Creature of the Deep
It’s been around since the dinosaurs, but it may now be close to extinction. What can we do to save the amazing sturgeon?
My first encounter with this ancient chimera came on a research vessel trolling just outside New York Harbor, within sight of Coney Island’s Cyclone roller coaster. The big fish lay still on the deck, enduring its examination with an uncanny self-possession as we ran our hands across its mottled brown crocodilian form and measured its massive armored torso -- some four feet long and dense as a log sheathed in leather, studded head to tail with rows of hard, barbed scutes. Of course the antediluvian form was remarkable, but more so was the fish’s composure, a Zen-like patience we decided must derive from its antiquity.
Few animals are more ancient than the sturgeon. Two hundred million years ago, when the first dinosaurs were appearing and before the continents separated, sturgeon ancestors already inhabited the Triassic seas. The way they look now is pretty much the way they looked some 85 million years ago. Those that survived the spreading of continents, a global extinction, and the coming and going of ice ages inhabited the Northern Hemisphere’s largest river basins, lakes, and inland seas -- in Europe the Baltic, Black, and Caspian, the Danube and Volga; in Asia the Amur. In North America, a freshwater species colonized the Great Lakes, and other species flourished in the Missouri and Mississippi rivers and the Gulf of Mexico. Sturgeon roamed the estuaries and rivers of the Pacific Northwest; Atlantic sturgeon migrated along North America’s eastern coast from Labrador to Florida, spawning in nearly every major coastal estuary.
Yet for all their evolutionary prowess, sturgeon are now critically endangered. Once humans developed a taste for their roe -- processed as caviar -- and a craving for the profits it brought, species that had survived millions of years were devastated in little more than a century. The International Union for Conservation of Natureconsiders 18 sturgeon species worldwide to be endangered, 16 of them critically. The U.S. Fish and Wildlife Service lists four of the country’s nine species as endangered, two as threatened.
So it would not have seemed controversial when, in 2010, the National Marine Fisheries Serviceproposed adding all but one population of Acipenser oxyrinchus oxyrinchus, the Atlantic sturgeon, to the Endangered Species List. Concern for the precarious state of this once spectacularly abundant species was not new: in 1998 the Atlantic States Marine Fisheries Commission had called for a minimum 20-year ban on all sport or commercial fishing for the Atlantic sturgeon. Nine years later, an NMFS study found that, despite the ban, "only a few subpopulations seem to be increasing or stabilizing" and the majority "show no signs of recovery."
And yet if NMFS was looking for consensus among sturgeon scientists, it wasn’t finding any. The departments of natural resources and fisheries in nine states on the eastern seaboard opposed an endangered listing; only two supported it. The opponents called the move premature, unnecessary, an impediment to continuing research, a precursor to onerous new regulations at a time when their own as well as the federal agency’s resources were finite, and, most of all, not based on good -- or sufficient -- science. Many fisheries scientists pointed out that NMFS’s own 2007 status review, despite its grim findings, recommended only regional "threatened" listings -- meaning some populations of sturgeon were likely to become endangered within 20 years if nothing improved.
Proponents of an endangered listing, however, considered a 20-year bet on an 85-million-year-old species a reckless gamble. NMFS and the Natural Resources Defense Council, which filed a listing petition in 2009, claim that recent research shows Atlantic sturgeon face increasing environmental risks. Worsening water quality in the estuaries and rivers where the fish were once most abundant threatens young fish. In the Delaware Bay and the Delaware River, once the staging area for the greatest aggregations of Atlantic sturgeon, sightings of juveniles are rare and spawning adults rarer still. (Delaware and Pennsylvania already include the sturgeon on their state endangered lists and favor federal listing.)
Atlantic sturgeon are, of course, not the lone suffering species: 100 years of development, ship-channel dredging, and runoff have reduced to a shadow of their former selves populations of American shad, blueback herring, alewife, and American eel -- all of which migrate between freshwater and salt water.
Those arguing for an endangered listing believe it may be the only way to initiate the coast-wide effort they feel is needed to keep the Atlantic sturgeon from disappearing altogether. The population trend across the fish’s entire range, they contend, is clear, troubling, and in some cases alarming. Declare the Atlantic sturgeon endangered now, they say; fill in the scientific blanks later.
Andrew WetzlerQ&A with Andrew Wetzler, co-director of NRDC’s land and wildlife program and an expert on the Endangered Species Act.
Congress recently asserted that it has the right to make decisions about listing endangered species -- in this instance, wolves -- rather than leaving the matter to scientific experts.
It’s not easy to defend against that kind of attack. High-profile species such as wolves tend to be controversial, and unknown species tend to have few champions. But there is hope. Recently, the House of Representatives rejected a proposal that would have prevented the federal government from spending any money to place new species on the endangered species list. Both Democrats and Republicans voted to kill the measure.
Read the rest here.
No one disputes that, for the Atlantic sturgeon, those blanks are big and plentiful. While charismatic is the first word many scientists use to describe the sturgeon, cryptic is usually the second. Its life history remains frustratingly inscrutable, a Rumsfeldian collection of knowns, known unknowns, and unknown unknowns.
Atlantic sturgeon can live past 60 (a lake sturgeon might live twice as long), grow to eight feet or more, and weigh 600 pounds. Yet despite their size and battle-ready appearance, they are a reclusive species. They are at home, out of sight, along deep river bottoms and coastal seabed channels, where they graze on an assortment, from large to microscopic, of mollusks, worms, crustaceans, and insects -- food that even 200 million years ago would have been plentiful. It’s an ecological niche that no other large fish evolved to exploit and that sturgeon make the most of, thanks to some splendid evolutionary adaptations.
Electroreceptors allow them to locate prey in the dark depths -- an adaptation also found in sharks, an even more ancient species to which sturgeon, because of their cartilaginous skeleton, were once thought to be related. The two species also share an airplane-like tail fin, but the sturgeon’s is truncated at the base, so the fish can move swiftly but still remain close to the riverbed or seabed. The four gangly barbels that dangle beneath the fish’s snout are not feelers but tasters, covered with chemoreceptors that detect prey buried in the bottom sediment.
The sturgeon extracts its prey through an extraordinary process made possible by a mouth that is unique among fishes. (It can’t properly be called a jaw because no bones connect it to the skull.) When a sturgeon locates food, the mouth bulges outward from beneath the snout like a fleshy hose, flushing out prey. The fish then separates food from sand and gravel and expels the grit through its gills.
While other anadromous fish such as salmon, shad, or striped bass may, within a few years of their birth, return to their natal rivers to spawn, once a young Atlantic sturgeon goes out to sea it may not return for a decade. Sturgeon from South Carolina reach maturity between the ages of 5 and 19, Hudson River sturgeon between 11 and 21, and in the St. Lawrence not until they’re between 24 and 34 years old. This, combined with the fact that younger females carry fewer eggs, means that new generations of some Atlantic sturgeon populations emerge less frequently than generations of humans. A depleted population, therefore, can take a very long time to recover. And it is for this reason, many opponents of an endangered listing contend, that the effects of the 1998 fishing ban have only recently become apparent.
All Atlantic sturgeon make their major spawning runs in spring: southern fish as early as February, northern fish as late as June. The gravid females swim in from the sea and continue upstream until they find freshwater or deep river channels. There they release their eggs, which stick to the sand and gravel. Hatched within a few days, the young begin a slow migration downstream, scuttling along the bottom like little crocodiles that have sprouted fins and adapting over the course of the following year to more and more saline surroundings. Once acclimated to salt water, they’ll spend their first few years in the lower reaches of their natal estuary, "hanging out like kids at a 7-Eleven," as one scientist put it, with seemingly little urgency to get on with their adult lives.
Most of the rest of their lives will be spent on wide-ranging coastal peregrinations that are not well understood. What is known is that sturgeon rarely go into waters deeper than 100 feet, and that while some remain close to home (fish from the south seem to be the less daring travelers), they can travel far -- very far -- from their native estuaries. Hudson River fish have been tracked as far north as the Bay of Fundy, and last year a sturgeon tagged in the Delaware River was followed by telemetry up to Cabot Strait, between Nova Scotia and Newfoundland, a thousand-mile journey made in 53 days. Scientists have even come up with evidence that sometime in the Middle Ages, East Coast sturgeon found a route across the North Atlantic and established themselves in the Baltic Sea.
What’s also known is that these peripatetic fish often gather in large aggregations close to shore or at the mouths of estuaries. Exactly why, or how frequently, they form these groups is not known, but when they do huddle up they can find themselves in harm’s way, in areas targeted by commercial fishermen. Sturgeon caught in nets set for smaller species may not survive.
While this bycatch may not be substantial in any one place, it becomes significant when multiplied by fisheries all along the coast. And it is complicated by the fact that these gatherings can be made up of fish from anywhere along the Atlantic seaboard. In other words, a Georgia fisherman could easily haul up a Hudson River sturgeon rather than one from Georgia. Under an Endangered Species Act recovery plan, suggests Keith Dunton, a Ph.D. student at the Stony Brook School of Marine and Atmospheric Sciences, the key sturgeon staging areas could be found, defined, and, when inhabited by sturgeon, declared to be critical habitat and closed to commercial fishing or restricted to certain types of fishing gear.
All the sturgeon’s undisciplined comings and goings and heterogeneous mingling "throw a monkey wrench into our understanding of Atlantic sturgeon biology," says Isaac Wirgin, a geneticist in the department of environmental medicine at New York University School of Medicine. They also create statistical havoc for those hoping to find out whether one particular sturgeon population is in good or bad shape, or whether the entire population is in decline or recovery. A simple head count in the native river won’t do, since many of the fish may be out at sea. But counting them in the ocean won’t work either, because without doing an extensive genetic analysis, you can’t be certain which river a sturgeon came from.
As Wirgin puts it, the sturgeon that are there may not be the sturgeon you think they are.
When I spoke last spring to Dunton, he and his adviser, Michael Frisk, had just caught 80 sturgeon in several sweeps of their trawl net off the southwestern shore of Long Island. While some scientists, like Wirgin, say numbers like these prove that sturgeon populations are in good shape, Dunton and Frisk say they prove nothing: "When you’re on the fish, you’re on them; when you’re not, you’re not." By the same token, even if you aren’t on them, they may still be out there.
Over millennia of fidelity to the rivers in which they spawned, Atlantic sturgeon formed genetically distinct populations and subpopulations. In the 1990s, when scientists began looking into sturgeon genes, they found themselves staring down an evolutionary rabbit hole. While a human cell has 46 chromosomes, an Atlantic sturgeon has about 120 (some species may have as many as 500), the result of a long, reproductively complex, and highly successful evolutionary history.
By examining variations in particular segments of DNA, scientists identified at least nine genetically distinct Atlantic sturgeon populations. (Some are more closely related than others, and geneticists often disagree on how different is different. They also continue to find further genetic diversity within these larger groups -- more in southern fish than in northern ones, perhaps because northern fish settled in their rivers only after the last ice age ended.)
For the sake of the endangered species listing, the National Marine Fisheries Service settled on five distinct population segments (DPS) of Atlantic sturgeon, proposing to list four as endangered and one as threatened. (Under the Endangered Species Act, individual population segments, as well as an entire species, can be listed.) This was not a popular decision. Delaware and Hudson fish, for instance, which most scientists agree are genetically distinct, are lumped together into a New York Bight DPS. This pleases neither Hudson River nor Delaware River biologists, who don’t believe that their populations are equally endangered -- the Delaware fish are much worse off -- and so can’t be managed in the same way.
Genetic IDs have made it possible to determine from a tissue sample whether a sturgeon caught in Maine was a Penobscot native and not a Delaware River migrant, or whether a fish caught in South Carolina didn’t roam down for the winter from the Hudson. But knowing where a sturgeon comes from doesn’t necessarily tell you where it’s going. That, it appears, depends on its age. Matthew Fisher of the Delaware Division of Fish and Wildlife, who has been tracking Delaware Bay and Delaware River sturgeon with acoustic tags, says, "There are early-stage juveniles from 0 to 2 years old that need freshwater to survive and grow in low salinity. There are late-stage juveniles that mix at the mouth of the bay and offshore with others from the Hudson, Connecticut, Roanoke, and James rivers. And then there are the adults. It’s almost as if there are three different species that all behave in different ways."
To further understand the sturgeon’s travels, scientists are implanting transmitters in the abdomens of the fish that will, in some cases for years, report their whereabouts as they pass gauntlets of sensors now being arrayed in rivers and bays and along the coast.
Dewayne Fox, of Delaware State University’s department of agriculture and natural resources, is working with Kevin Wark, a commercial fisherman from New Jersey, to implant transmitters into large sturgeon caught offshore, hoping to follow the fish for several years. That will allow them to learn where the fish go to spawn, where they roam, where they congregate, whether juveniles mingle with adults, and whether the fish move in response to changing food resources or shifts in temperature.
"The rubber hits the road," Fox says, "when I’m able to say that Atlantic sturgeon are in this location at this time and maybe restrict our activities there to minimize human impacts."
Fox believes that within the Delaware estuary, the Atlantic sturgeon faces enough challenges from ship strikes, dredging, and alterations in habitat related to climate change that current protections are not enough to save the Delaware fish. At the same time, he hopes that the data being gathered and shared by researchers using acoustic tags, from northern Florida to Canada, will begin to refine the outlines of the sturgeon’s natural history. For now, the data are sparse and anecdotal, but intriguing.
"We’ve seen females over 300 pounds go up [the Hudson] to Catskill, New York, then turn around and return to the Delaware," Fox says. "We’ve caught fish from South Carolina, the Hudson River, Virginia, Maine, Georgia, and Delaware all sitting less than three miles off the Delaware coast," in waters that also harbor migrating shad and striped bass. "If we could see what was going on offshore," he says, "it would put the Serengeti migrations to shame."
But what is going on offshore is nothing close to the migrations that once were.
***
Native Americans valued the sturgeon for its meat and oil and netted, speared, or corralled them on their upstream spawning runs. The fish held little interest, however, to the early European settlers (although a strong spring run up the James River in 1607 may have saved John Smith’s starving colony). Sturgeon flesh was considered a lesser meat, and later immigrants who ate sturgeon were derided for their consumption of "Albany beef." Besides, America’s rivers teemed each spring with far less unwieldy fish, such as striped bass, herring, shad, and eels. Sturgeon were for the most part unwelcome brutes that mangled fishing nets and were deemed remarkable mostly for the sight of huge individuals leaping from the water.
Native Americans valued the sturgeon for its meat and oil and netted, speared, or corralled them on their upstream spawning runs. The fish held little interest, however, to the early European settlers (although a strong spring run up the James River in 1607 may have saved John Smith’s starving colony). Sturgeon flesh was considered a lesser meat, and later immigrants who ate sturgeon were derided for their consumption of "Albany beef." Besides, America’s rivers teemed each spring with far less unwieldy fish, such as striped bass, herring, shad, and eels. Sturgeon were for the most part unwelcome brutes that mangled fishing nets and were deemed remarkable mostly for the sight of huge individuals leaping from the water.
The sturgeon’s status changed, however, after the Civil War, when a method for preserving its roe, for shipment by train along new routes to major cities or by ship to Europe, incited a late-nineteenth-century caviar rush. Centered on the Delaware Bay and Delaware River (the town of Bayside, New Jersey, was once called Caviar), the industry began in earnest around 1870. Within 20 years, 1,000 sturgeon fishermen were working the Delaware, bunking during spring migrations in crowded houseboats along the shore. They netted the fish, stripped the cows of their eggs, and often left the heavy carcasses to rot on the riverbanks. The industry spread up and down the coast. In 1888 East Coast fishermen harvested more than seven million pounds of sturgeon.
The population crash was swift and severe -- by 1901 fishermen caught only 650,000 pounds -- and manifested in the rising price of caviar. In 1885 a keg that held some 135 pounds sold for $9 to $12; by 1899 the price had risen to $105. The carnage has been compared to the massacre of the buffalo and the slaughter of the passenger pigeon.
A handful of fishermen persevered through much of the twentieth century, catching sturgeon when not netting shad or striped bass, mostly selling the fish for meat and enjoying the roe for the very high price it brought in, sold no longer by the keg or pound but by the ounce. But the great sturgeon migrations never resumed.
Gone as well were the nearly pristine rivers that spawned the great migrations. The Industrial Revolution took its toll on all river species. In 1895 the Pennsylvania Fish Commission’s report on shad stated that "the general impression among fishermen is that the decrease in the catch during the past four springs is due to the increase of coal oil, gas and bone factories along the Delaware River. The obnoxious poisons and gases are all turned into the river, killing the young fry."
The marine biologist John Waldman, of Queens College in New York, who has been studying sturgeon for more than 20 years and worked on some of the earliest and most important population and genetic studies, believes a key problem is assessing the present state of the sturgeon on the basis of historical populations. This, he says, ignores the fact that the estuaries where the fish now spawn and spend their early lives have been so altered by pollution that they may no longer be able to support anything like the large populations they once did.
Forget what once was, Waldman suggests. Regulators would make far more realistic decisions if they hitched their expectations to a postindustrial baseline. Yet the baselines for the sturgeon are blurred by historical and statistical unknowns as well as by biological uncertainties.
Brad Sewell, a senior attorney with NRDC who played a key role in the 2009 petition to have the sturgeon listed as endangered, believes there are certain certainties. The 13 years since fishing for sturgeon was banned, he says, have only proved the need for better protection. "If it was adequate or effective, you’d see a lot of juveniles out there, but you’re not seeing them," Sewell says.
"I understand the perspective of the researchers," he adds. "But from the perspective of the species, more research is not as important as [the problem of] significantly reduced habitat. You need high genetic diversity to withstand changing conditions." In Sewell’s view, by the time all the unknowns are known it may be too late -- especially if, as the NMFS study team estimated, after 85 million years we may have reduced the sturgeon’s window for survival to a matter of decades. "I think," Sewell says, "a listing will save it."
While many argue that a threatened rather than an endangered listing would be sufficient -- and present data to back up that view -- there is one thing few would dispute: that time is not on the side of this ancient and mysterious species.
Bruce Stutz, former editor-in-chief of Natural History, became a contributing editor to OnEarth in the fall of 2004. He is the author of Chasing Spring: An American Journey Through a Changing Season (Scribner).
No comments:
Post a Comment