Fewer than 1,000 Digger Crayfish believed to be living in Pennsylvania

A species of crayfish that’s estimated to have a population of less than 1,000 in Pennsylvania is under state review regarding its future.

In Pennsylvania, the digger crayfish is only found in the northwestern part of the state. They were first discovered by the Pennsylvania Fish and Boat Commission in 2014 on State Game Land 101 in Crawford County near the border of Erie County.

David Lieb, invertebrate biologist with the commission, said the agency’s staff has surveyed more than 3,000 crayfish sites across the state since 2005.

“It’s the most thorough crayfish study ever conducted (on the state level),” he said during a presentation Feb. 15 to the agency’s Habitat and Environmental Committee.

The digger crayfish work was a collaboration with West Liberty University including professor Zachary Loughman and several graduate students, including Tanya Khan and Patrick Allison.

Lieb believes the digger crayfish, which grow to about 3 inches long, weren’t found in earlier studies, which date back to 1906, because the sites where they were recently found had been more of a wetland, swampy area previously. Some of the habitat areas have been drained and are gone.

“It was inhospitable and tough to access because of the swamps and wetlands and marshes. It was very difficult to get in there to sample. The digger crayfish were probably there, but it was difficult to get in there by horseback and train, which is what the (researcher team) was using to get around,” Lieb said, talking about a survey done more than 100 years ago.

“Flash forward to modern times, we do have ways to get into those areas now, however a lot of that habitat was destroyed in the intervening area and was never sampled,” he said.

After surveying 673 square miles and 456 sites since that first finding, they found nine places with Digger Crayfish. Seven of them are in the western side of the Conneaut Creek watershed, Lake Erie drainage area.

The other two locations were along the Pymatuning Reservoir/Shenango River watershed, which has drainage from the Ohio River.

They found 250 to 300 individual digger crayfish.

It’s difficult to get a population estimate of the burrowing digger crayfish in Pennsylvania, but Lieb guessed that there's less than 1,000 in the state, maybe less than 500.

There are 17 species of crayfish in Pennsylvania, and five of them are known to burrow into the mud.

Digger crayfish burrow down below the ground water table and create a network of tunnels and resting chambers.

“They live there for almost their entire life. So they are essentially creating their own aquatic environment in a terrestrial area,” Leib said.

The most visible sign of a burrowing crayfish is a chimney-like mound of dirt around their burrow holes which are about an inch or two wide.

“They create unique habitats through burrowing activity,” he said. More than 200 other species likes snakes and insects have been know to use crayfish burrows and the aeration and mixing of soils is believed to lead to plant diversity as well.

Lieb is concerned about the future of digger crayfish.

“Any small events can wipe out the entire species from the state. If you have a disease outbreak, for example, in and around Game Lands 101, all those populations would be gone and would probably, likely spread to the Pymatuning, since we are only 10 to 12 miles away, and the species would be eliminated from the state.”

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Threatened or endangered?

Christopher Urban, chief of the Natural Diversity Section nongame, threatened and endangered species coordinator for the Fish and Boat Commission, said the process has started to determine if this species crayfish should be listed as a threatened or endangered species.

“It’s probably threatened or endangered,” he speculated. The agency defines endangered as species in imminent danger of extinction or extirpation throughout their range in Pennsylvania. Threatened means the species may become endangered within the foreseeable future throughout their range in Pennsylvania.

If the research is supported in peer reviews and is tentatively approved by the Fish and Boat Commission’s board as threatened or endangered, there will be a public comment period. After that period ends, the agency’s board will vote again for final approval. If that happens, the package will advance to the attorney general’s office to have the regulation changed. The process takes about a year.

If that happens, a recovery plan for the digger crayfish will be created.

“It’s a blueprint. There’s actions we can do in species management that can recover the species, bring it back to a healthy population," he said.

The process would examine if it’s a good idea to augment the population with Digger Crayfish from other areas like Ohio.

Some of the protections would include reviews of any new building developments in the crayfish’s home range. “How we can still allow progress in the state with development but at the same time protect the species? That’s a challenge itself,” Urban said.

Lieb said it’s a delicate situation to monitor.

“You can do damage to these colonies. Once you dig in and destroy a burrow, it’s gone. Obviously these crayfish spend a tremendous amount of effort creating their burrows and if they are forced to create another one, that’s energy they don’t have to reproduce or survive,” Lieb said.

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Crayfish regulations

If you find crayfish, Lieb said it needs to remain in that waterway. For example you are permitted to use crayfish as bait for fishing, but you have to use them where you find them.

“It’s illegal to transport crayfish away from the site where they were collected in Pennsylvania,” Lieb said.

He said there have been problems where exotic crayfish found their way into an area, and they take over the stream and eliminate the native crayfish. He said it probably happened when someone dumped out their crayfish from their bait bucket into a place where that species of crayfish didn’t already exist.

“Appreciate their value to the ecosystem to which they reside,” he advised. Crayfish have been considered a nuisance to farmers and people with lawns have detrimentally poured chemicals in the burrows to remove the crayfish. “They are an important part of the ecosystem, and many other species depend on them. It’s a good thing if you have them on your property,” Lieb said,

Having crayfish is an indicator that the property has good habitat and good water quality. “If you are pouring chemicals down into a crayfish burrow, you’re essentially pouring chemicals into your groundwater because they dug their tunnel into the groundwater. You’re not only going to hurt the crayfish, but yourself and your neighbors.”

“They are rare and they are important and they are something we need to conserve,” Leib concluded.

Brian Whipkey is the outdoors columnist for USA TODAY Network sites in Pennsylvania. Contact him at bwhipkey@gannett.com and sign up for our weekly Go Outdoors PA newsletter email on this website's homepage under your login name. Follow him on Facebook @whipkeyoutdoors ,Twitter @whipkeyoutdoors and Instagram at whipkeyoutdoors.

This article originally appeared on Erie Times-News: Where are burrowing Digger Crayfish found in Pennsylvania