Meeting Abstract

78.1  Friday, Jan. 7  Decline in nudibranch gastropods following a climate-related range shift of a large predatory aeolid in the northeast Pacific Ocean GODDARD, J.H.R; GOSLINER, T.M.; PEARSE, J.S.*; Univ. of California, Santa Barbara; California Academy of Sciences; Univ. of California, Santa Cruz pearsester@gmail.com

In 1977, Phidiana hiltoni (O’Donoghue, 1927) began spreading northward from Monterey, California. By 1992 it had reached Duxbury Reef (37° 53’ 23”, 122° 41’ 59”), where other nudibranchs subsequently appeared to decline. The role of P. hiltoni in this decline was investigated through diet analysis, feeding trials, and comparison of historical and recent abundance data. In the wild, P. hiltoni preyed largely on hydroids, but also showed evidence of predation on nudibranchs. In the laboratory, P. hiltoni attacked most of the dendronotid and aeolid nudibranchs presented to it, ingesting small individuals whole. The pooled abundance of nudibranchs vulnerable to attack by P. hiltoni has declined an average of two-thirds at Duxbury Reef since its arrival, compared to no change in the non-vulnerable species. Phidiana hiltoni likely caused this decline, through competition for prey and direct predation. A brief larval period, combined with cyclonic re-circulation in the lee of Point Reyes, may be driving self-recruitment of P. hiltoni at Duxbury Reef, as well as preventing its continued northward spread.