PORT ANGELES — The Elwha River mouth’s 80 acres of new beaches are bringing back a very small fish to places it hasn’t been seen in a long time.

That’s the prognosis of the Coastal Watershed Institute, which is surveying such things.

Surf smelt, a small forage fish that nourishes salmon and other larger fish, have begun spawning on beaches near the Elwha River mouth, and eastern Freshwater Bay beaches nearby, said Anne Shaffer, a biologist who is executive director of the Coastal Watershed Institute.

“As soon as the new habitat appeared, they were spawning there,” Shaffer said.

Surf smelt, which can grow as long as 8 inches, spawn on sandy beaches with gravel at low tide, and return to the water as the tide returns.

Their young are dispersed into the water at later high tides, where they eat plankton and become an important food source for larger fish.

Previous surveys dating back to 2006 found that surf smelt were spawning only in a small area on the western shoreline of Freshwater Bay, Shaffer said.

The areas where the new surf smelt nests were found are entirely built from sediment released by the removal of the Elwha River dams, she said.

In recent decades, the area around the Elwha River mouth has been covered primarily in large, dinner-plate-size cobbles — far too large for the small fish to reproduce.

The river mouth was starved of sediment for nearly 100 years while its beaches were washed away by tide and wave action.

Since the dam removals, geologists have estimated that more than 3.3 million cubic yards of sediment, trapped behind the former Elwha Dam and Glines Canyon Dam for decades, has been deposited at the mouth of the river.

That sediment has rebuilt between 80 acres and 100 acres of new beaches, Shaffer said.

Removal of the dams is part of the $325 million Elwha River restoration project, designed to open the 70 miles of river to salmon and steelhead — and now apparently surf smolt.

The Elwha Dam was demolished by March 2012. The Glines Canyon Dam has been blasted down to the waterline, and the final remnants are expected to be removed this fall.

The Coastal Watershed Institute survey was performed on Freshwater Bay beaches July 28 by more than 20 volunteers from the institute and teenage participants from National Geographic Young Explorers, a science research grant program for future environmental scientists.

Survey volunteers collected 20-pound bags of sand from areas thought to be used as smelt nests

The sand was examined by a laboratory to determine the concentration of smelt spawn, which attach themselves to the sand for about a month before juveniles move to nearshore areas for rearing.

Results of the survey showed that the original surf smelt spawning beaches still maintained the same concentration of spawn — and newly colonized areas had similar concentrations of the next generation of smelt.

“We hypothesize that the expansion will continue,” Shaffer said.

Shaffer said she believes that the next fish to return to the nearshore Elwha will be the sand lance, a small nearshore fish that only spawns on sandy beaches in winter months.

Sand lance have not been seen on Freshwater Bay beaches in any previous survey because there was no habitat for them, she said.

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Reporter Arwyn Rice can be reached at 360-452-2345, ext. 5070, or at arwyn.rice@peninsuladailynews.com.