HARRISBURG (TNS) — Crossbreeding between two invasive crayfish species has been found in the Juniata River basin of central Pennsylvania, raising concerns that the hybridization could help the invaders gain an even stronger foothold in the watershed.

Researchers at Juniata College found DNA evidence of hybridization between rusty crayfish and Allegheny crayfish in the Juniata system, where neither species is native.

“Hybridization of non-native crayfishes with native crayfishes can facilitate invasion success of the non-native,” they noted in the Journal of Crustacean Biology. “Hybridization may be an additional means by which invasive rusty crayfish increase their fitness and dominance at the expense of existing species and their habitat.”

The rusty crayfish, native to the Ohio River basin, has been spread to other waters in at least a dozen states outside its native range and Ontario. It was first discovered in Pennsylvania in 1976 in the lower Susquehanna River. Initial spread into each new waterway is believed to be launched by anglers dumping bait buckets of crayfish bought at bait shops when they finish fishing for the day.

The Pennsylvania Sea Grant describes the rusty crayfish as “an aggressive crayfish with a huge appetite. It has not only managed to outcompete native crayfish species but has also devastated aquatic ecosystems in several states including Pennsylvania.

“The rusty crayfish is very aggressive and often displaces native crayfish species. Studies show that rusty crayfish can eat twice as much as similar-sized native crayfish, consuming plants, aquatic worms, snails, leeches, clams, aquatic insects and crustaceans, decaying plants and animals, fish eggs, and small fish.”

They grow rapidly into a size too large for fish in the invaded ecosystems to eat, removing themselves as a critical part of the food chain.

“They also impact native crayfish reproduction as male rusty crayfish will mate with female native crayfish,” PSG notes. “This produces sterile offspring and reduces native crayfish populations.

“Perhaps the most serious impact of the rusty crayfish is destruction of aquatic plant beds. Rusty crayfish devour so much underwater vegetation that food, shelter and spawning sites for other organisms are dramatically reduced.”

The Allegheny crayfish is native to streams of the Allegheny, Monongahela, Genesee and Ohio River drainages and the Lake Erie Drainage in eastern Ohio, West Virginia and Western Pennsylvania. In 2014 it was found farther to the east, in the Lower Susquehanna and Upper Juniata rivers.

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