Boy, those U.S. Fish and Wildlife Service guys don't waste time. Just last week, while talking to Bob Williams about the plight of the Devils Hole Pupfish located in an extension of Death Valley National Park, he told me they'd try to move some of the tiny fish into captivity in June. Well, word came to me today that they've moved some of the fish already in a bid to get them to breed in captivity.
Yesterday biologists scooped two adult male pupfish out of Devils Hole, placed them in plastic bags of water pumped with oxygen, and trucked them down to the Shark Reef at the Mandalay Bay Casino in Las Vegas. At the same time, two adult female Devils Hole pupfish were similarly transported to the Shark Reef from the Hoover Dam pupfish refuge that had been established back in the 1970s. Plus, five pupfish fry also were taken from Devils Hole and shipped to the Willow Beach National Fish Hatchery for rearing.
It soulds like a bit of a gamble, but the biologists are confident they can keep these guys alive.
At first blush this all sounds kinda risky to me, particularly when you've got fewer than 100 pure Devils Hole Pupfish left in the world. I mean, there were only 38 pupfish counted at Devils Hole back in mid-April, and another 29 at the Hoover Dam refugia.
On top of that, it was only a few weeks ago that the Shark Reef captive-breeding plan was launched. After talking to Williams this afternoon, though, I've got a bit more confidence in this program, which actually could begin showing success before the end of the month.
For starters, taking two adult males out of Devils Hole isn't expected to create any problems because biologists say there's a preponderance of males in the spring, and so removing a few isn't expected to impact spawning.
On top of that, though it's only been a few weeks, the fish experts at Mandalay Bay and Willow Beach have learned a few things about raising pupfish in captivity. For starters, while the fish's natural environment is a warm spring that simmers at roughly 92 degrees Fahrenheit, in captivity the water temperature is being kept around 86-87 degrees and so taking some of the stress off the fish.
"The hybrids did really well," Williams told me. "We've cooled the water down a bit and they seem to be doing really well."
The experts also seem to have come up with the right diet -- a mix of black worms, zooplankton and a flake fish food supplement.
Now, not everything is moving smoothly. There have been some deaths among the hybridized pupfish brought into the captive-breeding program earlier this month. In all ten have died -- nine at the Willow Beach hatchery and one at Shark Reef. It's believed that three died from post-transportation stress, six perhaps from feeding problems, and one possibly from natural causes.
"In all, we moved over 60 fish and we've lost ten," Williams told me. "It wasn't a massive thing. It was a couple here, a couple there."
As for the four adults moved yesterday, they settled in quickly to their new digs and started feeding. "Things are looking really good," Williams said.
So, where do things go from here? Well, the biologists hope the four adults moved into Shark Reef will spawn within the next two weeks. While females only produce one or two eggs at a time, if the eggs are successfully fertilized, hatch and survive, it will mark a pretty big success for the captive-breeding program.
Of course, the biologists are also hoping the 36 adults left in Devils Hole will do what comes naturally and help boost their own numbers in the wild.
While there currently are no plans to remove any more adults from the wild, Williams said biologists plan to move five more pupfish fry out of Devils Hole and down to the Willow Beach facility within the coming week.