Changes

Journal of Applied Phycology 15: 201–207, 2003. © 2003 Kluwer Academic Publishers. Printed in the Netherlands.

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Changes in amino acid content of an algal feed species (Navicula sp.) and their effect on growth and survival of juvenile abalone (Haliotis rubra)
S. Daume 1,3,*, B.M. Long 2 and P. Crouch 2
School of Ecology & Environment, Deakin University, Warrnambool, Victoria, Australia;2School of Botany, La Trobe University, Bundoora, Victoria, Australia; 3Current address: Department of Fisheries, Mariculture Research and Advisory Group, Western Australian Marine Research Laboratories, P.O. Box 20, North Beach, 6020, WA, Australia; *Author for correspondence (e-mail: sdaume@fish.wa.gov.au; phone: +61-8-9239-8106; fax: +61-8-9239-8105)
Received 1 July 2002; accepted in revised form 16January 2003
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Key words: Abalone, Amino acids, Diatom, Growth, Haliotis rubra, Nitrogen Abstract The growth and survival of juvenile Haliotis rubra, when fed with the diatom Navicula sp. cultured in f/2 medium containing combined nitrogen at 24.71 mg NO 3-N L −1 (high), 12.35 mg NO 3-N L −1 (standard) or 2.47 mg NO 3-N L −1 (low), were compared in a 33-day trial. The alga in the low nitrogenmedium contained 37% less total amino acid than that in the high and standard nitrogen media. There was a slightly greater reduction in essential amino acids (40%) compared to non-essential amino acids (35%). Juvenile abalone feeding on Navicula grown in medium with low nitrate and lower total amino acid content grew more slowly than when fed on the same species grown in standard or higher nitrogenmedium with a higher amino acid content. The growth rate of juveniles was highest (43 µm d −1) in the high nitrate treatment followed (40 µm d −1) by the standard nitrate treatment and lowest (31 µm d −1) in the low nitrate treatment. The survival of the juveniles was also effected by the diet. Survival was better in the high and standard nitrogen media (88%) than the low nitrogen medium (75%). Theresults suggest that in order to achieve uniformity in nutritional quality of diatoms and good growth of abalone juveniles in commercial abalone nurseries, the nitrogen concentration in tanks should be monitored and additional nitrate added to provide an optimum concentration of between 2 and 12 mg NO 3-N L −1. Introduction Abalone, like other herbivores, grow under conditions leading potentiallyto nitrogen-limitation (White 1978; Mattson 1980), because the ratio of nitrogen to fibre and carbohydrates in plants is low. Fleming (1995) suggested that nitrogen is a limiting nutrient for the growth of the adult abalone Haliotis rubra when feeding on seaweeds, because the intake of digestible nitrogen directly influences their growth rates. Shpigel et al. (1999) stated that the good growth oftwo abalone species when fed enriched Ulva lactuca was attributable to a consistent supply of a higher amount of protein. In addition Boarder and Shpigel (2001) fed ammonia enriched Ulva rigida to the adult abalone Haliotis roei and observed that the enriched green seaweed, with a higher protein content than wild seaweed, generated a growth rates in the abalone similar to that achieved fromformulated feeds. However, the effect of varied amino acid composition of a selected feed species on the growth and survival of young juvenile abalone has not been reported in the literature. Young juvenile abalone feed mainly on benthic diatoms (Kawamura et al. 1998) until animals reach 7 to 8 mm in shell length and switch to eating macroalgae (Hahn 1989). Growth rates of juveniles are thereforeinfluenced by the availability, digestibility and nutritional composition of the diatoms (Kawamura et al. 1998; Roberts et al. 1999; Daume et al. 2000). To ensure a constant supply of food to the growing juveniles, the control of suitable diatoms on the plates

202 is crucial to the success of nursery operations (Hahn 1989). The biochemical composition of microalgae varies between species (Brown et al....