The only remaining evidence of the Scioto madtom’s existence floats in jars of ethanol tucked in the bowels of a squat warehouse in Ohio. Extracted from its jar, a madtom carcass, with its pale flesh and dull bluish eyes, looks more like a pinky-sized ghost than a venomous, bottom-feeding catfish.

The International Union for Conservation of Nature, which organizes the international species lists, declared the Scioto madtom extinct in 2013. It had last been seen alive in 1957. But the United States still classifies the catfish as endangered, despite the U.S. Fish and Wildlife Service—the federal organization in charge of the endangered species list—agreeing that the fish is gone. Without clear incentive to delist the Scioto madtom, yet also without proof that there are any left to save, the catfish has drifted into extinction purgatory.

It might seem simple to determine when a species has gone extinct, but declaring it is trickier than expected. Researchers can’t prove that an animal no longer exists by simply not finding it when they go out looking for it. Often biologists rely on models of population trends based on extensive surveys—which are done as funding permits, not as needed—but a recent paper in the journal BioScience supports longstanding concerns that these surveys don’t always match real population trends. Biologists believe dozens of species should be declared extinct, yet remain on the endangered list. Concerns about protecting habitat and troubles determining whether these species are really, truly extinct keep these critters in a kind of limbo.

“It’s tricky because there are two competing things that are going on with keeping on [them] on the endangered species list,” says Easton White, a population biologist at the University of Vermont. “On one hand, you don’t want to make the mistake of delisting a species that is still in existence; but on the other, if you don’t declassify species that are extinct, and leave them on the endangered species list, it dramatically inflates how you’re doing, because it keeps the extinction rate low.”

Some scientists and regulators argue that it’s time to accept that the Scioto madtom and other vanished species are gone forever, and shift focus onto species that can still be saved. “People are very uncomfortable declaring a species extinct,” says Eben Paxton, a Hawaii rare bird ecologist with the United States Geological Survey. He says species like the Kaua’i ‘akialoa, a yellow-breasted bird with a long, curved beak, the greater ‘akialoa, and the po’o-uli, are among twelve Hawaiian birds that biologists agree are extinct, but remain on the endangered list. Allowing the list to remain inflated by animals that are actually extinct, Paxton argues, “could dilute the attention from the species that really need it.”

But the stakes of delisting are high. Besides preventing people from collecting, threatening, or harming an at-risk animal or plant, a species’ presence on the endangered list also protects its habitat. Once a species is officially declared extinct, those protections can be dropped. This happened in the Burma grasslands, where the supposedly extinct Myanmar Jerdon’s babbler lived. The bird’s rediscovery in 2015, 74 years after it was last seen, spurred renewed attempts to protect the grasslands. More of the birds have since been discovered and the Wildlife Conservation Society is working with the local farmers in the Ayeyarwady Delta to implement sustainable rice farming to help the birds cohabitate with the local community, says Rob Tizard, a technical advisor for the Wildlife Conservation Society in Myanmar. These kinds of habitat protections, along with species recovery efforts like breeding and reintroduction attempts, do more than just help individual species like bald eagles, black-footed ferrets, and the Topeka shiner fish—they revitalize entire ecosystems.

There’s a credibility issue, too, according to Angela Boyer of the Ohio branch of the U.S. Fish and Wildlife Service. It is important, she says, “to make sure that we’re not protecting something that no longer exists.”

But not all researchers are persuaded by that argument.

Though dramatic rediscoveries like that of the Myanmar Jerdon’s babbler are admittedly rare, some activists worry that animals like the Scioto madtom could be clinging to survival somewhere, too. The extremely rare purple catspaw mussel, thought to be extinct in 1984, was spotted in Kilbuck’s Creek in Ohio ten years after biologists had given up hope. “I’m a hell of a lot more worried about being wrong about the extinction of the madtom than some kind of political credibility,” says Kierán Suckling, the executive director of the Center for Biological Diversity, an Arizona-based environmental group active in endangered-species issues. Suckling has identified 86 species on the endangered species list that are in a similar situation to the Scioto madtom, about five percent of the 1,704 species listed. Of these species, 62 of them were likely extinct before they were even added to the list.

endangered species that went extinct
Many of these species didn’t even make it onto the endangered list until after they were already extinct Infographic by Sara Chodosh

In the case of these species, Suckling argues retaining them on the Endangered Species List is the better option. “It costs very little money to keep potentially extinct species on the ESA list (because no conservation is done for them other than an occasional survey) and may mean the difference between saving them from extinction or not if they are later discovered,” he wrote in an email. “There is little harm and great conservation benefit to doing so.”

The only Scioto madtom ever caught are the eighteen saved in the collection of the Museum of Biological Diversity at Ohio State University. Between 1943 and 1957, renowned biologist Milton Trautman caught them in a single location on Big Darby Creek where the water bounced over large stones on a sandy creek bed, making it possible for him to spot the elusive, nocturnal swimmers. Trautman never discovered the nesting habitat of the madtom, and speculated that the fish lived elsewhere during the rest of the year.

Since so little is known about the Scioto madtom, local scientists are left to speculate about its disappearance by studying its environment. “One of the reasons that the Scioto madtom disappeared, along with competition with other species, was extreme modifications to the burrows and banks of Big Darby creeks where the madtoms like to hide,” says Marc Kibbey, Associate Curator of Fish Collection of the Ohio State Museum of Biological Diversity. Development along the river had increased the area’s predilection to flash flooding and undercutting of the banks.

The area the Scioto madtom was originally discovered is the least protected part of Big Darby Creek, as most of those banks are private property, says Brian Zimmerman, a research associate in the Stream and River Lab at Ohio State University. The middle section of the river is tightly protected because of other endangered species, like the seven endangered mussels found there and in the nearby Scioto River. Zimmerman spends significant time surveying the populations of fish in the area and says the habitat protections for all these species have drastically increased the water quality, making the Scioto River the most biologically diverse river in the state of Ohio. He points out that when Troutman discovered the madtom, Big Darby Creek was at its very worst, full of field runoff and untreated sewage. “A lot of the species in the river that made it through that time are really thriving,” Zimmerman says. “Everything else has pretty well recovered so if it was still there we would find it. And a lot of people have looked.” Despite regular surveying for the past 60 years, no one has seen a Scioto madtom since Trautman’s original sighting.

One possibility is that biologists aren’t surveying enough, though it’s hard to know what is the right amount. In order to figure out if there was a minimum amount of time needed to determine how a species’ population is changing, White took the best datasets he could find across 822 species that had at least 35 years of continuous monitoring and figured out the minimum number of years you’d need to survey them on average in order to accurately predict the actual population changes that occurred. “On average, you get about 16 years is required,” White says, “but there is huge variability in that, so it really sheds doubt in using a simple rule of thumb.”

That’s about in line with the 10-year or three generations rule that the IUCN currently uses to model changes. But that doesn’t mean it’s necessarily sufficient. “It’s not really about the species, or generation time of a species, but how variable a species is from year to year,” White says. “For example, if you have a small mouse species that varies a lot per year, you could sample for a short amount of time and draw the wrong conclusion.” Based on his results, Whites says that each species really has to be modeled individually, using empirical results, or even similar species to create population models. And even with that level of evidence, extinction is still a difficult case.

“It comes down to a judgment decision, because you can’t prove extinction,” says Hawaii’s Paxton, “you can’t prove an absence.” Even for less enigmatic animals than the Scioto madtom, finding a species on the verge of extinction poses a problem: How can you tell how many of the creature are left? Paxton and others have developed mathematical models that estimate whether standard surveys miss endangered birds in an attempt to determine how many might be hiding in the Hawaiian jungle. These models incorporate estimates of population density, analyses of how well the bird hides in its environment, and information on where surveys occurred and for how long. They’re thorough, but they’re also incredibly time-consuming. The IUCN is working to incorporate this method into its own judgments of whether species are really extinct, but so far it’s not widely used.

madtom research
Scioto madtom specimens Dyani Sabin

For now, we still rely on a long, bureaucratic process for determining which species should make the endangered list. The process generally involves researchers gathering information every five years to assess a species’ status and make recommendations for conservation. These reviews aren’t necessarily new surveys. They’re more about collecting the latest information and recording any changes since the last status update.

If an animal is determined to be extinct, it goes into the delisting work plan, which is where the Scioto madtom currently resides. The last government search specifically for the Scioto madtom was in 1985, and between that and local biologists’ efforts looking for it the fish was recommended for delisting in 2009. At that point, the madtom should have gotten a specific date within a three year period by which the government would gather all the possible information available on the species, potentially including an official survey, to determine its extinction status once and for all.

Eleven years later, the U.S. Fish and Wildlife Service has still not been delisted. The fish is scheduled to be evaluated by September 2019, says Georgia Parham, a spokesperson for the U.S. FWS, and if it’s determined to be extinct at that point there will be a proposed rule to delist it. That will be followed by a public comment period and an official ruling a year later, which could schedule it to be officially declared extinct in the fall of 2020, 11 years after it was originally recommended. “People are very reluctant to give up hope,” explains Parham.

Even if it is removed from the list, Parham says, there is an emergency re-listing process should the madtom be rediscovered, so “we forestall any kind of catastrophic event.”

But Suckling at the Center for Biological Diversity worries that once a species is delisted, even an emergency re-listing would not occur fast enough to save it. Almost half of the species that have gone extinct did so while waiting to get on the endangered species list, he says, citing a Center report examining 108 U.S. extinctions from 1973-1994. And although eight species since 1995 have gotten onto the list within a year of their emergency petitions, no species has ever returned to the list after being removed. For an animal as historically elusive as the madtom, Suckling argues, agencies should be especially conservative about delisting. “For my mind, all of the stakes point toward giving the species the benefit of the doubt until it can be properly established that it’s extinct.”

But even researchers who know the Scioto madtom best say the point of no return passed long ago. “As far as we know, this one is gone, unfortunately,” says Zimmerman. Even without government requests for official surveys, Zimmerman has continued looking for the madtom during his collecting trips over the last five years. Species like the madtom that can only survive in highly specific habitats are always vulnerable, but he says it’s disappearance is nonetheless surprising because it was last found in what is now one of the most protected streams in Ohio.

“As far as the Scioto madtom, the general agreement is that it’s gone,” says Kibbey. He starts thinking out loud, reviewing the return of water quality to Big Darby Creek, the fact that he hasn’t been there himself for several years, or that he hasn’t specifically searched for the madtom. He laughs, having talked himself back around again. “Well, who knows it might be time to look again!”

As rare as rediscoveries are, they keep scientists like Kibbey and Suckling from losing track of species and from giving up hope. But Paxton, the Hawaiian ecologist, thinks that extinction declarations can have an important public impact, too. Extinction can draw attention to broad threats species are facing due to global concerns like climate change and the spread of tropical illnesses. “Often in conservation we are looking for positive stories,” Paxton says, and although extinction is not a happy topic, “I think highlighting it could be used to be sort of a rallying point.”

That moment may come for the Scioto madtom, but it’s not officially dead yet. For now, it remains a specter floating in ethanol, waiting for its final bell to toll.