SAMS news room

Global warming threat to Scottish fish stocks

Herring could be on the move from Scottish waters
Herring could be on the move from Scottish waters

Cod, herring and haddock may vanish from Scotland’s west coast waters by the turn of the century because of global warming.

Researchers at the Scottish Association for Marine Science (SAMS), near Oban, have predicted that by 2100 commercially important species could migrate out from this ecosystem, most likely to colder waters further north, in response to rising sea temperatures.

The findings, published in the journal Scientific Reports, show that cod and herring off Scotland’s west coast are already nearing the edge of their temperature tolerance range.

Over the forthcoming decades these species will gradually be replaced by more abundant communities of saithe, hake and whiting. From 1985 to 2013, the population of saithe and hake off the Scottish west coast increased four-fold.

The paper’s lead author Dr Natalia Serpetti, a marine ecologist at SAMS, said: “These results highlight the importance of considering environmental change, as well as fishing quotas, to achieve sustainable fisheries management at an ecosystem level.

“We initially tested the impact of current advised fishing quotas, along with predator/prey interactions, within the ecosystem. Cod, whiting and herring stocks, that historically showed declining trends due to high fisheries exploitation and predation, recovered under a sustainable fishery management.

“However, we subsequently tested the impact of rising temperature under Intergovernmental Panel on Climate Change (IPCC) climate change scenarios, while keeping fishing rates consistent with current advised maximum sustainable yields, and found that there would be a collapse of cold water species stocks.

“Our results showed that warmer climate could jeopardise sustainable fishery management: rising temperature showed strong negative impact on cold water species such as grey seals, cod, haddock and herring, which all declined by 2100 under the worst case climate warming scenario.

“Even under the best case climate change scenario, cod and herring stocks were predicted to collapse off Scotland’s west coast.”

Dr Serpetti’s research updated an existing marine model of the west coast of Scotland ecosystem, situated in the north-east Atlantic from the coastline to the edge of the continental shelf.

Her model looked at how rising temperatures would affect 41 groups of species, from top predators such as whales and seals to many fish species and animals such as crabs and snails living on the sea floor.

The research is part of the Marine Ecosystem Research Programme (MERP), funded by the Natural Environment Research Council (NERC) and the Department for Environment, Food and Rural Affairs (DEFRA).