Cod and haddock stocks on the Faroe Shelf and the Faroe Bank are likely shaped by changing ocean currents, according to new scientific findings.
The study shows that the supply of young fish depends not only on fishing pressure and local conditions, but also on the amount of cold, nutrient-rich subarctic water that flows into the region.
Recruitment depends on food at the right time
The growth of cod and haddock stocks begins with the arrival of young fish. Good recruitment happens when there is plenty of plankton and other food in the shallow shelf waters.
Historically, strong recruitment was seen in 1983, 1994 and 2000, with more modest peaks in 1987, 2009 and 2017.
However, good feeding conditions do not always lead to bigger stocks. Scientists have long asked why some strong year-classes never grew into larger spawning populations.
Currents are the missing piece
The new research points to shifts in the inflow of cold subarctic water. Warm Atlantic water dominates around the Faroe Shelf, but it contains fewer nutrients.
When more cold water from the Subpolar Gyre and the East Icelandic Current mixes in, the nutrient level rises, plankton increases, and young fish thrive.
Between 2002 and 2014, there was little subarctic water around the Faroes. During those years, conditions for both seabirds and fish were poor.
After 2014, the inflow of cold water increased again. As a result, cod numbers rose sharply on the Faroe Bank, and haddock stocks improved both on the Bank and on the Shelf.