Fish Health Management in Recirculating Aquaculture Systems

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Fish Health Management in Recirculating
Aquaculture Systems

• Julie Bebak-Williams, VMD, PhD
• Freshwater Institute
• Shepherdstown, WV

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Two areas of concern for fish health in culture
systems

• Water quality fish produce ammonia and carbon
  dioxide and consume oxygen concentrations in
  water must be kept within required range for
  optimum health and performance
• Pathogens (bacteria, viruses, parasites)
• Obligate requires fish to replicate
  specific-pathogen-free
• Opportunistic present in soil and water
  thrive in conditions with a high organic load
  (bacteria, parasites)

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Serial-Reuse in Raceways
paired raceway 1
paired raceway 2
paired raceway 3
paired raceway 4
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Serial-Reuse in Raceways
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Cleaning Solids From Quiescent Zones
Big Springs State Fish Hatchery (PA)
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Fully-Recirculating Systems

• Typical hydraulic profile.

stripper
fluidized sand biofilter
LHO
LHO sump
pump sump
culture tank
drum filter
(courtesy of PRAqua Technologies)
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Freshwater Institute RAS
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FI Fully-Recirculating System

• Culture Tank
• 9.1 m dia x 2.5 m deep tank
• 150 m3 (40,000 gal) culture volume
• 31.5 min HRT

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Biosecurity in Recirculating Aquaculture Systems
(RAS)

• Strategies to
• reduce entry of specific pathogens
• Specific-pathogen-free water supply
• Specific-pathogen-free eggs
• prevent spread of pathogens once introduced
• Meticulous husbandry in an easy to clean system
• UV and/or ozone
• Monitoring and surveillance program
• reduce susceptibility to disease
• Optimum nutrition, gentle handling, use of high
  quality fish

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Biosecurity

• Plan biosecurity during design stage!
• System must be easy to clean (e.g., cleanouts
  unit processes)
• Viewing ports to assess fish condition
• Take tanks off-line for treatment, separate
  discharge
• Traffic flow patterns

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Water Quality and Fish Health in RAS

• To keep fish healthy, need constant monitoring of
  water quality variables (complete with alarms!)
• Improper function of
• Biofilter - ammonia, nitrite and (possibly)
  nitrate toxicity
• Carbon dioxide (CO2) stripper and low head
  oxygenator - CO2 toxicity, insufficient dissolved
  oxygen concentrations and/or nitrogen gas
  supersaturation
• Ozone or UV units - ozone toxicity insufficient
  inactivation of pathogens
• Tank hydraulics, drum filter high
  concentrations of suspended solids

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How treatment of a problem is different in an RAS

• Longer retention time of chemicals
• The treatment can affect unit processes
• Chemicals can affect biofilter function
• Chemicals can be affected by unit processes
• Ozone breaks down formaldehyde to carbon dioxide,
  oxygen and water

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WV Aqua (Man, WV)