Category: Invasive species

You’re calling me a . . . WHAT?

In the midst of a pandemic, climate change, and the resurgence of fascism, it wouldn’t seem that a warning about a fish from the Virginia Department of Wildlife Resources (DWR) could be that big a deal.

According to the DWR, the Alabama bass has invaded some of Virginia’s big impoundments, and it continues to move north. I checked in with Maryland and West Virginia, and they’re bracing for the new fish as well. 

As I dug deeper, I began to realize that the DWR threat alert has less to do with any objective reality about the world out there, but a lot to do with the subjective reality in people minds. It’s mostly about us, and about what we think and do. It’s a complex story, full of twists and turns, sometimes funny and ironic, but other times disturbing.

A brand called “bass.” Let’s begin with a paradox: How could anybody have a problem with a fish called a “bass?”

Some of us even honor the bass with a place on the Christmas tree.

“Bass” is the most iconic name in America’s ichthylogical lexicon. It’s a familiar, friendly word. When you say it, your mouth opens into a relaxed smile. The word is a seal of approval that signals “good to catch,” “good to eat,” “good to think.”

As a brand name, we pin the label “bass” onto a lot of fish that are not really bass at all, just because we like them or because we want others to like them (see A Name by Many Other Fish). We don’t care that that the Alabama bass and the other dozen or so black bass species in North America are actually kinds of sunfish.

As a small boy I caught many sunfish (my mom called them “round fish”), but the fish I proudly brought home to show my parents was a largemouth bass (a “long fish”), all smelling of muck and algae from the little farm pond where I caught it. Today, my fish of choice is the smallmouth bass, the star of the Potomac River.  

Motor roaring, gelcoat gleaming, a bass avatar races to some secrete cove.

Aggressive and hard-fighting, bass rank number one with anglers, according to a US Fish and Wildlife study. They swim at the center of a sport fishing subculture that accounts for a large share of the $70 billion generated annually by freshwater fishing. The avatars of the sport zip around reservoirs in metal-flaked gel coat speedboats that can cost $50,000.  

The bass is also a handsome creature, with the classic lines of what we think a fish should look like. If a child draws a fish, chances are it will look like a bass. Among the various black basses, the Alabama bass stands out, its golden green flanks punctuated by a row of dark spots.

Fighting words. So again, how could the Alabama bass ever be a problem? I went back to the Virginia DWR website to search for clues. As expected, I found the usual Ecology 101 explanation of how a species entering a new ecosystem can sometimes overwhelm and outcompete native species. If they succeed, they’re invasives. If they don’t, they’re just fish.

But the DWR had a far more potent argument for why this native of the Mobile River watershed poses a threat to Virginia than the quantitative evidence of population biology. The really powerful pitch comes from the qualitative power of words.

It turns out that the DWR had put the Alabama bass on its Predatory and Undesirable Species List. If you want to vilify a fish or anything else, you can’t do much better than label it a “predator” and “undesirable.”

Let’s take a closer look at these two words, starting with “predatory.” The term conjures up the media-stoked imagery of ferocity, viciousness, stiletto teeth dripping blood, a threat to suburbia, dogs and small children, God and country.   

But in the real world of biology, a predator is simply a creature that makes its living eating other creatures. It’s not a word meant to condemn or to pass judgment. It simply describes the place a creature occupies on the food web. Of course bass are predators, along with trout, tuna, perch, and most of the other fish that we esteem. Take a look in your fishing tackle box at all of those lures that resemble minnows, crayfish, worms, and bugs, all designed to attract the kinds of fish we like the most, all predators. I’ll bet you don’t have anything in there that imitates algae, duckweed, or bladderwort. I’ll bet you can’t even name a fish that is strictly herbivorous.

A predator is no more loathsome than an omnivore or an herbivore. Either out of ignorance, carelessness, or craft, the DWR is simply weaponizing an otherwise perfectly useful word.  

An “undesirable.” But the second epithet in the title of the DWR’s list gets us into dangerous terrain. “Undesirable” is not merely a descriptive term, such as “predatory,” but judgmental. It doesn’t describe a creature—even misleadingly so—but rather how we should feel about it. It is a word that takes us into a dark realm of human psychology, where it has helped drive some of the most shameful events in our country’s history. It’s a word that conjures up the “other,” the unknown, the treacherous, the unclean. It’s not a word of science, but of nativism and of hate-mongering mythologies.

An “undesirable” gets an unequivocal “no” from a representative of America’s Great Race in a cartoon from the turn of the last century.

I’m particularly thinking of our country’s history of immigration. The Immigration Act of 1882 identified foreigners deemed “undesirable” for entry into the US, a category that would be broadened in succeeding years to keep out poor people generally. In 1903, the Immigration Restriction League, alarmed at the influx of peoples from Southern and Eastern Europe, issued a report that identified those immigrants it deemed “undesirable.” The Undesirable Aliens Act of 1929 Act criminalized crossings on the southern border as a way of barring Mexican immigrants. 

Great Race under siege. This was a period in US history when the country’s scientific and political elites promoted the hollow concept of race and the misguided theory of eugenics. They insisted that human races and ethnic groups are non-equal and must be kept separate. Immigrants, they warned, were inferior, both mentally and morally, to the native descendants of Northern and Western Europe, which a leading public intellectual of the time called the Great Race. In only one way were the immigrants superior: producing large numbers of children. Even worse, immigrants were interbreeding with the native (white) existing population. If left unchecked, undesirable immigrants would turn America into a land of imbeciles and degenerates.

In much the same way, the Alabama bass can  “genetically pollute” the “native” bass population as it creeps northward from its original range, states the website of Maryland’s Department of Natural Resources. Particularly at risk are America’s “Great Races” of fish, the largemouth bass and smallmouth bass.

“They’re not sending us their best.”

Starting to sound familiar? Let’s imagine that there is such a thing as a Mexican bass (Micropterus mexicano), and that its population is expanding north, crossing the Rio Grande and into Texas and beyond. “They’re not sending their best,” Donald Trump would have thundered in the 2015 speech in which he announced his candidacy. “They’re sending fish that have lots of problems, and they’re bringing those problems with them. They’re bringing crime. They’re bringing murder. They’re rapists.”

Change denial. The idea of keeping races pure depends on how we think about change in the natural world. Before I saw the DWR website, I might have regarded the expanding range of the Alabama bass as another example of the mixings and migrations and emergences and extinctions of life on earth that have been going on since life began. But most people take a more immediate view of nature. For them, nature operates in a time frame defined by human life spans or stories in the Bible. They seek safety in the bubble called the status quo, like residents of a gated community with a 24-hour security guard.  

The idea of an ever-mutating natural world also runs counter to the mission of a state wildlife agency. The mission of the agency is to protect the environment. But which environment? The concrete, objective environment that you can see and touch and feel? Or the one that the agency’s constituents regard as normal? 

As stamp collectors collect stamps Linnaeus (aka Linné) collected plants and animals, gave them Latin names, and organized them according to his revolutionary system.

Even up two a couple of centuries ago, the intellectual elite assumed that we live in a static world: After the Biblical flood, nothing much changed of any consequence. Carl Linnaeus, the founder of modern taxonomy and also a highly religious man, summed up his faith and his work in the phrase, “Deus creavit, Linnaeus disposuit” (God created, Linnaeus organized). Each species inhabits its own box, sturdy and impenetrable.  Largemouth bass have always been largemouths, and must remain so. Lions are lions, and could never share genes with tigers (in fact, they can).

People still believe in this view of natural history, and I found many of them at the Creation Museum in northern Kentucky a few years ago. Sneer as you want at this temple of Biblical literalism, but I genuinely enjoyed spending three days there exploring a view of science embraced by millions of believers. I saw dioramas where humans mingle with dinosaurs. I spoke with interpretive guides who were unquestioning in their Bible-based view of the creation. I attended lectures given by PhD “scientists” who could overwhelm skeptics with rapid-fire facts and Biblical references.  

But facts don’t add up to science. In many cases, they’re rooted in anecdotal and myth-based assumptions that can ensnare long-ago taxonomists and present-day creationists, as well as the folks at state fish and wildlife agencies. If the Creator had anything to do with laying these traps He must have had a sense of humor, just like my own Patowmack the Trickster, the guiding spirit behind this website.

Taxonomic tempest. One such clever trap has to do with boxes, a standard prop of magic shows and pop-up toys for small children. Recall that Linnaeus created taxonomic boxes, each of which contained one species, as it always had and always will. The box occupied by the Alabama bass today carries the label Micropterus henshalli, the fish’s scientific name.

When people think about taxonomy, if they think about it at all, they conjure up notions of anonymous toilers in the vineyard of science, their eyes bleary from hours bent over microscopes. But not when it came to writing the taxonomic history of the black basses. Here we find a tale of buffoonery, comical errors, twists and turns, and ultimately, findings that pull the rug of scientific gospel out from under the dire warnings about the Alabama bass.

Briefly, the tale goes as follows. All black bass are members of the genus Micropterus, a name that was created by French naturalist Bernard Germain de Lacépède in 1801, when he received a smallmouth bass specimen for study. He noted its diminutive (micro) dorsal fin (pterus), the inspiration for the name. Unfortunately, Lacépède didn’t realize that the fin was small because several of its rays apparently had been bitten off when it was young.

Along with black bass taxonomy, Henshall offers practical advice to the angler, such as the proper form for casting to the left.

The species name, henshalli, honors Dr. James A. Henshall, revered by the literary subset of the angling fraternity (there are some!) as author of the 1881 classic Book of the Black Bass. In a prose both dry and sly, Henshall recounts the deliberations, disputes, and missteps of scientists―mostly French―who gave the different bass species their scientific names. It could only have been described as a farce. In one instance, a haughty Professor Rafinesque proposed different names for the same bass species, each name corresponding to a different size fish. For the largemouth bass alone, these learned men of science delivered up some 57 judgments and a minor lexicon of Latin names, according to Henshall. “The scientific history of the Black Bass is a most unsatisfactory one,” he concludes.

In the end, Henshall explained this comedie taxonomique as an example of Gallic people “indulging their national love of novelty.” But, as we’ll see, later scientists, politicians, and bureaucrats solemnly used these same taxonomic distinctions as criteria for formulating environmental policies.

A leaky box. Let’s take another look at the taxonomic box that contains the Alabama bass and see how sturdy it really is. Is it a box for eternity, or for some lesser span?

We first see that the box containing the Alabama bass is still shiny and pristine. And no wonder, since it’s practically brand new, dating back to only 2010. Before then, it was safely stuck inside another box containing the very similar-looking spotted bass, since it was regarded as a spotted bass subspecies. (For its part, the spotted bass was described scientifically only in 1940.)

The Alabama bass shed its subordinate rank thanks to the development of conceptual tools that would give biologists a far more detailed and accurate understanding of the evolutionary  relationships among living things. By using these new methods, called phylogenetics, biologists came to the agreement that the Alabama bass was a separate species. In 2010 it was officially recognized as such.  

And so, for some 70 years, the fish we now call the Alabama bass was considered a kind of spotted bass, which is a proud native of southwest Virginia, and not an alien and certainly not an undesirable. But when scientists found the Alabama bass to be a separate species, it lost its Virginia residency status. One stroke on a biologist’s return key turned what had been a native fish into a non-native, an esteemed bass into an invader.   

More leaks. But although the taxonomic box containing the Alabama bass is phylogenetically valid, it is itself full of holes. As with other species of black bass, the Alabama bass can freely hybridize with other members of the larger bass community, notably with the largemouth and especially the smallmouth.  

It reminded me of the fears the eugenicists had over the impact of immigrants on the Great Race. It was bad enough that they were arriving on our shores and packing into crowded tenements—boxes for undesirables—in the big cities. Even worse was the threat that they and their genes would leak out of these boxes and into the general population.  

Ironies of invasion. Into this muddle steps another reality, further complicating the meaning of native/non-native and desirable/undesirable. It turns out that the Alabama bass is no less “native” to Virginia and Maryland than the “native” largemouth and smallmouth bass it presumably threatens.

The largemouth’s original range (at least back when people started recording such things) encompassed the Mississippi River basin, the southern Atlantic seaboard, and a few other places. People liked it, and so government agencies teamed up with eager fishermen and landowners to release it into lakes and farm ponds throughout much of the US. No worries that the newcomers reduced or eliminated existing populations of many native fish and amphibian species.

From there the largemouth spread around the world. In some places, the people welcomed the new fish. I once was proudly served largemouth bass on the shore of Lake Yojoam in Honduras. The whole fish came to the table deep fried to a golden brown, flanked by black beans and tortillas. On the other hand, the Japanese consider it a threat to their own native species.  

The same goes for the smallmouth bass. Its original range included the St. Lawrence River, the Great Lakes, and part of the Mississippi River basin. It’s now established throughout much of the US and elsewhere around the world. One of the earliest introductions was carried out by a General William Schriver (he wasn’t really a general, like a bass is not really a bass), who used the newly completed railroad connection to the Ohio River town of Wheeling to ship smallmouth fry over the continental divide to the Potomac. Despite the explosive impact the smallmouth surely must have had on the Potomac’s native fish populations, the general’s act was widely praised.

For its part, introduced smallmouth have decimated populations of native fish and amphibians. In the Pacific Northwest, smallmouths consume up to 35 percent of outmigrating salmon, a fish which is already in a very precarious situation due to dams and development. In the Potomac River, the introduction of smallmouths may have lead to the demise of a population of trout-perch, an elegant little fish with spotted sides.

Plastic bags and tiny fish. As we’ve done for thousands of years, when we come across a plant or animal we like in our travels, we bring it home. Sometime the outcomes are good, sometimes not.

Fishermen mostly like the Alabama bass. Many call it the ‘bama bass. Imagine a couple of buddies in a pickup driving from Virginia drive down to Alabama to visit kinfolk. They do some fishing and manage to net some Alabama bass fingerlings, which they stick in a plastic bag full of water. Hopefully they’ll survive the trip home where the fishermen will dump them into a local lake.  

It would seem like an innocent act, even rising to a First Amendment right protecting a person’s esteem for the fish of their choice. But not in the eyes of government fish and wildlife agencies, which condemn such acts as forms of environmental vandalism.

“Anglers are the primary vector for the spread of Alabama Bass in Virginia,” according to the DWR. “Current populations are the results of angler introductions that have occurred over the last ten years.” Fishermen as vectors? Here we go again with the loaded words. In epidemiology, a vector is an organism that does not cause disease itself but which spreads infection by conveying pathogens from one host to another. Think mosquitoes, bats, ticks, snails, fleas. And if fishermen are the vectors, the fish are the disease.

Oops, never mind. When it comes to introducing new species, the bad guy is the one with the bag; the good guy is the one with the badge. One gets a fine and the other works for a government agency that issues a celebratory press release when it introduces a new species. The press release touts the admirable qualities of the creature and describes how its introduction will “expand recreational opportunities.”

Jonah’s whale didn’t have much over the formidable vacuum cleaner state biologists released into Virginia.

No surprise that the state biologists don’t always get things right, such as when Virginia introduced the blue catfish into Chesapeake Bay tributaries in the 1970s. A native of the Mississippi River drainage system, this monster grows to well over 100 pounds, fights like a bulldozer, and is good to eat. But it’s also an aquatic vacuum cleaner that consumes most anything it can get its mouth around, which is just about everything. Today, it continues to increase its numbers, and in some places accounts for 75 percent of fish biomass. The losers in this game of species roulette are the native fish and crabs that the state agency is supposed to protect. Oops.

In other cases, government support for introduced species creates scenarios that could be written by the Jokester Creator or my Patowmack the Trickster. For example, Maryland’s Department of Natural Resources monthly report touts the risk assessment it’s preparing for the “potentially invasive” Alabama, and then goes right on to highlight its work in promoting other non-native species: brown trout (from Europe), rainbow trout (from the North American west), tiger muskellunge (cross between muskellunge and northern pike, upper Midwest and Canada), northern pike, smallmouth bass (upper Mississippi basin), and the walleye pike (Canada and northern US).

The bottom line. Just when it looks like the Alabama bass issue has devolved into a game of leaky taxonomy and fuzzy thinking, along come some actual facts that may or may not concern fishermen.   

As the state agencies say, the Alabama bass has sharp elbows. It rapidly expands its population and outcompetes native species, at least for a while. In North Carolina’s Lake Norman, for example, numbers of largemouth bass dropped to less than 8 percent of their former abundance after the new bass’s introduction.

At first the Alabama bass grow big in their new homes, but then their average size falls as they eat their way through the prey species. A lake formerly holding 2-3 lb largemouth or smallmouth bass will end up being dominated by 1 lb Alabama bass, according to Virginia’s Department of Wildlife Resources. Fishermen want big fish, and particularly so if they bought a $50,000 bass boat to catch 3-lb fish. If they’re now catching 1-lb fish, it’s like their boat lost 2/3s of its value (of course, I’m no economist).

In any event, the stakes can be high. The Virginia DWR estimates that 60 percent of fisherman target largemouth and smallmouth bass during the course of a season, and spend “millions of dollars” in the process. “Declines in either population will result in not only the loss of sportfishing opportunities, but in economic harm to the region,” according to the agency.

Of course, nature doesn’t care about such things as fisherman satisfaction and economic benefits, but they matter to anglers and to the businesses that supply them with rods, reels, boats, plastic rubber baits, beer, guide services, and everything else 21st century Americans need to catch a fish.

In this sense, the problem with Alabama bass comes down to what fishermen are presumed to want, what government fisheries managers are able to do about it, and the complete lack of interest the fish themselves have in these issues.

As they always have been, the black bass tribe and their environment are works in progress, shape-shifting and boundary crossing without regard to the policies of government biologists or the whims of their angler admirers.

Why do weed warriors love to hate the garlic mustard?

The garlic mustard: From potherb
to invasive species of choice.

This is the time of year when weed warriors armed with shovels and pruning shears do battle with that subset of the plant kingdom called Invasive Plants. They march into woods and fields, fearless in confronting any leafed alien that poses a threat to our native plants. They emerge at the end of the day exhausted from their pulling and hacking, often with arms bearing badges of honor in the form of nasty scratches and cuts.

Clearly not all weed warriors fit this heroic mold. There are many others—perhaps the majority—who also believe fervently in the crusade against alien plants, but not so much in hard physical labor. They opt to express their beliefs in symbolic acts, a little like casual church-goers or Earth Day marchers.

A devil’s nursery. I recently came across what seemed like an illustration of this idea at a place near the Potomac River called Hughes Hollow. It’s a kind of “natural” area, favored by birders, where a system of canals and sluice gates control the water level of two artificial ponds covered with lily pads.

A dirt road runs across a dike at Hughes
Hollow, an unnatural area brimming
with life, both native and exotic.

A dirt service road separates the two ponds. Alongside grows a tangle of plants, nearly all of them non-native species. For a weed warrior, I’d imagine it’s like walking down the aisle of a devil’s garden nursery.

As for myself, I admired the exuberance—if not the purity—of this plant profusion. Bumble bees buzzed past my head as a yellowthroat warbler went “witchety-witchety-witchety” in a stand of willows.

A modest experiment. I walked along for a short distance, and then I came upon something curious. It was a neatly laid out stack of withering plants, followed by another, then another.

A withering bunch of garlic mustard
lies on a bed of more fortunate invasives.

The plants were garlic mustard, widely distributed in the Old World. It was brought to our shores in the middle of the 19th century to perk up the salad bowl and vegetable pot with its garlicky flavor.

Out of all of these invasive species it appeared that the weed warrior only pulled out garlic mustard. I found no sign that any of the other invasive plants along the roadway had received similar treatment. Why ?

I had a suspicion, but I needed to confirm it by performing an experiment. My method of analysis would be straightforward, requiring no replication, peer review, or even any actual data. I would simply walk down this service role and pull on every plant I encountered. I set off on my botanical adventure.

Death to dandelions! I first approached a dandelion. I admired the fierce yellow of its blooms, rivaling the sun itself. Italian immigrants once used its bitter leaves in salads. I knelt down and hooked my forefinger around the plant’s stem, right at ground level, and gave it a yank. All I came up with was a rosette of leaves oozing white sap from their base.

My next intended victim was vetch, a plant of slender vines, purple flowers, and delicate compound leaves. The nodules on its roots contain bacteria that convert nitrogen from the air into a form usable to other plants. Again I knelt down. With my fingers I traced the plant’s sinewy stem through the neighboring plants until I found where it entered the ground. This time I pulled more gently. But the results were the same.

Equal-opportunity invasive. I tried uprooting one non-native plant after the other. Some were tiny and delicate. Others were thorny and prickly. In all cases, try as I might, their roots refused to give up their hold on soil from which they sprang.

With one exception. As you have already guessed, it was the garlic mustard. I found a small patch that the weed warrior had evidently missed when he passed through earlier.

Their stems were tall and easy to spot and substantial enough that I could get a firm grip on them. I didn’t even have to kneel down to do so. I pulled, and as I knew would happen, out they came, roots and all. It was almost like these latter day pot herbs welcomed their demise.

I lay my first bunch down on the side of the roadway. I pulled up several more and lay them over the others, noting how naturally they seemed to nestle into a state of repose, like cordwood or neckties in a bargain bin.

This was all the proof I needed. Weed warriors love to pull out garlic mustard because, well, it’s easy to pull out. Science doesn’t always have to be complicated.

The Potomac’s hard-working immigrant

Seeing the bottom of the Potomac River through a facemask is a little like looking through a microscope. It’s a new world down there, and you never know what you might find.

I was looking sponges. The previous year they were right here, at the head of Watkins Island, near Pennyfield Lock. It was apparently the first sighting of sponges in the river’s main stem. What happened to them? Would they come back?

I examined the bottom minutely, admiring the shimmering pebbles and the green patina on the mussel shells. I poked at anything that looked even the slightest bit spongy.

The clams suck water into one
opening and expel it out the other,
removing silt and other pollutants.

Then I saw something that made me come to a full stop. Wedged among the pebbles was a pair of tiny white tubes, then another, and another. Hundreds of them. I had found a colony of freshwater clams.

This was interesting, but not because clams are unusual in the Potomac. Far from it. The shells of this little bivalves literally pave parts of the river in Montgomery County. Along some stretches of shoreline, their shells crunch under every footstep.

But I had never seen these little creatures actually at work. And here they were, drawing water through one tentacle-lined tube, retaining nutrients other matter, and then expelling the same water through the other tube.

It struck me that they might be a little like the Higgs boson of the Potomac. Even though most people don’t know anything about them, their vast numbers could give them a decisive role in the river’s ecology. Are they another of Charles Darwin’s humble creatures that rule the earth, such as the  barnacles that were the subject of his first book and earthworms which he lovingly saved for his last?

Oysters of the Upper Potomac. It seems so, at least according to biologist Harriette Phelps, a professor emeritus at the University of the District of Colombia. Phelps is widely known for her work with this clam species in the tidal Potomac.

Biologist Phelps sorts through
a haul of Asian clams destined
for research on pollution.

She told me the clam’s scientific name is Cobicula fluminea. Its common name will have to wait, so as not to give away the second part of the story.

“Hard working Corbicula,” she calls them. Put a layer of them on the bottom of a pail of murky water, and an hour and a half later the water will be clear. Multiply this effect by the countless millions of clams in the river, and you have what Phelps calls a “key species.”

Forget the feisty bass, the graceful heron, the majestic eagle. One of the real drivers of life in the river is this humble mollusk, most of them no bigger than a quarter. Darwin would have understood.

Corbicula almost seems designed with the express purpose of purifying water. The particles it extracts from the river are not simply cast back again. Instead, they are combined with mucus to build up the sediment in which they live.

Does this sound familiar? Elsewhere on this site I wrote how oysters were the cheapest and most efficient water purifier system in the Chesapeake Bay, until they were nearly wiped out.

Stands of stargrass grow so thickly
that canoes barely penetrate.

Clearing up the water kicks off a chain of happy events. More sunlight penetrating the water fuels the growth of aquatic plants. With oxygen-producing plants come fish and birds, and pretty soon, the river environment becomes whole again.

Phelps saw this happen in the tidal Potomac.  There’s “absolutely every reason” to assume that Corbicula is providing the same service in our upstream portion as well, she says.

Certainly something good is going on out there. In some places in the river, plants are so thick that you can barely plow your kayak through them. In the channels through the vegetation you see darting shoals of minnows and bass slipping back into the cover. Big catfish chug along the bottom like monster tadpoles.

A dark secret. But these sunlit waters contain a dark secret.  Corbicula is not a native of the Potomac region or anywhere else in North America. It originally came from eastern Asia, and is know by the popular name Asian clam. It arrived first on the West Coast around 1930, then showed up in the Potomac in 1977.

Once in the Potomac the clams rapidly increased their numbers, carpeting many parts of the river bottom. This would seem to qualify Corbicula for membership in that increasingly familiar “genus” of the world of advocacy ecology called “invasive.” Here we have another foreign creature that has invaded our own natural communities, like a shiploads of Vikings burning monasteries, slaughtering townspeople, and carrying off treasure.

Clam gathering isn’t much
sport, but it’s a sure thing.

But not according to Phelps. “Corbicula were not invaders,” she said emphatically. “They occupied areas that were previously unoccupied.” And like many immigrants, they got their start by doing jobs that natives wouldn’t or couldn’t do themselves.

In the tidal Potomac, Corbicula inhabits the upper layer of the river bottom, she explained. The estuary’s native clam lives deeper down. “Even with Corbicula, the native clams are all over,” said Phelps.

Paradoxically, Phelps worries that this “invasive” species might disappear. It already has in her former study areas in the tidal Potomac. The same could happen in the upper river as well.

If Corbicula disappears, the river’s ecological clock could start to go in reverse. With no more clams filtering out so much stuff that gets washed into the river, the water could again lose its clarity, and with it, many of its plants, fish, birds, and other life forms.

Tiny, but considered a
perfect addition to soup.

The clams’ disappearance would also be felt by one group of local people whose ties to Corbicula extend to long ago and far away. You can sometimes see them, the men bent over the water, raking out clams with fan covers, the women sitting in the river, plastic baskets resting on their outstretched legs, picking the clams out from the stones and empty shells.

These people are also immigrants, harvesting the same clams in the same way they they and their families have done for many generations in their southeast Asian homelands. Following age-old traditions they will cook the clams in a wok with ginger, chile peppers, basil, and soy sauce.

Evidently it’s an acquired taste. “They’re good,” says Phelps, “but not really clam-like to me.  I like clams that are saltier.”