Sea Grant Marine Advisor Completes 23-year Study Of Smith River Chinook Salmon

July 31, 2006

Contact: John Stumbos: jdstumbos@ucdavis.edu, (530) 754-7770

A newly published long-term study of a tributary to Northern California's Smith River provides a rare and revealing glimpse into how changing oceanic and stream conditions affect survival and development of Chinook salmon.

For 23 years Jim Waldvogel, a coastal marine advisor with the California Sea Grant Extension Program (SGEP), has been monitoring the comings and goings of some of the state's largest Chinook on a tributary of the Smith River. His findings have just been published in a report now available from California Sea Grant for $10.*

What emerges in the study is a picture of a resilient, once-logged watershed inhabited each winter with modest numbers of huge Chinook. Yet this vital spawning ground is vulnerable enough to see an entire year's offspring severely curtailed by one major flooding event.

California Sea Grant marine advisor Jim Waldvogel observing spawning salmon. Credit: John Stumbos

The need for the Mill Creek study became readily apparent shortly after Waldvogel transferred as marine advisor from Monterey Bay to Crescent City in the late 1970s. The Smith River is the largest undammed, free-flowing river in California that drains directly into the Pacific Ocean. Its remoteness in the far northwestern corner of the state has helped to preserve and sustain runs of steelhead, cutthroat, coho salmon and legendary Chinook salmon prized by sport anglers. Thirty- to 40-pound Smith River Chinook are not uncommon. Occasionally, they reach 50 to 60 pounds.

"There was a lot of interest in adding the Smith River to the wild and scenic river system, and people were throwing around all kinds of guestimates about the number of salmon in the Smith River in general and in Mill Creek in particular," Waldvogel said. Early estimates of the size of the Chinook spawning population were probably 10 to 20 times too high. In fact, the only previous estimate of salmon and steelhead populations on the Smith River was an old Department of Water Resources report from the mid-1960s.

Waldvogel identified a 1.7-mile stretch of Mill Creek's west branch on private timberland to generate more current and thorough information on Smith River fall Chinook. This stretch of Mill Creek provides excellent spawning habitat for Chinook. Its crystal clear water flows over a gentle gradient through clean gravel that these powerful fish use to build nests or "redds." Deep pools formed by an abundance of bedrock outcroppings and redwood debris provide resting spots and refuge from predators. Stream bank vegetation consists of 40- to 50-year-old alders, maples, willows and redwoods. Upstream stretches are protected in Del Norte Redwoods State Park. Downstream, where the west and east branches of Mill Creek converge, lies Redwood National Park.

Beginning in 1980, Waldvogel would don chest waders and walk the study section once a week, stream flows permitting, during the November through March spawning season. On each outing he would methodically and carefully cross the creek 20 to 25 times. A long pole with a gaff on the end served the dual purpose of stabilizing the marine advisor in the sometimes swift current and providing a tool to retrieve the carcasses of spent salmon.

Waldvogel urges caution in referring to the number of reported Chinook spawners in the creek. "It was literally the fish I saw live or the carcasses I counted—and that's one of the things I emphasize in the report. It's not a population estimate. It's a relative abundance, minimum fish count."

Credit: John Stumbos

The greatest number of fish he saw in any one year was 361 in 2001. The lowest number, 31, occurred in 1990, four years after torrential rains ripped through Mill Creek, all but obliterating the Chinook from that year's "age class." Indeed, no female Chinook hatched in 1986 were ever detected in subsequent years.

The age of Chinook can be determined from scale samples, much the way the age of a tree can be determined by tree rings. Salmon scales under a microscope look a lot like fingerprints.

Waldvogel's observations on the age composition showed that most female Chinook returned to spawn as four-year-olds the first 10 years of the study but shifted toward more three-year-olds in the second half of the study for unknown reasons. Male spawners were predominantly two-, three- and four-year-olds. Some male and female Chinook returned as five-year-olds and a few even as six-year-olds.

In 23 years only one female returned as a two-year-old, but 195 two-year-old males or "jacks" returned.

The Mill Creek study shows how changes in oceanic patterns can affect fish populations. "We definitely saw an impact in terms of growth and size of fish during each of the El Niño periods," Waldvogel said. "The average length of fish decreased." Low Chinook counts in 1983 and 1984 were also linked to El Niño. Most West Coast Chinook salmon spawning surveys showed significant decreases in the number of fish during that time. Since then, Chinook numbers have rebounded.

More recently Mill Creek Chinook numbers have increased dramatically to record highs: 296 in 2000, 361 in 2001 and 285 in 2002. This trend may reflect increased salmon survival caused by a long-term shift in ocean conditions known as the Pacific Ocean Decadal Oscillation.

Three distinct Chinook spawning runs exist in the Mill Creek's west branch. The first and largest run occurs late November through mid-December. The second run appeared to spawn more quickly, lasting only a week or two toward the end of January. The third and smallest run lasts only five to 10 days in late February.

Waldvogel also observed some interesting things about the Chinook mating ritual. Most females paired up with a single male. However, in numerous instances, large dominant males would mate with two to three females on a single spawning riffle. Chinook usually made one redd, sometimes two but never more than that. When no large adult male Chinook were present, spawning females could be seen with two to three young jacks. If a large male appeared, he'd chase away the younger fish. Occasionally, three or four large males in the neighborhood of 30 to 40 pounds could be seen biting and ramming each other in a bid to gain dominance over available females.

Other species of fish and wildlife inhabit the region, as well. Coho salmon typically migrated to the upper reaches of Mill Creek about the same time as the first run of Chinook, although in far fewer numbers—25 the most in any year of the study. Even rarer were chum salmon, but they showed up in 10 different years.

Predators were a common sight. Many salmon carcasses showed signs of bear feeding activity. Badly decomposed carcasses were often smashed and had been rolled on by bears. Yet in all those years, Waldvogel saw a live bear only three times—one of those instances giving him pause.

I was walking down the creek one day, and on one side of the stream bank was a big adult mother bear and on the other side was her cub," he said. "I remember thinking, 'I'd better not walk between the two of them. I'm going to go around this.'"

The marine advisor also witnessed mink, raccoons, eagles, red-tailed hawks, egrets and osprey feasting on spent salmon carcasses. Other critters like river otters made their presence known. After nearly a quarter century of meandering alongside this idyllic, near-pristine waterway, however, the pilgrim of Mill Creek decided it was time to hang up his chest waders. Walking through a swift current over uneven submerged cobbles and rocks has been hard on him physically. But the work is continuing. A private consortium of three biologists continues to monitor the 1.7 mile stretch and has branched out into other areas of the Mill Creek watershed.

Eventually state or federal biologists may take over the monitoring work. In 2002 the Mill Creek watershed was acquired by Save the Redwoods League and donated to the California State Parks system. The area is now overseen jointly by the state and Redwood National Park. A long-term management plan is in development.

"The Mill Creek Chinook salmon spawner survey is one of the few such long-term data sets that exist in California," said SGEP Director Paul Olin. "The information on salmon abundance and the tissue archive created during this study will be tremendous assets. They will help us understand how ocean conditions and major climate events affect salmon populations."

Waldvogel continues his many and varied activities as a Sea Grant Extension Program marine advisor in Del Norte County and in Curry County in Southern Oregon. But get him back out to Mill Creek for a visit among his ocean-going friends, and you'll hear the sounds of a man who has thoroughly enjoyed his front-row seat to one of nature's most compelling dramas.

"This has been one of the highlights of my career with Sea Grant - to observe a natural population of Chinook salmon sustain itself for more than two decades," Waldvogel said. "It's crucial that this type of population monitoring continue over time with the changing management in this pristine Smith River watershed."

Waldvogel can be reached in his Crescent City office at (707) 464-4711 or cedelnorte@ucdavis.edu.

The California Sea Grant Extension Program is part of the University of California Division of Agriculture and Natural Resources.

NOAA's California Sea Grant is a statewide, multi-university program of marine research, extension services, and education activities. It is the largest of the nation's 30 Sea Grant programs and is headquartered at Scripps Institution of Oceanography at the University of California, San Diego. The National Sea Grant College Program is part of the National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Commerce.

*"Fall Chinook (Oncorhynchus tshawytscha) Spawning Escapement Estimate and Age Composition for a Tributary of the Smith River, California—23-Year Analysis" by Jim Waldvogel. Pub. # T-060, 2006, 32 pp. with color photos, $10. Also now available: journal article reprint, "Habitat Use by Juvenile Salmonids in the Smith River Estuary, California" by Rebecca M. Quinones and Timothy J. Mulligan, Transactions of the American Fisheries Society 134:1147–1158, 2005. Single copies free. Call 858-534-4446 and leave a message.