Modelling of the SABBAC zones has the following objectives: • to test scenarios which encourage careful feeding, so waste feed and nutrient input to the environment is minimised; farmers will also save money • to encourage use of better quality feed, where better digestibility of feed means less feed is needed; better quality feed also breaks up less, so more goes to growth The modelling approach also aims to: • maintain enough spacing between cage rows so that remediation of sediments can take place – impact should be low between rows in each zone • maintain enough space between cage rows to prevent reduction of currents by high aggregation of cages – although not predicted by TROPOMOD, this effect is known to exist and has been shown by MSI models • prevent overlap of zones by predicting the extent of the zones and recommending minimum spacing between zones The TROPOMOD model was therefore set up to evaluate the following: • How severe is the impact – what is the maximum impact underneath cages? • How far to the boundary of the impact? • How can husbandry practices be optimised to use the zone most productively?

1. TROPOMOD modelling of six
SABBAC aquaculture zones
PHILMINAQ project
Chris Cromey
Patrick White
Cesar Villanoy, Evangeline Mandong
All of the PHILMINAQ team made
contributions to this modelling effort
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1

2. Particles settling under a fish cage
result in a ‘footprint’ of deposition of solids on the sea bed
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2

3. Currents move in different speeds and direction at
different depths. Faeces settle more slowly and so
are transported further away from cages
0
C u r re n t V e lo c ity
S o u rc e
Milkfish waste
faeces settle
very slowly
F in e
C o a rs e
M e d iu m
Waste feed particles settle quickly
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3

4. Contour map of waste flux
Benthic
community
(grams waste feed and faeces m d )
-2
-2
-1
grams solids m bed d
-1
75
Severe impact
(no animals)
75
15
High impact
(some effect)
15
1
Moderate impact
1
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5. PHILMINAQ project modelling approach with TROPOMOD
3 important aspects:
1. How severe is the impact – what is the maximum impact underneath
cages?
2. How far to the boundary of the impact? (Scotland = Allowable Zone of
Effect)
3. How can husbandry practices be optimised to use the zone most
productively?
Objectives
Predict if impact is SEVERE underneath cages
as shown by this deposition footprint
Zone colour
Predict distance to boundary of MODERATE impact
Edge of zone
Zone colour
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5

6. PHILMINAQ project modelling approach with TROPOMOD
Maintain enough spacing between cage rows so that remediation of
sediments can take place – impact should be LOW between rows in each
zone
Zone
colour
Maintain enough space between cage rows to prevent reduction of currents
by high aggregation of cages
Not predicted by TROPOMOD, but this effect is known to exist and has
been shown by MSI models
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6

7. PHILMINAQ project modelling approach with TROPOMOD
Encourage careful feeding, so that there is less waste feed and
less wastage of money
Encourage better quality feed:
Feed digestibility is increased
Less feed is needed
Better quality feed also breaks up less, so more goes to
growth
Test these scenarios
Prevent overlap of zones by predicting the extent of the zones
– e.g. 600 m between zones for this site
S c a le ( m )
0
200
400
600
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800
7

8. Method - common model input data between scenarios
Model input data
Value
Zone size
600 m by 200 m (12 ha)
Current (modelled by MSI)
Modelled
Feed settling rate for different
scenarios
FCR 2.8 – pellet break up (estimated)
FCR 2.0 – intact pellets (measured
by PHILMINAQ)
Faeces settling rate – measured by
PHILMINAQ for Milkfish
8.9 cm/s (5%), 4.5 cm/s (65%), 1.6 cm/s (30 %)
8.9 cm/s (100%)
0.84 (cm/s)
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9. Scenarios tested
A range of feed inputs are used between 0 and maximum to
simulate fish at different stages of growing cycle in each zone
Therefore, these are not worse case scenarios
Method – what is varied between scenarios?
Model input data
Scenario 1
Poor feeding
Low digest.
Scenario 3
Careful feeding
Better digest.
Feed wasted
27%
10%
Feed digestibility
49%
56%
FCR
2.8:1
2.0:1
Feed input
Between 0 and 323
kg/cage/d
Between 0 and 231
kg/cage/d
Data source: EMMA and PHILMINAQ projects
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9

10. Square cages – 12m * 12m * 8m
Zones 1 – 3, 5 and 6: feed ration used in the simulations – each cage
randomly allocated a feed ration to simulate fish at different stages of cycle
FCR = 2.8:1
Days
Size
Number
Biomass
(kg)
Feed rate
(%/day)
Feed/day
(kg)
April
0
0
0
0
0
0
May
25
20
27247
545
8.5
46
June
30
41
26873
1091
8.9
97
July
31
91
26498
2406
7.1
171
August
31
162
26124
4224
5.1
214
September
30
247
25749
6358
4.4
278
October
31
386
25375
9799
3.3
323
November
19
433
25000
10825
1.8
193
Data source: EMMA project
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10

11. Large circular cages – 20m diameter * 8m means 2.18 times more
biomass can be contained in cages if stocking density is maintained
Zones 4: feed ration used in the simulations – each cage randomly allocated
a feed ration to simulate fish at different stages of cycle
FCR = 2.8:1
Days
Size
Number
Biomass
(kg)
Feed rate
(%/day)
Feed/day
(kg)
April
0
0
0
0
0
0
May
25
20
59444
1189
8.5
101
June
30
41
58628
2404
8.9
214
July
31
91
57810
5261
7.1
374
August
31
162
56994
9233
5.1
471
September
30
247
56176
13875
4.4
611
October
31
386
55360
21369
3.3
705
November
19
433
54542
23616
1.8
425
Data source: EMMA project data on previous slide scaled by 2.18
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11

12. Aquazones identified by the hydrodynamic model
Current used in
TROPOMOD were
taken from the MSI
hydrodynamic model
of the area (left) – 30
days of current were
used
Zones 1 to 6 are
shown in the map
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12

13. Current velocity distribution
North
e.g. At zone 1, current is flowing east and west in the
Bolinao Narrows
Zone 1
Zone 3
Zone 2
35
25
25
25
15
15
15
5
-35 -25 -15
35
35
5
5
-5
-5
5
15
25
35
-35
-25 -15
-5
-5
5
15
25
-35
35
-25
-15
-5
-5
-15
-15
-25
-35
15
25
35
Zone 6
Zone 5
25
25
15
15
5
35
35
5
-5
-5
5
15
25
35
-35 -25
-15
-5
-5
-15
-15
-25
-25
-35
-35
25
15
5
15
25
35
v (cm/s)
35
-25 -15
35
-35
Zone 4
-35
25
-25
-35
15
-15
-25
5
5
-35
-25
-15
-5
-5
5
-15
-25
-35
u (cm/s)
For each site, lines of cages were orientated parallel with the main axis
of current e.g. cages in © www.akvaplan.niva.no
zone 4 were aligned NE-SW
13

14. Modelled current at the zones from MSI Bolinao model
showing a rank of the most dispersive and deepest
Zone
Depth (m)
Depth rank
Mean
speed
(cm/s)
Max
speed
(cm/s)
Current
rank
1
20
1
10.8
28.6
3
2
14
2
11.5
30.6
2
3
13
3
8.9
23.7
4
4
10
4
7.9
24.8
5*
5
10
5
6.0
18.8
6
6
9
6
13.3
39.9
1
This table shows tidal currents – site 4 is exposed to waves from the east,
which will increase dispersion
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14

15. Zone colouring
Definitions
Impact areas:
Low/None
Moderate
High
Severe
Zone colour
Predicted flux
(g m-2 d-1)
<1
1 – 15
15 – 75
75 +
% of zone area HIGH
and SEVERE impact
>15
Is more than 1 % of
zone SEVERE
impact? Yes or No?
> 75
Distance to boundary
of zone of effect - 1 g
m-2 d-1 contour
1
Measured sediment flux at Bolinao during workshops by
PHILMINAQ project - 114.0 g m-2 d-1 (0 m) and 148.7 (25 m) - Both
stations devoid of fauna
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15

16. Aquaculture Zone 1 – Bolinao Narrows
M o d e l w a s t e f lu x - g r a m s m
-2
-1
d
Impact
FCR 2.8:1
Severe
75
High
Less feed
wasted,
higher
digestibility
FCR 2.0:1
N
15
Moderate
S c a le ( m )
1
0
200
© www.akvaplan.niva.no
400
600
800
16

17. Aquaculture Zone 2 – ??
M o d e l w a s te flu x - g r a m s m
-2
d
-1
N
FCR 2.8:1
Impact
Severe
75
High
15
Less feed
wasted,
higher
digestibility
FCR 2.0:1
S c a le ( m )
0
200
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400
Moderate
1
600
800
17

18. Aquaculture Zone 3 – ??
M o d e l w a s te flu x - g r a m s m
-2
d
-1
Impact
N
FCR 2.8:1
Severe
75
High
Less feed
wasted,
higher
digestibility
FCR 2.0:1
S c a le ( m )
0
200
15
400
600
Moderate
800
1
© www.akvaplan.niva.no
18

19. Aquaculture Zone 4 – 2 rows of 12 large cages
M o d e l w a s te flu x - g r a m s m
N
Less feed
wasted,
higher
digestibility
FCR 2.0:1
FCR 2.8:1
-2
d
-1
Impact
Severe
75
High
15
Moderate
S c a le ( m )
0
200
400
600
800
1
Zone 4 is exposed to waves from the east, so the model will overpredict
impact
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19

20. Aquaculture Zone 5 – ??
M o d e l w a s te flu x - g r a m s m
-2
d
-1
Impact
Less feed
wasted,
higher
digestibility
FCR 2.0:1
FCR 2.8:1
Severe
75
High
N
15
S c a le ( m )
0
200
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400
600
800
Moderate
1
20

21. Aquaculture Zone 6 – Pens
M o d e l w a s te flu x - g r a m s m
-2
d
-1
Impact
Less feed
wasted,
higher
digestibility
FCR 2.0:1
FCR 2.8:1
Severe
75
High
N
S c a le ( m )
0
200
© www.akvaplan.niva.no
400
600
15
800
1
Moderate
21

22. Prohibited Aquaculture zones
1 6 .4
1 6 .3 9
1 6 .3 8
1 6 .3 7
Hr 61
G u ig iw a n e n
29
27
B O L IN A O
25
23
21
S ia p a r
19
1 6 .3 5
D e p th (m )
L a titu d e (N )
1 6 .3 6
1 6 .3 4
1 6 .3 3
17
15
13
11
9
ANDA
1 6 .3 2
7
5
1 6 .3 1
3
1 6 .3
1 6 .2 9
1 6 .2 8
1 1 9 .8 8
1
C a q u ip u ta n
S tr a it
1 1 9 .9
R e fe r e n c e V e c to r s (m /s )
0
0
0
0
1 1 9 .9 2
1 1 9 .9 4
L o n g itu d e (E )
© www.akvaplan.niva.no
1 1 9 .9 6
1 1 9 .9 8
.1
.3
.6
.9 3
120
22

23. Avoiding impact overlap between aqua zones
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23

24. Recommended cage culture zones
1 6 .4
1 6 .3 9
1
Hr 61
29
27
B O L IN A O
3
1 6 .3 7
G u ig iw a n e n
2
1 6 .3 8
25
23
1 6 .3 6
21
S ia p a r
D e p th (m )
1 6 .3 4
7
L a titu d e (N )
4
19
6
1 6 .3 5
1 6 .3 3
17
15
13
11
9
ANDA
1 6 .3 2
7
5
1 6 .3 1
3
1 6 .3
1 6 .2 9
1 6 .2 8
1 1 9 .8 8
1
C a q u ip u ta n
S tr a it
1 1 9 .9
R e fe re n c e V e c to r s (m /s )
0
0
0
0
1 1 9 .9 2
1 1 9 .9 4
1 1 9 .9 6
1 1 9 .9 8
.1
.3
.6
.9 3
120
L o n g itu d e (E )
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24

25. Recommended cage culture zones
1 6 .4
1 6 .3 9
1
1 6 .3 7
G u ig iw a n e n
Hr 61
2
1 6 .3 8
29
27
3
B O L IN A O
25
23
1 6 .3 6
21
S ia p a r
D e p th (m )
1 6 .3 4
6
7
L a titu d e (N )
4
19
1 6 .3 5
1 6 .3 3
17
15
13
11
9
ANDA
1 6 .3 2
7
5
1 6 .3 1
3
1 6 .3
1 6 .2 9
1 6 .2 8
1 1 9 .8 8
1
C a q u ip u ta n
S tr a it
1 1 9 .9
R e fe r e n c e V e c to r s (m /s )
0
0
0
0
1 1 9 .9 2
1 1 9 .9 4
© www.akvaplan.niva.no
1 1 9 .9 6
1 1 9 .9 8
.1
.3
.6
.9 3
120
25

26. Zones – what area is impacted
Zone
Scenario
Area impacted - % of
zone HIGH/SEVERE
SEVERE
(% of zone)
Rank
1
FCR 2.8
54
6.1
1
2
FCR 2.8
53
6.5
2
3
FCR 2.8
50
9.3
4
4
FCR 2.8
53
20.3
6(Exposed)
5
FCR 2.8
45
13.5
5
6
FCR 2.8
52
7.2
3
1
FCR 2.0
36
0.0
2
FCR 2.0
35
0.0
3
FCR 2.0
36
0.0
4
FCR 2.0
44
5.9
5
FCR 2.0
35
0.0
6
FCR 2.0
35
0.0
Exposed
Zone 4 is exposed and therefore model probably over estimates impact
because the model does not take account of waves
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26

27. Zones – how severe is the impact
Zone
Scenario
Average flux in
HIGH/SEVERE zone
(g/m2/d)
1.0
FCR 2.8
43
1
2.0
FCR 2.8
44
2
3.0
FCR 2.8
50
4
4.0
FCR 2.8
73
6 (exposed)
5.0
FCR 2.8
58
5
6.0
FCR 2.8
46
3
1.0
FCR 2.0
24
2.0
FCR 2.0
26
3.0
FCR 2.0
29
4.0
FCR 2.0
45
5.0
FCR 2.0
33
6.0
FCR 2.0
30
Rank
Zone 4 is exposed and therefore model probably over estimates impact
because the model does not takewww.akvaplan.niva.no
account of waves
©
27

28. Zone
Cages
Spacing between cages
Zone biomass
modelled
Average situation
with all different
fish sizes in zone
(EMMA data)
Zone biomass if all
fish 386 grams in all cages
Maximum biomass in zone
1, 2,
3, 5,
6
2 rows of 18
20 m between cages
120 m between rows
137 tonnes
353 tonnes
A
4
2 rows of
12
30 m between cages
120 m between rows
277 tonnes
514 tonnes
B
Zone 4 cages are large circular cages (20 m diameter* 8m deep)
Zones 1,2,3,5,6, are square cages (12m* 12m*8m deep)
386 gram fish require highest feed, 9.8 tonnes per cage *36 = 353 tonnes in
zone (square cages)
A
386 gram fish require highest feed, 21.4 tonnes per cage *24 = 514 tonnes in
zone (large circular cages)
B
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28

29. Large, circular cages versus small, square cages
Scenario – for zone 5 which has the lowest currents, can the zone support a
higher biomass if large circular cages are used instead of small square
cages?
Scenario
Configuration
Area impacted - %
of zone
HIGH/SEVERE
FCR 2.8
2 * 18 square cages
45
13.5
353 tonnes
FCR 2.0
2 * 18 square cages
(353 tonnes)
35
0.0
353 tonnes
SEVERE
(% of zone)
Zone peak
biomass
FCR 2.8
FCR 2.0
YES - ? tonnes can be at peak biomass as opposed to 353 tonnes
with small cages ( a x % increase)
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29

30. Zones ranked in terms of dispersiveness
Overall rank
Zone
Rank magnitude of
SEVERE
impact
Rank extent of
SEVERE
impact
Rank - depth
Rank current
1
1
1
1
1
3
2
2
2
2
2
2
3
6
3
3
6
1
4
3
4
4
3
4
5
4
6
6
4
5
6
5
5
5
5
6
However, zone 4 is exposed to waves which are not modelled so zone 4 is
likely to be more dispersive in reality
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30

31. Summary
TROPOMOD model predicted impact with 2 scenarios, FCR of 2.8:1 and 2.0:1.
Results are for different sized fish throughout the zone, which is realistic, not worse
case.
Improvement of FCR of 2.8 to 2.0:1 resulted in:
•
reduced feed needed by 29 %
•
there was no/little SEVERE impact under cages
•
HIGH impact areas were less than 50 % of the total zone area
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31

32. Recommendations
Zone
Cage
configuration
Peak biomass
(tonnes)
Spacing
1, 2, 3, 5, 6
2 * 18 square
cages
353
20 m between
cages, 120 m
between rows
4
2 * 12 large
circular cages
514
30 m between
cages, 120 m
between rows
As the deposition footprints extend between 200 and 400 m from the edge
of the zone, it is recommended the distance between zones should be a
minimum of 600 m.
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32

33. TROPOMOD has been developed using a similar concept to the following
models:
MERAMOD – Sea bass/bream in the Mediterranean – scientifically tested at
several sites with sediment traps and benthic fauna sampling
DEPOMOD – Salmon/cod for North Atlantic – used in the Scottish regulatory
system to consent farms in Scotland
DEPOMOD and MERAMOD have 100+ users worldwide
Tests with TROPOMOD at Bolinao were satisfactory – the model predicted on
average 104 g m-2 d-1, which corresponded to an average value measured in traps
of 131 g m-2 d-1 in May 2007.
ECASA toolbox - a tool box of environmental impact and socioeconomic
indicators, including descriptions of models and where to find them
www.ecasatoolbox.org.uk
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33