Unusual fish threat afloat in the Atlantic.
Heavily stocked with cod, haddock, and other cold-water fish, Georges Bank in the Northwest Atlantic Ocean was for centuries a magnet for fishermen. Now closed because of overfishing Overfishing occurs when fishing activities reduce fish stocks below an acceptable level. This can occur in any body of water from a pond to the oceans. More precise biological and bioeconomic terms define 'acceptable level'. , the steep underwater mountain pulls in researchers studying this important ecosystem's recovery and its vulnerability to climate change.
In 1994, an unusual phenomenon resurfaced from that work. Clear, gelatinous gelatinous /ge·lat·i·nous/ (je-lat´i-nus) like jelly or softened gelatin.
1. Of, relating to, or containing gelatin.
2. Resembling gelatin; viscous. creatures that normally live as tiny, tentacled ten·ta·cled
Provided with or having tentacles.
Adj. 1. tentacled - having tentacles stalks on the ocean floor were filling up the nets used to sample the waters. "We noticed nets were coming up slimy," recalls Barbara K. Sullivan of the University of Rhode Island History
The University was first chartered as the state's agricultural school in 1888. The site of the school was originally the Oliver Watson Farm, and the original farmhouse still lies on the campus today. Graduate School of Oceanography in Narragansett.
An obscure report from 1915 also described large numbers of the organisms, which turned out to be hydroids A hydroid is a type of cell contained in many mosses. When it dies, it leaves a tiny channel which water can travel through. The hydroid may be the progenitor of the tracheid, the characteristic water-conducting cell of the tracheophytes. , cousins of jellyfish and anemones.
From their studies of the hydroids at Georges Bank and in the lab, reported at several forums this fall, Sullivan and her colleagues are amassing evidence that the floating creatures (Clytia gracilis) are unrecognized, yet major players in the Georges Bank food web. Hydroids may be competing with cod and haddock larvae by consuming significant amounts of minute crustaceans known as copepods, which the fish also eat.
The hydroids, with their stinging tentacles, prey directly on fish larvae, too. Sullivan reports that in large tanks, hydroids at the densities found in Georges Bank can reduce the survival of fish larvae by 50 percent.
The floating forms of hydroids may account for 90 percent of the planktonic biomass pulled up in sampling nets, says Laurence P. Madin of the Woods Hole (Mass.) Oceanographic Institution, one of Sullivan's collaborators. "Normally these things wouldn't be found floating in the water at all," he adds.
"Biologically, it's interesting because it's something you don't suspect is going on," says Peter Auster, a fish ecologist at the University of Connecticut The University of Connecticut is the State of Connecticut's land-grant university. It was founded in 1881 and serves more than 27,000 students on its six campuses, including more than 9,000 graduate students in multiple programs.
UConn's main campus is in Storrs, Connecticut. in Groton. Researchers point to evidence that the ocean turbulence around Georges Bank is a big factor in keeping the hydroids afloat.
They've also floated another possibility: Commercial trawling For fishing by dragging a baited line after a boat, see .
Trawling is a method of fishing that involves actively pulling a fishing net through the water behind one or more boats, called trawlers. for fish, which scours the seafloor habitat (SN: 10/26/96, p. 268), may have stirred up the hydroids. "Most of Georges Bank prior to the recent closing was trawled extensively," says Madin. "It seems like a reasonable hypothesis, although it may only be part of what's happening."