Fish are going north for the cool, study shows

Many fish stocks are fleeing warming waters, moving northward and off-shore, some of them now all but extinct in US waters, a new American study shows.

The survey, performed by researchers at the National Oceanic and Atmospheric Administration’s (NOAA) science centre in Woods Hole, Massachusetts, studied 36 stocks in the Northwest Atlantic Ocean, many of them commercially important, ranging from Atlantic cod and haddock to winter flounders and Atlantic herring. The science centre at Woods Hole conducts annual spring and fall trawl surveys and has the world’s longest time series of standardised fishery population data.

The stock assessments were compared to historic ocean temperature records.

About half of the 36 stocks in the study were found to be shifting northward over the last four decades.

“Many familiar species have been shifting to the north where ocean waters are cooler, or staying in the same general area but moving into deeper waters than where they traditionally have been found,” said Janet Nye, lead author of the survey. “They all seem to be adapting to changing temperatures and finding places where their chances of survival as a population are greater.”

The researchers took into account fishing pressures on the species over time, as well as natural cycles in ocean temperature. Ocean temperatures have increased since the 1960s and 1970s, and the authors found significant changes in species distribution consistent with warming in 24 of the 36 stocks studied.

It appeared that heavily fished stocks were more sensitive to climate change than others, and often showed bigger shifts.

The shifts were mainly in area or in depth; the temperature at which each stock was found did not change over time, which indicates that fish move to stay in their preferred temperature range when the water gets warmer.

For consumers and fishermen this will mean that fishermen will have to go further off-shore to get the fish consumers are used to, and/or that consumers will see some less familiar species in the markets in the future.