Heasman MP, Liu W, Goodsell PJ, Hurwood DA & Allan GL (2007) Development and delivery of technology for production, enhancement and aquaculture of blacklip abalone (Haliotis rubra) in New South Wales.  Final Report to FRDC Project No. 2001/033. NSW Department of Primary Industries – Fisheries Final Report Series No. 95, 226 pp.

Summary

The NSW abalone fishery is based entirely on H. rubra and is largely confined to the southern half of the state.  Annual catch peaked at about 1,200 t in 1971/72 but has been progressively reduced to 130 t in 2005.  One potential method of reversing the declining production is to enhance the fishery by stocking hatchery produced juveniles.

During the course of a preceding 3 year project, considerable progress was made towards enhancing the abalone fishery by reducing costs of producing and transporting H. rubra seed and by identifying that “button size”, 6 to 9 month old juveniles are the most appropriate class of seed for enhancing depleted sub-populations. The current project was initiated to address the following key remaining priorities for cost-effective abalone enhancement: 1) to develop methods for producing triploid abalone and to evaluate whether triploid abalone were faster growing and sterile (thereby reducing potential problems with enhancement negatively affecting genetic integrity of wild populations of abalone), 2) to evaluate methods of improving post-release survival, 3) to develop indigenous capacity for production of abalone seed, and 4) to produce economic models for enhancement of blacklip abalone fisheries using hatchery produced seed.

Optimised methods to induce triploidy (three rather than the usual two sets of chromosomes in body cells) in blacklip abalone were developed.  The triploid abalone were shown to be sterile (incapable of breeding) which renders them low risk candidates for enhancing depleted abalone fisheries stocks.  The triploid abalone were also found to have grown considerably larger and to have higher proportions of marketable flesh than their normal diploid siblings at 3.6 years of age.  This technology has received intellectual property protection and is attracting considerable interest from industry.

A previously encountered problem of very high losses suffered by “button-size” (7-15 mm) abalone when released onto depleted reefs in NSW was not solved by lowering seeding rates from 1000 to 100/ m2.  The unusual blue-green shell colour of hatchery-produced seed abalone did not reduce survival after release and seeding abalone under and around the common purple urchin did not increase survival.  Results suggest that very low stocking density is required to reduce mortality and a very large long-term experiment to test possible benefits of low density (8/m2) dispersed seeding of depleted blacklip abalone populations was instigated.  55,000 “button-size” abalone were used to stock six 1000 m2 sites (~ 9,000 abalone/site) and numbers of abalone within these sites will be compared with numbers found in six similar unstocked sites in 2008/2009 when abalone are expected to approach minimum legal size.

A key initiative of the NSW Government’s Indigenous Fisheries Strategy was to support the development of an indigenous hatchery on the NSW south coast with a specific goal of producing abalone juveniles for aquaculture and enhancement. While an indigenous hatchery has not yet been established, complementary activities of indigenous training and the preparation of a comprehensive hatchery manual have been completed.  A total of 11 study tours and 8 one week training courses were staged for coastal indigenous community groups and students enrolled in training courses at the Tomaree and Wollongong colleges of TAFE. These tours and courses were developed and implemented collaboratively by NSW TAFE and NSW DPI. A comprehensive operations manual for high efficiency hatchery and nursery production of blacklip abalone was also prepared and published. 

Economic viability will determine whether abalone enhancement will be considered by fishers or fishery managers.  This project developed a simple cost/benefit model that demonstrated that key factors affecting economic viability were age and size specific growth rates, natural mortality (and especially the effect of stocking density on mortality) and the carrying capacity of abalone habitats.  The assumptions that stock enhancement is economically viable when “button size” abalone are seeded at low densities (~8/m2) is being verified as part of the experiment described above.