Demersal fish assemblages along the continental shelf and upper slope of the east coast of the South Island, New Zealand

Abstract

Data collected during five winter and three summer research trawl surveys in Pegasus Bay and Canterbury Bight (10-400 m), east coast of the South Island, New Zealand, were used to identify demersal fish assemblages from hierarchical cluster analysis and non-metric multidimensional scaling. The environmental variables - depth, latitude, season, water temperature, sediment type, sea surface condition, and sea colour - were examined to determine their relationship to fish assemblages using multivariate redundancy analysis. Patterns of species richness were examined and described. Catch rates were generally higher in summer than winter (21 of 28 species) and higher in south Canterbury Bight in the depth range 30-200 m. Preferred depth was greater in winter than summer (21 of 28 species). Species richness declined with depth in winter. Four main demersal species assemblages were identified (inner shelf, outer shelf, shelf break, and upper slope) with minorchanges in membership between summer and winter mostly as a result of a change in species preferred depth. Depth was the primary variable influencing fish assemblages with secondary effects of latitude, sediment, and bottom temperature.