A sampling method was developed to quantify changes in the abundance of abalone on reefs in NSW from Port Stephens to the Victorian border. The method is based on the repeated sampling of the same, fixed areas and has been used each year since 1994 to provide indices of the relative abundance of abalone of different sizes. The number and distribution of the fixed areas has been expanded each year since 1994. The relative abundance of small (<60 mm) and medium (<115 mm) abalone in NSW increased between 1994 and 1997. This information now provides an essential part of an annual stock assessment program for abalone in NSW, and is now funded by the NSW abalone industry.

A sampling program was developed to quantify changes in the abundance of sea urchins on reefs in NSW from Port Stephens to the Victorian border. The program is based on the use of random transects within Barrens habitat in a series of permanent sites to assess the abundance of sea urchins of different sizes. There was no evidence suggesting that the abundance of sea urchins (Centrostephanus rodgersii, hereafter Centrostephanus) increased in the four years of the present study. This duration of sampling is, however, unlikely to be sufficient to describe important changes in the abundance of sea urchins. For this reason, a comprehensive series of maps of the Barrens habitat were completed to provide a point-in-time estimate of its areal extent.

The extent of the Barrens habitat on reefs in NSW differed along the coast, but overall it represented approximately 50% (SE= 3.9) of the nearshore reef between Port Stephens and the Victorian border. Barrens were most dominant in Disaster Bay where the represented 68% (SE= 6.7) of the nearshore reef, but just south of there only l % (SE= 0.3) of the nearshore reef was Barrens. The time-scale of this study was not long enough to observe large-scale changes in the area of reef occupied by Barrens habitat, but a detailed baseline now exists for future comparison.

There was a strong influence of habitat on the abundance of abalone. Very few abalone were found in Barrens habitats, and abalone were most abundant in Fringe habitats. Manipulative experiments demonstrated that by reducing densities of Centrostephanus, Barrens habitat can be modified to alternative habitats that can enhance the recruitment, survival and growth of abalone. Such a strong negative interaction between an established high-value fishery, and an under-exploited resource with considerable potential for development, offers a rare opportunity to develop complimentary fishery management plans.

A variety of factors influenced the quality of Centrostephanus roe. The greatest yield of high quality roe was obtained from small urchins (60-80 mm) in the Fringe habitat during summer and autumn. Roe harvested from larger urchins, from the Barrens habitat, or during the spawning season, was generally of a poor quality. Because of the logistic difficulties and expense associated with processing sea urchin roe for markets, the fishery will need to consistently harvest roe of a high quality. Preliminary experiments suggested several techniques to enhance roe quality, in areas or times where it is poor, enabling the more reliable harvest of higher quality roe.

The development of the sea urchin roe fishery should be viewed within the larger context of their interaction with abalone, and the future of the abalone fishery. We recommend the further development of a management framework that facilitates an experimental approach to the management of both these fisheries. This approach should be carefully structured to allow both the development of a stock assessment program for sea urchins, and further research to help the development of the fishery. This would allow an increased sophistication in the management of both the sea urchin and abalone resources of NSW.

Keywords: Abalone, Haliotis rubra, Sea Urchins, Centrostephanus rodgersii, Stock Assessment, Competition, Recruitment, Abundance, Habitat, New South Wales, Australia.