Three Algal Propagation Methods Assessed to Create a Rhodophyta Diet for Juvenile Greenlip Abalone (Haliotis Laevigata) in the Later Nursery Phase (Report‪)‬

ABSTRACT A variety of red algal species have been identified as potential food sources for juvenile Greenlip Abalone, Haliotis laevigata (5 mm shell length). To provide the red algal species in a diet suitable for juvenile abalone three propagation methods; spore production, protoplast isolation, and fragment culture were investigated. The potential algae requirements and consumable costs for each propagation method were determined, using experimental data and values from the literature, to assess the viability of utilizing each of these propagation methods in a commercial abalone nursery. The use of red algal spores required 592-52,000 kg of algae, depending on the level of spore release and the percentage of fertile algal thalli collected. Protoplast isolation reduced the amount of algal biomass to 8.55-910 kg but was affected by the efficiency of the isolation procedure. Even at an efficient production of 1 x [10.sup.8] protoplasts x [g.sup.-1] wet weight alga the cost of consumables (enzymes) was $US 13,576. A feeding trial utilizing Laurencia sp. fragments adhered to the plates using agar, produced juvenile abalone growth rates comparable to those obtained with the current commercial nursery diet of the green alga Ulvella lens plus the diatom Navicula cf. jeffreyi. The Laurencia fragments did not regenerate on the plates so it was reapplied weekly, which is not feasible on a commercial scale because it would require 10.6 t of Laurencia and 443 kg of agar at a cost of SUS 34,899. Gracilaria sp. fragments were able to regenerate with a growth rate of4.42%-[day.sup.-1] and therefore the algal fragments would only need to be applied to the PVC plates once, at the start of the later nursery phase (5 mm SL), reducing the amount of algal biomass to 432 kg. We therefore conclude that regenerating fragment culture (fragments 1 mm) is the only method that could successfully produce red algal diets for juvenile abalone on a commercial scale in the later nursery phase. KEY WORDS: juvenile abalone, Haliotis laevigata, red algae, spore formation, protoplast isolation, fragment culture, algal biomass