Wednesday, September 8, 2010 Rare freshwater jellyfish sighted in area lake
By DAVID BROOKS
Staff Writer
MERRIMACK – Peer over the edge of a boat in the middle of a small Merrimack lake and what do you expect to see? Fish, weeds, water beetles, maybe a duck – but jellyfish?
“It was like seeing Bigfoot or something,” said Mike Malzone, recalling the moment in the middle of Naticook Lake recently when he realized that he was floating over hundreds, maybe thousands, of tiny jellyfish.
“I’ve been fishing my whole life, and I go there at least six or seven times a year, but I’ve never seen anything like it,” he said.
For good reason. Freshwater jellyfish, officially called “Craspedacusta sowerbii,” are known to exist in a dozen or so New Hampshire water bodies in recent decades, but they are rarely seen.
Sightings are so unusual, in fact, that the state Department of Environmental Services once had a website for people to report them. The site is now defunct, mostly for money and staffing reasons, but also because the jellyfish are so rarely spotted in New Hampshire.
“If you’re not really looking for them – and unless they’re in a swarm – you won’t see them,” said Jody Connor, director of the state Limnology Center, which handles freshwater research. “If there’s one or two, you can’t see them because they’re pretty much transparent.”
To answer the obvious question: Yes, they do sting. However, they’re so small – no bigger than a quarter – that people can’t feel the stings, which are used to paralyze tiny fish or invertebrates.
Freshwater jellyfish are non-indigenous, the official term for species that have been introduced from afar but which haven’t become a pest, or invasive, species.
According to a Web report from the U.S. Geological Survey, the freshwater jellyfish originated in the Yangtze River in China, and were first seen in the U.S. in 1908. They are now found in most of the world’s temperate water bodies.
Officials think they usually hitchhike along with ornamental aquatic plants such as water hyacinth, or in the water of introduced fish such as tilapia. They seem to cause no real ecological problems – they don’t disrupt the food chain or crowd out native organisms, for example.
The jellyfish have been in New Hampshire for at least 30 years, Connor said.
Naticook Lake is one of the places where they have been reported most often. Baboosic Lake is the only other water body in the Nashua region listed on a 2004 state FAQ about the jellyfish.
The jellyfish spend much of the year in the “hydra” stage, as tiny (quarter-inch or less) polyps that live at the bottom of lakes. They become what we think of as jellyfish, technically the “medusa” stage, in mid- to late summer, when they move up into the water column, a change that may be triggered by warmer water temperatures.
“They stick around for a few days, then disappear,” Connor said.
Repeat appearances are erratic, so any jellyfish-spotting expeditions to Naticook Lake in 2011 might come up empty-handed.
That makes Malzone even happier with his unexpected findings.
“It was,” he says, “awesome.”
David Brooks can be reached at 594-5831 or dbrooks@nashuatelegraph.com.
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