April 2015 Warming seas pose habitat risk for fishy favourites

Popular North Sea fish such as haddock, plaice and lemon sole could become less common on our menus because they will be constrained to preferred habitat as seas warm, according to a study published this afternoon in Nature Climate Change and authored by a team including Professor Mark Johnson of the Ryan Institute at NUI Galway.

The team took survey data dating back as far as 1980 and used the change is distribution between decades to derive predictive models. In the last 40 years the North Sea has warmed four times faster than the global average and further warming is predicted over the coming century. The North Sea is associated with fish landings valued at over $1 billion, leading to great interest in how changing environmental conditions will impact on commercial species.

Fish distributions are limited by a number of factors, including water temperature, and some species can only thrive in certain habitats and depths. The research developed models that combining long-term fisheries datasets and climate model projections to predict the abundance and distribution of the consumers’ favourite fishes over the next 50 years. As the North Sea warms, species appear to choose habitat of a suitable depth over the benefits of moving to cooler waters. Due to higher temperatures in the future, many of the species studied are may reduce in relative abundance.

“The modelling technique we used allowed us to look at important variables as we try to predict what will happen should the North Sea continue to warm. It turns out that the right depth is more important than temperature, so that the fish are more likely to stay where they are than move. This will mean that populations will be living at higher temperatures, with the effect of this depending on how well species can cope with the warmer temperatures”, explained Professor Johnson.

The modeling technique used in this analysis performed remarkably well when tested on available long-term datasets. This provides real confidence in the model’s ability to predict future patterns of fish distributions around the UK and similar processes may be at work around the coasts of Ireland.

Louise Rutterford, postgraduate researcher at the University of Exeter, said: “Our study suggests that we will see proportionally less of some of the species we eat most of as they struggle to cope with warming conditions in the North Sea. We provide new insight into how important local depths and associated habitats are to these commercial species. It’s something that is not always captured in existing models that predict future fish distributions.”

Dr Steve Simpson, Senior Lecturer in Marine Biology & Global Change at the University of Exeter, said the findings are important for both consumers and the fishing industry: "We will see a real changing of the guard in the next few decades. Our models predict cold water species will be squeezed out, with warmer water fish likely to take their place. For sustainable fisheries, we need to move on from haddock and chips and look to Southern Europe for our gastronomic inspiration.”

‘Future fish distributions constrained by depth in warming seas’ is published in the journal Nature Climate Change.

ENDS