48,834 fish escaped after Storm Ellen hit Mowi farm

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Four out of ten pens were structurally compromised.

Mowi Scotland’s salmon farm at Carradale North, consisting of ten circular net pens containing 550,700 salmon (~4.2kgs), shifted its position after becoming detached from its seabed anchors during Storm Ellen and strong tides in Kilbrannan Sound on August 20th.

The company’s immediate priority was to secure the fish pens in place until Storm Ellen subsided, and to safeguard staff, contractors and fish stock – this was achieved by August 22nd.

By August 25th, the farm was secured back in its proper location and all ten pens either visually inspected for integrity and/or inventoried. The recovery operation was completed by teams of trained staff and service contractors without injury or incident.

One of the broken ropes from Carradale North mooring system

Following thorough inspection by dive teams, the root cause of the incident appears to be breakage of mooring ropes that attach to the main system seabed anchors. The farm was installed five years ago according to the Marine Scotland A Technical Standard for Scottish Finfish Aquaculture, and the infrastructure inspected three months ago. The rope type is marine grade, 4.8cm in diameter with a break strength of 89.5 ton – roughly twice the maximum strength required for its application (ranging from 33t to 51t). The rope has been sent to third-party testing facilities in Aberdeen, with further investigation to follow, according to a press release from Mowi.

Of the ten pens, six were found to be structurally sound with fish in good condition and are now secured back in their original position. The remaining four pens were structurally compromised (two of which experienced torn netting), and the salmon contained within the four pens have now either been harvested (125,900), removed as mortality (30,616), or escaped (48,834).

There have been local reports of the salmon being predated upon by seals and other wildlife, and being caught by anglers. The salmon raised at the Carradale North farm are healthy, with some having already been processed for market.

The company continues to engage with local and national wild fisheries groups to monitor and assess the presence or absence of salmonid genetic introgression.

Photo: Mowi