SHORT- AND LONG- TERM MODELLING IN SUPPORT OF SEA LICE BATH TREATMENTS AZAMETHIPHOS, CYPERMETHRIN AND DELTAMETHRIN

Transcription

1 ANDERSON MARINE SURVEYS LTD. Croabh, Tighnabruaich, Argyll. PA21 2DY Tel/Fax: co.uk Report To: The Scottish Salmon Company Ltd Report No: 14/12.2 Issued By: Checked By: Status: Rev 0 Date: 15 SHORT- AND LONG- TERM MODELLING IN SUPPORT OF SEA LICE BATH TREATMENTS AZAMETHIPHOS, CYPERMETHRIN AND DELTAMETHRIN Summary This report describes the site-specific methods and findings of modelling of appropriate consent limits for the bath sea lice treatment medicines Azamethiphos, Cypermethrin and Deltamethrin, at the site, Loch Seaforth, Harris. The location is on the west side of the loch, approximately 7km from the entrance and is relatively sheltered from wave action. The following modelling assessment is for a configuration of eight 120m circles in an 88m grid. Site details and model output are summarised below: Site Data Site name : Company : The Scottish Salmon Company Modelled By : Site NGR : Current meter NGR : page 1 of 6

2 Input Data Loch/Strait/ Open water : Loch Loch area (km2) : 8.00 Loch length (km) : 8.00 Distance to head (km) : 1.70 Distance to shore (km) : 0.20 Width of Strait (km) : ( only required for Strait) Average water depth (m) : Flushing time (days) : Mean current speed ( m/s) : Residual Parallel Component U (m/s) : Residual Normal Component V (m/s) : Tidal Amplitude Parallel Component U (m/s) : Tidal Amplitude Normal Component V (m/s) : Model Ouput Azamethiphos Cypermethrin Deltamethrin 3 hour proposed treatment value [g] : 268.1g 48.5g 18.2g 24 hour proposed treatment value [g] : 240.7g No. of cages treatable in 3 hours : No. of cages treatable in 24 hours : 1.0 The technical summary is supported by a generic methods statement (AMSL 2005, SEPA reference AMMR02v02) for consent assessments using the modelling package AutoDepomod. Model output files are provided on the enclosed CD -ROM. Introduction This report describes the site-specific methods and findings of modelling of appropriate consent limits for the bath sea lice treatment medicines Azamethiphos, Cypermethrin and Deltamethrin, at the site, Loch Seaforth, Harris. The location is on the west side of the loch, approximately 7km from the entrance and is relatively sheltered from wave action. The following modelling assessment is for a configuration of eight 120m circles in an 88m grid. The assessment follows the approach and methods specified by SEPA (2007) Regulation and Monitoring of Marine Cage Fish Farming in Scotland Annex G, Models for assessing the use of medicines in bath treatments (v.2.1, January 2007). Standards are applied by SEPA, as Environmental Quality Standards (EQS) or Maximum Allowable Concentrations (MAC). Relevant standards for bath treatment chemicals are tabulated below: page 2 of 6

3 Azamethiphos 6h Azamethiphos 72h Azamethiphos 72h Cypermethrin 6h Deltamethrin 6h 250 ng/l as an EQS 40 ng/l as an EQS 100 ng/l as a MAC 16 ng/l as an EQS 6 ng/l as an EQS Figure 1. location Input data Of the available options (loch, strait or open water), the location has been modelled as a loch. The site is close to the head of the lower basin of Loch Seaforth, Current data current velocity and direction were acquired, analysed and provided by The Fish Vet group (2005). Data were derived from a Nortek 500kHz ADCP deploument in June-July The analysis considered three depth bins (surface, mid-water and bed) at heights above seabed of 28m, 25m and 2m respectively. The averaging period was 20min. Orthogonal (lateral and longitudinal) components of sub -surface residual velocity and tidal amplitude were calculated from surface current data, using the SEPA Excel tool HGdata_analysis_v7.xls. Magnetic variation of applied at the time of survey. page 3 of 6

4 Calculated input parameters for the modelling were: Mean current speed ( m/s) : Residual Parallel Component U (m/s) : Residual Normal Component V (m/s) : Tidal Amplitude Parallel Component U (m/s) : Tidal Amplitude Normal Component V (m/s) : The complete input data used for modelling is listed below: Site Data Site name : Company : The Scottish Salmon Company Modelled By : Site NGR : Current meter NGR : Loch Data Loch/Strait/Open water : Loch Loch area (km2) : 8.00 Loch length (km) : 8.00 Distance to head (km) : 1.70 Distance to shore (km) : 0.20 Width of Strait (km) : ( only required for Strait) Average water depth (m) : Flushing time (days) : Cage Data of cages : 8 Cage shape : 1 Diameter/ Width (m) : 38.2 Working depth (m) : 15 Stocking density ( kg/m3) : 18.2 Treatment No. of cages possible to treat in 3 hours : 1.00 Initial Treatment Depth ( m) : 2.3 Treatment Depth Reduction Increment ( m) : 0.1 page 4 of 6

5 Results Azamethiphos ug/l) area (km^2) days are 3 hour proposed treatment value : 268.1g 24 hour proposed treatment value 240.7g No. of cages possible to treat in 3 hours : No. of cages possible The TS plot for azamethiphos is shown below: n ( conc' Cypermethrin 3 hour proposed treatment value : 48.5g No. of cages possible to treat in 3 hours : 3.7 Deltamethrin 3 hour proposed treatment value : 18.2g No. of cages possible to treat in 3 hours : 3.5 page 5 of 6

6 Discussion The local area of the site is topographically constrained in all directions, with exchange to the Minch via the entrance to Loch Seaforth approximately 6km to the south. To the north there are tidal rapids and therefore turbulent exchange with the upper basins of Loch Seaforth. The site is characterised as moderately deep, and moderately flushed at all depths (20-30% <0.03 m/s). The limiting 3h recommended mass for azamethiphos is 268.1g, with a treatment interval of 24hrs and a 24 hour treatment value of 240.7g. This long-term model solution is for one cage per treatment, one cage per day, with a shallowing depth of 2.1m; therefore requiring 8 treatments over 8 days to complete the site. The recommended 3h consent mass for cypermethrin is 48.5g, sufficient to treat a volume of 9705m3; corresponding to two cages per 3h with a shallowing depth of 4.2m; three cages per 3h with a shallowing depth of 2.8m; or four cages with a shallowing depth of 2.1m. For deltamethrin, the 3h consent mass is 18.2g, sufficient to treat a volume of 9099m3; corresponding to two cages per 3h with a shallowing depth of 4.0m; three cages per 3h with a shallowing depth of 2.6m; or four cages with a shallowing depth of 2.0m. References Edwards A and Sharples F (1986). Scottish Sea Lochs: a catalogue. Scottish Marine Biological Association / Nature Conservancy Council. SEPA (1997a). Risk assessment of azamethiphos. A review of ecotoxicity and current policy, Scottish Environmental Protection Agency Fish Advisory Group. 10 pp. SEPA ( 1997b). Use of cypermethrin in marine fish farming. Risk assessment, EQS and recommendations. Scottish Environmental Protection Agency Fish Farm Advisory Group. 11 pp. SEPA (2007). Regulation and Monitoring of Marine Cage Fish Farming in Scotland Annex G, Models for assessing the use of medicines in bath treatments ( v.2.1, January 2007). Available from fish_farm_manual/ annex/ G.pdf page 6 of 6