Chapter 2 - On the Structure and Dynamics of Temperate Reef Fish Assemblages: Are Resources Tracked?

Abstract

Two long-term data sets of assemblages of temperate reef fish were studied to explore population and community trends in relation to environmental disturbances. The King Harbor assemblage included a total of 75 reef-associated teleost fishes and has been observed for 20 years; the Santa Cruz Island data set included five species of fish and detailed information about reef resources during a 13-year period. The assemblages responded to regional environmental perturbations such as E1 Nifio Southern Oscillation events and changes in regional upwelling patterns that greatly influenced reef resources (especially food supply). Analysis of the chapter reveals that species of northern, cold-water affinity declined sharply during the 1970s, stayed more or less constant during the 1980s, and fell again during the early 1990s. Southern affinity species tended to increase in abundance during the 1970s into the 1980s, but since the mid-1980s, these species have generally been declining as well. Similar patterns are detected at both sites. Analyses of crustacean food supply at Santa Cruz Island reveals a tremendous decline since 1990, and so the chapter concludes that local populations of these reef-associated species of fish have been tracking a declining resource base.