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Invaders from Inner Space: Revealing Nemo's True Colors
By Alex Brylske
Photos by Marty Snyderman
You know a kid younger than 10, then you
also know the names Nemo and Dory. And just in case you're one of the
few humans on the planet who don't know what I'm talking about, these
were the "stars" in the phenomenally successful animated film, "Finding
Nemo." Nemo was the lovable, kidnapped clownfish, and Dory the memory-impaired
surgeonfish. Even if your feelings toward children are more akin to those
of W.C. Fields ("go'way kid, ya botha' me"), I encourage you
to see this movie. It has perhaps the best animation you'll ever see,
plus there's also more than a little tongue-in-cheek humor that adults
will appreciate.
An inevitable consequence of all popular movies is a heightened, if
not frenzied, interest in the subject matter. "Finding Nemo" is
no exception. So it was probably no surprise when kids wanting their
own "Nemo" sent the demand for clownfish through the roof.
Of course, as parents and kids soon found out, keeping Nemo was a lot
more demanding task than merely finding him.
Faced with the reality of an expensive pet and a child who has lost
interest, countless numbers of parents faced the dilemma that's the crux
of our story. In most areas of North America, many unwanted Nemos ended
up taking their final swim in a toilet bowl. But flushing the family
pet can be a tough decision to explain to a kid, so for those who live
close to the ocean, the outcome could be quite different. With the options
of a final swim in the porcelain aquarium, or the possibility of a new
life back in the sea, many choose the one depicted in yet another movie, "Free
Willy."
One can sympathize with good intentions, and attempting to save a family
pet certainly qualifies. Realistically, though, most of the freed Nemos
never survive. The local waters are too cold, or the poor fish becomes
a quick snack for some predator that never saw the movie and was unaware
of his star status. But given the right environment, and a bit of luck,
the intended consequence does occur, Nemo survives. So, end of story;
everybody's happy and no harm done, right? Not quite.
The truth is that this is neither a happy ending nor even the end of
the tale. The survival of Nemo, and many of his distant cousins, in waters
where they were never intended, may have grave consequences for the environment,
for what was once a family pet is now an invader.
Alien Invasion!
When species become established by some human-facilitated introduction
to a range where they don't occur naturally, they are termed an invasive,
exotic or non-native species. While on the surface it may appear that
this is a relatively inconsequential problem, it is all but. In a recent
article published in the journal BioScience, the authors estimated that
about 50,000 non-native species have been purposefully or accidentally
introduced into the United States. In fact, the problem is so serious
that in 1999 a new international scientific journal, Biological Invasions,
was launched. Some examples of invasive species are quite well-known,
such as the Japanese vine kudzu which for decades has been creeping its
way north from the southern region of the United States. When it comes
to aquatic examples, the prodigious zebra mussel began its invasion sometime
in the mid-1980s when it was introduced somewhere in the Great Lakes
region from a ship's ballast water. Today they have reached as far south
as the Mississippi Delta and as far west as the Missouri River, changing
the local ecology through their voracious feeding, clogging intake pipes
and fouling anything in their path that stands still.
It's no wonder that biologists refer to exotic species as "biological
pollution," as they can have a severe effect on the environment,
economy and even human health. Economic damage happens when invasive
species compete with or reduce commercial fish stocks, erode shorelines,
clog water intake pipes or foul fishing gear, boats and buoys. And the
amount of money involved is staggering. According to the BioScience article,
exotic species cost the U.S. economy about $137 billion each year, and
the damage isn't all economic.
Alien species affect human health by spreading infections or toxins
in wild-harvested fish and shellfish, or by providing new intermediate
hosts for human parasites (such as with West Nile fever). The complete
toll they take on human health is unknown, but it's certainly significant.
Alarmingly, a study published four years ago in the science journal Nature
found high concentrations of viruses and bacteria, including cholera,
in water and plankton samples from ballast water in ships entering Chesapeake
Bay.
The effects exotic species can have on the marine environment are numerous.
They can alter the availability of food, space, and spawning areas through
direct competition, or they may alter the physical environment by reducing
water movement, eroding shorelines, or altering the bottom. Introduction
of new functional groups of organisms can cause detrimental changes in
the food web, or cause harmful algal blooms. Even future generations
of organisms are at risk because exotic species can alter gene pools
through hybridization. Sometimes, entire populations can be displaced
in favor of the invaders. The long-term consequences of this alien invasion
aren't well understood, but aren't likely to be good. What the final
price tag is on compromised biological communities only future generations
can tell us.
A general overview of how alien species affect major regions of U.S.
waters was published last year by the Pew Oceans Commission (see sidebar).
Here are just a few of the highlights: San Francisco Bay now has more
than 230 alien species, and they are growing at a rate of one new introduction
every two weeks. The bay has been so fundamentally changed by alien species
that many ecologists no longer consider it a "natural" ecosystem.
While this invasion took many years, others have not. Since 2001 alone
other major invasions have occurred or have become rampant. For example,
vast populations of the Pacific spotted jellyfish (Phyllorhiza punctata)
have invaded the Gulf of Mexico, along with the brown mussel (Perna perna).
The Gulf of Maine now sees billions of small carnivorous European flatworms
(Convoluta convoluta) blossom each summer. The Asian whelk (Rapana venosa)
has arrived and continues to grow in the Chesapeake Bay. This shellfish
predator could spell the end for the bay's long-suffering oyster industry,
once the largest in the world. The Japanese mahogany clam (Nuttallia
obscurata) has reached southern Oregon, and the Asian shore crab (Hemigrapsu
sanguineus) has reached astronomical numbers in Long Island Sound. Asian
kelp (Undaria pinnatifida) was discovered in Southern California, and
in the Pacific Northwest tens of thousands of farmed Atlantic salmon
(Salmo salar) escape into the wild to cross-breed with native species.
And these are only some of the more well-documented events.
Another invader that's received quite a bit of attention is the green
seaweed Caulerpa taxifolia. Known as the "killer algae," Caulerpa
was introduced into the Mediterranean from an aquarium, and has wrought
environmental destruction to large portions of the region's coastal ecosystems.
Today, acres of algal mat cover habitat that was once rich marine communities.
It's now well established in California, and a different species (Caulerpa
vertisilada) is covering vast tracks of coral reef in Florida's Palm
Beach County.
Another frightening consequence of biological invasions is what scientists
term the "homogenization" of ecosystems. The Black Sea is one
tragic example of not only environmental damage but economic collapse.
The unremarkable comb jelly (Mnemiopsis leidy) was introduced there in
the early 1980s by ballast water from a visiting ship. Incredibly, it
now comprises up to 95 percent of the biomass in the Black Sea. It feeds
on zooplankton, eggs and fish larvae, and has devastated the anchovy
fishery, which was once worth more than $250 million a year. Just how
serious is this problem worldwide? Some biologists believe that invasive
species may be second only to habitat loss as a leading cause of extinction.
How They Got Here
A primary mechanism for biological invasions is the ballast water needed
to stabilize ships for transit at sea. While this may not seem like a
major factor, consider this: According to the United Nation's International
Maritime Organization (IMO), some 10 billion metric tons of water are
moved around the world each year, with about 79 million metric tons discharged
yearly into U.S. waters. In a recent study, it was shown that 367 different
plants and animals were found in the ballasts of 159 ships arriving in
Oregon from Japan. It has been estimated that, on any one day, some 3,000
species are in motion around the world in ballast water.
Still, hitching a ride in the bilge of a ship isn't the only way invaders
arrive. Other sources of marine introduction and distribution include
the import of live bait; canals and connecting waterways such as those
in Suez and Panama; biological control programs where non-native species
are deliberately released to control pests; releases and escapes from
laboratories and aquaria (as was the case with the killer algae, Caulerpa)
and through escape from aquaculture facilities. The Pew Oceans Commission
report even cites distribution by aquatic recreational equipment such
as scuba gear. (Remember that the next time you put off rinsing your
equipment.)
From Ships to People
 One
pathway for invasion that's received little attention was illustrated
in the story of Nemo's journey, through home aquariums. Some scientific
studies have looked at the consequence of invasions by freshwater aquarium
fish. This is a significant problem throughout the Florida Everglades.
In fact, it's almost impossible to find a puddle of water in the famous
River of Grass that doesn't contain an alien fish species; and it's not
uncommon in many cases for the aliens to outnumber the natives. Yet,
the role saltwater aquarium enthusiasts play has, until recently, received
very little attention.
Earlier this year a sighting of an Indo-Pacific lionfish off of Palm
Beach County, Florida, by a staff member at Pura Vida Divers got widespread
local and even some national attention. Currently, both Florida's Department
of Environmental Protection and the National Oceanic and Atmospheric
Administration (NOAA) are asking divers to report additional sightings.
(See the news item on Page 22 of Dive Training's August 2004 issue for
more details.) But to savvy Florida divers, these sightings are anything
but novel or limited to the glamorous lionfish. They just haven't been
well-studied scientifically. It turns out that the most widely distributed
non-native species reported are actually the sailfin tang and emperor
angelfish.
I n
January of this year, University of Washington researcher Brice Semmens
and his colleagues published an important study in the journal Marine
Ecology Progress Series entitled, "A Hotspot for Non-Invasive Fishes:
Evidence for the Aquarium Trade as an Invasion Pathway." The results
probably weren't startling to anyone familiar with Florida's reefs, but
they brought the nature and magnitude of the problem into focus. The
report demonstrated for the first time that the alien fishes probably
reach Florida's reefs not through ballast water, but through aquarium
enthusiasts releasing their pets into the wild. Our story about Nemo
is probably dead-on. What's more, the trend started long before the movie
was even conceived.
The problem was first identified in Florida several years ago by the
fish survey project maintained by the Reef Environmental Education Foundation
(REEF). The organization has monitored fish populations in many areas
of the world for well over a decade, but nowhere longer than in Florida.
REEF volunteers began sighting species that weren't Florida nor Caribbean
natives in 1994 when a pair of Indo-Pacific batfish took up residence
on Molasses Reef. To date, at least 16 species of Indo-Pacific reef fishes
have been seen. At the time Semmens' paper was published, there were
40 reported sightings, with 32 of those documented by multiple independent
sources or photographic evidence (see Tables 1 and 2 for details). REEF
has reports of even more species sightings since then.
The Key is Education
As with most environmental problems, the solution begins with education.
Of course, some people still blithely throw trash out their car window
so, for some, the consequence of releasing some organism into the wild
where it doesn't belong will get little or no consideration. These are
people for whom nothing will ever change their attitudes or behaviors.
However, divers and serious aquarists are usually more concerned with
the marine environment than the average Joe. That's where the educational
effort has to start. Recently there's been a novel approach that both
addresses the problem directly and provides an ongoing educational opportunity.
It involves a collaborative effort among the Florida Keys National Marine
Sanctuary, Dynasty Marine Inc., REEF and the New England Aquarium. The
team collected two of three batfish that have called Molasses Reef in
Key Largo home for nearly a decade. While two were caught, the third
escaped, but has since been sighted. The captives now reside at the aquarium's
home in Boston Harbor, where senior aquarist Holly Martel Bourbon calls
them "poster fish for the dangers posed by invasive species."
Semmens and his colleagues agree that education is the key to overcoming
the alien invasion. But, he says, "The problem is that there isn't
any mechanism currently in place to educate aquarium enthusiasts about
the potential pitfalls of releasing pets into the wild." Indeed,
it is technically against the law to release non-native marine species
into coastal waters, but enforcing the law is virtually impossible. People
can't simply be told not to do it, but also must be informed why they
shouldn't. Additionally, the aquarium industry, as well as the diving
community, needs educational programs and mechanisms to distribute information
that clearly explains the problems and encourages alternatives. One such
alternative could be selling back or trading in unwanted fish.
Some may wonder what all the fuss is about over adding more fish to
the reefs of South Florida. After all, isn't that why divers go there?
Semmens answers that question in two ways. From a scientific perspective,
he compares releasing non-native reef fish to playing "environmental
Russian roulette." The consequences are completely unknown, and
ample evidence exists that what often happens isn't for the good.
But there's an aesthetic issue that we must also consider. "Divers
visit the reefs of Florida to see the region's natural beauty and diversity," says
Semmens. "It's a unique and magical experience to dive on these
reefs, and adding new species to the region is comparable to adding a
few finishing touches to one of da Vinci's masterpieces. It doesn't matter
if you believe in divine creation, or the balance of nature resulting
from the struggle for existence: Either way we are messing around with
a work of art." It appears that finding Nemo was only the first
part of the saga. His appearance on your local reef could be the sequel
we don't want to see.
Resources
For more information about the problem of exotic marine
fishes on coral reefs in Florida, check out REEF's
Exotic Species Sighting Program at www.reef.org/exotic/
More information on the NOAA, REEF,
Dynasty Marine and New Aquarium batfish collaboration can be found
at www.fknms.nos.noaa.gov/news/press_release/batfish.html
For further information on exotic species,
see the following resources: "Introduced Species in U.S. Coastal
Waters: Environmental Impacts and Management Priorities" by J.T.
Carlton, 2001; available at www.pewoceans.org/ (Click
on "this page" and then click on "Introduced Species
in U.S. Coastal Waters,"
"Biotic Invasions: Causes, Epidemiology,
Global Consequences, and Control," by R.N. Mack et al., 2000,
published in Ecological Applications, 10(3): pages 689-710. An abbreviated
version of this report is available at http://www.esa.org/science/Issues/FileEnglish/issue5.pdf.
"Management Plan: Meeting the Invasive
Species Challenge," by the National Invasive Species Council,
2001; available at www.invasivespecies.gov/council/mp.pdf.
"Environmental and economic costs
of nonindigenous species in the United States," by D. Pimentel
et al., 2000, published in BioScience 50(1): pages 53-64.
"Global spread of microorganisms
by ships," by G.M. Ruiz et al., 2000, published
in Nature 408, pages 49-50.
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