Rising sea temperatures hit fish health

Mowi Scotland said several of its farms had been affected by warmer waters, which resulted in higher mortalities in the third quarter of this year.

The company, which reported record Q3 harvest volumes earlier today, had to contend with harmful algal blooms related to the above average sea temperatures.

Mowi CEO Alf-Helge Aarskog said at today’s Q3 announcement in Oslo that rising sea temperatures could present serious biological challenges ahead for Scotland.

‘Incident based mortality losses were high in the third quarter, and amounted to €8.8 million related to an algal bloom and fish health issues (€1.2 million in the third quarter of 2018).’

In a statement, issued this afternoon, Mowi Scotland said the conditions, beginning late winter to a peak in July, provided challenges to salmon and lumpfish survival at some of its sites.

A recent inspection of Mowi’s Bagh Dail nan Ceann farm by the Animal and Plant Health Agency (APHA) raised concerns that lumpfish health and welfare was not adequately managed, during a month that saw the highest average sea temperatures, the statement said.

In a letter sent on September 16, the APHA told Mowi: ‘You have not been able to show that adequate actions were taken in the period between 10/7/19 to the 12/08/19 in order to promote the welfare of the lumpfish under your responsibility.

‘Not taking effective decision at earlier date has prolonged the period while the lumpfish still at the site have been in need to be protected from suffering and disease.’

Mowi said its staff have since met with APHA inspectors to discuss the agency’s concerns and to ensure fish welfare remains top priority for the company and its employees.

The company said warm sea temperatures – the second highest annual average recorded in the last decade – have aided in providing ‘ideal growing conditions for harmful algal blooms and has exacerbated health challenges common to salmon’.

‘Unfortunately, some farm locations have suffered higher than normal mortality rates over the past few weeks,’ said Gideon Pringle, Mowi Scotland’s production director.

‘Our farmers are devastated to have lost fish after spending months raising them at their farms, and are doing what they can to protect their fish from this prolonged change to their environment.’

To help alleviate fish stress from high water temperatures and associated reduced saturated oxygen, Mowi farmers have provided their fish additional air bubbling where feasible, and are harvesting affected crops earlier than scheduled to reduce biomass or fallow, the company said.

‘Despite this challenge, the company still plans to harvest guided volumes and remains committed to its open seas site development programme at locations best suited for our fish and the local environment,’ Pringle added.

Mowi Scotland’s weekly salmon survival at its farms can be found at https://mowiscotland.co.uk/category/lice-mortality-reports/.