Towards an abalone weaning diet: evaluation of agar-bound fishmeal and spirulina as dietary ingredients
AbstractSurvival of post-settlement abalone when ‘weaning’ them from diatoms onto macroalgae/artificial feed remains unpredictable for farmers. It is hypothesised that spirulina algae, which are high in protein, may be a suitable feed ingredient for weaning abalone. Over a period of 27 days, the growth and survival of juvenile (4–6 mm shell length) Haliotis midae were compared when weaned from diatoms onto agar-bound, 48% protein diets with either spirulina, fishmeal, or fishmeal and spirulina as the sources of nutrition. Agar-gel alone was used as a control (0% protein) and a commercial abalone diet, Abfeed®-S34 (34% protein), was included as a reference. Abalone that were fed fishmeal and spirulina combined performed best in both weight and shell-length gain (36.87 ± 2.19 mg and 2.29 ± 0.05 mm). The growth of agar-fed control animals was worst of all treatments (1.26 ± 2.03 mg and 0.19 ± 0.14 mm) and had a markedly reduced survival rate (18.6 ± 5.5%). Growth in abalone that were fed the spirulina only (9.41 ± 3.39 mg and 0.58 ± 0.27 mm) was better than the control-fed abalone and was substantially lower than other diet treatments, but not significantly different from them. Abalone that were fed Abfeed®-S34 only had a significantly higher condition factor (0.91 ± 0.02) compared with those fed the control (0.70 ± 0.09) and the combined diet (0.75 ± 0.01), and a significantly higher soft-body tissue to shell mass ratio (2.38 ± 0.14) than those fed spirulina only (1.67 ± 0.15) or the control (1.05 ± 0.09). Agar was a suitable medium for binding and presenting dietary ingredients to abalone at weaning, and fishmeal or a fishmeal–spirulina combination provided sufficient protein and energy for good growth and survival. Spirulina as a single-ingredient feed is not recommended.
Keywords: algae; energy; formulated diet; Haliotis midae; nutrition; protein
African Journal of Marine Science 2009, 31(1): 103–106