Former Norwegian marine researcher claims mackerel stock far larger than official estimates

A former senior researcher at Norway’s Institute of Marine Research (HI) has dismissed warnings of overfishing, arguing that the Northeast Atlantic mackerel stock is severely underestimated—potentially by millions of tonnes—while accusing authorities of ignoring competition pressures caused by the fish’s dominance.

Jens Christian Holst, now a paid advisor to the Pelagic Association, told Dagbladet that the International Council for the Exploration of the Sea (ICES) and HI’s estimate of a 2.9 million-tonne spawning stock is “still far too low.” He claims the actual figure is “at least eight to ten million tonnes,” suggesting current quotas may constitute underfishing rather than overfishing. “I’d jokingly argue my CV on mackerel assessment outweighs HI and ICES combined,” he said.

Holst, who previously led herring stock assessments at HI before leaving amid disputes over methodology, asserts that management has relied on figures “two to four times too low” for over a decade. He points to ICES’ autumn 2025 report as partial validation of his earlier estimates (2010–2014), which he claims were closer to reality.

The researcher frames the mackerel’s sheer abundance as an ecological problem, arguing that its “gigantic biomass” has outcompeted other species—including red-listed seabirds like the puffin and razorbill—for food, while also threatening wild salmon stocks. “The mackerel has been too dominant because quotas were too small,” he said.

Authorities reject claims, warn of collapse risk HI and ICES maintain that the stock has been critically depleted since 2010 due to persistent overfishing, with reproduction now impaired. “The spawning stock is below the critical threshold,” said HI’s Geir Huse, warning that ignoring scientific advice risks “a very dangerous” collapse to historically low levels, citing the 1960s herring crash as precedent.

Daniel Howell, Norway’s ICES delegate, acknowledged estimation challenges but stressed that “all indicators” show the stock below safe limits. “Claiming uncertainty justifies higher catches is something I fundamentally oppose,” he said.

Holst counters that fishermen report “days when the sea is thick with mackerel,” followed by sudden absences—a pattern he says underscores the stock’s volatility and the difficulty of accurate assessment. He dismissed accusations that industry demands drive his stance: “Fishermen hold unique knowledge of the ocean.”

Norges Fiskarlag (Norwegian Fishermen’s Association) acknowledges the stock is smaller than in previous decades but questions the severity of the decline.