California’s Favorite Sea Slug Makes A Comeback
March 18, 2013

California’s Beloved Sea Slug Rebounds

Brett Smith for - Your Universe Online

A team of California marine biologists is seeing encouraging signs for the recovery of the nudibranch Felimare californiensis, a colorful and popular sea slug that once thrived in the Pacific waters off the coast of the Golden State.

Discovered in 1901, the blue and gold-flecked nudibranch, also referred to as the California chromodorid, has been a favorite sea slug of California marine biologists and students for decades. Despite its popularity, the slug slowly and mysteriously disappeared from coastal waters over the course of the last century and was declared locally extinct in California by 1984.

However, an increasing number of sightings since 2003 has led a team of researchers to claim that the nudibrach is experiencing a nascent recovery. A report of their findings was recently published in the journal Marine Biology.

According to Jeff Goddard, the study´s lead author and project scientist with the University of California´s Santa Barbara's Marine Science Institute, the slug´s decline is unique among the 130 species of sea slugs that inhabit California´s coastal waters.

"Its decline is not shared by closely related nudibranchs with similar historical geographic distributions and modes of development, and is not predicted by warming trends and climate variation over the past 40 years, including the strong El Niño events of 1983 and 1998," Goddard explained.

In the report, Goddard and his team reviewed the recent and historical sightings of the nudibranch. The researchers concluded that water pollution from the highly-urbanized southern California mainland is most likely the biggest factor in the nudibranch´s decline. They said that the decline was compounded by over-collecting by slug aficionados and habitat loss through the development of marinas and ports.

The team also suspects that degraded water quality, which reached a low point in the 1970's, could have directly affected either the slugs' food supply — sponges — or the sponge´s symbiotic cyanobacteria.

The scientists noted that the recovery in water quality has coincided with the recovery of the nudibranch. They said that the slug has been spotted once again in the waters off Santa Cruz Island and off the coast of San Diego.

"Since the passage of the Clean Water Act in 1972, big strides have been made in reducing pollutants in the Southern California Bight, especially from large wastewater outfalls, and these improvements may have allowed“¯Felimare californiensis to regain a foothold in the region," Goddard said.

The researchers said that they plan to continue to monitor the Felimare californiensis population at Catalina and keep tabs on the genetic variation in the population there. They said they also plan to study the distribution and abundance of its sponge prey.

To help raise awareness of the nudibranch´s plight, Goddard said he is collaborating with Mike Miller who runs the popular website SlugSite to produce a video on F. californiensis for the 2013 San Diego Undersea Film Festival.

The film festival is run by a volunteer board of directors“¯who are active underwater videographers. This year´s festival is scheduled for September 22 and 23.