Cages for salmon farming. (Photo: Marine Harvest)
Strong increase in hydrogen peroxide use on Scottish salmon farms
Monday, February 13, 2017, 22:10 (GMT + 9)
Major salmon farmer Marine Harvest has expressed concern about the use of chemicals to combat fish diseases, after data from the Scottish Environment Protection Agency (SEPA) show that about 20 million liters of hydrogen were dumped in Scottish waters, The Sunday Times reported.
This chemical compound is frequently used to treat topical skin and gill infections.
According to SEPA, more than 160 farms resorted to the chemical in 2015 to tackle parasites such as sea lice.
Hydrogen peroxide is regarded as environmentally safe as it quickly breaks down into its constituent parts of hydrogen and oxygen. The chemical does not kill parasites, but stuns them. As farmed fish knock against each other in crowded pens, the parasites fall off.
However, there is evidence that the chemical harms fish. Academics from Bergen University in Norway recently presented a report showing that hydrogen peroxide weakens the immune system of fish by damaging gill tissue and protective mucosal layers.
After the treatment, fish need at least two weeks to recover during which time they are susceptible to aquatic pathogens.
In 2001, Compassion In World Farming (CIWF) warned that hydrogen peroxide posed “serious animal welfare drawbacks”.
The SEPA data, obtained by the Global Alliance Against Industrial Aquaculture, shows that since 2010, the chemical has been used in increasing quantities, sometimes with devastating effects.
Last year, 60,000 salmon reportedly perished on Marine Harvest’s fish farm in Soay Sound, off the Isle of Harris, after the chemical was used to treat the parasites that cause amoebic gill disease, according to The Sunday Times.
In 2015, the latest year for which figures are available, 19.6m litres of hydrogen peroxide were used by Scottish fish farms. Marine Harvest depended most heavily on the chemical (8.4m litres) followed by the Scottish Salmon Company (4m litres) and Grieg Seafood (3.1m litres).
The biggest quantity used at a single site was just over 1m litres at Marine Harvest’s Camas an Leim farm at Loch Torridon, on the west coast of Scotland.
A company's spokesman said the company used less hydrogen peroxide in 2016 (6.3m litres) despite farming more fish than in previous years and added that it is exploring new ways to protect farmed fish from deadly infections such as amoebic gill disease.
For his part, Grant Cumming, managing director at Grieg Seafood Shetland Ltd, said its increased use of hydrogen peroxide had been “driven by our desire to treat our salmon for sea lice at lower levels, which has meant more treatments, and our wish to minimize the use of medicines, which may persist for some time in the environment.”