Effects of nutrient enrichment and biochemical composition of diets of Palmaria mollis on growth and condition of Japanese abalone, Haliotis discus hannai and red abalone, Haliotis rufescens

摘要

Two growth experiments were conducted with juvenile red abalone, Haliotis rufescens and Japanese abalone, Haliotis discus hannai. The first experiment was set up to determine if nutrient levels used for co-culture of the Rhodophyte, Pacific dulse (Palmaria mollis) directly affected abalone growth. No significant differences (ANOVA; P = 0.117) were found in growth of abalone cultured in either ambient seawater alone or seawater supplemented with different NaNO_3 loads (1176, 1765, 2353, and 2942 μM day~(-1) NO_3-N), NaH_2PO_4 (83.3 μM day~(-1) PO_4~-), and a modified version of Guillard and Ryther's [Gran. Can. J. Microbiol. 8, (1962) 229] f medium containing Fe, Zn, Mn, Cu, Mo, and Co. The second experiment was designed to determine the effect of different nutrient levels on the nutritional value of P. mollis when fed to abalone. P. mollis was cultured with different NaNO3 loads (1176, 1765, 2353, and 2942 μM day_(-1) NO_3-N) and NaH_2PO_4 (83.3 μM day_(-1) PO_4~-) in the presence or absence of f medium trace metals (Fe, Zn, Mn, Cu, Mo, and Co). H. discus hannai showed the highest LGR and SGR when fed on P. mollis supplemented with nitrate loads ranging from 1176 to 2353 μM day~(-1) NO_3-N. In contrast, H. rufescens showed the highest linear growth rate (LGR) when fed on P. mollis supplemented with higher nitrate loads of 2353 to 2942 μM day~(-1) NO_3~-N, while nitrate load had no significant effect on specific growth rate (SGR). Both abalone species grew better on P. mollis supplied with 0.75f+Zn (day~(-1)) metal solution [Gran. Can. J. Microbiol. 8 (1962) 229] compared to those without trace metal additions, with H. discus hannai showing a further improvement in food conversion efficiencies (FCE). The present work shows that understanding and manipulating the culture environment of P. mollis can significantly affect growth, FCE, and daily food consumption (DFC) of H. discus hannai and H. rufescens.