NYT article about (new) jellyfish damage to Gulf of Mexico fish.
October 3, 2000
Jellyfish Damage in Gulf Is Raising Concern for
Aquatic Life
By BEN RAINES
Swarms of jellyfish consumed
so many fish eggs and larvae
in the Gulf of Mexico this
summer that some scientists are
talking about the potential for serious
future threats to commercial and
recreational fisheries in the northern
Gulf.
The jellyfish, a native species and an
invading one, appeared in prime
spawning areas just as breeding
season for many of the Gulf's most
important species kicked into high
gear.
According to the National Marine
Fisheries Service, the number of
jellyfish in the Gulf has been rising
for at least 13 years, since scientists
started studying their population.
Scientists say the jellyfish are
exploiting three major
human-induced changes in the
environment: thousands of oil rigs and artificial reefs established to attract
game fish have greatly increased the breeding habitat for jellyfish, which need
a hard surface for spawning; nitrogen pollution from farm runoff and
industrial sources feeds plankton blooms, providing extra food for jellyfish;
and commercial fishermen in the Gulf take great numbers of menhaden, a
soft-finned, bony fish that competes with jellyfish for the plankton.
Dr. Monty Graham, a researcher at the Dauphin Island Sea Lab in Alabama,
worries that with all these advantages jellyfish cannot help but multiply at an
astonishing rate.
Making matters much worse, he said, is the advent of Phyllorhiza punctata,
or Australian spotted jellyfish. The giant species, previously unreported in the
Gulf, Phyllorhiza punctata is a 25-pound bruiser of a jellyfish native to the
Pacific.
Some time ago the basketball-size jellyfish established themselves in the
Caribbean. This summer, after apparently riding ocean currents north, they
concentrated themselves in the passes between the barrier islands that
separate the Mississippi Sound from the Gulf of Mexico.
The Australian jellyfish, whose numbers normally peak in the Caribbean in
August and September, have now mostly died off in the Gulf. But fishery
scientists worry that their egg and larvae consumption may already have
affected next year's fish populations. And scientists say the animals were
spawning prodigiously, broadcasting millions of their own eggs as they ate
the eggs and larvae of native species.
Popular sport fish, including redfish, speckled trout, white trout and Spanish
mackerel, as well as commercially important species like crabs and
menhaden, spawn just outside the barrier islands in August and September.
This year, their eggs and larvae had to drift with tidal currents through the
jellyfish-choked passes to reach the estuaries that serve as nurseries for the
baby fish.
"These things are incredibly efficient at turning the water over, cleaning it of
everything in it," Dr. Graham said. "We're finding them with 200 fish eggs in
their guts."
The newcomers had a frighteningly effective feeding pattern that involved
swimming to the surface, then diving down to the bottom, scouring the
water of virtually every living thing smaller than a BB pellet. After flowing
through the jellyfish gantlet, scientists said, the water was almost devoid of
living things.
"You really have two problems in terms of commercially important fish," said
Harriet M. Perry, director of the fisheries section of the Gulf Coast Research
Laboratory in Mississippi. "First the jellies are ingesting the larvae and eggs of
these commercially important species, and then the fish larvae must compete
with these incredibly efficient jellies for the same food source."
Ms. Perry said she worried that the Phyllorhiza might become permanent
residents, exploiting the same changes in the Gulf that have allowed native
jellyfish species to explode. Dr. Graham said he feared that their offspring
might appear in larger numbers next spring.
He noted, though, that the newcomers represented a small threat compared
with the monstrous herds of native moon jellyfish still swarming offshore
below Alabama, Mississippi and Louisiana in a huge swath roughly 100 miles
long and 30 miles wide.
It is these jellyfish that worry Dr. Joanne Lyczkowski-Shultz, a larval
specialist with the National Marine Fisheries Service.
Dr. Lyczkowski-Shultz said the long-term picture might be bleak, especially
if the jellyfish populations continued to grow at their current pace. "I'm just
dazed," she said. "This is pretty serious. It could be totally devastating."
Copyright 2000 The New York Times Company |
