The effects of tactile stimulants on feeding, growth, behaviour, and meat quality of cultured Blackfoot abalone, Haliotis iris

The New Zealand Blackfoot abalone or paua, Haliotis iris uses both tactile and chemosensory cues to detect and feed on drifting seaweed in its natural habitat. In aquaculture situations, abalone are usually provided with static artificial food pellets, effectively removing the tactile stimulus. This study investigated the effects of tactile stimuli from suspended particles on pellet ingestion, growth, behaviour and meat quality of juvenile paua (length 40–45 mm). Over eleven months, individuals were offered a commercial pellet diet (AbFeed™) and small quantities of one of four particulate materials: macerated seaweed (Gracilaria spp. and Macrocystis pyrifera) and 2 sizes of synthetic PVC fragments. There was seasonal variation in the ingestion rate of abalone from all treatments and the control (no stimulants) with lowest rates during winter (June to September) and highest rates in summer (December to February).The specific growth rate (% body weight gain per day) and shell length increase varied seasonally. Of the four treatments, the only effective stimulant was Gracilaria spp. which resulted in summer shell growth of 110.6±3.2 μm d−1 compared with 86.9±4.0 μm d−1 for control abalone. Behavioural observations showed that when Gracilaria particles were present, abalone spent >80% of their time engaged in feeding-related activity. Control abalone, without the algal stimulant, spent most of their time in a sedentary position. None of the particulate stimulants tested had any significant effect on food conversion ratio, water content, protein, lipid and glycogen levels or meat tenderness. These parameters were, however, significantly affected by season. A preliminary trial of the Gracilaria particle treatment in a commercial system over 90 days enhanced the growth of cultured H. iris (45±5 mm shell length) by 15.3%. The main commercial implication of this research is that the addition of algal stimulants is suggested as a cost-effective means of improving abalone performance using pre-existing culture systems and food types.