Invasive Australian Crayfish Spotted In Texas Waters — 8,000 Miles From Home

Aquatic biologists are tracking an invasive crayfish species native to Australia that’s turned up 8,000 miles from home in the waters of southern Texas. They worry its spread could threaten local wildlife and ecosystems.

The discovery of Australian redclaw crayfish in the Rio Grande Valley followed reports from locals who spotted an unusual critter in the waters near Brownsville on the western Gulf Coast. In response, scientists from the Texas Parks and Wildlife Department and the University of Texas at Tyler began casting nets to investigate.

Sure enough, among the typical local swimmers, they found Australian redclaw crayfish (Cherax quadricarinatus). These large-bodied freshwater crustaceans have smooth blue-green shells with red and maroon highlights and can grow to be 9.8 inches long, weighing up to 2 pounds, as big as lobsters. They’re usually found in Queensland, Australia’s Northern Territory and Papua New Guinea.

Spotlight On ‘Aquarium Dumping’

The species is “not supposed to be in Texas,” Lance Williams, a conservation biologist at UT Tyler, said on Texas Parks & Wildlife, a weekly, half-hour PBS show about the Texas outdoors that spotlighted the surprising issue, and its potential impact on biodiversity, during its Sunday episode.

So how did the crayfish from Down Under end up so far from home? Likely as a result of “aquarium dumping,” which can introduce invasive species into local ecosystems. Well-meaning aquarium owners may think they’re doing the right thing by releasing their pets into the wild, but the opposite can be true.

“Dumping anything out of an aquarium — fish, animals and plants — can have devastating consequences for Texas’ natural water bodies,” explains Texasinvasives.org, a consortium of conservation organizations and state and federal agencies that aims to educate the public about the perils of aquarium dumping. “When they’re dumped into the wild they can introduce disease or become serious predators, killing off local fish colonies, and damaging reefs and vegetation that keep our underwater ecosystem alive and healthy.”

The Australian redclaw crayfish thrives in warm water, making it well-suited for aquarium life, though in Texas, it’s illegal to buy, sell or own one in an aquarium. It’s also illegal to release these crustaceans into a public body of water.

In the wild, they’re bottom-dwelling predatory scavengers that will vacuum up just about anything they come across.

“We do not know how it could affect the native fish and crayfish species,” Archis Grubh, an invertebrate biologist with the Texas Parks and Wildlife Department, said during Sunday’s episode.

Currently, the Aussie crayfish in Texas appear to be isolated to one resaca in Brownsville, Williams said in an interview Tuesday. A resaca is a dry riverbed that fills up during heavy rains.

“They can travel overland for short distances, so they have the potential to spread,” Williams said. “What we do not know is how fast they could spread.”

Spotted In Other States, Too

The first sighting of an Australian redclaw crayfish in Texas, a female walking with several young, was reported to iNaturalist 2013, with more reported in the state in 2022. The species has also been detected in the wild in California and Nevada, according to the National Oceanographic and Atmospheric Administration, though not in the same numbers as in Texas.

“We don’t know when these invasive crayfish were first introduced or how far they have spread, but we do know they can have a negative effect on local species and biodiversity,” Grubh said in 2022 when the Texas Parks and Wildlife Department announced the presence of Australian redclaw crayfish in the state. Other countries have grappled with invasive crayfish too.

Grubh and other the biologists have been monitoring the species’ presence in Texas since last spring — determining their location, population size, and whether they are successfully reproducing — in an effort to mitigate any threats to biodiversity.

They have collected around 100, so far, according to Williams. “This fall we collected a female with fertilized eggs on her abdomen,” he said. The females can brood up to five times a year, with 1,000 eggs per clutch. How much they reproduce in Texas, and how quickly, remains to be seen.