Ballagh, Debra A., Fielder, D. Stewart, and Pankhurst, Patricia M. (2010) Weaning requirements of larval mulloway, Argyrosomus japonicus. Aquaculture Research, 41 (10). e493-e504.

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Abstract

Mulloway (Argyrosomus japonicus) is an emerging aquaculture species in Australia, but there is a need to improve the production technology and lower costs, including those associated with larval rearing and live feeds. Three experiments were conducted to determine appropriate weaning strategies from live feeds, rotifers (Brachionus plicatilis) and Artemia, to cheaper formulated pellet diets. Experiment 1 examined the e¡ects of feeding Artemia at di¡erent levels [0%,50% or 100% ration of Artemia fed from18 days after hatching (dah); based on current hatchery protocols] and a pellet diet from two larval ages (14 or 23 dah). In addition, rotifers were supplied to larvae in all treatments for the duration of the experiment (14^29 dah), at which time all larvae were successfully weaned onto the pellet diet. No signi¢cant (P40.05) di¡erences existed between the growth of ¢sh fed a 50% and 100% ration of Artemia; however, ¢sh fed a 0% ration of Artemia had signi¢cantly (Po0.05) reduced growth. The time of pellet introduction had no signi¢cant (P40.05) e¡ects on the growth of larvae. Experiments 2 and 3 were designed to determine the size [total length (TL),mm] at which mulloway larvae selected Artemia equally or in preference to rotifers, and pellet (400 mm) equally or in preference to Artemia respectively. Each day, larvae were transferred from a holding tank to experimental vessels and provided with rotifers (2mL�1), Artemia (2mL�1) or a combination of rotifers (1mL�1) and Artemia (1mL�1) (Experiment 2), and Artemia (2mL�1), a pellet diet or a combination of Artemia (1mL�1) and a pellet diet that was broadcast every 15min (Experiment 3). After1h, a sub-sample of larvae was randomly selected fromeach replicate vessel (n55) and the gut contents were examined under a light microscope. Mulloway larvae began selecting Artemia equally to rotifers at 5.2 � 0.5mmTL and selected pellets equally to Artemia at 10.6 � 1.8 mmTL. Our results have led to the establishment of weaning protocols for larval mulloway, which optimize larval growth while reducing feed cost by minimizing the amount of Artemia used during production.

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