This document discusses recirculation aquaculture systems. It notes that these systems are used worldwide at large scales to intensively produce fish. The key advantages are that they allow precise environmental control, high production capacity, and up to 99% less water usage than conventional aquaculture. However, high initial investment and the complexity of the technology also present challenges. Proper system design, monitoring, staff training and market planning are essential for success.

1. The Potential for
Recirculation Aquaculture
Dr Mark Burdass

2. Recirculation Systems
• Systems used worldwide
• Production capacity depends on treatment
system
• Defining Recirculation Systems:
– System that recycles and renovates water for
the culture of aquatic organisms!

3. Global Perspective
• Successful large scale recirculation
aquaculture facilities in UK, Norway,
Europe, US, Canada & Australia.
• Highly intensive recirculation facilities used
in Scotland to produce salmon smolts

4. Definition
• Original definition 95% recycle (based on
flow), means 5% exchange per pass
• More recent systems defined by daily
volumetric exchange rates (10% per day)
• Lots of challenges with systems
recirculating water at < 5% per day

5. Advantages
• Controlled Environment
– Controlled temperature environment
– Allows controlled product growth rates
– More efficient food conversion
– Predictable harvest routines
– Allows production all year round
– Biosecurity advantages
– Enclosed environment means production free of
predators and other damaging wildlife
– Allows efficient inventory control
• The systems designed to conserves heat and
water through water reuse
– Reconditions the water through filtration processes
• Allows effective economies of scale
– This results in high production per unit area
– Save on handling equipment as used more
intensively.

6. Advantages
• Environmentally sustainable
– Use up to 99% less water than a conventional
aquaculture facility
– Less than 1% of the land area
– Allows waste to be managed in an
environmentally safe manner
– Allows waste to be further processed or used
for hydroponics
– Producing tropical fish locally has low carbon
footprint because of low food foodmiles in
production

7. Advantages
• Not restricted to traditional aquaculture
production locations
• Not restricted to traditional UK aquaculture
species
– Species such as barramundi, tilapia and
catfish possible in UK
• Allows production to be placed near to
market

8. Why Recirculation Systems
• Challenges
– High Initial Investment
• Compared to other production methods
– Financing can be an issue because investors often
want fast returns
– Technology is not well known
• Getting better
– Very short response time
– Reliability of electricity supply critical
– Lack of track record
• Failures common
• Hard to finance

9. Challenges
• Not as yet able to compete with large
scale aquaculture production
• Most Recirculation farms are under 500
tonnes in size
• Don’t have the economies of production
volume
– Supermarket product volume requirements
often above production of a single unit

10. Other Challenges
• There have been a number of high profile failure
in UK and across Europe
• Often difficult to determine why they failed,
however:
• The reasons are various but have included:
– Technology was labour intensive and therefore
running costs were too high
– Poor Design
• Often under-capitalised
– Poor management decisions
– Over optimistic market forecasts for product sales
– Inexperienced staff

11. System Comparison
• Conventional
intensive tilapia • Recirculation tilapia
farm farm
• 17.4 tonnes per ha • 1,340 tonnes per ha
per year per year
• Water use: 21 m3 per • Water use: 0.5m3 per
kg of production kg of production

12. Uses for Recirculation Systems
• Hatchery
• Nursery
• Quarantine
• Advanced fingerling production
• Purging market sized product
• Grow-out table production
• Near market site holding system

13. Running Costs
• Food and labour are the still the two main
costs
• Heating and pumping often amount to less
than ¼ of the above
• Initial capitalisation is a very significant
cost compared to conventional
aquaculture
• Possibility for large units of using
renewable energy supplies thereby
reducing costs in the long term

14. Systems
• High Stocking densities do not constitute
an efficient recirculation system!
• High feed rates per day do!
• It takes feed to grow fish!
• Food is the main consideration when
designing and predicting the capacity of a
system.
• An intensive recirculation system has a
high capacity to grow fish rather than hold
them

15. Technology
• The technology has been available for
over 30 years
• Reliable
• Efficient
• Most failures are down to mismanagement
of systems or producing inappropriate
species

16. Filtration System must:
• Remove solid wastes
– Settleable, suspended and dissolved
• Convert ammonia and nitrite to nitrate
• Remove CO2
• Add oxygen
• Maintain acceptable pH
• Control Pathogens
• Keep up with the generation of waste

17. Recirculation Process Diagram
MAKE-UP
WATER
BIOFILTER NH3
CO2 REMOVAL AIR BLOWER
REMOVAL
OZONE
DESTRUCTION O3
BY UV MONITOR
O2 ADDITION
O3 ADDITION
CULTURE TANKS
CLEAN WATER FROM BOTTOM DRAIN
UPPER LEVEL IN TANK 15%
(SIDE BOX) 85%
DRUM FILTER SWIRL
SEPARATOR
PUMP SUMP
FILTRATE
BOTTOM DRAIN
15%
SLUDGE TO SEPTIC TANK
WASTE

19. Key Water Quality Parameters
• Dissolved Oxygen
+
• Ammonia-Nitrogen (NH3 & NH4 )
-
• Nitrite-Nitrogen (NO2 )
• pH
• Alkalinity
• Carbon dioxide (CO2)
-
• Nitrate-Nitrogen ( NO3 )

20. Misperceptions
• Overly complicated
• Prone to catastrophic failure
• Only suitable for high value species
• Needs highly educated staff to run

21. Key Issues for success
• Use proven technology in system
construction
• Ensure system has effective monitoring
systems
• Build in back up systems to key processes
• Most success has come from small units
which have scaled up
• Use species with a track record in
recirculation systems
• Be sure of the market

22. Key Issues for success
• Business plan assumes market prices will
drop once production starts
• Grow species with a short production time
to improve cash flow
• Ensure product is fit for market
• Ensure have the trained staff to operate
the systems