Scottish cod stocks hit by food shortage

Published on Friday 17 December 2010 22:43

DWINDLING cod stocks in the seas surrounding Scotland have been partially caused by a rise in summer ocean temperatures which has left the fish with a deplenished food source, according to new research.

An increase in the temperature of the waters in the North Atlantic has reduced the abundance of plankton, which underpins the marine food chain.

Despite widespread concern that the decline in cod is down to decades of overfishing, the study suggests the dramatic downturn can in part be attributed to centuries of climate change.

Scientists at the University of Glasgow have warned that if the trend continues, it could have a considerable impact not just on cod, but the entire marine food chain.

The team, led by Dr Nick Kamenos, a post-doctoral research fellow at the university's school of geographical and earth sciences, found that summer temperatures in the waters of the North Atlantic have been increasing since 1353.

By analysing deposits of fossilised algae on Scotland's west coast they found that over the centuries summer temperatures have risen by around 2.7 degrees celsius since compared to an increase of just 1.4 degrees in wintertime.

The rise has meant that zooplankton known as Calanus finmarchicus - a key food source for several fish, including cod - has reduced both in terms of quality and quantity. Levels of plankton are forecast to be "significantly lower" than present by 2040.

Dr Kamenos explained: "Since the Little Ice Age, from around 1400 to 1700, summer marine temperatures in the North-east Atlantic inshore shallow waters have increased nearly twice as much as those in winter, but winters experienced greater temperature extremes.