Early weaning of winter flounder (Pseudopleuronectes americanus
Walbaum) larvae on a commercial microencapsulated diet
I.B. Khemis, C. Audet, R. Fournier, J. de la Noüe-2003
Aquaculture
Research, 34(6) : 445-452
Abstract:
Like
most small marine fish larvae, the stomachs of winter flounder Pseudopleuronectes
americanus are undeveloped at first feeding and have relatively reduced
digestive capacity. This work was undertaken to test whether larvae at the
onset of stomach differentiation (larval size about 5.5 mm) could be
early weaned onto a commercial microencapsulated diet. We assessed the
effect of early weaning by first comparing growth performance (standard
length, total protein content and age at metamorphosis) of larvae fed
enriched live prey from first feeding to a size of 5.5 mm and then
reared on three different feeding regimes until metamorphosis: (1) live prey
(LP) as a control group; (2) mixed feeding of live prey and
microencapsulated diet (LP-ME); (3) exclusively microencapsulated diet (ME)
after fast weaning over 4 days (to a larval size of 6.2 mm). No
differences were observed between larval development in the two first
groups, which began metamorphosis at 40 days old. The larvae of the
third group showed significantly slower growth that resulted in a delay of 4 days
in the onset of metamorphosis. Differences in live prey availability between
the treatments and the short transition period to allow the larvae to adapt
to the new diet were identified as possible contributing factors to the
slower growth and to the delay in metamorphosis of early weaned larvae. In a
second experiment, the transitional weaning period was increased until the
larvae were 6.6 mm in length. Weaning at that size resulted in no
slowing of growth or delay in metamorphosis, suggesting that the feeding
schedule was adequate.
(Institut des Sciences de la Mer de Rimouski (ISMER), Université du Québec
à Rimouski, 310 Allée des Ursulines, Rimouski (QC), Canada G5L 3A1. E-mail
of C. Audet: celine_audet@uqar.qc.ca)