouth of the American River, near a sandy beach just below the Jibboom Street Bridge.

"He's 600 pounds if he's a pound," Dendy said as he watched Brutus through binoculars. "He's obviously lost interest in breeding. He's more interested in dining, I guess."

Brutus was not seen dining that morning. But he would stay submerged as long as 15 minutes, then surface and watch activity on the beach with curiosity. The long dives, Dendy said, indicate Brutus may be eating small fish underwater. He was trolling the watery seam where the clear American meets the silty Sacramento.

Dendy said he does not know the impact sea lions have on the river's salmon population. He hopes to start a new research to find out.

A lingering mystery is where the sea lions sleep. They usually have preferred "haulout" areas on shore. But Dendy has been unable to find any such spots along the river. Finding these would be useful to collect scat to analyze the animals' diet.

Dendy said having resident sea lions is probably not a good sign; it indicates an imbalance in nature. They are here, he said, because of overpopulation, a shortage of food or habitat – or all three.

"I don't really begrudge the sea lions eating the fish," said J.D. Richey, a Sacramento fishing guide who shot his own video, posted on YouTube, of a sea lion eating a salmon at the Sacramento-American confluence. "I mean, they've been doing that longer than we have. But now that every salmon is precious, I think the sea lion factor gets a little bit bigger."