In the Stream of Things

Goldfish, turtles and crayfish may not be your idea of invaders, but when it comes to the water quality of mountain streams, that is exactly what they are.

So says National Park Service Ranger Barbara Applebaum of the Santa Monica Mountains National Recreation Area.

Applebaum will lead a hike Saturday along the stream running through the Peter Strauss Ranch in Agoura Hills to teach visitors about threats to water quality and how to keep streams, creeks and rivers pollution-free.

As for the goldfish, turtles and crayfish that people set free in streams, they eat tadpoles, thus lowering the native frog population, Applebaum said. Unwanted pets, including cats that devastate the native bird population, are among the nonnative species folks have been known to leave in or near the recreation area, she said.

“Deliberately planted or brought-in species to ‘solve a problem’ in the area, like kudzu and ice plants, create new problems,” Applebaum said.

“We were surrounded by development when we inherited these parklands in recent decades. In order to promote the return of native plants and animals there, we have to clean up our act,” she said.

She will point out the common-sense steps people can take to make a difference, such as reducing water runoff from nearby lawns, roads and golf courses.

“The creeks here are still fairly clean,” she said. “The species living in and near them are ‘indicator species’ and require our protection.”

Visitors will learn about the technology rangers use to monitor water quality in park streams and how that quality affects people as well as native species. When the creeks become polluted, that flow goes into the ocean and fouls beaches.

“What happens upstream affects downstream,” she said.

BE THERE

“Return of the Native Plants and Animals,” Saturday, 2-4 p.m., Peter Strauss Ranch, National Park Service, 30000 Mulholland Highway, Agoura Hills. Meet in main parking lot. Free. Call (805) 370-2301.