Farmers need to successfully spawn farm-grown abalone for the continuation of the national breeding project (FRDC 2000/201). In addition, farmers need to be able to spawn off-season to allow for multiple batches, to utilise the nursery infrastructure all year around. Hence broodstock needs to be conditioned on site. The long-term effects on abalone spawning success and offspring performance, from formulated diet fed broodstock, need to be assessed and compared to those of animals, which have been feeding on seaweeds (from the wild and conditioned on seaweeds). Animals have been regularly conditioned on seaweeds in other countries like South Africa. Whether a formulated diet enriched with arachidonic acid will improve spawning success and offspring performance and hence whether high levels of arachidonic acid is essential to abalone reproduction, need to be examined.

Farmers need to reduce size variation and weaning mortality efficiently and hence need a cost/benefit assessment of alternative nursery management strategies for animals between 5 and 15 mm. Ideally, they would like to maintain a high stocking density per unit area while maintaining optimal feed availability. However, they would like to know whether it would be just as economic (in terms of improved growth rate and survival) to invest in more nursery infrastructure and maintain a low stocking density. In other words, whether increased growth rates can be achieved by better food availability or lower stocking density, both of which incur greater costs. The improvements over the rest of the growing cycle justify a certain amount of increased cost. The question is how much?

The alternative systems that farmers want to compare are a low stocking density approach where no additional food needs to be provided when animals reach 5mm in shell length, with a high stocking density approach where additional food is provided at that stage. The specific alternative feeding strategies that needs to be compared are: 1) the early removal of animals off plates (at about 5mm) into an intermediate tank system that allows animals to feed on formulated feed versus 2) maintaining animals on plates and introducing another algal food source at the time animal numbers are split between the old and new plates (at about 5mm), thus allowing animals to remain in the nursery system until 15+mm versus 3) current industry practice where animals are fed Ulvella lens and natural diatoms throughout the nursery phase, with new diatom and Ulvella lens-covered plates introduced at 5 mm. The two components are related as egg quality influences larval survival and nursery performance after the non-feeding larval phase.