Salmon are piled in a bin for charities after Mokelumne Fish Hatchery employees collected eggs. (Jennifer M. Howell/News-Sentinel)

Biologists work to protect salmon

An underwater migration of more than 16,000 salmon is underway in the Mokelumne River.

Each fish is struggling against the rushing river current to get back to its birthplace to spawn and then finish its life cycle.

It's a massive movement of fish that goes widely unnoticed on land, but there are some for whom this is the busiest time of the year.

The damming of rivers throughout the state has changed the natural salmon run, creating obstacles and destroying spawning habitat for millions of fish, said Joe Merz, a fisheries biologist with the East Bay Municipal Utilities District.

But the salmon have proven to be a resilient species, with the help of humans, Merz said.

"What we have now is far from natural, though," he said. "The Mokelumne is a highly managed river."

Fall-run Chinook salmon of the Mokelumne River historically spawned above what is now the Camanche Reservoir. The Camanche Dam, built in 1964, essentially destroyed the natural spawning habitat of the salmon, which was replaced with the Mokelumne River Fish Hatchery.

The hatchery is responsible for more than half of the Mokelumne River salmon produced each year — the first step in restoring the salmon population. Merz and a team of biologists are now working on the next step — getting as many salmon as possible to spawn naturally in the river.

Without removing the dams along the Mokelumne river, the task is somewhat complicated, requiring constant monitoring of water flow and temperatures to create prime spawning conditions, adding gravel to the river bed to recreate the natural flow of sediment impeded by the dam and restricting recreational fishing to give salmon the best chance possible to reach their spawning destination.

Not including staffing costs, the spawning and restoration projects cost EBMUD $520,000 annually.

Biologists also count the salmon carcasses and redds, or salmon nests, found in the spawning area between Camanche Dam and Mackville Road.

To an untrained eye the redds could go unnoticed, but biologist Jose Setka surveys the river while floating down it, looking for areas where the gravel seems cleaner than normal.

Gravel along the riverbed accumulates algae and mud throughout the year, but in order for their eggs to be properly fertilized, the female salmon has to have a clean area to work. She uses her tail to stir up any settled grime and dig a space large enough to lay about 5,000 pea-sized eggs.

When she's finished, she covers the pile of orange eggs with the now clean gravel to hide the nest from predators. All this work makes Setka's job a little bit easier.

Setka said his group performs the redd counts the same way every year so they can get comparative results.

If numbers are down or up by a large margin research is done to try to figure out what changed from one year to the next.

"It's important to remember that the salmon run is cyclical, so it peaks and then the numbers go down again," Setka said. "Our job is to ensure the low side of the cycle isn't as bad as it used to be."

Setka is referring to poor river conditions between 1987 and 1992 due to drought that caused the salmon run to drastically decline. In 1990 only 71 redds were found in the Mokelumne River. Last year Setka's group found more than 2,400.

Wildlife biologists, specializing in habitat restoration on land, like Kent Reeves, are also helping the salmon by working with landowners along the riverbanks to restore natural vegetation, which in turn brings native species, reduces water pollution, stabilizes riverbank erosion and improves the overall river ecology.

He said buy-in from farmers is especially important because it can significantly reduce the amounts of pesticides that enter the river.

Chris Locke, whose walnut grove runs along about one-and-a-half miles of the Mokelumne River, began serious habitat restoration along his property in 2001 with the help of Reeves.

"It's a very effective and inexpensive way to control pests," Locke said. "There are aesthetic benefits, too. It beautifies our ranch and it makes the riverbank look more natural for people floating down the river."

The restored habitat acts as a buffer between recreational river users and Locke's crops, while also increasing the population of natural pest predators, such as bats and owls.

Attracting natural predators for moths and mosquitoes means decreasing the need for pesticides, which will increase water quality.

Reeves said trees along the riverbanks also creates shade, which keeps the water cool during warm winter months. Cooler water is better habitat for salmon and steelhead, and it keeps diseases from breaking out in aquatic species.

"It's good for the crops and it's good for the wildlife," Reeves said. "Everybody benefits from the restoration effort."

Contact reporter Rebecca Adler at rebeccaa@lodinews.com.

First published: Wednesday, December 6, 2006