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4.2.3 Fish Growth
Fish growth was monitored using weekly sub-sampling data and biomass data collected during
stocking and harvesting activities.
4.2.4 Feeding Practices
Fish were fed to satiation with appropriately sized feed, delivered in at least three separate rations
daily throughout the growing season and every three days during winter months. All feeds utilised
were commercial fish diets with protein contents between 35 and 45 per cent. Feed inputs to each
culture unit were recorded as quantity fed on a daily basis. A combination of both floating and sinking
feeds were used through out the study period dependent on feed size and type of culture unit being
used in conjunction with visual observations of feeding behaviour.
4.2.5 Systems Maintenance
Culture units (cages, tanks and raceways) were cleaned and maintained when possible. All units were
kept covered to prevent bird predation. Units were thoroughly cleaned and maintained prior to
stockings and between stock movements. Raceway uplift banks and screens were cleaned as required.
4.2.6 Disease Monitoring and Treatments
Fish suspected of suffering from pathogen related problems were examined using wet slide
preparations and a light microscope (Olympus). Samples of fish from units with significant observed
mortality were analysed at the Department of Primary Industries, Animal Research Institute Veterinary
Laboratory at Yeerongpilly Brisbane as required.
Fish requiring treatment for pathogens were given formalin or salt baths as required. During treatment
supplemental aeration was supplied and stock was closely monitored for signs of stress, principally
respiratory distress, and/or incidence of moribund fish.
4.2.7 Purging and Sale of Fish
Fish were purged for no less than 10 days in 10t HDPE tanks supplied with bore water at ambient
temperatures of between 12 and 28ºC. This water was exchanged twice daily and salt added
periodically to reduce pathogen loads and reduce post handling stress. Fish were principally sold live
or euthanased in an ice slurry and sold whole. Some were slaughtered, filleted and frozen (as a shatter
packed product) at a commercial seafood processor and sold through a local seafood retail outlet in
Dalby.
4.3 Results
4.3.1 Production Systems
Raceway production represented the major culture unit used for production of silver perch at this site.
The first raceway was stocked in the beginning of May 2001 and all stock was transferred to raceways
by the end of October in 2001, after which cages were no longer used. A total of 16 raceways were in
operation at the completion of this study (Table 4.3.1).
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