Research to develop and manage the sea urchin fisheries of NSW and eastern Victoria

Abstract

Boreholes of the sea urchin Centrostephanus rodgersii (Agassiz) provide a microhabitat for a diverse assemblage of macrofauna on New South Wales’ subtidal reefs. The aim of this study was to quantify patterns in the distribution and abundance of fauna associated with C. rodgersii at a variety of spatial and temporal scales, and between habitats, since this has not been done previously and because there is potential for the fishery for C. rodgersii to expand. Natural patterns in abundance were investigated at four locations along the coast of New South Wales. Over 100 taxa were sampled, 53% of which were represented by present, variations in abundance of individual species occurred between sites within locations and only one species exhibited significant differences in abundance between the fringe and barrens habitats. Abundances of individual taxa changed in different ways at two sites over a period of 10 months. The composition of whole assemblages under urchins differed between sites, locations and habitats and also changed over time. Several models that may explain this variation and are discussed, as well as the implications for detecting changes related to fishing. Introduction Temperate areas in Australia’s marine environment are diverse in their assemblages of plants and animals, with many endemic fishes (85% endemic), molluscs (95%), red algae (75%) and echinoderms (90%) (Poore 1995). Absolute numbers of species are not known for many marine environments, including rocky subtidal reefs, and trends in species diversity are poorly documented along Australia’s coastline (Poore 1995; O’Hara 2001). Studies of the patterns of distribution and abundance of benthic marine fauna in eastern Australia have concentrated in the intertidal (e.g. Fairweather 1988; Underwood and Verstegen, 1988; Worthington and Fairweather 1989; Underwood and Chapman 1992; Peake and Quinn 1993; Chapman 1994; Underwood and Chapman 1996; Beck 1998; Underwood and Chapman 1998a, b). Fewer studies have been made in subtidal reef habitats and consequently our knowledge of these areas is considerably less (Edgar 1984; Underwood and Kennelly 1990; Underwood et al. 1991; Keough and Butler 1995; Smith et al. 1996; O’Hara 2001). Studies on the fauna of subtidal reefs have been largely restricted to commercially important species such as abalone (Shepherd 1973; Andrew and Underwood 1992;