The amount of Norwegian spring-spawning herring in the Kvænangen area of northern Norway has dropped by two-thirds this winter. A recent survey estimates that 780,000 tonnes of herring are in the region. Last year, the figure was around two million tonnes.
The result is derived from the annual winter monitoring cruise conducted by the Norwegian Institute of Marine Research. The findings show that far fewer fish overwintered in the fjord system this season.
Survey shows large shift in behaviour
Measurements were taken in December by the research vessel Johan Hjort and the remote vehicle Frida. Scientists used echo sounders and trawl samples to estimate the stock.
Survey leader Erling Kåre Stenevik stated that the decline in numbers does not indicate that the herring stock is in decline. “The measurements only show how much herring overwintered in the survey area,” he explained.
Most of the fish found were from two age groups. Nine-year-old herring made up just over one-third of the total. Four-year-olds accounted for just under one-third.
Fish likely stayed at sea
Researchers believe much of the stock spent the winter elsewhere, probably in open waters. An international herring fishery has taken place in the eastern and central parts of the Norwegian Sea during late autumn and winter.
Before Kvænangen became the main wintering site in 2017–2018, large amounts of herring stayed near Kvaløya, earlier in the Norwegian Sea, and before that in Vestfjorden.
Unpredictable migration patterns
Scientists report that winter behaviour can vary from year to year. Large new year classes may lead the stock to new areas. Only about one-third as many herring came to Kvænangen compared with last winter.
Stenevik summed up the challenge: “The result is that herring are unpredictable. That is how it is when billions of individuals decide where to go.”