Late last year, a flotilla of fluorescent jellyfish covering 16
sq km of ocean was borne by the tide into a small bay on the Irish
Sea. These mauve stingers, venomous glow-in-the-dark plankton
native to the Mediterranean, slipped through the mesh of
aquaculture nets, stinging the 120,000 fish in Northern Ireland's
only salmon farm to death.
Closer to home, the Asian carp, which has been working its way
north from the Mississippi Delta since the 1990s, is now on the
verge of reaching the Great Lakes.
This voracious invader, which weighs up to 45 kg and eats half
its body weight in food in a day, has gained notoriety for vaulting
over boats and breaking the arms and noses of recreational
anglers.
Having out-competed all native species, it now represents 95
percent of the biomass of fish in the Illinois River and has been
sighted within 40 km of Lake Michigan. The only thing preventing
this cold-water-loving species from infesting the Great Lakes, the
largest body of fresh water in the world, is an electric barrier on
the Chicago Sanitary and Ship Canal.
One of the great unsung epics of the modern era is the worldwide
diaspora of marine invasive species. Rising water temperatures
brought on by global warming have allowed mauve stingers and
harmful algae to thrive far beyond their native habitats.
Supertankers and cargo ships suck up millions of gallons of ballast
water in distant estuaries and ferry jellyfish, cholera bacteria,
seaweed, diatoms, clams, water fleas, shrimp and even good-sized
fish halfway around the globe.
The first recorded case of species invasion dates to 1245, when
Norse voyagers brought a soft-shelled clam to the shores of the
North Sea on the sides of their wooden ships. What is new is the
rate of introduction and the extent of impact - 80 percent of world
trade is conducted by ship, and a new marine invader is now
recorded in the Mediterranean every four weeks.
Zebra mussels have to be power-hosed from the intake pipes of
Great Lakes electric companies, and sea squirts form dense colonies
that smother the scallops and clams of Georges Bank. According to
one estimate, invasive species in the United States cause major
environmental damage and losses totaling about $137 billion per
year.
There is an easy solution, however: If cargo ships were required
to empty and refill their ballast tanks at sea, rather than in
harbors and estuaries, marine invasions could be brought to a near
standstill. Unfortunately changing ballast water at sea takes time
- and time in the shipping industry is money. So far, ship owners
the world over have blocked laws seeking to limit shipping's role
in spreading bio-invaders.
In the absence of any concrete action by the shipping industry,
I would like to make a modest proposal. To save our oceans and
lakes from their apparently inexorable slide back to the Archaean
Eon - when all that was moving on the face of the waters was
primitive cyanobacteria - it is high time we developed a taste for
invasive species.
Diners in Asia, where sesame-oil-drenched jellyfish salad has
long been considered a delicious, wholesome dish, are way ahead of
us.
The increased the amount of phosphorus and nitrogen in the
waters off China reportedly created an ideal breeding ground for
Nomura's jellyfish, a monstrous 200 kg creature that can tear apart
fishing nets.
In the summer of 2005, a half-billion were estimated to be
floating from the shores of China to the Sea of Japan every day,
forming a ring of slime around the entire nation.
The citizens of Fukui, a northern Japanese island, coped by
marketing souvenir cookies flavored with powdered jellyfish.
Returning from a fact-finding mission to China, a professor from
Japan's National Fisheries University offered up 10 different
recipes for preparing Nomura's jellyfish. "Making them a popular
food," he told a Japanese newspaper, "is the best way to solve the
problem".
Precisely. And if we want to forestall our looming carp
quagmire, this is the kind of attitude we need to adopt on our
shores. Sports fishermen are already doing their part by angling
for the pests.
Restaurateurs from Tupelo to Toronto could pitch in by replacing
the bland-fleshed channel catfish on their menus with equally
bland-fleshed Asian carp. It seems only fair: it was catfish
farmers in the South who imported the fish to filter algae from
their ponds in the 1970s and allowed them to escape into the wild
during the Mississippi floods of 1993.
For years now, fisheries scientists have been telling us that,
for our own health and the health of the oceans, we need to start
eating down the food chain - closer to the level of oysters than
tuna. So, next time you are in the mood for seafood, ask the chef
to whip you up a jambalaya of rapa whelks and Asian mitten
crabs.
The New York Times
(China Daily February 21, 2008)
