August 18, 2016 — When a tropical fish called a crevalle jack turned up this summer in the Narragansett Bay trawl survey, which the University of Rhode Island conducts weekly, it was the first time the species was detected in the more than 50 years that the survey has taken place.
The Rhode Island Department of Environmental Management’s seine survey of fish in Rhode Island waters also captured a crevalle jack this year for the first time.
While it’s unusual that both institutions would capture a fish they had never recorded in the bay before, it’s not unusual that fish from the tropics are finding their way to the Ocean State. In fact, fish from Florida, the Bahamas and the Caribbean have been known to turn up in local waters in late summer every year for decades. But lately they’ve been showing up earlier in the season and in larger numbers, which is raising questions among those who pay attention to such things.
“There’s been a lot of speculation about how they get here,” said Jeremy Collie, the URI oceanography professor who manages the weekly trawl survey. “Most of them aren’t particularly good swimmers, so they probably didn’t swim here. They don’t say, ‘It’s August, so let’s go on vacation to New England.’ They’re not capable of long migrations.”
Instead, fish eggs and larvae and occasionally adult fish are believed to arrive in late summer on eddies of warm water that break from the Gulf Stream. Collie said they “probably hitch a ride” on sargassum weed or other bits of seaweed that the currents carry toward Narragansett Bay.
Most of these tropical species, including spotfin butterflyfish, damselfish, short bigeye, burrfish and several varieties of grouper, don’t survive long in the region. When the water begins to get cold in November, almost all perish.