US declares species once found in Kentucky extinct. What does it mean for water quality?

The U.S. Fish and Wildlife Service recently declared 21 species extinct, including an environmentally significant one previously found in the Bluegrass State.

The tubercled-blossom pearly mussel was native to Kentucky, as well as seven other states across the nation. It was one of the first to be placed on the Endangered Species Act in 1976, but had not been seen for years prior to its recent delisting.

It’s been upwards of 50 to 60 years at least since the mussel species was last seen alive in Kentucky, Zach Couch, program coordinator at the Kentucky Department of Fish and Wildlife Resources Wildlife Division, told the Herald-Leader. The last confirmed sighting of the tubercled-blossom pearly mussel in the U.S. was in 1969, according to the USFWS.

This species was one of eight mussels declared extinct by USFWS in October.

Mussels perform several functions important to humans, including being a great ecological indicator and filtering the water supply.

“Mussels are essentially filter feeders, so they sit down on the bottom of the stream and they open up their siphons,” Couch said. “The way that they feed is by pulling water in and then filtering nutrients out of it, which essentially means that they are also filtering and purifying the water as they are feeding.”

The extinction of mussel species leads to not only a loss of biodiversity, but also less filtration to our water supply, Couch continued.

“They’re like little miniature water purifiers, so they’re really a very important part of aquatic communities,” USFWS spokesperson Georgia Parham said.

Kentucky is home to about 100 native mussel species, and more than half are listed as species of greatest conservation concern in the commonwealth’s wildlife action plan, Couch said. Several dozen of those species are also listed federally as threatened or endangered under the Endangered Species Act.

An ideal mussel habitat includes clean, clear, flowing water and stable substrates, and the mollusks are intolerant of pollution. Habitat destruction, dam construction and draining of wetlands all pose risks to the livelihood of individual mussels and species.

In addition to habitat loss, invasive species have also contributed to the decline of mussel populations. The invasive zebra mussel species harms native mollusks by directly colonizing them and eating their food.

“They are prolific as far as their ability to reproduce and overtake any water system,” Couch said.

Along with zebra mussels, the Asian clam and black carp are also invasive species in Kentucky threatening to drive mussels to extinction. Black carp, which have been reported in Western Kentucky, eat native mussels, though the full extent of how dangerous they may be to mussel survival is still being investigated.

What’s being done to save mussels?

Although mussels face a variety of threats and their numbers have declined, state and federal officials are spearheading programs to support their survival and even potentially revive critically endangered species.

Ecologists at fish hatcheries across the nation are working to propagate native mussels, raise the juveniles and release them into the wild. Officials with the U.S. Fish and Wildlife Service, the Kentucky Department of Fish & Wildlife Resources and other state agencies participate in propagation programs, and they’ve been effective in many cases.

The Kentucky Department of Fish & Wildlife Resources runs a Center for Mollusk Conservation, where staff bring in rare mussel species, culture juvenile mussels and release them into the wild to boost the numbers of declining species. The department has been involved in mussel propagation for nearly 20 years, Couch said.

One species center staff have begun working on in the last five years is the purple cat’s paw mussel, which was “on the brink of extinction” when it was listed as endangered in 1990.

When wildlife staff with Kentucky’s Center for Mollusk Conservation began their focus on the purple cat’s paw species, scientists estimated fewer than 50 individual members of the species remained in the wild. Staff brought 20 into the lab for propagation, and as of this year have released more than 5,000 juvenile purple cat’s paw mussels into the wild as a result of the program.

Couch said the number of mussel species the center propagates at one time fluctuates, but they’ve worked with several dozen species over the last 20 years.

“It’s always sad to see something be declared as extinct, but hopefully some of the work we’re doing at our center for freshwater mollusk conservation will prevent that from happening with some of the species that we have in the state now that are continuing to decline,” Couch said.

How are species declared extinct?

The USFWS is tasked with maintaining an endangered species list, as well as determining when a species is no longer found in the wild. The agency considers a variety of factors, including the best available scientific information when making a decision, Parham said.

The federal governmental agency works with state departments to identify documented sightings of endangered species and also conducts five-year reviews to maintain species’ current status, move them off of the endangered species list due to recovery or declare them extinct.

It’s not overly common for federal officials to declare a species extinct, Parham continued, as they conduct extensive research to look for remnant populations.

Eight bird species native to Hawaii were among the 21 species recently declared extinct. Here’s a full list of the species declared extinct by USFWS Oct. 16:

• Tubercled-blossom pearly mussel

• Flag pigtoe (mussel, last confirmed sighting in 1984)

• Southern acornshell (mussel, last confirmed sighting in 1973)

• Stirrupshell (mussel, last confirmed sighting in 1986)

• Upland combshell (mussel, last confirmed sighting in the mid 1980s)

• Green-blossom pearly mussel (last confirmed sighting in 1982)

• Turgid-blossom pearly mussel (last confirmed sighting in 1972)

• Yellow-blossom pearly mussel (last confirmed sighting in 1966)

• Little Mariana fruit bat (last confirmed sighting in 1968)

• Bachman’s warbler (bird, last confirmed sighting in 1980s)

• Bridled white-eye (bird, last confirmed sighting in 1983)

• Kauai akialoa (bird, last confirmed sighting in 1960s)

• Kauai nukupuu (bird, last confirmed sighting in 1899 )

• Kauaʻi ʻōʻō (bird, last confirmed sighting in 1987)

• Large Kauai thrush (bird, last confirmed sighting in 1987)

• Maui ākepa (bird, last confirmed sighting in 1988)

• Maui nukupuʻu (bird, last confirmed sighting in 1996)

• Molokai creeper (bird, last confirmed sighting in 1963)

• Po`ouli (bird, last confirmed sighting in 2004)

• San Marcos gambusia (fish, last confirmed sighting in 1983)

• Scioto madtom (fish, last confirmed sighting in 1957)

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