Simply Blue Aquaculture/Loch Long Salmon have proposed a semi-closed ‘Beinn Reithe’ fish farm in upper Loch Long. It does not yet have planning permission or a SEPA pollution licence
It will probably reduce the sea louse and pesticide problem, but there was no sea louse or pesticide problem at that place in Loch Long previously, and it will add the waste from the equivalent of about 500t of fish to that area too. The fish may become diseased and spread pathogens to wild fish. They may also escape, although the site is pretty sheltered so this is less likely than in other sites.
The company discussed their Loch Long proposal with Argyll and Bute planners last year. We received some information under FOI after the usual battle with the council, eventually forcing them to release it via an appeal to the Scottish Information Commissioner.
The planner’s (non-binding) pre-application opinion was that the farm would probably be turned down on landscape grounds and for lack of a suitable site for a shore base. At that time the proposed site was spread across the boundary Argyll and Bute and the Loch Lomond National Park planning authority. The Royal Navy was not keen, as the southern-most cages were too close a fuelling pier.
In summary, the proposal is for a 4000t biomass farm which would have the benthic pollution footprint of a 500t farm. The great majority of its solid waste would be captured inside an impermeable bag and piped to a shore base for processing. Water to fill the bag would be pumped up from 30-40m deep, where there are very few sea lice. The running costs of a farm like this are about double the open net type but there are huge savings to be made by not treating for sea lice, having no fish die due to lice or frequent handling, which also, by reducing stress, means they grow more quickly and with fewer diseases. It also means a large farm like this can be sited where it would certainly not be allowed otherwise.
Deep water, near-shore sheltered sites are not very common but the company seems to have identified five suitable places in Scotland. I do not know if one of these is Ardentinny.
The waste can be compressed or heated to remove salt water, and may have a value as fertiliser or for generating gas. The water will need to be frequently topped up with oxygen. An electricity or oxygen failure would be catastrophic. The farm would have to have good back-ups for both.
The great majority of nutrient discharge (90%) is aqueous. None of this would be captured by this system, which is the main concern flagged up in SEPA’s preliminary screening risk identification modelling for this proposal.
SEPA’s reports of this type tend to be optimistic in tone, while hedging their bets:
It states:
Following screening modelling and risk identification we have concluded the following:
• It is possible that discharges from Beinn Reithe (BNRT1) will be able to comply with the relevant aspects of the SEPA Aquaculture Regulatory Framework. This is dependent on the results of the CFD modelling, and the percentage of waste capture demonstrated to be realistic. A standard 4000t (i.e. not semi – enclosed) farm would not be suitable for this area as the slow flow dynamics are not suitable for this large biomass.
• Features at risk, identified at this stage, do not appear to influence the feasibility of the proposed site with respect to the regulatory framework. These risks should be examined using a 2D marine model.
• Nutrient influence has been identified as a potential risk from this farm. Marine modelling should be undertaken to examine this risk.
• Beinn Reithe (BNRT1) is suitable to progress to the next stage of the preapplication process. For this semi enclosed novel farm, a CFD modelling method statement will be required as the first step. Once CFD modelling has been completed, this screening report will be updated to reflect any perceived changes to the risk.CFD (Computational Fluid Dynamics) modelling is to be undertaken to assess the proportion of waste expected to be captured. As this proportion is currently unknown, screening has been done to investigate the risks associated with 90%, 50% and 0% waste capture. No medicines are being applied for due to the semi – enclosed nature of the site, therefore no bath medicine screening modelling has been undertaken. Instead, we have used bath medicine modelling output to examine the potential influence on nutrients released from the farm.
Screening modelling demonstrates sediment discharges from Beinn Reithe (BNRT1) may influence the Shellfish Protected Area in the upper sections of Loch Long. Although levels of risk associated with this site are difficult to predict without CFD modelling demonstrating realistic levels of waste capture at this site, higher resolution marine modelling will likely be required to ensure risks to shellfish are low. Whilst known PMFs within this area have been considered, screening modelling does not predict any significant sediment influence to these from Beinn Reithe (BNRT1), nor does it predict interactions between farms, as material is expected to remain within a small area close to the farm.
Whilst the aim of reducing the environmental impact by developing semi-enclosed farms is appreciated, implications of the novel approach not meeting expectations should be considered. Screening modelling at 0% waste capture demonstrates very high levels of sediment would be deposited over a small area. Had this application been for a standard farm, it is very unlikely that it would be able to meet the current regulatory framework standards, as the flow conditions are clearly unable to support the biomass. Therefore, in order to ensure structural/engineering failures of do not result in a substantial risk to the environment, this proposal needs to demonstrate that the likelihood of significant failures have been assessed, and that plans for appropriate measures to mitigate the environmental risk should failure occur, have been developed. In addition to the sediment material released directly from the pens, the waste captured material will be processed at a dewatering plant (nearby barge or shore base), and then returned to the loch. It is expected this will remove approx. 95% of the solids, releasing only the smaller sediments. This outlet pipe will need to be assessed using initial dilution calculations, as consistent with point source applications, but should also be included in any marine modelling of this site. Sea lice are not considered to be an issue in this proposal as the influx water pipe is expected to be below the sea lice zone. This is based on evidence from similar systems used in Norway. Considering this is an application for a very large farm, with no sea lice medicines applied for, a short description of processes which can be put in place to deal with an unexpected sea lice infestation will be required.
This is the most interesting section:
3.4 Potential risks due to increased nutrient release
Available oceanographic measurements from Loch Long indicate that tidal currents in the area are low. The loch also experiences heat and freshwater stratification, where less dense water near the surface can influence water flow and mixing. Low tidal currents and stratification often inhibit the mixing of soluble material in a water area. The low level of mixing is illustrated in Figure 10, where a simulation of a bath medicine discharge shows material still being resident in vicinity of the farm four days after release. Whilst medicines are not proposed to be used at this site, the screening output suggests that other dissolved material released from the farm, such as nutrients, is unlikely to be mixed quickly through the surrounding water. A build-up of nutrients, under specific conditions, in a water area can influence plankton growth. This may, in turn, lead to a deterioration in water quality. As outlined on our website, guidelines, prepared by Marine Scotland, can be used to assess the likelihood of nutrient risks to the marine environment. The applicant has used the most recent guidance available [3] and [4] to conduct an assessment of potential nutrient impacts by calculating the potential change to the “nutrient enhancement index” (NEI) arising from proposed new farm. The most recent assessment available in [3] identifies that Loch Long (inc. Loch Goil) currently has a NEI enhancement of 1. The addition of the proposed farm is not predicted to alter the current status of the NEI.
The “hydrographic assumptions” which underpin the assessment of the NEI are simplified. The so called “tidal prism” method is known to “overestimate the exchange of water and therefore underpredict the flushing time” [4]. Whilst the calculated NEI for the larger Loch Long/Loch Goil system may be low, the proposed farm is located in a relatively shallow basin in upper Loch Long, behind a “sill” (a small shallow area of a sea loch). Given the simplified nature of the calculation of the flushing time used in [4] we feel that a more robust assessment of the flushing characteristics of the Loch Long system is required to address any potential influence on water quality and how this may be reduced.We recommend that a 2D marine model is used to derive a more accurate flushing time for Loch Long which can be used with the NEI calculation. Additionally, modelling should be carried out to provide a conservative estimate of the likely nutrient concentrations in the upper basin of Loch Long. Particular focus should be given to the assessment of two key sources of nutrients from the farm: 1. Nutrients entering the Loch from the exchange of water with the farm pens. 2. Nutrients entering the Loch from a marine outfall linked to the processing of solid waste collected from the farm. It will be important to identify, and model correctly, the release location and depth of any sources. Estimates of initial dilution of nutrients at the marine outfall will also be required. The assessment of nutrient concentrations in upper Loch Long should include other major sources such as those from Arrochar Sewage Treatment Works (STW), the Loin Water and Croe Water. The approach to modelling these sources will be agreed in the Modelling Method Statement for the application.
John Aitchison is a wildlife filmmaker who works for the independent production company Otter Films Ltd. He is the author of The Shark and the Albatross, published in the UK by Profile and in North America in May 2016 by Greystone Books.