Fish population soars in wetlands lagoon area

Scientists surprised at volume, speed of recovery

The San Dieguito wetlands restoration project is showing signs of success much faster than scientists anticipated.

Since a newly created lagoon was opened to the ocean and tidal flow in January, an estimated eight to nine million fish have populated the large basin west of Interstate 5 and south of the Del Mar Fairgrounds.

“We were pleasantly surprised and pleased,” said Dr. Steve Schroeter, a marine ecologist monitoring the restoration project for the California Coastal Commission. “It’s good habitat and it has a good connection with the ocean.”

The man-made lagoon, the size of about 40 football fields, went from having zero fish eight months ago to about four million by June. When scientists measured the population again in August, the numbers had more than doubled - more than three times the volume in the adjacent pre-existing lagoon.

“The water quality is a lot better; there is better flushing,” Schroeter said, which means the lagoon is more fully and regularly replenished with new oxygenated ocean water.

Several types of fish are swimming in the subtidal basin, including halibut and mullet.

The most abundant species is gobi, a tiny fish that burrows in the sediment and forms the foundation of the lagoon’s food pyramid.

Gobi galore

The presence of the gobi, which makes the lagoon its home, shows the ecosystem is really beginning to flourish, scientists said.

“Anytime you have tidal flow you are going to get fish,” Schroeter said. “The thing that is different about this is there is a lot of gobi.”

In addition to the fish, grasses are taking root, and various species of snails and other invertebrates are starting to appear.

Snails that populate mature wetlands by the thousands per square meter have already laid eggs; and their colorful sea slug predators are already on the prowl.

The $86-million restoration of the lagoon and 150 acres of surrounding wetlands is funded by Southern California Edison as mitigation for environmental damage caused by the San Onofre Nuclear Generation Station.

Unexpected returns

“We didn’t expect this big of numbers,” said Pat Tennant, a marine biologist with Southern California Edison overseeing the restoration project. “To see it succeed so quickly is really neat.”

Besides restoring precious habitat, the project is providing a unique opportunity to study how lagoon ecosystems develop from the ground up. Schroeter and his team from University of California, Santa Barbara’s Marine Science Institute have monitored the lagoon from day one.

Often, restoration projects are of existing wetlands and much smaller, Schroeter said. The area that is now a budding lagoon was once an airfield where World War II blimps landed.

By studying this unique wetland, the scientists’ data collections and observations may provide insight for other restoration projects.

The San Dieguito restoration project began in mid-September 2006 and is slated for completion in late 2009.

A diverse range of habitats will be revitalized, spanning from Dog Beach to El Camino Real, east of Interstate 5, and from Via De la Valle to the edge of Crest Canyon. Eventually a 55-mile Coast-to-Crest trail will connect the area to Julian’s Vulcan Mountain.