Stock assessments carried out in 2005 have shown that sandeels in the North Sea are at half the minimum level needed to sustain a fishery. This has prompted the European Commission to propose a total closure of the fishery.
The breeding failures of seabirds seen along the North Sea coast of Scotland in 2004 were thought largely to have been caused by a shortage of sandeels, on which many species feed, and it is feared that the pathetically low levels recorded in 2005 bode ill for the current breeding season.
Research carried out by staff from the Centre for Ecology and Hydrology on the Isle of May has shown that sandeel numbers are adversely affected by rising sea temperatures as well as the industrial fishery. In combination, they are likely to lead to a very steep decline in sandeels and the species of seabirds that depend on them. Sea surface temperatures in the Southern North Sea have risen by 2C over the last 25 years and even the temperature at the sea bed, normally more stable, has risen by 1.5C since the 1970s.
Yearling sandeels are in particularly short supply after a warm winter and this period is critical in determining the success of seabirds as they are preparing to breed. Sandeel numbers, in turn, are believed to be linked to the abundance of the microscopic plankton on which they themselves feed.
Seabirds, such as terns and kittiwakes which feed mainly on sandeels, are particularly badly affected, though even guilemots and puffins, which can access other fish prey through deeper diving, are beginning to show signs of breeding failure.