The effects of density on
the behaviour and growth of juvenile blacklip abalone (Haliotis rubra)
S.M.H. Huchette, C.S. Koh,
R.W. Day-2003
Aquaculture International, 11(5):
411-428
Abstract:
The growth of juvenile abalone in aquaculture is
known to be affected by density as a result of competition for food and
decreases in water quality. Our results suggest that behaviour is also
affected by density and this also has a significant impact on the growth of
individual abalone. 1800 juveniles of Haliotis rubra were
individually tagged and reared for 5 months in 12 gravity-fed tanks at two
levels of density. The experimental design allowed the differentiation of
the direct from the indirect effects of density. The abalone growth and
distribution was monitored monthly along with the water quality. The
distribution of abalone during daytime was closely related to the
availability of preferred shelter space. The percentage of abalone stacked
on the top of others increased with density. Preferred shelter space was
characterized by low light intensity and a corner or edge for the abalone to
rest against. Hides at the ends of the tanks were not occupied as much as
others. Abalone were found crawling on the side of the tank during daytime
when tanks were shaded. Abalone juveniles of 15–60
mm showed fidelity to their resting shelter during daytime but this
fidelity was significantly reduced at the higher density. Shading of the
tanks totally changed the distribution of the abalone and their daytime
behaviour. Competition for shelter space reduced growth more than water
quality.
(Department of
Zoology, The University of Melbourne, Gate 12 Royal Parade, 3052 Parkville,
Melbourne Australia, tel: +61 3 8344 6262; fax: +61 3 8344 7909, e-mail: sylvain.huchette@wanadoo.fr)