Life History & Behaviour
Abalone have a one to one ratio of distinct male and females sexes within the species and are fully mature aged between three to five years, but may continue to grow in size after this time. Some of the larger species can live for up to 50 years. Abalone reproduce by broadcast spawning where eggs and sperm are released into the water column where fertilisation occurs. These events are synchronised and appear to be linked to predictable events like spring tides (Geiger and Poppe, 2000; York et al., 2012). After about two weeks post-fertilisation, juvenile abalone settle on encrusting red algae which produce a chemical cue that induces settlement (Morse and Fenteany, 1993).
Abalone are largely sedentary but move short distances for feeding. Encrusting organisms like barnacles, bryozoans, algae and sponges are often found growing on abalone shells and in some cases these are parasitic (Geiger and Poppe, 2000). Abalone are prey for many reef species such as rays, moray eels and some fish like wrasses (Geiger and Poppe, 2000). They are also eaten by sea stars (Asteroidea) some species of which elicit an escape response in the abalone. This resonse is though to be triggered by the reception of chemical cues from the predator (Geiger and Poppe, 2000; Mach and Bourdeau, 2011).
Picture of various macroalgae on Heron Island Reef.
Like the other two tropical abalone species found on Heron Island (H. asinina and H. varia), H. ovina is a herbivore that feeds on macroalgae. There is little information in the primary scientific literature to identify the feeding preferences of H. ovina. A number of studies have shown that H. asinina which is found in similar habitats on Heron Island has a preference for red algae such as Hypnea spp. and the green algae Ulva spp., but will also feed on brown algae such as Padina spp. (Angell et al., 2012). The reasons for this preference hierarchy is not known and further research has been suggested by Angell et al. (2012).
Due to the scarcity of available information on the dietary preferences of H. ovina, a feeding trial was conducted over the limited time period available on Heron Island by the author of this web page, and the details can be found on the 'Feeding Preference Experiment' tab.
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