Surveys of three streams in the Russian River watershed show the first encouraging signs that a ground-breaking recovery effort is making headway rescuing coho salmon from the brink of extinction in part of its historic California range.
Recently completed snorkeling and electrofishing surveys estimate survival of more than 12,000 young fingerlings released last spring into Palmer, Sheephouse and Gray creeks at 54, 60 and 71 percent, respectively.
"We're thrilled to see these kinds of numbers," said Paul Olin, director of the University of California's Sea Grant Extension Program (SGEP) and one of the partners in the Russian River coho recovery program. "Coho spend their first year and a half in fresh water, which presents extraordinary survival challenges. To see significantly more than half the juvenile fish released last spring survive to the fall is a very hopeful sign."
Young coho have been planted in Russian River tributaries by personnel from the California Department of Fish and Game (CDFG) three times since October 2004, when 6,160 fingerlings were first released. Winter survival estimates for the first batch of young fish ranged as high as 56 percent. They migrated out to the ocean last spring and are expected to make their return as adult spawners about a year from now. An additional 14,000 coho fingerlings were released into the creeks in the fall of 2005. Those spring- and fall-planted fish that survive the winter will migrate to the ocean next spring.
Not unlike the effort to save the California condor from extinction, the effort to save Russian River coho is a "captive broodstock" program. Individual members of a species are taken from the wild and reared in captivity. Winter-run Chinook salmon in the Sacramento River are experiencing a dramatic return from near extinction following a similar recovery effort. Other efforts to restore coho populations exist elsewhere in California and the Pacific Northwest, but the Russian River project is one of few attempts to resurrect viable coho populations with a captive broodstock program. Fisheries managers had little choice. These fish were on the verge of extinction in the Russian River.
Biologists believe coho numbers dropped in the late 1990s to a mere 100 adult fish in the entire Russian River system, a precipitous decline caused by factors such as loss and degradation of freshwater habitat and changing ocean conditions. Surveys of prime coho streams found no returning spawners several years in a row. Throughout its entire California range, coho numbers have dropped to between 6 percent and 15 percent of their abundance during the 1940s.
In 2001 CDFG biologists captured about 200 juvenile coho from Russian River tributaries. The fish were carefully gathered in the wild, vaccinated to prevent disease and reared to adulthood in specially designed circular tanks at the Don Clausen Warm Springs Hatchery near Geyserville. After two years these adult fish were spawned at the hatchery and their progeny subsequently reared to restock Russian River tributaries where coho have historically ranged.
Hatchery rearing challenges
"Rearing coho in a hatchery to retain wild characteristics presented formidable challenges," said Louise Conrad, a biologist who manages the coho hatchery and restocking program for CDFG. Special diets and feeding protocols had to be developed. Visual contact with people had to be minimized so fish wouldn't lose their natural tendency to seek shelter upon observing movement -- a natural flight behavior in response to a potential predator.
The first group of juvenile coho collected in 2001 was raised in rectangular troughs or raceways. But the raceways stunted growth at a critical period for successful reproduction. The second group of spawners spent a limited amount of time in the raceways and was then moved to large dome-covered, circular tanks that dot the hatchery grounds like turquoise and black igloos. Inside the tanks, small schools of silvery adult coho swim against a gently swirling current until they're ready to be harvested for eggs and milt during December.
"The circular tanks provide more depth and a greater volume of water for each fish," Conrad said. "The circular flow pattern creates superior rearing conditions that enabled our spawners to grow to a larger size. The larger spawner size has translated into improved egg quality and ultimately more juvenile fish to plant in the streams."
Genetic "matrix" developed
Advanced genetics are playing a critical role in ensuring a wild future for coho salmon. Fin tissue samples are collected from juvenile fish when they are tagged for future identification. These samples are shipped to scientists at a National Marine Fisheries Service laboratory in Santa Cruz. Through genetic fingerprinting a "spawning matrix" is developed so hatchery personnel can determine which male and female coho are optimal mating partners.
"If we didn't use this spawning matrix, we would probably end up spawning fish together that may be related at the level of siblings or half-siblings," Conrad said. "If we did this, we would still be able to produce fish, but we would be jeopardizing the long-term persistence of the population. The more inbreeding that happens now, the more likely it is that ensuing generations would suffer from lower fitness."
Landowners learn stewardship
Another key element of the coho recovery project has been educating landowners, vineyard managers and equipment operators about salmon biology and managing streamside vegetation for maximum shading of the deep pools where coho find summer sanctuary. Approximately 90 percent of the Russian River watershed is in private hands.
"The fate of coho salmon in this region is tightly linked to protection and restoration of privately owned critical habitat," Olin said. "We in UC Cooperative Extension (UCCE) and the Department of Fish and Game saw an opportunity to provide assistance and information on restoration design and planning and created an outreach program to enlist the support of landowners. They responded enthusiastically."
Between 1998 and 2004, multiple free workshops were offered to local landowners throughout the Russian River watershed. They were attended by 428 people representing 73 tributaries and more than 1,000 miles of streams. The restoration portion of the program resulted in more than 40 completed stream enhancement and habitat restoration projects on targeted tributaries. Wall-sized woven willow baffles were installed to shore up eroding stream banks. Invasive plant species were ripped out and replaced with natives. Roads were regraded. Vineyards added permanent cover crops. New cattle fences kept cows out of sensitive in-stream spawning habitat. Redwoods were planted to help keep water cool on hot summer days.
Landowner interest and participation continues through the granting of access to streams for the release of fingerlings and to monitor coho survival. "This willingness by landowners is critical to achieving the goal of recovery for coho in the Russian River," said David Lewis, the region's UCCE Watershed Management Advisor. "Without the landowners and their stewardship, this would not be possible."
Monitoring enhances success
One of the aims of the recovery effort is to maximize the amount of time coho are raised in the wild to allow for adaptations that will enhance fitness. Monitoring survival rates for spring- and fall-released coho will help determine the stocking strategy that has the highest chance of restoring coho to the Russian River. "We're trying to figure out whether it's better to stock fish in the spring or in the fall," said Mariska Obedzinski, UCCE's coho monitoring coordinator for the project. "In all likelihood mortality will be higher for the fish released in the spring, but in the long run the additional time in the stream may give them an adaptive advantage over fall-released fish.
"The results of summer population estimates showed excellent survival rates," Obedzinski continued. "That may have been because of the good rainfall we had late into the spring this year. Our stream surveys will help us plan for the future. Everything we're learning goes right back into the program."
Next spring the coho planted this year will undergo a physiological transformation to prepare them for life in the saline waters of the ocean. These "smolts" will begin a downstream migration that Obedzinski and other UCCE biologists will be monitoring, with in-stream traps, to generate a coho head count and provide information about the other species that share their nursery waters. They will also be monitoring other factors, such as stream temperature and flow and the make-up of aquatic insects (natural fish food) to search for clues to coho survival.
Agency collaboration critical
The recovery effort includes many additional public and private groups that have contributed financial assistance, staff and equipment. The Department of Fish and Game heads up the hatchery and broodstock efforts with support from the Army Corps of Engineers and NOAA Fisheries. The Sonoma County Water Agency aids in the monitoring efforts led by UCCE and Sea Grant. Other partners include the University of California's Bodega Marine Laboratory, Point Reyes National Seashore, Americorps Watershed Stewards Project, Russian River Watershed Council, Trout Unlimited, City of Santa Rosa, Marin Municipal Water District and the Institute for Fisheries Resources.
"This multi-agency collaboration and landowner involvement is what will make recovery of the coho possible," Olin said. "Ultimately we'd like to see self-sustaining runs of coho throughout the Russian River watershed." What happens with this project could have long-term ramifications in other areas. Healthy populations of coho salmon remain scarce throughout their Central California Coast range - an area extending from the Mattole River in Humboldt County to the San Lorenzo River in Santa Cruz County.
"If we can document success in this program," Conrad said, "then I think it is possible that other captive broodstock programs very much like ours will sprout up in drainages where certain salmon populations are on the verge of extinction."
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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