For several years, scientists have projected that New England’s beloved cod and other fish would move northward or into colder, deeper waters as ocean waters warmed.
But they didn’t have detailed observations to back up their forecast. Now they do, from studying how juvenile fish that tend to hug the coastline in estuaries are faring. Coastal waters, which are very dependent on air temperatures, are warming faster than the larger ocean.
A group of National Oceanic and Atmospheric Administration and University of North Florida scientists have examined the gray snapper -– a fish associated with tropical reefs and mangroves -– to conclude it will move northward.
The work is important because as goes the gray snapper, so could go valuable summer flounder, black sea bass, weakfish, and pink shrimp that also use estuarine systems during their life.
Gray snapper is found from Florida through the Gulf of Mexico and along the coast of Brazil. While juvenile gray snapper have been reported as far north as Massachusetts, adults are rarely found north of Florida. So researchers honed in on studying estuary temperatures as a gatekeeper to gray snapper’s northward expansion.
"Many fish species are expected to shift poleward or northward as a result of climate change, but we don’t fully understand the mechanics of how temperature interacts with a species' life history, especially differences between juvenile and adult stages,” said Jon Hare, lead author of the study and director of NOAA’s Northeast Fishery Science Center Narragansett Laboratory in Rhode Island. The researchers' work was recently published in the journal PLOS One.
Hare and NOAA colleague Mark Wuenschel, a fishery biologist at the center’s Woods Hole Laboratory, worked with Matt Kimball of the University of North Florida to conduct lab experiments to understand how cold it needs to be for an extended period of time to kill off juvenile gray snapper.
The group then figured out what estuary temperatures were and projected changes in the young snappers' habitat based on global and regional warming projections.
They conclude that snapper will move north -– but how far and how fast depends on how rapidly the atmosphere warms. And that is highly dependent on how much carbon dioxide is emitted from power plants, cars and factories.
(Photo credit: Jon Hare)
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