Temporal Variation in Fish Communities Off Santa Cruz Island, California

The assemblage of fishes inhabiting subtidal rocky reefs off Santa Cruz Island, California has changed noticeably since the 1970s. Subtidal surveys were conducted annually in 1971-74, in 1996, 2004 and 2005, using the “cinetransect” method. The period 1971-74 fell during the last cool “regime” of the Pacific Decadal Oscillation, while 1996 was near the end of the recent warm phase. Some of the changes observed between the 1970s and 1996 were consistent with ocean warming, while others seemed associated with a large-scale decline in kelp. Several southern species increased in abundance, while a number of northern species either declined in abundance or disappeared altogether. Current oceanographic data indicate cooler ocean conditions from 1999 through early 2005. Although kelp has returned to the south side of Santa Cruz Island, there appears to be little recovery of kelp at the original survey sites on the north side of Santa Cruz Island. However, analysis of data collected in 2004-05 suggests some interesting changes since 1996, including a slight increase in more northerly-distributed species.