Mortalities show the need for new sites, says salmon farmer

Scottish Sea Farms (SSF) has pointed out the importance of being able to site pens in high energy sites after it reported fish mortality incidents in Shetland in October.

Environmental and gill related challenges led to the deaths of 23.6% of fish at its East of Papa Little site, and 10.5% at nearby Cole Deep.

SSF’s Holms Geo site had gill related mortality of 19.6% in October, although cumulative mortality for the full production cycle of 3.2% suggests there were few fish left in the site by then. Holms Geo had monthly mortality monthly levels below 1% until August, when it rose to 1.4%, then 6.4% (gill health related) in September.

Cooke Scotland, which also farms in Shetland, reported October mortality of 10.9% at its Bay of Cleat (North) site due to gill health issues.

Mortalities buck the trend

In the west of Scotland, salmon farmer Mowi reported that four sites had mortalities above 10% (11.3%, 11.7%, 10.6%, and 10.5%) due to bacterial or viral disease in October. Bakkafrost Scotland had mortality of 17.6% at its Vuia Mor farm due to gill health challenges. Bakkafrost, which doesn’t use antibiotics, also harvested out farms at Portree and Portree Outer, Skye, after an outbreak of bacterial disease.

Gill health issues also impacted Loch Duart, which reported mortalities of 13.2% and 20.3% at two sites in October, and mortality of 45.2% due to jellyfish/plankton at Gob na Hoe.

The mortalities followed a period of months during which the Scottish salmon farming sector enjoyed the highest fish survival for several years.

Record temperatures

In a statement reproduced by The Shetland Times, SSF said Shetland experienced record-breaking sea temperatures this year, leading to plankton blooms and micro-jellyfish events which affected gill health at some sites, contributing to the complex gill disorder seen at Cole Deep, East of Papa Little, and elsewhere in October.

“Where conditions deteriorated, we acted quickly. Fish were removed from East of Papa Little in November to protect welfare, with all five local jobs retained across our wider farming operations. At Cole Deep, the situation has stabilised and fish remain on site,” wrote SSF.

It said it continues to invest in understanding and managing gill health challenges, contributing £6.7 million to research and development since 2013.

Lowest levels in five years

“Despite this year’s exceptional environmental pressures, SSF Shetland is recording its lowest year-to-date mortality levels in five years, reflecting the commitment of our local teams and the wider national improvements highlighted by [trade body] Salmon Scotland,” stated SSF.

The company said October’s mortalities underlined the value of farming in higher-energy marine environments, such as its proposed Fish Holm site, which would be Scotland’s largest salmon farm.

“Proposals such as Fish Holm offer stronger tidal flows, improved water exchange and greater resilience to environmental change, in contrast to more static areas like parts of St Magnus Bay [where Cole Deep and East of Papa Little are located]. Our priority at all times is the health and welfare of our fish, our people, and the long-term sustainability of salmon farming in Shetland.”