Design and development of a
geothermal temperature control system for broodstock management of channel
catfish Ictalurus punctatus
S.G.
Hall, J. Finney, R.P. Lang, T.R. Tiersch-2002
Aquaculture Engineering, 26(4): 277-289
Abstract:
A control system was designed to raise and maintain
water temperatures within ~0.03-ha earthen ponds to a range conducive for
spawning (24–30 °C) channel catfish Ictalurus punctatus.
Heating was done during February 2001 to April 2001, when temperatures would
have otherwise prohibited spawning (<24 °C). Temperature was
increased from ~10 °C (ambient) by ~2 °C per day, and maintained
at ~27 °C, by the addition of geothermally warmed water (~36 °C).
The control system substantially increased the controllability and precision
of heating ponds compared to manual operation. Systems were designed to
control sets of four ponds. In designing this control system, consideration
of biological constraints was essential. Reproduction in channel catfish is
most strongly influenced by temperature. Because cold fronts are common
during the winter and early spring (January–March), it was essential to
ensure that pond temperatures did not fall below the range for spawning.
Constraints on the heating rate and temperature variability to maintain fish
health and stimulate spawning behavior were considered. Components of the
control system included temperature measurement devices (type-T
thermocouples), a central electronic control unit, electronic switches and
electrically actuated ball valves. In response to the temperature sensed by
each thermocouple, the controller sent a message to close or open the valve.
When the valve was opened, warm water was added to the pond to increase the
average pond temperature. Hardware and algorithm design and initial system
testing were the major components of this project. The final design
incorporated information on relevant biological parameters and safety
features including peak pond temperature, independent aeration and water
pressure control mechanisms. Initial results indicate successful control of
this biological system, and ongoing studies suggest similar mechanisms may
be used for additional control objectives. In particular, this system could
be used to vary pond temperatures to study biological responses and to cool
ponds by addition of well water during summer months.
(Department of Biological and Agricultural
Engineering, Louisiana Agricultural Experiment Station, Louisiana State
University Agricultural Center, 143 Doran, Baton Rouge, LA 70803, USA, Tel.:
+1-225-578-1049; fax: +1-225-578-3492; email: shall@bae.lsu.edu)