The creature from Topanga Creek

The intruder. Photo/Resource Conservation District of the Santa Monica Mountains Stream Team

Louisiana red swamp crayfish may be a delicacy in the gumbo pot, but these voracious Cajun imports are an unwelcome ingredient in Topanga Creek, where they cloud the water and chow down on native fish, bugs and amphibians.

They’ve been in residence since 2001, when a local resident is said to have dumped a batch of live crayfish into the creek in hopes of cultivating a perennial free bait supply. Since then, there have been intermittent community clean-ups, and those efforts—coupled with winter storms that traditionally have washed many of the crustaceans out to sea—were usually enough to keep the population in check. But a lack of significant rainstorms since March 2011 has spawned a crayfish baby boom.

“We’ve had perfect growing conditions for crayfish. The water is slow-moving. It’s warm. And they have gone berserk,” says Rosi Dagit, a senior conservation biologist with the Resource Conservation District of the Santa Monica Mountains. “They’re a very intense predator…It’s kind of gotten out of control.”

That’s bad news for the health of the creek and also for creatures like the California newt, a snack of choice for hungry crayfish.

“One day we literally witnessed a newt in the hands of five crayfish,” says Lizzy Montgomery, 25, a Watershed Stewards Project intern working at the site. Montgomery and her fellow intern, 24-year-old Crystal Garcia, are in the midst of a crayfish research and removal plan now underway at the creek.

They rescued the newt, but the sight of the near-carnage was enough to help Montgomery get over her qualms about dispatching the crayfish with extreme prejudice. (The creek is clean but the crayfish are bottom-feeders and probably not suitable for people to eat, Dagit says. The collected specimens have been frozen and donated to the Nature of Wildworks wildlife center as food for raccoons being rehabilitated there.)

The interns haven’t been working alone. Starting in October, they mobilized a brigade of local schoolchildren from Calvary Christian School in Pacific Palisades and the Topanga Wildlife Youth Project to conduct weekly crayfish removals in a section of the creek. Their haul to date: more than 400 crayfish.

With the end of the school year, the program has gone on hiatus but Montgomery and Garcia say they hope to bring it back. Supervised removals are important because of Topanga Creek’s delicate eco-system; the creek is home to several endangered or threatened species and fishing is prohibited, with special permission required for any crayfish removal, Dagit emphasizes.

Meanwhile, Montgomery and Garcia also are conducting scientific research comparing the cleaned-up area with an adjacent part of the creek where the crayfish continue to run wild. They’ve already created a scientific poster that they’ve presented at two conferences, and hope eventually to have their findings published by the Southern California Academy of Sciences.

Their internships, funded by a grant from the office of Supervisor Zev Yaroslavsky, are set to end in August. After that, it will be time for an all-too-common Southern California pastime—hoping for rain. Even a wet winter probably wouldn’t be enough to completely eliminate the crayfish, which Dagit says are now established in most of the creeks in the Santa Monica Mountains. But it would help keep the invaders in check.

“What we’re hoping is that we’ll get some really good rains and that the population will get severely diminished,” Dagit says. “And at that point we will mobilize people as best we can to do a really concerted removal.”

For a peek at how it’s done, check out the YouTube video below.

Posted 5/28/14