Clifford A. Goudey Center for Fisheries Engineering Research

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Engineering Challenges and Opportunities in
Offshore Aquaculture
Clifford A. GoudeyCenter for Fisheries
Engineering Research MIT Sea Grant College
Program Massachusetts Institute of Technology,
Cambridge, MA USA Second US-Korea Workshop on
Offshore Aquaculture Jeju, S. Korea 18-19 July
2005
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Motivation
Sheltered-water technologies bring unacceptable
risk and high labor costs when used in
high-energy locations. The scale of operations
needed to operate economically offshore will
support technology development.
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Topics

• Mooring systems
• Robotic applications
• Cage design

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Mooring Systems

• Conventional multi-point mooring systems
• have no place offshore.

• Fixing a cage over specific location exacerbates
  benthic impacts.
• Weather can come from any direction.
• Depth and scope requirements result in excessive
  footprint.

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Anchoring Conventional methods of cage
anchoring become impractical at depths over 100
meters
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Single Point Moorings

• Lower cost
• Reduced benthic deposition
• Reduced overall cage loads
• Operational advantages

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Deadweight/Drag Embedment Anchor for GoM OAC S.S.
cage

• Omni-directional design
• Concrete with re-bar armature
• 12 tonne

3.2 m
3.2 m
0.97 m
45 deg.
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Robotic Applications in Offshore Aquaculture

• Automated feeding
• Predator control
• Biofouling removal
• Environmental monitoring

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Automated Feeding
Robofeeder - a 500 lb capacity, cage-mounted
system designed for both surface and
submerged operation.
P.E. cone-bottom tank
UNH OOA
Pneumatic gate valve
Battery/timer box
30 cu. ft. scuba tank
Dispensing tubes
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Predator Control
Autonomous Underwater Vehicles (AUVs) are
commercially available that could be used to
deter biological intrusion
MIT Odyssey II
WHOI Remus
Others are under development
MIT RoboTuna
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Biofouling Removal
An autonomous net cleaner powered through a
tether from the surface, attaching to the net,
and removing biofouling using H.P. water jets or
brushes.

• Control
• Random (pool cleaner)
• Intelligent (robotic vacuum)
• Navigating using net plan (Net Cleaning Spider)

MIT, Leonard
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Environmental Monitoring
Water column surveys using an Autonomous
Underwater Vehicle (AUV) operating in a long
base-line acoustic array, carrying nutrient
sensors, conducting an intelligent survey.
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The Cage-size Conundrum

• Capital costs favor very large cages V/A
  l3/l2
• Operational efficiency in the open ocean may
  favor whole-cage harvesting from smaller cages
• Its not stocking density, its how many fish are
  between you and the source of clean water.
• Possible Solutions
• New methods for large-cage servicing
• and partial harvest
• 2. Smaller cages

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M/V Cage Tender A purpose-built aquaculture
support vessel
Goudey, 2001
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M/V Cage Tender Designed for installing,
stocking, maintaining, and harvesting ocean cages
up to 100 (30.5 m) in diameter and live fish
transport.
LOA 44 m
Disp. 1,100 T
Beam 40 m
CAGE TENDER
Goudey, 2001
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100 m2 China/ASA Cage

• Design requirements
• Full exposure to South China Sea
• 100 m3, fixed volume, surface cage
• Protected feed enclosure for floating pellet
• Site 4 km offshore, 22 m depth
• Self-submergence during storm
• PE construction

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Cage assembly and Deployment at Lingshui Bay on
China's Hainan Island, July 2004
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100 m2 Corner Weldment
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6.5 tons per cage in 2004 (65 kg/m3)
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The Ultimate Autonomy - Ocean Drifter
Manned or autonomous cages capable of low-speed
self-propulsion operating in reciprocal or gyre
coastal currents or in oceanic circulations.
How else can we exploit the majority of the EEZ
where anchoring is impossible?
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Final Points The future lies with the right
combination of technologies and species
facilitated by a suitable regulatory scheme.
Systems, species, and the legal framework need
to be developed in concert for economic viability
to occur. Many of the required pieces are in
hand. The integrated system is not, and it must
be developed and demonstrated. Offshore
technology requirements tend to converge,
presenting opportunities for international
collaboration. cgoudey_at_mit.edu