A power outage, and deadly disease, killed tens of thousands of fish in separate incidents on two County Galway salmon farms last year, new reports show.

Among the diseases killing farmed salmon in Galway in 2022 was salmonid rickettsial septicaemia (SRS), which both the Marine Institute and Galway Bay Against Salmon Cages both agree is a cause of concern.

The entire stock of smolts held by Salmon Springs Limited at Bunatubber, Corrandulla, were wiped out during an incident on February 11 and 12 last year.

According to a mortality report submitted by the company to the Fish Health Unit of the Marine Institute, 100% of stock was killed due to a system failure. They died by asphyxia, although the total number of mortalities was not included.

The Marine Institute clarified to the Connacht Tribune that these mortalities “were associated with a power outage resulting in the loss of otherwise healthy fish on site”.

Meanwhile, disease killed 30% of stock at Bradan Beo Teoranta fish farm at Ardmore in Cill Chiaráin Bay in Conamara.

There was a stock level of 680,000 salmon there in October and November of 2021, but two disease incidents wiped out 204,000 of them, according to a veterinary inspection form.

The first disease problem of 2022 at that site hit in May and June, when Amoebic gill disease affected the livestock.

Then in August, a disease known as Piscirickettsia also impacted on the level of stock at the site. The reports did not say which of the two diseases was responsible for the greater mortalities at Ardmore last year.

The mortality and veterinary reports were obtained by the campaign group Galway Bay Against Salmon Cages (GBASC) under Access to Information on the Environment Regulations, which is similar to Freedom of Information.

GBASC said that this was the first occasion Piscirickettsia had been indentified on a salmon or trout farm in Ireland.

It said the bacterial disease, also called salmonid rickettsial septicaemia (SRS), was a “cause of high mortalities” on Irish salmon farms.

“We fear this new fish disease, on top of the ones that are already endemic on Irish salmon farms, will have further devastating effect on our wild salmon and sea trout stocks,” said Billy Smyth, chairperson of GBASC.

SRS is not a notifiable disease, and so records of mortalities and outbreaks are voluntarily recorded. GBASC said it fears that the true extent of the losses associated with SRS is higher due to under-reporting of mortalities.

The Marine Institute confirmed to the Connacht Tribune that it was addressing concerns about SRS, which is affecting salmon farms here and around the world.

It is caused by the bacteria Piscirickettsia salmonis and can lead to significant mortality rates in farmed salmon if not diagnosed and treated early.

A spokesperson said SRS was not new, was first reported in Chile in the 1980s and has since become a significant cause of mortality in salmon farms worldwide. In Ireland, SRS was first observed in 1991 and “has recently become increasingly associated with disease and mortality on Irish salmon farms”. Antibiotic treatment can be effective if the disease is diagnosed early, and it poses no risk to human health.

The Marine Institute said it has taken several steps to support the control of SRS.

This includes “a molecular method for the rapid and specific detection” of the bacteria, allowing vets to make early diagnoses; it is also developing this method to allow accurate quantification of levels of bacteria.

“The Marine Institute is proposing further work in collaboration with academic partners and industry to develop more rapid and informative diagnoses, as well as the potential development of a vaccine. The Marine Institute recognises SRS as a significant health challenge for the Irish salmon industry.

“The Institute has a long track record of working with industry to address such challenges and will continue to do so to minimise the risks and impacts of SRS on Irish salmon farms,” a spokesperson said.

It said treatment is by two specific antibiotics, authorised by the Health Products Regulatory Authority (HPRA), depending on the life stage of the fish.

“These are administered by medicated feed and are generally effective,” a Marine Institute spokesperson added.