Monday, August 28, 2006

Tropical Waters

How warm has the water in our area been this year? Jean Bambara, who maintains an aquarium for Save the Bay in Rhode Island, seines about once a week to collect fish. This summer her aquarium has turned tropical:

Among her catches so far this season have been juvenile orange filefish, snowy grouper and lookdowns -- "all the pretty tropical ones that people pay a lot of money for." Often she will catch banded rudderfish, spotfin butterflyfish, grey triggerfish, bandtail puffer fish and bicolor damselfish.

Larger tropical fish such as crevalle jacks, permit and sennets -- which are a smaller version of a barracuda -- are also being caught in Rhode Island waters, said Torgan.

Bambara said she received a phone call from a local lobsterman the other day who wanted to donate to the center something he caught in one of his traps: a large trigger fish.

Dave Beutel works as a sustainable fisheries specialist at the University of Rhode Island, where he is often talking to commercial fisherman, several of whom run fish traps off the Rhode Island coast.

Among the fish caught in those traps so far this summer, he said, have been cobia, which looks like a cod with a flatter head, red drum, which rarely travel north of Virginia, a pilot fish and a sheepshead, a fish common off Florida and Georgia that looks like a giant scup and eats barnacles off pilings.

"I'm going to bet that somebody will call any day with a report of a barracuda," Beutel said. "That usually happens around now."

Tarpon were reportedly caught off Newport a few weeks ago, which was not the first time.

The Providence Journal explained how they got there (via the Narragansett Baykeeper’s blog):

All seemed to have hitched what for most will be a one-way ride on the Gulf Stream. For once the local waters, now in the 70s, start to cool, swimming home won't be an option.

The Gulf Stream is a warm and powerful current that originates in the Gulf of Mexico and swings around Florida before flowing north along the eastern United States and Newfoundland. Its strongest current is usually found over the continental shelf that sits about 90 miles off Rhode Island's coast.

Often in summer or the start of autumn, winds or storms will force a bubble or eddy of warm Gulf water to split off from the stream. As the Gulf Stream heads northeast, the eddy will spin off, continue traveling north, and get trapped between the islands of Southern New England and arm of Cape Cod.

I spent a few minutes this morning looking through Long Island Sound fishing reports and saw nothing that indicated the tropical fish have moved into the Sound, but those reports concentrate on the fluke, blues and stripers that fishermen like to catch and probably wouldn’t pay much attention to the occasional tropical species. But it would be interesting to hear if tropical fish have turned up in the nets of any researchers.


Blogger Sam said...

That's fairly remarkable, folks, triggerfish and cobia - some of the best fish to eat in the world, by the way. Usually the swordfish hitches a ride up the coast in the early summer along with the tuna. That's why all those swordfish were caught off Block Island in the old days. Nothing new there, but triggerfish and cobia? That's insane! What's next, Lion Fish?

Tom, maybe we could break out the SST maps (sea surface temperature) and see if there is a warm core off Montauk and Cape Cod, since that could be a better explanation than just "global warming," although I won't discredit that.

Perhaps we should explain. The Gulf Stream is not a continuous stream because it meanders, has branches, and sometimes some energy spins off to form cold cores which have upwelling cold water, and warm cores, where Gulf warm water breaks off and creates round pools of quite warm water.

The two tools you need are SST and relative sea altitude. Warm cores actually have higher altitudes and scientists are somewhat mystified as to why. Many offshore fishermen and sailors know to watch for these, as their currents can be quite strong and circular. The warm cores will contain tropical fish and maybe the odd manatee. Pelagic fish will feed around the edges of cold cores because cold water upwelling brings in the nutrients and baitfish up to the top.

It is rather fascinating stuff. The two kinds of cores will rotate in opposite directions, similar to high and low pressure cells in the atmosphere. Great posting, dude.

Let me know if you'd like a few links. The 3-D stuff is way cool. /Sam

8:40 PM  
Anonymous Anonymous said...

A black and white striped fish about 5 inches long was spotted near our swim ladder on our boat in Hempstead Harbor. He stayed with us even when I went into the water.

8:40 PM  

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