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Moving Mussels Offshore
24 September 2007
Trish DalyBIM
Killary Harbour
Rope mussel Production and value 1990-2006
-
2 000
4 000
6 000
8 000
10 000
12 000
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
Year
Vo
lum
e
0
1,000
2,000
3,000
4,000
5,000
6,000
7,000
8,000
Val
ue
Volume(tonnes)
Value('000)
Licensed Areas in Kilmacillogue
Licensed Areas in Ardgroom
Licensed Areas V Hectarage in use
0
50
100
150
200
250
300
350
Loug
h S
willy
*
Mul
roy
Bay
McS
wyn
nes
Bay
Bel
acra
gher
Bay
Cle
w B
ay
Killa
ry H
arbo
ur
Clif
den/
Bal
linak
ill
Leiti
r M
ealla
in
Nor
th G
alw
ay B
ay
Kin
vara
Bay
Sne
em
Kilm
akillo
gue
Har
bour
Ard
groo
m B
ay
Ban
try
Bay
Gle
ngar
riff H
arbo
ur
Ber
ehav
en S
ound
Dun
man
us B
ay
Roa
ringw
ater
Bay
Production areas
He
cta
res
Licensed
In use
Production V FloatationProduction versus floatation
0
500
1000
1500
2000
2500
3000
Loug
h S
will
y*
Mul
roy
Bay
McS
wyn
nes
Bay
Bel
acra
gher
Bay
Cle
w B
ay
Kill
ary
Har
bour
Clif
den/
Bal
linak
ill
Leiti
r M
ealla
in
Nor
th G
alw
ay B
ay
Kin
vara
Bay
Sne
em
Kilm
akill
ogue
Har
bour
Ard
groo
m B
ay
Ban
try
Bay
Gle
ngar
riff
Har
bour
Ber
ehav
en S
ound
Dun
man
us B
ay
Roa
ringw
ater
Bay
Production areas
To
nn
es
0
500,000
1,000,000
1,500,000
2,000,000
2,500,000
3,000,000
Lit
res
Production
Floatation
Why Move Offshore
• Many established Bays are overcrowded• Growth rates have dropped off in some Bays• Risk of bacterial and viral pollution is reduced• Conflict with other Bay users is reduced• The nature of our coastline offers many
opportunities• There is possible reduction in incidence of
biotoxins
Offshore Mussel Trials in Ireland
• Semi submerged mussel longlines, single headrope lines
• Submerged mussel longline, Seaflex mussel float
• Longtube longlines, Smart Farm system
Semi-submerged longlines
• First trial 1990, Seal Harbour
• Adopted and modified a system from IFREMER, France
• Single headrope longline, 1-3m below surface
• Purpose built Irish mussel floats
• Floatation kept to a minimum
Seal Harbour
Outer Bantry Bay
Galway Bay
• Started in 2005, 7 longlines and 2 Smart lines• Maximum site depth is approx. 30m• Hard sandy bottom• Fully exposed to southwesterlies• Difficulties with droppers tangling• Collected on a new heavier Spanish rope,
400g/m• Preference for single anchor at either end • Site access limited
Submerged Mussel Longline
• “Seaflex mussel float• 2 x 20m x 300mm sandor hose• Moored at both ends and in the centre• Buoyancy in the water controlled through a
hose connected at one end• Situated 5m below surface• Trial abandoned• No dedicated workboat
Longtube System Smart Farm
• Individual HDPE pipes, 126m x 250mm, wall thickness 7.7mm
• 2 – 2.8m deep collector made from square mesh, 8mm p/p, 250mm x 250mm square
• 32mm headrope lashed to pipe• Stainless steel clamp• Pipes generally moored as grid system with
prefabricated fan.• Two machines available for husbandry &
harvesting
Collector mesh & fan system
Thinning machine, Kenmare
Harvesting machine, Kenmare
Smart Farm in Ireland
• Three Bays selected: Lough Swilly, Bantry Bay, Kenmare River
• Different focus for each trial site
• Lough Swilly: strong currents, seed collection
• Bantry Bay & Kenmare River: Varying degrees of exposure
Lough Swilly
Lough Swilly
• Max depth 20m• Strong current, up to 4 knots• Traditional system tried and failed, as did semi-
submerged lines• The lines yielded about 10 tonnes of seed each
but a dive survey had estimated 14 – 16 tonnes.• Brushes were not strong enough for removing
the crop • Collector mesh offered great potential for seed
collection and relaying
Smart Farm in Bantry Bay
• Three potential sites
• Permission for two, licensed to Southward Ltd at Horse Island and Whiddy
• Lines moored individually
• Two lines damaged, clamp failed.
• Clamp design has since changed
• Slippage at more exposed site
Kenmare Bay
Kenmare Trial Site
Kenmare Bay Site characteristics
• Maximum depth 40m
• Seabed varies from hard sand to rocky
• Fully exposed to prevailing southwesterlies
• Over 12m swells recorded, current speed of about 2 knots
• Highly productive site
Mooring point specification
Trial Results
• Disappointing• Pipes failed on all sites.• Harvesting machine never operated to its full
potential• Availability of workboat and machinery major
limiting factor• Load cells attached to 2 westerly anchors, 2
anchor ropes and fan ring unreadable.• Currently 32 lines on commercial site in Kenmare
Summary results
• Semi-submerged lines have been the most successful to date
• A dedicated, purpose built workboat is essential.
• Limited opportunities to manage and harvest lines
• In all these systems the tidal range of 4m is always a major factor
Strengths
• Growth rates, shell quality and meat yield all improve
• With advancements in reusable drop ropes and the natural flushing out associated with exposed sites the environmental impact of these farms is greatly reduced
• Significant advances in husbandry technology in recent years make it more achievable on a practical level
Weaknesses
• Limited technical data available on sites• Workboat must be capable of operating in
exposed conditions• Cost of setting up V market price of
mussels• Weather windows limited from Autumn
through to Spring• Results to date did not show an improved
biotoxin profile for sites tested.
Opportunities for the Future
• Shellfish farming has a place offshore and Irish coastal waters offer huge potential for mussel production in exposed and semi-exposed sites.
• A detailed understanding of environmental parameters, including wave climate, topography, water exchange, current speed, temperature, salinity, oxygen and assessment of risk of harmful algal blooms is needed
• Collaboration between the Agencies and between the sectors is essential
Recommended