The
Encyclopedia of Biodiversity tells us that
“Marine ecosystems may be defined as major units of
ecological function in the marine environment.
Ecosystems are communities of organisms and their physical, chemical,
and geological environment—distinct assemblages of species coevolved with a
particular environment over long periods of evolutionary history…In comparison
to ecosystems on land, ocean ecosystems have less clearly defined boundaries, a
greater variety of major taxonomic divisions of organisms, and a long
evolutionary history that predated colonization of land.”
Through many millions of years of evolutionary trial and
error, geological change at the continental level, and shifting oceanographic regimes,
current marine ecosystems have developed to most efficiently utilize the
resources available in each particular region.
From the lowest trophic level, fed by sunlight and the chemicals gleaned
from a fertile sea, to the largest sharks, bony fishes, and whales, all are
bound together in a complex web that has been optimized and perfected
by time.
At least, that’s how it was until people came along.
Since then, marine ecosystems have been disrupted.
Thoughtless removal of forage fish, large
predators, and various demersal species, as well as equally thoughtless development
that degraded fishes’ spawning and nursery habitats and polluted
once-productive estuaries, has tattered food webs and depleted fish
stocks. Some species are no longer found
in parts of their former range; others remain rare visitors in waters where
they once were abundant.
It is only appropriate that people now try to reverse some
of the damage that they caused, although that’s often not easy to do.
The contemporary scientist spent over a year in preparation. To minimize the impacts of gear on the results of his study, he had a net
made out of old-fashioned tarred rope, instead of today’s modern synthetics. He also went out of his way to find a boat rigged as a side-trawler, a less
efficient design than the stern trawlers that dominate today’s fishery. By using a boat and net that emulated those
used in the surveys made over a century ago, he could be confident that any
differences in the fish that he caught compared to those caught in the earlier surveys would reflect real changes in the Agulhas Bank ecosystem, and not merely differences
attributable to the gear used.
And there were startling differences in the composition of the catch.
The original surveys, made between 1897 and 1906 found an
abundance of fish known as kabeljou (Argyrosomus
japonicus), a large member of the family Sciaenidae, which includes
drum, weakfish and other croakers, that reaches more than six feet in length. A century ago, the Agulhas Bank also held many
of the closely-related kob
(Argyrosomus hololepidotus), another weakfish relative that can approach
200 pounds in weight (the terms “kabeljou” and “kob” are used to describe
both fish), the much smaller panga seabream (Pterogymnus laniarius), and
East Coast sole (Austroglossus pectoralis), a type of flounder.
But when the Agulhas Bank was surveyed over a century later, the fish mix was completely different.
There were no kabeljou caught at all.
Instead, 85 percent of the fish caught in the new survey consisted of gurnards belonging to the family Triglidae,
which we’d call “sea robins” here in New York; the same spiny dogfish (Squalis
acanthias) that we catch on the East Coast of the United States; Cape horse mackerel (Trachurus
capensis) which, despite its name, is actually a small member of the jack
family (Carangidae); shallow-water Cape hake
(Merluccius capensis); and white sea catfish (Galeichthys
feliceps).
Those five fish, taken collectively, made up only 3 percent
of the fish caught in the surveys performed a century ago.
Obviously, something had changed.
“To explain the difference, Currie says, you need to consider
how the Agulhas Bank itself has been changed.
The main species of the historical catches are associated with reef
habitats, whereas a far greater proportion of the modern catches prefer sand or
mud habitats. This indicates that trawling
probably changed the seafloor, which in turn led to changes in fish
communities. ‘In seems obvious in
retrospect,’ says Currie.
“If not for the historical data and meticulous repeat survey,
this insight would have been obscured forever.
‘We know so little of how our oceans were a couple of hundred years
before,’ says Currie. ‘But to know where
we want to go in the future, we need to understand our history.”
Unfortunately, knowing the history of the Agulhas Bank ecosystem
probably won’t help scientists to restore the damage that the trawlers wrought;
it is likely too severe to repair.
However, people can, and in some cases are trying to, undo less severe
insults to ocean ecosystems.
The
discussion draft of a possible Magnuson-Stevens Fishery Conservation and
Management Act reauthorization bill includes language to protect forage fish
and increase the likelihood of rebuilding overfished stocks; it also includes
strengthened language that would better protect essential fish habitat. Efforts
to remove dams that block anadromous fishes’ access to historical spawning
grounds and to prevent
polluted runoff from entering vulnerable estuaries also hold hope for the
future.
On the other hand, there are still people out there who care
more about their own interests, and their own convenience, than they do about maintaining,
or restoring, healthy marine ecosystems; such people are still arrogant enough
to believe that they can improve on eons of evolution and engineer a marine
ecosystem that will remain stable while catering to their particular needs.
That’s the kind of thinking that leads anglers to kill
so-called “trash fish”—sea robins, dogfish, toadfish and such—when they catch
them, instead of returning them to the water, out of some sort of twisted
belief that by doing so, they’re improving the fishing by removing “bait
stealers” and “pests” from the ocean.
The worst example of that sort of thing that I ever heard
was back in the late 1970s or maybe very early 1980s, when baymen were still
allowed to haul seine for striped bass in the waters off Long Island’s “Hamptons.” The striped bass stock had already collapsed,
but the baymen still deployed their seines, catching a lot of different fish,
but not many bass unless they happened to set around a migrating school.
Back then, there were a lot of big bluefish around—15-pound
fish were pretty common, and some went over 20—and one day a surfcaster noticed
that they baymen were picking the few striped bass out of their catch, but
leaving scores of big bluefish to suffocate on the beach. So he started grabbing the dying blues and
returning them to the water, at which point one of the baymen came over and, in
a somewhat threatening manner, told him to let all the blues die, because “We
can’t get anything for them, and if you put them back, we’ll only end up
catching them again tomorrow.”
Today, after seeing so many of our fish stocks—including bluefish—decline,
it’s hard to imagine that such thinking goes on, yet it does.
I was reminded of that once again while reading a
piece in The Palm Beach Post, which reported that recreational fishermen
and charter boat captains are complaining that sharks are eating the fish that
they hook, and that they’ve asked Florida state regulators for relief from
regulations that limit their ability to target the sharks.
The article notes that great hammerhead, sandbar, and dusky
sharks are among the species most often blamed for attacking hooked fish, and
that
“it will be 50 to 80 years before sharks such as the sandbar
and dusky rebuild their populations after being decimated by overfishing.”
Yet the paper also reports fishermen complaining that
“When we say that there are too many sharks and the
population has exploded, they say they have no data. But the same people will say that the data
shows sharks are getting wiped out,”
while also reporting that a scientist from Florida Atlantic
University, who has actual expertise in shark biology, noted that
“I’ve heard about people saying they are ready to harvest as
many sharks as they can within legal limits just to get rid of them.”
The same biologist, disagreeing with the fishermen’s
antipathy toward sharks, observed that
“A lot of fishermen are complaining, but, sadly, I think it
could be good news because it means that the shark populations are becoming
more healthy and robust. As species
rebound, you are going to see more interactions.”
Yet “more interactions” with sharks is just what the fishermen
want to avoid. They complain that
“The situation is horrific, with probably over 100 hooked
[yellowfin tuna] killed in a day by sharks,”
but see no similar problem when the tuna are killed by
fishermen, or when fishermen kill the sharks that take their tuna.
Unlike the scientist quoted above, they’d much rather see an
out-of-balance marine ecosystem, which lacks a full complement of its apex predators,
then an ecosystem that’s restoring itself and returning to some semblance of what
it had earlier evolved to be. They fail
to acknowledge their role of interlopers in that ecosystem. In their self-centered arrogance, they feel
that they have a greater right to the fish than the sharks do, even though Homo sapiens
first appeared on the Earth a mere 200,000 or so years ago, while sharks
have been swimming in this planet’s oceans for nearly 400 million years.
Before people begin trying to engineer marine ecosystems by
removing or reducing the numbers of species that they dislike, find
inconvenient, or compete with, and causing more damage to the integrity of
those ecosystems along the way, they would be well advised to first do
everything in their power to undo the damage that we have already done.
That should keep everyone busy for a very long time.
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