Aquaculture for all

Impact Of Climate Change On Aqua In EU


Presenting at Aquaculture Europe 2011, Oivend Bergh from the Institute of Marine Research Norway took a look at how rising ocean temperatures and wild weather will affect European aquaculture. Charlotte Johnston, TheFishSite editor, reports.

Rising ocean temperatures

Water temperatures are extremely diverse in EU waters.

Researchers have been surveying the same areas since the 1900s and have noted that there are systematic shifts between colder and warmer periods.

At the moment, the colder period is getting shorter and warmer.

"Climate change is nothing new," said Mr Bergh. "The natural components of climate change have always occurred. However as aquaculture is a young industry - it is new to us," he said.

The average water temperature is increasing. However the observed increase in temperature has been generally higher in northern than in southern European seas, and higher in enclosed than in open sea.

Studies of the future climate show that air temperatures will rise by 2-4°C in the course of this century, and in the seas off the coast of Norway, the temperature will raise by 1.5-2.0°C.

Observations on wild stocks go back over 100 years. "The general pattern," Mr Bergh said, "is that when temperatures rise, fish move northwards.

"At present we are seeing southern species moving into the North Sea. Greater numbers of cod can be found in the Barents Sea, and more than ever before in the North Sea."

However maybe there are more important changes for aquaculture than ocean temperature, he suggested.

Increasing 'wild' weather ...

Over the last couple of years, the industry has seen extreme temperatures become more frequent and intense - and it is likely this trend will continue. These extreme temperatures increase stress in fish pens, and consequently result in disease and mortality.

The number of storms and hurricanes has also increased, leading to an increase in the number of escapees.

Adapting to these changes

Mr Bergh said that wild stocks constantly adapt to climate change, however aquaculture must be adapted.

"Ignoring climate change would be disastrous in the long term for aquaculture," he warned.

Whilst a growth in warmer waters has many advantages for producers, there are biological limits. The growth rate for Atlantic salmon is at its maximum about 14 degrees.

Extreme temperatures also cause stress which in turn weakens the immune defence, leading to an increase in disease.

Disease outbreaks in large-scale aquaculture may have important ecological and economical consequences. Several diseases common in salmon and cod aquaculture, for instance, francisellosis, vibriosis and furunculosis are typically associated with high water temperatures.

With these changes it is likely the industry will see increased parasitic infections, however cold-water diseases such as winter ulcer and coldwater vibriosis could be less frequent.


The above highlights the need for change - whether this be through movement of farms or robust technology - such as closed farms with temperature control.

Mr Bergh said that the change is unavoidable, however it is a very slow process. Things will be different in 40 years time and it seems likely that these environmental changes will lead to a general movement of farmed species northwards.

"There will be a need for more expensive and robust farms. Adaption is an extremely long term process - but it must be done if the industry is to survive."

November 2011