Relationship between long-term changes in algal community structure and herbivore diet at the Three Kings Islands, New Zealand

Abstract

We examined temporal changes at the Three Kings Islands, New Zealand in 1993 and 2002 in the diet of the endemic herbivorous fish Odax cyanoallix (Family Labridae) and in habitat-forming macroalgae, and compared these with published accounts from 1979. The diet of O. cyanoallix predominantly comprised the laminarian Ecklonia radiata in 1993, and the fucoids Sargassum johnsonii and Landsburgia quercifolia in 2002. In depths <10 m, the endemic fucoid S. johnsonii was dominant in 1979 and 2002 and absent in 1993. E. radiata was absent in 1979, abundant in 1993, and rare in 2002. A period of significantly lower sea-surface temperatures (SST) at the Three Kings Islands in 1990-95 corresponded to an unusually long El Ni�o event. The low SST may have resulted in the failure of S. johnsonii to grow and/or recruit during the El Ni�o event, leading to the observed changes. This study demonstrates variability in fucoid and laminarian assemblages over large time scales that are reflected in diet shifts in a species of herbivorous fish.