DEMERSAL FISH COMMUNITY DIVERSITY OFF NEW-ZEALAND - IS IT RELATED TO DEPTH, LATITUDE AND REGIONAL SURFACE PHYTOPLANKTON

Recent studies of basin-scale patterns of diversity of benthic macrofa una reported strong latitudinal gradients of diversity in the deep Nor th Atlantic, in contrast to regionally variable patterns in the Southe rn Hemisphere. Here we use data from fisheries research trawl surveys to examine spatial patterns of species richness, Shannon-Wiener divers ity index, and evenness of demersal fish communities in relation to la titude and depth from 80 to 898 m off south-east New Zealand. We found species richness decreased latitudinally within regions in the polewa rd direction, and increased with depth. Areas of high species richness were concentrated along the margins of the Chatham Rise and were asso ciated with current intensification in regions of enhanced surface phy toplankton pigment concentration. Species richness was highest between the 500 and 1000 m contours on the Chatham Rise, where enhanced surfa ce phytoplankton pigment is associated with a major oceanographic feat ure, the Subtropical convergence. A predominance of species-rich locat ions was found on the more steeply shelving northern margin of the Cha tham Rise. The regional latitudinal pattern of diversity appears to be correlated with regional production, and to be influenced by mesoscal e oceanographic features constrained by the bathymetry, although the p roximal causes for high diversity remain speculative. (C) 1997 Elsevie r Science Ltd.