The Israeli Journal of Aquaculture - Bamidgeh 54(2), 2002
The Annual Dan Popper Symposium


NUTRITIONAL REQUIREMENTS OF POSTLARVAE OF THE JAPANESE
ABALONE HALIOTIS DISCUS HANNAI


Nurit Gordon¹, Amir Neori¹*, Sheenan Harpaz², Muki Shpigel¹

1 Israel Oceanographic and Limnological Research, National Center for Mariculture, P.O.Box 1212, Eilat 88112, Israel
2 Department of Aquaculture, Volcani Agriculture Research Center, Beit Dagan, Israel


Abstract

Diatoms were selected according to their attractiveness to veliger settlements and to postlarvae growth and survival in the Japanese abalone Haliotis discus hannai. Attractiveness was quantified as follows: Veligers were placed in Petri dishes and offered a choice of several diatom patches on solid media. The veligers that settled and metamorphosed on each patch were counted.

Several diatom species were examined. The three most attractive - Nitzschia laevis, Navicula lenzi and Amphora luceae - were selected for further experiments. The attraction by the diatoms was chemosensory and depended on their excreted compounds. Diatom extracts, their cell fragments and aspartic acid (the only free amino acid detected in the excretions of two of the tested diatoms) strongly attracted the veligers.

The three attractive diatoms were also nutritious for the abalone. They contained high levels of lipids and fatty acids, including polyunsaturated fatty acids n-3 (e.g., EPA-20:5n-3) and n-6. Arginine, proline and glutamate dominated the free amino acids in extracts of the attractive diatoms. Mixtures rather than single species of algae provided the postlarvae a better balance of required nutrients, resulting in better growth and survival. The best mixture -N.lenzi and A.lucea - resulted in a survival rate of 50% and a shell growth rate of 36 microns shell per day, 30 days after settlement. This compares to 3-5% survival in nonselected diatoms. The results of this research enable commercial hatcheries to achieve greatly increased survival of abalone larvae.

We thank Prof.J.Lee and H.Krogliak for their help.

*Corresponding author. E-mail: neori@.ocean.org.il

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