The red abalone, Haliotis rufescens, in California: Importance of depth refuge to abalone management

Two different approaches have been used for management of red abalone, Hali otis rufescens, in California. In central and southern California, use of c ompressed air has been allowed for both commercial and sport fisheries, per mitting take of red abalone throughout its depth range. In northern Califor nia, commercial fishing has not been allowed, nor has use of compressed air by the sport fishery, resulting in refuge from take at depths below 8.4 m. The central and southern California fisheries were recently closed because of stock declines, while the northern California fishery continues to prov ide high yields. Commercial catch and stock density showed parallel trends of significant decline at two of three southern California islands (Santa R osa Island and Santa Cruz Island, but not San Miguel Island) between 1983 a nd 1996. At Van Damme State Park, a highly fished northern California site, stock density increased threefold between 1986 and 1992. Dive survey data indicate major recruitment events are sporadic in northern California. Dens ity of young-of-the-year (YOY) recruits at Van Damme in 1990 to 1992 averag ed three times that at Santa Rosa Island in 1978 to 1982. The proportion of red abalone larger than the sport size limit was 43% at Van Damme in depth s >8.4 m, but was only 16% at depths <8.4 m, and 15% at Santa Rosa Island a t all depths. Refuge by depth at Van Damme apparently protected sufficient adults from harvest during protracted periods of low recruitment to allow s ustainable harvest.