Block water release looks hopeful for Eel River salmon; Pikeminnow population may be stabilizing

Redwood Times
Posted:   02/27/2013 10:27:38 AM PST

Virginia GrazianiRedwood Times

Detailed reports on a block water release from Lake Pillsbury into the main stem Eel River last spring and on programs to monitor water temperatures and pikeminnow populations in the river were presented to the Eel-Russian River Commission (ERRC) at its most recent meeting in Santa Rosa on Friday, Feb. 15.

Second district supervisor Estelle Fennell represents Humboldt County on the commission, which is made up of one member of the board of supervisors from Humboldt, Mendocino, and Sonoma counties. First district supervisor Rex Bohn, as Humboldt’s alternate commissioner, also attended.

The ERRC was established as a forum for the counties in the Eel and Russian watersheds, primarily to address issues arising from the diversion of water from the Eel River through an eight-mile tunnel that discharges the water into Pacific Gas & Electric’s Potter Valley hydroelectric plant and then into the East Branch of the Russian River.

Under the Reasonable and Prudent Alternative (RPA), a 2004 protocol to protect salmonid populations in the Eel River, PG&E is required to reserve 2,500 acre feet of water for release into the Eel River from its major reservoir, Lake Pillsbury, if needed to aid salmonid migration.

In May 2012 this block water was released in a series of pulses over a six-day period coinciding with the new moon in the hope of encouraging juvenile Chinook to move out of Van Arsdale Reservoir, where the diversion is located, and start their journey to the ocean before the water in the lower reaches of the Eel River became too warm to sustain them.

Scott Downie, senior biologist supervisor for the California Department of Fish and Wildlife (CDFW), expressed cautious optimism about the results in a preliminary report at the ERRC’s previous meeting in Eureka on July 30, 2012.

At the Feb. 15 meeting, both Downie and CDFW environmental scientist Scott Harris, who manages the fish counting station at Van Arsdale, made a more detailed presentation on the block water release.

The numbers of juvenile Chinook that left Van Arsdale during the release, which took place over eight days around the time of the new moon, May 18-25, 2012 increased and the young fish appeared to be growing fast, Harris said.

The water was released from the top of Lake Pillsbury rather than through the needle valve at the bottom of Scott dam because warmer water signals the fish to migrate. Juvenile fish also grow faster in warmer water.

It takes the young fish approximately three weeks to get to Alderpoint, where water temperatures can reach the 70s in early summer. It is important to make sure the fish get moving before downstream water temperatures become too warm, which is stressful and possibly lethal to salmonids.

The big surprise was the appearance of hundreds of Pacific lamprey, the eel-like fish after which the river is named. In two nights 600 lamprey were counted at Van Arsdale. At one point 160 lamprey crowded into a pipe, completely blocking it.

A total of 3,471 Chinook were counted during the overall spring 2012 migration, a record year. Harris counted 750 fish on a single day, “a record day in a record year,” he said.

But Downie and Harris stated that these numbers, while encouraging, are not a good index to the numbers of fish in the entire Eel River system because there are so many factors that can affect the migration.

Furthermore, even though block water is required by the RPA, the actual availability of that water depends on the level of water behind Scott Dam, since the warmer water at the top of the lake has to be released through gates at the top of the dam. If the lake level is too low to reach the gates, warmer water is not available for release.

This year, two months of plentiful rain have been followed by seven weeks without any significant rainfall or snow in the upper Eel, added Paul Kubicek, senior consulting scientist for PG&E.

Unless the dry spell is followed by another “miraculous March” Lake Pillsbury will be too low for a block water release this spring, Kubicek said.

Nevertheless, CDFW is starting to plan for a block water release this spring. “As long as we have questions to answer we’ll keep on doing this,” Downie said in conclusion.

Asked for comments on this report after the meeting, Scott Greacen, executive director of Friends of the Eel River said, “It’s important to note that [the report] starts with the relatively extraordinary admission that normal operation of the Potter Valley Project is retarding out-migration, hence reproductive success, of the fish that climb the Van Arsdale Fish Station. That suggests the relatively intact habitat in the between-dam reach is not necessarily as functional as we otherwise hope it to be, but it also undermines the VAFS numbers as an indication of the overall health of the run, and makes it all the more important that we find ways to gather more and better information about salmon across the whole Eel watershed.”

Fisheries biologist Park Steiner, PG&E’s outside consultant, joined Kubicek to report on the ongoing monitoring and pikeminnow suppression projects required by PG&E’s operating license.

Steiner began with a brief history, noting that the numbers of Chinook and steelhead counted at Van Arsdale increased in the 1980s when PG&E began fall releases of block water to aid up-migrating fish.

But in the 1990s the counts declined again, with only a handful counted in the late years of that decade. This coincided with the accidental release of pikeminnow, a predatory fish from the Sacramento River, into Lake Pillsbury, followed by the flood of 1986, which forced fish over the dam and into the main stem Eel.

The pikeminnow is particularly destructive to steelhead populations because young steelhead stay in the river system for several years and are eaten by the pikeminnow. Like the Chinook, steelhead need cold water to remain healthy, whereas pikeminnow thrive in warm water, giving them the advantage.

The RPA requires PG&E to monitor water temperatures as well as pikeminnow and steelhead populations. Additionally, the RPA calls for PG&E to develop and use a pikeminnow suppression program.

Steiner presented a series of graphs that indicate water temperatures at several sites predictably increasing through spring, summer, and into the early fall.

Also predictably, the most steelhead are found near Cape Horn Dam, which impounds the Van Arsdale reservoir, where the water is coldest. Some steelhead are found as far downstream as Outlet Creek (near Willits), where the Eel River makes an S-shaped bend that provides shade and cooler water temperatures.

Pikeminnow are evenly distributed among all the monitoring sites, but their numbers have somewhat decreased, both in total population and in comparison with the steelhead, Steiner said.

He believes that the pikeminnow population has peaked and is stabilizing. Large numbers of small pikeminnow first appeared in the Eel River after the 1986 flood, but the pikeminnow population has slowly matured.

Steiner speculated that as they grow the bigger pikeminnow eat or chase away the smaller ones, and now comprise a more stable population of fewer but larger fish.

He also pointed out that PG&E will continue to monitor temperatures and fish population, and said that they missed only one year of monitoring in 2011 due to danger from commercial marijuana grows.

On the other hand, pikeminnow suppression efforts were curtailed several years ago after gillnetting killed 13 steelhead as well as over 60 pikeminnow, which amounted to a “take” of an endangered species.

PG&E and its consultants still monitor fish at three sites between the two dams by raft electro-fishing, Kubicek reported. The fish are shocked, captured, identified by species, measured and returned to the water – except for pikeminnow, which are killed.

Various methods of eliminating pikeminnow have been studied and found inadequate or inappropriate. Fennell asked about derbies that reward fishermen for catching pikeminnow. Steiner replied that it’s both expensive and ineffective because so much of the river is inaccessible and because when they are hooked pikeminnow release a pheromone that warns off other pikeminnow.

Both Steiner and Kubicek pointed out that other fish species, including the Chinook, that once seemed to be disappearing have made comebacks.

“It appears that the pikeminnow is here to stay, but the good news is that the Chinook seem to be doing well,” said Kubicek.

“I’d like to see a lot more to convince me that pikeminnow are not a problem for the salmon or that they’ve come into equilibrium with severely depressed (at best) salmonids,” FOER’s Greacen said to the Redwood Times.

Greacen was also skeptical about reasons for the failure of the suppression efforts. “… Pikeminnow control was not supposed to be an optional duty for PG&E under the RPA as I understand. Rather, they are supposed to make a difference somehow. They keep coming up with problems, but the big one seems to be they don’t want to spend more money on it.”

The ERRC is also working on a memorandum of agreement to form an inter-county coalition to develop an invasive species management plan. The plan specifically will address the spread of quagga and zebra mussels, tiny but prolific freshwater mollusks that clog water systems, damage docks and piers, and consume plankton vital to the diets of other marine animals.

The next meeting of the ERRC will be coordinated with the field trip to the Potter Valley Project so it will probably be held in Potter Valley if a suitable meeting site can be found there, said commission chair Carre Brown.

The meeting after that will be held in Eureka, possibly in early July, and will address specific Humboldt issues as well as the invasive species management plan.

The ERRC has recently obtained a website, Although the site can be visited, it is still a work in progress.

For more information, contact Wells Hutchins, secretary of the Eel-Russian River Commission, or by phone at 707-234-6665.