by Scott Leslie
There may be little that can be done to ensure the Ganges shark’s survival, if indeed more than few dozen of them still exist. Although the Indian government has banned all fishing for the species, this measure is virtually impossible to enforce along thousands of kilometres of river populated by millions of independent fishers whose next meal might well be an endangered river shark.
IRRAWADDY RIVER SHARK
This river shark is known from just one museum specimen, a juvenile male about 60 centimetres in length that was caught in Burma’s Irrawaddy River in the late 1800s. However, since the Irrawaddy shark lives in some of the murkiest waters on earth, it hasn’t been presumed extinct by the IUCN—it could be easily missed swimming about in its chocolate milk–like environment. Everything we know about the species comes from that one specimen described in 1896 by Austrian scientist Franz Steindachner. Like others in the genus Glyphis, the Irrawaddy shark has very small eyes and small serrated teeth, which suggests that it hunts for small fish using smell, hearing, and electroperception. Based on its juvenile length, it’s thought the species reaches a length of up to three metres. Little else is known about the fish.
Although probably never common, its virtual non-existence is probably the result of the same factors affecting the Ganges shark: fishing and pollution. The destruction of mangrove forests along the Irrawaddy River, potentially an important part of the shark’s habitat, might also be an important factor in its decline, since some shark species use the shallows surrounding mangroves as nurseries.
NORTHERN RIVER SHARK
The northern river shark lives in a handful of rivers along Australia’s north coast, including in Kakadu National Park, and in the area surrounding the port of Darwin. Growing to about two metres in length, it inhabits muddy, slow-moving tidal rivers, as well as possibly spending some time in shallow salt water near the river mouths. It appears that individual sharks are loyal to their home rivers. Although they are protected as an endangered species in Australia and listed as critically endangered on the IUCN Red List, they are at great risk of extinction thanks to being taken as accidental bycatch at the hands of local gillnet and hook-and-line fishers. Moreover, given their specialized, limited habitat, northern river sharks are vulnerable to pollution and development along rivers. Only those individuals living within the protected Kakadu National Park might have a real chance at survival. Fewer than 40 northern river sharks have ever been recorded.
In contrast to the river sharks, which are challenging to protect because they are always moving and we don’t know the extent of their distribution in the typically murky waterways they inhabit, the Devils Hole pupfish faces the opposite problem: its entire world falls within a tiny, well-defined habitat that could be wiped out by a single catastrophic event.
DEVILS HOLE PUPFISH
On April 4, 2010, the 7.2-magnitude El Mayor-Cucapah earthquake violently shook Baja, Mexico, killing several people. Shock waves were felt hundreds of kilometres to the north in Death Valley National Park in Nevada, where US Geological Survey live-feed video cameras captured their effects on the tiny habitat of the highly endangered Devils Hole pupfish, a creature whose total known range is even smaller than that of the Gorgan Mountain salamander. The two-and-a-half-centimetre-long, guppy-like fish, with a population hovering around 100, lives only in Devils Hole, an otherwise inconspicuous pool of water deep within a crack in the Mojave Desert. The video footage shows the three-by-seven-metre pool sloshing violently back and forth, like a shaken bathtub (Devils Hole was once known as the Miner’s Bathtub). The seething water rips algae off the two-by-four-metre rock ledge that the species uses for spawning and feeding. Beleaguered pupfish can be seen bolting into clear water from the churning cloud of vegetation and silt. A few minutes later, once the drama has ended, they return to a changed habitat. The scary thing is, it wouldn’t take much to wreck the entire world of this species: living only in this little hole, it has the smallest distribution of any vertebrate on earth.
However, Devils Hole is more than simply a hole. Like the tip of an iceberg, the pool at the surface represents just a fraction of what’s below: a vast, mostly unexplored, flooded cave system, whose absolute depth remains a mystery but reaches at least 150 metres. For 20,000 years, the cave’s constant 34 degree Celsius water has provided a stable habitat for the iridescent blue pupfish. Little had changed in its environment until the 1960s. That’s when the development of nearby alfalfa farms began to take off. Lots of sunshine and water are important for growing alfalfa. There was no shortage of sun in the desert, but water had to be drawn from the caverns beneath Devils Hole. Its level began falling. You might think a drop of a few centimetres really wouldn’t bother a fish that lives in a practically bottomless shaft. But it does. That barely submerged, walk-in closet–sized rock ledge at the hole’s entrance, so crucial for feeding and reproduction, would be high and dry even with a slight drop in the water: bad news for the pupfish.
The Devils Hole pupfish was declared an endangered species in 1967, at about the same time big agriculture was beginning to draw down the area’s groundwater. At the time, its population was between 400 and 500. In 1973, while the battle between pupfish conservationists and developers was being waged, the US Endangered Species Act became law. Now the federal government was obligated to try to recover any species listed as endangered. The effort to save the pupfish would be a crucial early test for the act, the world’s first comprehensive endangered species legislation. In 1976, four years after conservationists filed a suit against land developers and the state of Nevada, the US Supreme Court found in favour of the Devils Hole pupfish, mandating a minimum water level to protect the species from extinction.
Nature itself had provided a few problems for the little desert fish to contend with besides water-hungry alfalfa farms. In the 1970s, a flash flood washed debris into the hole, and an earthquake shook things up. Nevertheless, the population stayed pretty stable at around 400 until the 1990s, when the species’ numbers began to mysteriously dwindle.
By 2006, it had hit its lowest count ever at only 38 individuals. As a precaution, conservationists began to supplement the fish’s food supply to try to stem a further decline. This appears to have worked. Since then, though still only modest, pupfish numbers had been growing steadily for the first time in over a decade, though the number still fluctuates between more than 100 after young are born to below 100 later in the year.
Then, just when it looked like some headway was being made, the April 2010 earthquake hit. Nobody knows yet what effect the loss of algae in its habitat will have on the endangered fish. Surprisingly, a population survey in the week following the quake showed 118 fish, nearly 50 more than one year earlier. But would this number hold in light of the damage done to the pupfish’s food supply? While there are no guarantees, biologists expect the algae will grow back. There may be another silver lining, too. It’s possible the quake’s sloshing washed away the accumulated fine silt that clogged up critical habitat between gravel particles where pupfish larvae find refuge. In fact, the survey done following the quake also showed more larvae than the previous survey.
We can only hope that the recent modest comeback of the Devils Hole pupfish continues and even accelerates. Our fingers should also be crossed that the US Endangered Species Act, so vital to the continued existence of the pupfish and a bevy of other species, will also persist strongly into the future.9 The act, however, may have been too slow in coming to the rescue of the Alabama sturgeon, another of the world’s rarest fish.
ALABAMA STURGEON
Some 200 million years ago, when the first sturgeons appeared on earth, the planet looked nothing like it does today. There was no North America, Europe, South America, Asia, or Africa; in fact, there really weren’t any separate land masses at all. The supercontinent of Pangaea had just begun breaking up into the pieces that would eventually become the continents we know today. When sturgeons first appear in the fossil record, T-rex hadn’t yet walked the e
arth, and flowering plants were still 100 million years in the future. By contrast, Homo sapiens have only been around for the last 200,000 years. If an animal deserves respect based on seniority alone, we should bow to the sturgeon, a thousand times our elder in the community of life.
Fossilized sturgeons look quite similar to their present-day descendants. They’ve changed little in the eons that they’ve been swimming the waters of the earth, a fact that has gained them the illustrious distinction of being living fossils. One of the oldest families among the fishes, sturgeons possess a skeleton of cartilage, as well as an elongated upper tail lobe, much like the sharks and rays. But unlike most fish, their body is covered with bony plates called scutes instead of the typical scales. At the business end, four sensitive barbels are found beneath an elongated snout, which is used to “snuffle” along the bottom in search of food.
Docile and slow moving, some sturgeon species are giants among fish. The largest species, Huso huso, grows up to five metres in length and can weigh 2,000 kilograms. Piscine methuselahs, a few can live for a century or more and may not breed until 20 years of age.
Slow growth rates, late sexual maturity, habitat destruction, and a high demand for the females of certain kinds for their caviar have pushed nearly all of the 26 sturgeon species toward extinction. The most threatened one of all lives in the southeastern United States.
Among the rarest fish in the world, the Alabama sturgeon was once found throughout the rivers of the Mobile Basin in Alabama and Mississippi. One of the smallest species in its family, the brassy-orange bottom-dweller reaches a length of only 45 to 75 centimetres and weighs in at about a kilogram. The species had been declining for decades owing to overfishing, dredging of its river habitat for navigation, and pollution. In recent decades it has become restricted to the Alabama River and its tributaries, where the construction of two dams in the 1970s is thought to be the real culprit in the species’ recent precipitous decline: its age-old passage up and down the river had been blocked.
Although locals have known about the sturgeons for a long time—records from 1898 indicate an impressive commercial catch of 19,000 of them—the fish was only formally recognized as a distinct species in 1991. By then it was so rare that some questioned whether it even survived. This made it very difficult to have it protected under the US Endangered Species Act. Opponents asked, why protect a species that might not even exist? Resistance to having it designated under the act was strong. An alliance of business and industry claimed, among other things, that the listing threatened to harm the economy because it would result in restrictions on the routine dredging of the river and on barge traffic. As part of their strategy against listing it under the ESA, opponents also argued that even if it did still survive, the Alabama fish was one and the same species as the Mississippi River shovelnose sturgeon and therefore wasn’t threatened with extinction. The US Fish and Wildlife Service (USFWS), the agency responsible for the act, abandoned its effort to protect the species in the early 1990s in the face of this opposition.
In 1993, a program began to captive-breed the Alabama sturgeon population back to health. One thing was missing: fish. So the search was on to capture breeding stock. By 1999, the state’s fisheries department and the USFWS had netted tens of thousands of fish of various species in the search for sturgeons. Only six were caught, all males. A female was never captured. The last captive male died in 2002. End of breeding program. At the time, no more Alabama sturgeons were known to exist.
Just a couple of years earlier, in 2000, an Alabama environmental lawyer won a lawsuit against the USFWS, requiring the agency to finally list the sturgeon as a federal endangered species. Was the endangered designation too little, too late? Maybe not.
In the spring of 2007, state biologists captured a single Alabama sturgeon, the first of its kind to be seen in a half decade. It was the second-largest on record, so biologists believe it is very old and may have been one of the last to breed before those dams were constructed on the Alabama River in the early 1970s. This time, instead of putting it into captivity, biologists decided to implant the fish with a tracking device, release it back into the river, and follow its movements in the hope it would lead them to other sturgeons. By the spring of 2008, they’d been tracking it for a year and had learned where the fish likes to travel and where it likes to linger in the summer. A year later, biologists found another one in a different area. These remain the only two Alabama sturgeon known to exist.
In May 2008, some eight years after the designation of the Alabama sturgeon as an endangered species, the USFWS finally released its plan to protect the habitat of the beleaguered fish. Designation of part of the Alabama River and its tributary, the Cahaba River, as critical fish habitat is being proposed. As well, scientists are hopeful that the southernmost dam on the Alabama River could be opened for a short time during the spawning season, and that fish ladders might be constructed at the dam to allow free passage up river for any sturgeon. Even so, it may, after all, be too little, too late. With a known population that currently stands at two, and even if there are a few other individuals out there, it’s quite possible that we may soon see the last of the Alabama sturgeon. Unfortunately, the same might be said of another bottom-dwelling river fish half a world away in China.
CHINESE GIANT PADDLEFISH
Struggling to survive in the same horrendous environmental conditions in the Yangtze River as the Baiji, the Chinese paddlefish is a giant among giants in the contest for the world’s largest freshwater fish, reaching seven metres in length. It dwarfs the closest runners-up, the European catfish and the white sturgeon, neither of which reaches the five-metre mark. Locally it is known as the elephant fish, both for its size and for its long snout, which is one-third its body length. Though its appearance is reminiscent of a sturgeon, the two aren’t closely related. The last confirmed sighting of one was back in 2003.
Living for up to 50 years, the Chinese paddlefish is one of only two species of paddlefish on earth, the other being the much smaller American paddlefish. Despite inhabiting the Yangtze River, where it has co-existed with millions of people for thousands of years, its habits remain obscure. Surpassed in size by few freshwater predators, it feeds on fish and crabs, and may also use electrical receptors along its long snout to help detect zooplankton in the water. Though it’s never been confirmed, scientists suspect that Chinese paddlefish are anadromous, which means they live some of their lives in the marine environment before migrating up the Yangtze River to spawn (similar to salmon in other parts of the world).
Historically common, the fish’s population had been steadily decreasing during the 20th century, mostly because of overfishing. The population plummeted after the Gezhouba hydroelectric dam was built in the mid-1980s. This giant barricade effectively severed the Yangtze into two rivers, an upper and a lower, thus separating the paddlefish’s feeding grounds from its spawning beds. Fish trapped upstream by the dam might be able to spawn, but they’d starve. Those trapped below could eat but produce no offspring. The beleaguered fish couldn’t have it both ways: its life cycle was cut in half. Another nail was added to its coffin with the construction of the world’s largest-ever hydroelectric project.
Begun in 1994, the Three Gorges Dam is located just 50 kilometres up river from the Gezhouba project, further fragmenting the already truncated paddlefish habitat. The Three Gorges Dam has proven to be an ill-conceived behemoth. It has created a 600-kilometre-long reservoir that has displaced 1.2 million people, while submerging 13 cities, 140 towns, 1,350 villages, and countless archeological and burial sites under 100 metres of water. Hundreds of factories, waste dumps, and mines have also gone under, releasing untold thousands of tonnes of toxic waste into the river’s ecosystem. And there are more dams to come: plans are afoot to build two additional ones upstream. The once-mighty Yangtze is becoming deadlier by the minute for anything that lives in it. Or beside it. Just ask any of the million or so environmental refugees whose homes now lie at
the bottom of the Three Gorges’ gigantic, polluted reservoir.
Despite all of this, and the fact that an extensive three-year search beginning in 2006 failed to find even a single Chinese paddlefish in the river, not everyone has given up on the species. It is still listed as critically endangered on the IUCN Red List, and scientists such as Qiwei Wei, China’s foremost authority on the paddlefish, feels that sonar surveys and net-capture surveys might have missed fish that were hiding in “holes” or along rough bottom areas in the Upper Yangtze. Adding another glimmer of hope for the species is the reported capture and death of a large paddlefish because of illegal fishing in 2007. However, even Mr. Wei has modest expectations: he thinks at most only a dozen of the world’s largest freshwater fish might survive.
9. In an ironic but not surprising twist in a country that has been deregulating itself wholesale at the behest of corporate America, today the US Endangered Species Act has itself become endangered. The legislation is being frayed around the edges by the constant attack of big business pro-development/anti-conservation forces in the United States. The recent de-listing of the still-endangered gray wolf in parts of the west is a good example of this.
UNEXPECTED ENDANGERMENT: INSECTS
The insects are the most abundant and diverse group of animals. Rough estimates of the number living at any one time is 10 quintillion (that’s about one and half billion of them for every human on earth). There are about 750,000 kinds described by science, or almost 20 times the variety of fish, amphibians, reptiles, birds, and mammals combined. Scientists who tally such things predict millions more species are waiting to be discovered. In spite of this, over 700 species of insects—and that’s of just the 3,300 that have been assessed so far—are listed as threatened with extinction on the IUCN Red List.