SEPA moots ‘protection zones’ for wild salmon

SEPA's survey vessel, the Sir John Murray

The new regime for regulating fish farming in Scotland will include wild salmon protection zones in which applications for new or expanded farm sites could be turned down if the risk to wild fish from sea lice is deemed to be too great.

The proposal is laid out in a consultation document from the Scottish Environment Protection Agency (SEPA), which is set to become the lead regulator for marine fish farming in Scotland.

The document, Proposals for a risk-based, spatial framework for managing interaction between sea lice from marine finfish farm developments and wild Atlantic salmon in Scotland, includes details of where the protection zones are likely to be located and how the acceptable threshold for sea lice will be calculated.

In October, the Scottish Government announced that SEPA would be the lead body for regulating marine finfish farming, and said that proposals for a spatial framework to guide future applications for new farms or increased capacity would be published shortly.

Explaining the proposals now out, SEPA said: “Whilst the causes of the poor conservation status of wild salmon stocks are complex and believed to be due to a range of different factors rather than a single cause, sea lice from open-net pen finfish farms in Scotland can pose a significant risk to wild salmon populations.”

SEPA said it has worked closely with scientists from Marine Scotland as well as with NatureScot and local planning authorities to develop a means of assessing the risk to wild Atlantic salmon posed by marine finfish farm developments.

Terry A’Hearn, Chief Executive of SEPA, said: “Scotland is renowned worldwide for the quality of its rivers, lochs and seas. Despite this, in nearly 60% of salmon rivers across Scotland, including on the West Coast and Western Isles, salmon populations are in poor conservation status. Whilst the causes of the poor conservation status of wild salmon stocks are complex and believed to be due to a range of different factors rather than a single cause, we know that sea lice from marine finfish farms can be a significant hazard.”

He added that the protection of wild salmon was “a national priority” for Scotland.

Protection zones

Under the proposals, permits for all existing farms that can contribute to infective-stage sea lice in wild salmon protection zones would be changed to enable inclusion of conditions that (a) appropriately control the factors determining the number of juvenile sea lice emanating from the farms so that those numbers cannot significantly increase without prior authorisation; and (b) require sufficient information to be provided about the operation of the farms to enable calculation of the number of  juvenile lice hatching from lice on the farms’ fish and the resulting infective-stage sea lice concentrations in wild salmon protection zones.

This is needed, SEPA said, to assess the impact of a development proposal on infective-stage lice densities in the protection zones.

Wild salmon protection zones are defined as “narrow or constrained areas of sea (e.g. sea lochs and sounds) that wild salmon post-smolts have to pass through, and are hence concentrated, as they migrate away from the coast to the open sea.”

The proposed zones identified in the document cover each graded salmon river under the Conservation of Salmon (Scotland) Regulations 2016 and rivers designated as Special Areas of Conservation or Sites of Special Scientific Interest for the conservation of Atlantic salmon or the freshwater pearl mussel (which is dependent on salmonids for part of its life cycle).

All the proposed zones are located on the west coast of Scotland or the Hebrides. There are no zones on the east coast – where there is no marine finfish farming – or the northern isles, where there are no relevant salmon rivers.

Although they are also subject to sea lice, sea trout are not part of the proposed framework for now, SEPA said, because too little is known so far about their interactions with the parasite.

SEPA: proposed wild salmon protection zones

Risk thresholds

The threshold for risk to wild salmon is based on the likely exposure of post-smolts to sea lice (Lepeophtheirus salmonis) as the fish migrate from the coast to the open sea.

SEPA is proposing an exposure threshold of 0.7 infective-stage sea lice-days m2 integrated over the upper two metres m of the sea. This could mean, for example exposure for one day to a concentration of 0.7 infective-stage sea lice per m2, or exposure to 0.3 infective-stage sea lice per m2 on the first day of migration and to 0.4 infective-stage sea lice per m2 on the second day. The number of days exposure depends on how long it is expected that a post-smolt would take to pass through the zone to the open sea.

The thresholds are aimed at preventing the number of mobile sea lice per gram of fish from exceeding a “safe level” of 0.1 lice per gram of wild salmon.

The anticipated number of juvenile sea lice dispersing from open-net pen farms will take account of the number of fish on the farm and the average number of adult female sea lice with eggs per fish, as well as hydrodynamic factors such as sea currents.

Farms in the protection zones will need to provide SEPA with sufficient information in order to calculate the risk threshold for their zone.

The document makes it clear that: “Any proposal where expected contribution of sea lice into the environment could not be accommodated within the sea lice exposure threshold would not be granted authorisation.”

SEPA is proposing to integrate controls for protecting wild salmon fully into its wider regulatory framework for controlling other pressures on the water environment from marine finfish farms, including discharges of fish faeces and medicines.

The consultation is open for comment until 14 March 2022.

Terry A’Hearn, SEPA Chief Executive