Farming Abalone

Geographic Distribution and Habitat

Greenlip and Brownlip abalone are larger, more temperate, deeper water species which may grow to more than 200 mm in the wild, with the latter being more reclusive (Joll, in Foster 1996, pp.11-13). The Staircase abalone is generally seen as having ecological similarities with Greenlip abalone while Roe's abalone, in this state, inhabits shallow limestone inshore reefs, often in quite turbulent locations and at very high densities (Wells & Keesing, in Shepherd et al., 1997, pp. 209-218).

Figure 1. Distribution of abalone species (from Freeman, 2001).

General Biology

Abalone are marine gastropods which have one shell and a large muscular foot that is used to attach themselves by suction to hard surfaces.This is the edible part of the animal and can account for more than a third of the abalone's live weight.

The sexes in abalone are separate, and males and females are easily recognised by the colour of the gonad. The outer layer of the gonad in males is a creamy white to tan, and the gonad in females is a dark to light green. The gametes are expelled through the respiratory pores in the shell and broadcast into the water column. Fecundity, that is, the number of eggs produced, is very high (see Freeman, 2001 for estimates for each species).Fertilization occurs after the gametes (eggs and sperm) are released. Larvae develop quickly (5 to 7 days, depending on water temperature) and they are freeswimming until they settle permanently onto hard surfaces. Abalone larvae are able to complete their entire larval development on the yolk furnished by the egg.

Settlement is a critical phase when the larva begins crawling over surfaces to select an appropriate habitat that will subsequently allow the resultant juvenile to graze on bacteria, diatoms, encrusting coralline algae or small turf-like algal species (Takami et al., in Shepherd et al., 1997, pp. 143-151; Daume 2002)

Abalone have a circular mouth with a tongue-like organ called a 'radula' with rows of tiny teeth that allow abalone to rasp particles off large kelps and smaller algae (Daume et al., in Shepherd et al., 1997, pp. 119-130). At least for Greenlip abalone, the complex gut does not seem to sustain the high bacterial densities typical of terrestrial ruminants such as cows (Harris et al., 1999).

Adult abalone along the coast of southern Australia feed on drift algae with most individuals showing a preference for red algae (for example, Gracilaria spp.) rather than brown algae (for example, Ecklonia spp and Macrocystis spp.) or green algae (for example, Ulva spp.) (Joll, in Foster 1996, pp. 11-13). However, abalone will consume a wide variety of algae if provided and Ulva has proved to be a useful ingredient in Roe's abalone feeds (S. Boarder pers. comm.).