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Just 35 Devils Hole Pupfish Remain—Does Extinction Loom?

The views expressed are those of the author and are not necessarily those of Scientific American.

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devils hole pupfishOne of the world’s rarest fish species just got a lot rarer. The latest twice-annual count of tiny Devils Hole pupfish (Cyprinodon diabolis) at their sole habitat in Nevada has revealed just 35 of the critically endangered fish remain, down from 75 this past fall. This is the lowest count since the species was federally protected back in 1967.

Devils Hole pupfish live exclusively in a deep geothermal cavern in Ash Meadows National Wildlife Refuge, where their population has undergone precipitous declines over the past several decades for reasons that remain unclear. The 25-millimeter fish appear to be adapted by both high temperatures (33 degrees Celsius) and the water’s low oxygen content, but little else about them is understood by science. Efforts to breed them outside of Devils Hole have not been fruitful, and two captive populations died out in 2006. According to the U.S. Fish and Wildlife Service (FWS), there are now too few of them to risk transferring any more of the fish from their natural environment.

Biologist Jim Deacon, who has been visiting Devils Hole for more than 50 years, told the Las Vegas Review–Journal that he thinks the species might be approaching “genetic meltdown.” Back in the 1970s Deacon testified that local groundwater use threatened the geothermal cavern, and therefore the fate of the species. The case, Cappaert v. United States, went all the way to the Supreme Court in 1976, resulting in additional protections for the pupfish.

Local groundwater use was the first strike against the species, but even with protection the recent decades have not been kind. A flood in 2004 pushed some fish traps and several cubic meters of debris into Devils Hole, killing as many as a quarter of the fish. More recently the region has experienced three earthquakes and one major rain runoff event, which the FWS says may have influenced this year’s decline, although they do not know for certain.

FWS biologists continue to study the fish and supplement their food in hopes of keeping the population alive. They have also tried hybridizing C. diabolis with another pupfish species in the hopes of jump-starting its genetics, a controversial effort recounted in Wired last year.

Even with this year’s low count, all hope is not lost for the Devils Hole pupfish. In 2007 there were just 38 fish, but their number had rebounded to 126 by the fall of 2008. It fell again to 104 for the spring count two years ago, and then dropped to 63 in the spring of 2012. The species normally has a natural population fluctuation, with breeding in the spring and higher populations typical in the fall, but the last few years have not followed that trend. At this point we’ll have to wait to see what the October count reveals. If the population enjoys its normal autumn boom, then the fish just may have a fighting chance at survival.

Photo: Olin Feuerbacher/U.S. Fish and Wildlife Service

John R. Platt About the Author: Twice a week, John Platt shines a light on endangered species from all over the globe, exploring not just why they are dying out but also what's being done to rescue them from oblivion. Follow on Twitter @johnrplatt.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. jpersonna 9:34 am 05/1/2013

    It may actually have been a disservice to make private ownership and breeding illegal. Remember, some corals have been repopulated from aquaria to the wild.

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  2. 2. sault 10:48 am 05/1/2013

    If they let one person take a few pupfish and try to breed them, then more and more people would want to take a few fish out of Devil’s Hole and do the same. Where would you draw the line? And since the captive populations died out in 2006, it would have been a waste of fish to let private breeders take a stab at it.

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  3. 3. YangHui 10:54 am 05/1/2013

    @jpersonna: I agree with sault’s point. While in some cases private ownership and breeding can be beneficial to conservation, in this case it clearly isn’t; the population is so low that removal of fish for private breeding could push it over the edge, while it is so difficult to raise that it is very unlikely that private breeders will have a chance.

    I fear that barring another unexplained recovery as in 2008, the fish is, in fact, on track to extinction.

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  4. 4. greenhome123 1:55 pm 05/2/2013

    It says that biologist continue to study the fish and supplement food in hopes of keeping the population alive. I would not be surprised if the good intentions of the biologist are actually killing the fish. I’m sure there are many types of fish foods that contain ingredients which could be harmful to these unique fish. If scientist can’t even keep the fish alive in captivity, then they should think twice before trying to feed the fish in their natural habitat, as the fish food they give the fish may be what is killing them in captivity.

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  5. 5. Sarah J 2:48 am 05/23/2013

    jpersonna: While captive breeding has helped many species, I don’t think it could do much in this case. It seems these fish require a very specialized environment. If scientists can’t keep them alive in captivity, I’m not too confident in the ability of private breeders to keep them alive AND breed them.

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