Intensive rearing system for
fish larvae research
I. Marine fish larval
rearing system
S. Kolkovski, J. Curnow, J. King-2004
Aquacultural Engineering, 31(3-4): 295-308
Abstract:
Larvae nutrition and in general larvae culture is
considered to be the ‘bottle neck’ for marine finfish culture. Fish
larvae rearing experiments investigating nutritional factors or rearing
protocols are carried out in various systems, from small beakers to very
large commercial tanks, making it difficult to compare data across systems.
A continuous supply of live or dry feeds and a
controlled environment, i.e. temperature, filtration, photoperiod, oxygen
and pH, are essential for any experimental or commercial system. These
environmental factors are best controlled automatically in order to minimize
variations between tanks. However, only a few automatic systems have been
developed for marine finfish hatcheries.
An experimental larval rearing system was developed
to reduce variability amongst tanks (due to manual feeding and other
parameters) and enhance control of environmental parameters while reducing
the workload. The system includes 24 conical tanks with the option of either
an up-welling or bottom draining flow through water delivery system. The
inlet water passes through a gas exchange column that saturates the water
with dissolved oxygen and stabilizes the pH. The system was originally
designed for nutritional experiments using formulated feeds. The use of an
up-welling water inlet method extends the suspension time of inert particles
in the water column and also helps to suspend very small or passive swimming
larvae. However, when the system is used to grow-on larvae or juvenile fish
it can easily be switched to bottom draining to provide self-cleaning water
dynamics for high organic loads.
A unique outlet filter was developed that eases the
daily routine of replacing screens when enriched live food is used. This
filter can be exchanged with a screened standpipe and outlet surface skimmer
when the bottom draining flow characteristics are engaged.
The system is fully controlled by a single
programmable logic controller (PLC). The PLC controls the light intensity,
photoperiod, dimming time, live food and algae pumping intervals,
substantially reducing labor requirements.
(Research Division, Department of Fisheries, Western
Australia, PO Box 20, North Beach, WA 6920, Australia, e-mail: skolkovski@fish.wa.gov.au)