A Balancing Act
A leading UMaine marine
scientist says better management is needed to save the world's oceans
that are drastically out of sync
About the Photo:
Invasive species like the green crab
are just one of many problems facing the health of marine ecosystems
and the sustainability of marine fisheries. By feeding on native
shellfish and other organisms, and competing with native crabs and
lobsters for food and shelter, green crabs and their imported
brethren have been a scourge along both coasts of North America.
More than 20 years ago, in an attempt to assess the ecological
impacts of the cod's disappearance in the Gulf of Maine, Bob Steneck
spent months monitoring predator-prey interactions along an undersea
mountain known as Cashes Ledge.
Dynamics of Diversity
From microscopic mudworms to 100-pound cod, all marine organisms are
part of a complex web of interdependence that forms the foundation
for the system's overall health.
Links Related to this
In 1982, they were everywhere.
Thousands of mushy, globular bodies attached to tens of thousands of
tiny, tubular feet, each moving slowly across the ocean floor with
clear, instinctual determination. Driven by the urge to eat and defended
by a dome of stubby spikes, Maine's population of green sea urchins (Strongylocentrotus
droebachiensis) were the miniature versions of so many punk rock
buffalo, grazing their way across the Gulf of Maine in seemingly
endless, insatiable herds. Fast forward to 2002. In less than 20 years,
the gulf's vast, prickly carpet of urchins was reduced by hundreds of
millions of animals by overfishing, the survivors sprinkled far and wide
along Maine's ragged coast. But the urchins' story is not as simple as
it might seem. Like so many other organisms that have been harvested
from the waters of the Northeast, the urchin is just another character
in a very long and complicated story — a story marked by intricate plot
twists, shocking irony and a conclusion that is shaping up to be
With more than a quarter-century on the
front lines of marine research, Bob Steneck is a man who knows when to
fish and when to cut bait. The University of Maine School of Marine
Sciences researcher has spent his career unraveling the intricacies of
the world's marine ecosystems, and his "big picture" approach to
conservation and fisheries management has helped to tie the oceans' many
divergent plot lines into a single, unified tale of global turmoil and
anthropological excess. From searching for fish bones in 2,000-year-old
trash heaps to studying Caribbean corals with the help of high-tech
diving gear, Steneck has gathered considerable evidence that suggests
that the coming years may be particularly critical for many marine
ecosystems as they exist today.
The story is still being written, but
Steneck, for one, is bent on creating a happy ending.
"I'm generally an optimist at heart,
but there are some serious threats to the world's oceans," Steneck says.
"We tend to look at the planet, and in particular the oceans, as this
stable, permanent, nurturing source of life, but as science peels back
the layers, what we see is a global ocean in trouble."
Pointing to a growing list of health
threats to the world's oceans, Steneck describes a common pattern of
slow, incremental overload and sudden collapse, suggesting that the Blue
Planet's ability to absorb the insults of human misuse have clear
limits. The notion of ecological thresholds is at the core of Steneck's
assessment of the seas. As pressure on the marine environment continues
to grow, these thresholds are being met — and surpassed.
A classic example of the threshold
phenomenon can be found in the sad tale of the green sea urchin.
Prolific and plentiful across the Gulf of Maine, urchins spent decades
quietly munching at the Atlantic's undersea salad bar, unaware of the
socioeconomic tsunami on the horizon.
As urchin populations in other parts of
the world were rapidly depleted by overfishing through the 1970s and
'80s, a seemingly insatiable Asian market turned its hungry eyes toward
Maine, creating a boom-and-bust fishery that crashed a multimillion
urchin population in less than two decades.
Steneck used the urchin story to
illustrate the effects of roving bandits in a paper he coauthored with
UMaine marine scientist Jim Wilson and others, recently published in the
"The urchin story is classic
overfishing. Because of the globalization of fisheries, the Japanese
were able to deplete the global stock. They could afford to pay top
dollar in places like Maine, but they had no stake in the health of our
local ecosystem. Harvesters who move into a fishery and deplete the
resource without any kind of investment in the ecosystem's long-term
health are the definition of the roving bandit," says Steneck, who is
based at the Darling Marine Center in Walpole, Maine.
"The collapse of the urchin fishery was
marked by a cascade of ecological and socioeconomic effects. We can see
the effects of surpassing the economic thresholds in the fishery:
processors and distributors pull out, harvesters go out of business, but
the effects of surpassing the ecological threshold are unknown.
"We don't know the implications of
targeting the Gulf of Maine's most significant herbivore. But we do know
that there is more seaweed sprouting in the Gulf of Maine than there's
been in decades."
The prequel to the urchin story adds
yet another twist to the tale: the urchin's preharvest heyday itself was
due, at least in part, to yet another case of overfishing. For
millennia, the Gulf of Maine was ruled by the mighty cod. The powerful
carnivore's mustached mouth gobbled untold thousands of crabs, lobsters,
shrimp and, of course, urchins during its tenure as dominant predator.
But cod proved to be too tasty for its own good, quickly becoming the
target of an international race to capture the most fish.
Humankind's appetite for salted cod,
dried cod, boiled cod and cod chowder inspired a race for more traps,
bigger nets, more powerful boats and so on. The technological onslaught
proved too much, putting cod and other groundfish on Maine's long list
of collapsed fisheries. As the cod population dwindled, the urchin
population mushroomed. And now, kelp and other algae are taking
advantage of their freedom from the urchin's hungry herbivory.
With their big-brained ability to find
new ways to exploit marine resources, humans have proven again and again
their knack for surpassing ecological thresholds and upsetting the
natural balance beneath the waves. Steneck hopes to stabilize our
relationship with the sea by finding new ways to fish that work more
harmoniously with natural processes.
"Following the evidence drawn from
marine research over the years is like watching an episode of CSI: The
science is very good at telling us what made the victim die," says
Steneck. "What we are learning is that the role of consumers, or
predators, in marine ecosystems is much more significant than it had
been considered in the past.
"Loss of large predators from the
system has a much greater impact than nutrient run-off or invasive
species or any of the other factors threatening ecosystem health. One
could argue it is the biggest issue facing fisheries management."
Steneck maintains that marine
ecosystems are structured by their large predators, and that the lack of
large predators due to overfishing can cause the populations of other
organisms within the system to fluctuate uncontrollably. After nearly
400 years of intense groundfishing in the Gulf of Maine, declines in the
cod population led to increases in the number of shrimp, lobster,
urchins and other prey species.
While some might argue that an increase
in lobsters or other species humans find tasty is a good thing, the
population swings of prey species represent a system out of balance, and
it is that balance that is so important to maintaining healthy
ecosystems and sustainable fisheries.
Worldwide, many marine species once
abundant are now rare, and dramatic increases in populations are often
the precursor to disease outbreaks. In Maine, where fishermen once split
their efforts between several different species throughout the year,
fully 80 percent of the state's fisheries income now comes from a single
species: the American lobster.
To put that into perspective, there are
more than 50 other marine species that split the remaining 20 percent of
Maine's commercial fisheries income. Sales of bloodworms for fish bait
contribute more to the state economy than cod.
"We need to manage our fisheries in a
way that will bring back the dominant predators to restore diversity. A
diversified ecosystem can support diversified fisheries, and that is the
only way to maintain sustainable harvests," Steneck says.
With 80 percent of Maine's fishing
economy riding on lobster, a disease outbreak could devastate the
state's socioeconomic fabric. That's what happened in Rhode Island,
where lobster shell disease collapsed the industry. Fishermen know the
danger of depending too much on one species, says Steneck, who advocates
broad changes in how fisheries are managed.
"When I first began doing research and
working with fishermen, there was open hostility between managers,
fishermen and scientists. Just in the past five years, fishermen have
gone from being in denial to openly admitting there's a problem."
Steneck hopes to reinvent fishing by
changing the way we look at harvesting and management. Almost all
commercial fishing has aimed at capturing the biggest individuals of the
target species, leaving smaller, younger animals to replenish the stock.
But to increase a fishery population, it isn't enough to increase mesh
sizes or minimum lengths, Steneck contends.
As part of the natural process,
predators take the bite-size and injured, often leaving the biggest,
healthiest, reproductive animals. Steneck says it's important to do the
same in fisheries management by preserving the largest and smallest of
"If we could change our focus to target
the intermediate-size animals, our fisheries would be more sustainable
and the ecosystem would benefit," says Steneck.
By David Munson
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