The World's Rarest Fish is Where? The Most Restricted Vertebrate Habitat on Earth

There is a lonely nondescript mountain of limestone in the barren desert east of Death Valley National Park. There is a hole at the base of the slope, the entrance to a cavern. Lurking within are prisoners, creatures that have been trapped in the cave for perhaps 20,000 years or more. They are mutants, no longer the same as their cousins who live freely just a few miles away. They are alone in the world.

That sounds kind of dramatic I suppose, but all of it is technically true. The story becomes a bit stranger when one realizes that the trapped creatures are fish. In one of the driest climates in North America.

During the Ice Ages between 1.8 million and 10,000 years ago, glaciers in the Sierra Nevada were constantly melting in their lower reaches, and some of the resulting streams and rivers drained into the desert regions to the east. The faulted valleys would fill with water and spill over into the next so that at times an entire network of lakes and rivers existed. At some point a connection was made with the Colorado River system and fish worked their way into the widespread habitats. Dozens of species thrived in the freshwater lakes.

But then conditions began to change. The climate grew warmer and the glaciers mostly melted away. One by one the lakes dried up as the rivers that once fed them turned to trickles and then disappeared. Most of the fish died out, but here and there springs or remnant lakes allowed some species to survive. The most isolated species of them all lives in this one hole, the Devil's Hole. The Devil's Hole Pupfish (Cyprinodon diabolis) is in all likelihood the rarest fish in the world. There have never been more than five or six hundred of them, and their population has reached lows of only three dozen at times. They are living at the extremes, as the water is at a constant temperature of 93 degrees. Only a few other species of pupfish can survive those kinds of temperatures (you can read about some of the other species here: http://geotripper.blogspot.com/2015/02/you-think-some-fish-you-caught-was.html ).

Their rarity explains the monitoring equipment and fencing that surrounds the cavern opening. The pool is visible from in side a caged tunnel, but the individual fish are a bit difficult to see. They're only an inch long, and the viewing platform is around a hundred feet away. I saw nothing on my previous visit five or six years ago, but this time I did.

The efforts to protect the fish almost became their undoing when a 2004 flash flood dumped the monitoring platform and other debris into their pool. Something like a third of the population was lost. The platform was gone and there was a limited amount of equipment. And, there were three squares of what looked like white astroturf in the water. I don't know their purpose, but one idea is that they may protect eggs. Or maybe someone was making it possible to see the fish from so far away.

The fish feed from the algae covered bench on the near side of the pool. That bench was the crux of a Supreme Court decision in 1976 that prevented the extinction of the fish. At the time developers were digging deep industrial wells to promote the agricultural development of the adjacent valley, and the water level at Devils Hole began to drop. The court put a stop to the drilling, and the surrounding region became the Ash Meadows National Wildlife Refuge. It turns out to have been an astonishingly lucky turn of events, as the refuge has the largest concentration of endemic species in the continental United States (Hawaii is the only state with more endemic species).

In any case, I got to see the Devils Hole Pupfish, the rarest fish on the planet, for the first time ever. Thank goodness for a good zoom lens (bring binoculars or a good camera if you ever visit). The squares are only a foot or so across, but one could make out the shapes of the fish as they swam over the light colored material.

So here is the cropped and enlarged version of the image above, which doesn't show much, but remember I was more than 100 feet away.

If it helps, here (from the interpretive sign at the site) is what they really look like:

I even managed to get a very short video of the fish (all of 8 seconds or so).
It's not every day that one can see the rarest of anything. If you ever find yourself in the Death Valley region, don't pass up the opportunity to see these fascinating creatures. They could be extinct any day despite our incredible efforts.

The Last Animal Anyone Expects to Find: The Rarest Creature in Death Valley

Looking over the blasted barren rocks of Death Valley National Park, one is struck by the apparent lack of life. A region that averages less than two inches of rain in a year, with summer temperatures regularly topping 120 degrees, is just not going to have a lot of moisture left over to support life. and yet life persists, and sometimes in incredible ways. Hundreds of species are found in the region, including dozens of endemic and endangered species.

What is the last kind of animal you would ever expect to find in a place like Death Valley? Here's a candidate: in an outlying part of the park, just over the border in the state of Nevada, there is a barren hillside of carbonate rock (limestone), that has been twisted upwards and fractured. Strolling towards the base of the hill, one notices a cavern opening surrounded by reinforced fencing. It's a deep cave, more than 900 feet, but surprisingly, it is filled with groundwater at a constant temperature of 92 degrees.

Looking through the fence, one can see the small pool of water at the bottom of the narrow cleft. The monitoring equipment is a clue that something extraordinary lives here. It's a fish! And not just any fish, it is probably the rarest fish in the world, the Devil's Hole Pupfish. The species has lived in this little bit of water for the last 20,000 years, when it was isolated here by the drying of the glacial meltwater lakes that punctuated the Death Valley region. Through droughts, climate change, cooling, and in the last few years, interference by human beings, the little community of a few hundred individuals has grown, reproduced and died in this opening.

A few decades ago, as many as 600 fish lived here, but by 2004 the population had crashed to just over two dozen individuals. The population had recovered by 2007 to 126 fish, but their continued existence will always be tenuous. They would have been extinct in the late 1970's had the Supreme Court of the United States not stepped in. It was an early major test of the Endangered Species Act. As can be seen below, major efforts have been expended to monitor the health of the population.

It is not really possible to see the individual fish at Devils Hole, but a much larger and more stable population of a related species can be seen a few short miles away at Ash Meadows. The pool below is Crystal Spring, which produces 2,600 gallons per minute of 87 degree water. The Ash Meadows Pupfish lives in the pond and nearby stream, and is far easier to see, as we did today.

My picture of the Ash Meadows fish didn't come out, so I am slipping a picture of the Salt Creek pupfish from a previous trip. The Salt Creek fish live in the bottom of Death Valley not too far from Furnace Creek Resort.
Four species of pupfish live in various parts of Death Valley, with some living in the hottest and saltiest water of any fish species on the planet. Others live in fresh water. They are all descended from a single species of pupfish that lived in the glacial meltwater lakes of the ice ages. An example of real resilience in the face of difficult conditions!

I Don't Believe in Evolution Either...

I'm off to Death Valley for what promises to be a wet and wild weekend in drought-stricken California. The storm door is open across the state, and I am sincerely hoping that the rain and snow can ease the dry conditions. That remains to be seen, of course. I just don't know why the storms seem to be always coming on the Presidential Birthday weekend when I take the students on our long field trip.

In addition to a presidential birthday, it also happens to the be the 200th birthday of Charles Darwin. When I am making my way across the desert in the next few days, I will have a few opportunities to meditate on the intellectual advances that he and Alfred Wallace introduced to the world of science.

Like the Ethical Paleontologist, I would like to state here in no uncertain terms that I DO NOT BELIEVE IN EVOLUTION. Of course, I also don't believe in gravity, and I most certainly do not believe in atoms. What I DO believe, especially in the subject area of higher beings, is actually not your business, and is not germane to a discussion about evolution. If you would like a serious discussion about such issues, you are free to contact me in other ways.

Of course, despite my professed non-beliefs listed above, the world continues to behave EXACTLY AS IF evolution, or gravity, or atoms exist. My continued existence is in fact possible only because each of these phenomena do exist, and science has provided a framework for understanding each of them. In the case of evolution, my continued existence is actually threatened as I continue to fight off an infection that has proved resistant to antibiotics (don't worry, it's not that serious yet).

Death Valley National Park is a place to witness a few incredible examples of evolutionary change in action, both in the past and in the present day. The park contains something like seven vertical miles of sedimentary deposits that preserve one of the most complete fossil records of the development of life from over a billion years ago to the end of Paleozoic time to be found anywhere. The first picture above is a trilobite that same or crawled in the Cambrian coastline around 520 million years ago. Thousands of species evolved over millions of years before they went extinct around 250 million years ago.

The innocuous-looking fish in the second photo are cyprinodon pupfish, one of the most unlikely living creatures to be found in the driest place in North America. Sorry for the photo quality; they aren't easy to photograph. The pupfish are the ancestors of a species that lived in the Colorado River system and in fresh-water lakes that filled these desert valleys during the Pleistocene Ice Ages. As the ice ages ended, the lakes dried up, and doubtless many species and individual fish perished, but in a few watercourses and springs a few of the pupfish survived. In the last few tens of thousands of years, some of the fish populations thrived in freshwater springs, but others were trapped in increasingly salty ponds and creeks (like Salt Creek on the floor of Death Valley). The fish adapted to the conditions, eventually forming at least four or five species, and perhaps a dozen subspecies. No other fish is known to survive in water as salty as one of the species, and one of the species is known to survive in 100 degree conditions. No other fish is that hardy. Others survive in freezing conditions.

The most familiar species is the Devils Hole Pupfish. The entire species lives in a single water-filled cavern opening in the Ash Meadows area east of the main park. In that one hole, they have survived for thousands of years. Their population crashed a few years ago, down to a few dozen, but they may be recovering (several have been taken to other refugia to preserve the species in case of disaster).

They are luckier than the Tecopa Pupfish. The entire species was wiped out in an afternoon when bulldozers destroyed the springs they lived in to build a hot springs spa in the 1940's. What a shame to lose out due to human interence after so many thousands of years.

Happy birthday, Mr. Darwin! You enriched our understanding our world in many ways!