Pegal Bay, Scapa Flow and Chemicals in the Marine Environment

Cooke Aquaculture have applied to SEPA (the Scottish Environment and Protection Agency) for permission to increase the cage size at their Pegal Bay site, Orkney.  It is proposed to increase the sizes of the cages from 70m to 90m in circumference. According to Cooke Aquaculture this will be to decrease the density of the fish stocks.

The application also seeks to use Slice and ‘sea lice bath treatments Azamethiphos, Cypermethrin and Deltamethrin.’

Pegal Bay is located in Scapa Flow  between  Hoy and the island of Rysa Little.

Pegal Bay

Google maps

As you can see it is quite an enclosed sheltered stretch of water. Scapa Flow has a very delicate and finely balanced ecosystem. The area is used not just by the aquaculture industry but by Orkney’s successful Inshore fisheries.

Fish farming has faced mounting criticism over its use of chemicals and the effects this has on wildlife including the marine environment.

The Status Quo Is Not An Option: Have Your Say On The Way Forward For Scotland’s Fish Farming Industry

Urgent Changes Needed to Address the Environmental Impact of Scotland’s Salmon Farming Industry

Here is a brief overview of the chemicals Cooke Aquaculture propose to use at Pegal Bay.


Azamethiphos is an organophosphorus pesticide, which works by interfering with the transmission of nerve impulses.

When ingested, Azamethiphos is moderately toxic to mammals and highly toxic to birds and to aquatic species (particularly larvae). Great care must be taken over the dosage level of Azamethiphos used in fish farming because even a slight overdose can harm or kill the fish. Azamethiphos degrades in seawater within a matter of days – and its degradation products are removed within several months. Due to its high solubility, it is very unlikely to accumulate in sediments. Azamethiphos does not accumulate in exposed animals or aquatic organisms, as it is broken down and excreted.  (SEPA)


Cypermethrin is a mixture of several similar chemicals. Cypermethrin is highly toxic to aquatic organisms. It not particularly toxic to birds and other wildlife, except insects which are not usually exposed as they are repelled by it anyway. (SEPA)


Deltamethrin is potentially highly toxic to aquatic organisms. Discharges from the use of Deltamethrin at fish farms are limited by conditions in licenses issued by SEPA to protect non-target animals. It is not particularly toxic to birds and other wildlife, except insects which are not usually exposed as they are repelled by it anyway. (SEPA)

Slice – Emamectin benzoate

Emamectin benzoate is a pesticide which works by interfering with nerve impulses in the body. It is toxic to birds, mammals, fish and other aquatic organisms (particularly those living on the sea bed).

Scapa Flow is a Proposed Marine Protected Area. There is a reason for that. It is a unique marine environment. It appears from this application to SEPA from Cooke Aquaculture that the research recently conducted in Shetland and the reports from 2 Scottish Parliament Committees have had very little effect on their practice in the use of chemicals in fish farming.

The Orkney News has several articles in our archives on Fish Farming which you can find using our search facility. 

See also: 

“The biggest negative effect” was “on the crustacean abundance and richness.” SEPA Fish Farm Report

‘Welfare Dilemna’ Over Licensed Shooting of Seals in Scotland

Reporter: Fiona Grahame

hoy rackwick martin laird

Hoy Rackwick Photo Martin Laird

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