ORIGINAL PAPER Regional extinction of a conspicuous dorid nudibranch (Mollusca: Gastropoda) in California Jeffrey H. R. Goddard • Maria C. Schaefer • Craig Hoover • A ´ ngel Valde ´s Received: 24 November 2012 / Accepted: 14 February 2013 / Published online: 8 March 2013 Ó Springer-Verlag Berlin Heidelberg 2013 Abstract Felimare californiensis (=Hypselodoris cali- forniensis) was once common throughout the Southern California Bight (SCB) and California Channel Islands. This well-known shallow-water nudibranch, which spe- cializes on dysideid sponges, has persisted for decades in Mexico, but in California disappeared from its entire range by 1984. Since reappearing in 2003, it has been found only at Santa Catalina Island, plus sightings of single individuals in 2011 at Santa Cruz Island and San Diego. The decline of F. californiensis in California was documented using pub- lished historical records, museum collections, unpublished field accounts, and images posted online. The loss of this emblematic species is unique among Californian nudi- branchs, including (1) its congener Felimare porterae (=Mexichromis porterae), with which it appears to overlap in diet, and (2) opisthobranch species with similar historical geographic ranges and mode of development. The decline in F. californiensis is not predicted by warming trends and climate variation over the past 40 years, including the strong El Nin ˜o events of 1983 and 1998. Coastal pollution from the large human population in southern California may have impacted Dysidea amblia, the primary reported prey of F. californiensis. Historical overcollecting of the nudi- branch and habitat loss through the development of major ports likely also contributed to its decline. Sightings since 2003 are consistent with a nascent recovery, as elements of water quality have improved in the SCB in recent decades. Introduction Humans have heavily impacted marine biota and ecosys- tems in the Southern California Bight (Dayton et al. 1998; Tegner and Dayton 2000; Sagarin et al. 2007; Halpern et al. 2008; Puritz and Toonen 2011). However, despite our large population and pervasive reach, only a handful of historical extinctions of marine species have been documented in the region (Carlton et al. 1999; Dulvy et al. 2003; Re ´gnier et al. 2009). Sea otters and white abalone are the most prominent examples, not just for the ecological cascades triggered by their removal, but also for the stark realization that we could so quickly extinguish their populations (Jackson et al. 2001; Roberts 2007). In contrast, two obscure species, the marsh horn snail Cerithidea fuscata and the mid- intertidal limpet Lottia edmitchelli (=Collisella edmitchel- li), had such limited distributions that their passings were nearly missed (Carlton 1993). Here, we document the regional extinction of Felimare californiensis (Bergh 1879), an emblematic nudibranch gastropod once widespread and common in shallow-water, hard bottom habitats on the mainland coast of southern Communicated by J. P. Grassle. Electronic supplementary material The online version of this article (doi:10.1007/s00227-013-2204-x) contains supplementary material, which is available to authorized users. J. H. R. Goddard (&) Marine Science Institute, University of California, Santa Barbara, CA 93106-6150, USA e-mail: goddard@lifesci.ucsb.edu M. C. Schaefer 2558 Mardell Way, Mountain View, CA 94043, USA C. Hoover Department of Biology, California State University, Northridge, CA 91330, USA A ´ . Valde ´s Department of Biological Sciences, California State Polytechnic University, Pomona, CA 91768, USA 123 Mar Biol (2013) 160:1497–1510 DOI 10.1007/s00227-013-2204-x