scottish sea farms ltd st margaret’s hope biomass … · contours and spot depths from admiralty...

SCOTTISH SEA FARMS LTDST MARGARET’ S HOPE BIOMASSAND TREATMENT MODELLING

TECHNICAL SUMMARY

Report To: Scottish Environment Protection Agency

Report No: 171016- 01

Our Ref: RS

Status: V1

Date: 17 October 2016

Scottish Sea Farms Ltd

South Shian

Connel

PA37 1SB

Tel: 01631 574203 Mob: 07825030003

Email: rachel.speirs@scottishseafarms. com

IAUsermailto:[email protected]

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1. Summary

Modelling was carried out by Scottish Sea Farms Ltd ( SSF) for a proposed new marine cage site St

Margaret’ s Hope ( SMH). Appropriate maximum biomass, chemical consent limits and sampling

stations have been calculated, consent limits achieved are detailed in the table below:

Treatment Recommended consent mass

Biomass A maximum consent biomass of 1247.1 t and stocking density 17

kg/ m³ is recommended for this site.

Salmosan ( Azamethiphos) The total quantity of Azamethiphos to be discharged should not

exceed 78.2 g in a 3-hour period or 152.8 g in a 24-hour period.

This can be used to treat one cage in 3 hours or two cages in 24

hours at a maximum treatment depth of 1.5 m.

Excis (Cypermethrin) The total quantity of chemical to be discharged in a 3h period

should not exceed 14.2 g. The equivalent treatment volume is

2840.0 m³

Alphamax ( Deltamethrin) The total quantity of chemical to be discharged in a 3h period

should not exceed 5.3 g. The equivalent treatment volume is 2650

m³

SLICE ( Emamectin Benzoate) A maximum treatment quantity ( MTQ) of 436.5 g and a total

allowable quantity ( TAQ) of 2182.4 g. This is enough chemical to

treat the maximum biomass 5 times.

Table 1: Consent limits for Biomass and treatment chemicals at SMH.

2. Introduction

This document is a technical summary of an assessment carried out for a proposed new marine cage

site located west of St Margaret’ s Hope, Scapa Flow. Scottish Sea Farms plan to develop a site with a

cage configuration of 12 x 80 m circumference cages arranged 2x6 in a 70 m grid. Modelling has

been carried out in order to identify appropriate biomass and lice treatment chemical limits for this

proposed cage configuration. Sampling transects and sampling stations have been identified and are

detailed in section 4 below.

This summary provides site-specific methods only and is supported by generic method statements

AMMR12v01 and AMMR12v02.

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Figure 1: Location of the proposed marine cage site SMH, Scapa Flow.

3. Input Data

3.1 Site Data

The input data, including the bathymetry and the current data, for this site was provided by SEPA

and is summarized below:

Site Name: St Margaret’ s Hope

Site NGR: 343360 994633

Receiving Water: Water Sound

Company: Scottish Sea Farms

Peak biomass ( tonnes): 1247.1

Medicines applied for: Excis, Salmosan, Alphamax, Slice

Current Meter NGR: 343423 994652

Distance to Shore( km): 0.27

Water Depth at Site(m): 11.4

of Cages: 12

Round/ Square?: Round

Diameter/ Circumference/ Width (m): 80 m circumference

Working Depth ( m): 12

Treatment shallowing depth ( range?) ( m): 1.5

Table 2: SMH site data

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3.2 Bathymetry

The model configuration has been modified from the model setup created by Xodus Ltd on behalf of

SSF for the modelling of a proposed new site, SMH. The bathymetry was created by digitizing

contours and spot depths from Admiralty Chart No. 35-0 and includes depths collected during the

hydrographic survey, as outlined in report A-30530- S12-REPT- 001. The data limited to a 1km² model

domain with the grid limits:

DataAreaXMin= 342920

DataAreaXMax= 343920

DataAreaYMin= 994290

DataAreaYMax= 995290

3.3 Cage set-up

The cage grid consists of 12 x 80 m circumference cages arranged in two groups laid out in a 6x2 70

m grid with a working depth of 12 m. The cage configuration can be seen in figure 2.

Figure 2: Screenshot of cage configuration taken from Hope- FFMTv3. 0

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3.3 Current data

Current meter data was collected by Xodus Aurora in April and May 2011 on behalf of Scottish Sea

Farms Ltd. The survey was carried out using a 600 kHz RDI Workhorse ADCP moored on the sea

floor.

Statistics for this dataset were derived using HGdata_ analysis_ v7.xls. All data was corrected to grid

north using a magnetic variation of 3.15° W. Summaries of the derived statistical data for the 3 bins

are available in Appendix 1.

The raw data was formatted into hourly averaged data for use in AUTODEPOMOD using the SEPA

tool temp-20min- HGv3. xls ( input data displayed in Table 2). The intermediate Spring tide (SNS) and

Neap tides (NSN) were identified as occurring at hours 256 and 82 respectively.

Site name: St Margaret’ s Hope

Depth at mooring: 18.5

Height of surface meter from bottom ( m): 11.56

Height of middle meter from bottom ( m): 8.56

Height of bottom meter from bottom ( m): 2.06

Number of hourly record at which springs commence: 256

Number of hourly record at which neaps commence: 82

Identify current speed units (m/ s or cm/ s): m/ s

Mean Sea Level ( mCD): 1.93

Compass variation ( deg E/ W): 0 (correct using HGdata_ analysis)

Table2: Input parameters for the SEPA tool Hope- 20min- HGv3

Mean Sea Level (defined as the average of MHWS, MHWN, MLWS and MLWN for St Mary’ s (Scapa

Flow) was derived from Admiralty Total Tide software.

The current velocities at this site were found to be low indicating a quiescent to weakly flushed site.

3.4 Model set-up

Defaults values were used as described in SEPA guidelines Regulation and Monitoring of Marine

Cage Fish Farming in Scotland Annex H, Methods for Modelling In-feed Anti-parasitics and Benthic

Effects ( issue No. 2.3, 18 May 2005).

Initial runs were carried out using a constant feed input, auto- distribute set to on and an initial

stocking density of 17 kg/ m³. All runs used 1 particle initially and were then refined using 10

particles. MAX runs with an ITI of 10.5 were initially achieved; these were then followed by single

runs of 10 particles to limit the site to a maximum biomass of 17 kg/ m³.

3.5 Results

A passing run (Run 10) was achieved resulting in a maximum consent biomass of 1247. 1 tonnes with

a stocking density of 17 kg/ m³. Table 3 shows the flux, ITI and area results for this run while a

diagram of the flux contours and deposition footprint can be found in figure 3. A full summary of

results can be found in the marine sum spreadsheet in Appendix 2. The shape and size of the

deposition footprint is consistent with the local bathymetry and current profile at this site.

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Flux ( g/ m²/ y) ITI Area ( m²)

80% solids 1410 10.9 61842.7Cage Area Equivalent 11186 4 35845

Benthic Sampling Area 191.8 30 81556.7Table 3: Flux, ITI and Area results for run 10

Figure 3: Diagram of model output for run 10.

Transects have been aligned with the major axis of the deposition footprint (Fig. 3 & 4). The primary

transect has been placed at the point where the 30ITI contour is furthest from the cage group. While

a secondary transect has been included to offer a backup position if required in the field. Profiles of

each transect have been included below in Figure 5.

Sampling stations have been placed along each transect at the 30 ITI boundary and at 10m on either

side.

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Figure 4: Extract from Hope_Marine_Sum indicating position of transects and sampling stations.

Transect 1

Transect 2

Figure 5: Profile of sampling transects for run 10.

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4. Bath Treatments

4.1 Input

The input data for this model is summarised in table 4 below. The hydrographic statistics for this site

were generated using the SEPA tool HGdata_ analysis_ v7.xls. Distance from shore was measured

from Admiralty Chart No. 35-0 using ArcGIS v10.1.

Loch Data

Loch/ Strait/ Open water : Loch

Loch area (km2) : 9.2

Loch length (km) : 6.5

Distance to head (km) : 4.7

Distance to shore (km) : 0.27

Width of Strait (km) : ( only required for Strait)

Average water depth (m) : 11.4

Flushing time (days) :

Cage Data

of cages : 12

Cage shape : Round

Diameter/ Width (m) : 25.5

Working depth (m) : 12

Stocking density (kg/ m3) :

Treatment

No. of cages possible to treat in 3

hours :

1.00

Initial Treatment Depth ( m) : 1.5

Treatment Depth Reduction Increment

m) :

0.1

Hydrographic data analysis

Mean current speed ( m/ s) : 0.035

Residual Parallel Component U (m/ s) : 0.011

Residual Normal Component V (m/ s) : 0.002

Tidal Amplitude Parallel Component U

m/ s) :

0.051

Tidal Amplitude Normal Component U

m/ s) :

0.021

Table 4: Bath Treatment inputs for SMH.

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4.2 Results

The consent limits for all Bath treatment chemicals applied for are summarized in the marine sum

spreadsheet which can be found in Appendix 2.

Azamethiphos

Recommended consent mass (3h) – 78.2 g


Treatment Depth – 1.5 m

No. of cages per treatment – 1.0 in 3hrs, 2.0 in 24hrs

The TS plot for Azamethiphos is shown in figure 6 below:

Figure 6: Azamethiphos TS plot

Cypermethrin


No. of cages per treatment – 3.7

Deltamethrin


No. of cages per treatment – 3.5

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5. Infeed Treatments

5.1 Model Set-up

The model was setup using the method described in SSF’ s generic method report Bath and In-Feed

Method Statement and follows the guidelines and model defaults described in SEPA guidelines

Regulation and Monitoring of Marine Cage Fish Farming in Scotland Annex H, Methods for

Modelling In-feed Anti-parasitics and Benthic Effects ( issue No. 2.3, 18 May 2005) unless stated

otherwise below.

The Slice run parameters were set to 5 x maximum biomass ( 6235. 4 t) using an annual feed load of

3186. 3 tonnes.

All other options were set to default.

5.2 Results

The passing run ( run 2) for Slice results in a TAQ of emamectin benzoate of 2182. 4 g, this has an

equivalent treatable biomass of 6235. 4 t which is 5 x peak biomass. The MTQ is 436.5 g, this is

enough to treat the maximum consented biomass of 1247. 1 t in one treatment. This scenario results

in a mass balance is 1575 g and a mean near- field concentration of 222 gkg¹. The near- field

concentration levels exceed the EQS trigger value with a difference in concentration between

predicted near field residue concentrations and EQS values of 214.4 gkg¹.

Figure 7: Diagram of model output from Slice Run 2.

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6. Discussion

The footprint of deposition produced by the model is consistent with the bathymetry and current

data recorded at this site. This is also reflected by the volume of mass retained within the model

100 % of the mass released).

There is little to no export from the model grid with dispersion of material almost completely within

the deposition footprint.

SMH is characterized by a flat, relatively shallow bathymetry with no unusual features and a

comparatively simple hydrography. This implies that the short term and MLA bath treatment

models adequately simulate the behaviour of bath treatment chemicals released at this site.

The maximum consent mass for Slice at SMH has been calculated as 2182. 4 g, this is enough to treat

a biomass of 6235. 4 t. The MTQ is 436.5 g which is sufficient to treat 1247. 1 t.

The EMBZ mass balance for the passing run (118 days) is 1575 g, this is the mass of medicine residue

which is left in the model grid at the end of this run. In order to calculate the amount of medicine

lost from the model due to export the following equation is used:

2182.4 x 0.74) - 1575

39.98 g

Therefore around 1.8 % of the medicine released is exported from the model grid. This is consistent

with the low current speeds found at this site. The model shows that the vast majority of the Slice

residue is retained within the model grid.

Using the SEPA tool marine_ sum. v3.1 we can see that the overall affected area is likely to cover an

area of 0.4 km². This is around 6 % of the available receiving area of 6.5 km². Inspection of the bed

record indicates that any medicine exported from the grid is likely to be in the direction of Hunda

Island and into the wider receiving area of Scapa Flow.

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7. Conclusion

The recommended consent limit for this site is a maximum biomass of 1247.1 tonnes at a stocking

density of 17 kg/ m³.

The model output for this site is representative of a quiescent site with a deposition footprint

consistent with the relatively weak vector averaged residual current and bathymetry of the site.

The recommended chemical consent limits for this site are:

Azamethiphos - 3h hour recommended consent limit of 78.20 g and a 24h limit of 152.8 g. This

quantity is sufficient to treat one whole cage with a treatment depth of 1.5 m in 3hrs and two cages

in 24hrs. In order to treat the whole site six treatments of two cages over six days would be

required.

Cypermethrin – 3h recommended consent limit of 14.2 g; this is sufficient to treat a volume of 2840

m³, or 3 whole cages at a shallowing depth 1.5 m.

Deltamethrin - 3h recommended consent limit of 5.3 g, this is sufficient to treat a volume of 2650. 0

m³ or 3 whole cages at a shallowing depth of 1.5 m.

Slice – A recommended consent limit of 436.5 g (MTQ) and a TAQ of 6235.4 g. This is enough

chemical to treat the maximum biomass 5 times.

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8. References

SEPA ( 2006) In-Feed consent limits at dispersive sites – v3. Available online:

http:// www.sepa.org.uk/ water/ water_regulation/ regimes/ aquaculture/ marine_aquaculture/ modell

ing/ technical_ guidance_ notes.aspx# limits

SEPA ( 2005) Regulation and Monitoring of Marine Cage Fish Farming in Scotland Annex H, Methods

for Modelling In-feed Anti-parasitics and Benthic Effects ( issue No. 2.3, 18 May 2005). Available

online:

http:// www.sepa.org.uk/ water/ water_regulation/ regimes/ aquaculture/ marine_aquaculture/ modell

ing.aspx

IAUserhttp://www.sepa.org.uk/water/water_regulation/regimes/aquaculture/marine_aquaculture/modelling/technical_guidance_notes.aspx#limits

IAUserhttp://www.sepa.org.uk/water/water_regulation/regimes/aquaculture/marine_aquaculture/modelling/technical_guidance_notes.aspx#limits

IAUserhttp://www.sepa.org.uk/water/water_regulation/regimes/aquaculture/marine_aquaculture/modelling.aspx

IAUserhttp://www.sepa.org.uk/water/water_regulation/regimes/aquaculture/marine_aquaculture/modelling.aspx

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Appendix 1 – Current Meter Data Summaries

Sub- Surface

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Cage Bottom

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Near Bed

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Appendix 2 - Marine Sum Spreadsheet

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