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Endangered Species Act decisions for longsolid, round hickorynut and purple lilliput mussels

What is the U.S. Fish and Wildlife Service proposing?

The Service is proposing to list the longsolid and round hickorynut mussels as threatened under the Endangered Species Act (ESA). Although it has experienced a decline, the Service found that the purple lilliput has not yet met the threshold for ESA protection.

What is the longsolid?

In 1831, Isaac Lea described the longsolid (Fusconaia subrotunda), a medium-sized mussel up to 5 inches long, which can live up to 50 years. It is found in small streams to large rivers, including the Ohio River, and prefers a mixture of sand, gravel, and cobble stream bottoms. It is found in nine states (Alabama, Kentucky, New York, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia, and West Virginia) and has disappeared from three (Georgia, Indiana, and Illinois). With a historical high of 162 known populations, 60 are known to exist today, and 48 of those are small populations in poor condition.

What is the round hickorynut?

The round hickorynut (Obovaria subrotunda) is a small- to medium-sized mussel up to 3 inches long, which lives up to 15 years. It is found in small streams to large rivers, and prefers a mixture of sand, gravel, and cobble stream bottoms. The round hickorynut is found in nine states (Alabama, Indiana, Kentucky, Michigan, Mississippi, Ohio, Pennsylvania, Tennessee, and West Virginia), and has disappeared from three (Georgia, Illinois, and New York). With a historical high of 297 known populations, 65 are currently known to exist today, and 45 of those are in poor condition.

What is the purple lilliput?

Purple lilliput (Toxolasma lividum) is a small freshwater mussel, up to 1.5 inches long, with a thick shell, and thought to live up to 12 years.  It is found in small streams to large rivers, including the Tennessee River, and prefers a mixture of sand, gravel, and cobble substrates. It’s currently found in nine states (Alabama, Arkansas, Illinois, Indiana, Kentucky, Michigan, Missouri, Ohio, and Tennessee) and has disappeared from two (North Carolina, Georgia), and may have disappeared from two more states (Oklahoma and Virginia). Historically there were 272 known populations, with 146 remaining today, and of those, 87 are small populations, confined to a limited area, with no evidence of young mussels or mussels of multiple ages, as you would expect in healthy populations.

What threats brought the longsolid and round hickorynut to this point?

These mussels have suffered impacts from negative influences commonly found in central and eastern U.S. streams, including habitat degradation or loss from a variety of sources, including poorly managed agriculture and development, and site-specific threats from genetic isolation and invasive species.

Why are the round hickorynut and longsolid mussels proposed for listing while the purple lilliput isn’t?

Based on available information, although all three mussel species have a smaller range compared to historical levels, the decline of the purple lilliput hasn’t been as precipitous as the longsolid and round hickorynut. The longsolid has lost 63% of its populations, the round hickorynut has lost 78%, while the purple lilliput has lost 47%. Beyond the overall number of populations, the purple lilliput is still found in in all six major river basins where it is historically known to occur. Beyond looking at historical declines, biologists also assessed a variety of scenarios to get an idea of future trends, and the purple lilliput is likely to maintain more than 100 populations across all six river basins where it occurs.

The purple lilliput does not currently meet the threshold of endangered – in danger of going extinct throughout all or a significant portion of its range, or threatened – and neither is it likely to become endangered in the foreseeable future throughout all or a significant portion of its range.

What protections would these mussels receive by being on the threatened and endangered species list?

Federally funded or authorized projects would be reviewed for impacts to the listed mussels, and actions of the federal government may not jeopardize their existence. Listing would prohibit harassing, harming, pursuing, hunting, shooting, wounding, killing, trapping, capturing the listed mussels and attempts to engage in such activity, except where permitted or in certain cases where it is part of a broader effort to conserve the mussels. The listing would make recovery efforts for the mussels eligible for funding under the ESA.

What is critical habitat?

When the Service proposes an animal or plant for listing as endangered or threatened under the ESA, we identify specific geographic areas called critical habitat that are essential to conserving those species. The Service determines critical habitat based on what an animal or plant needs to survive and reproduce by reviewing the best scientific information concerning a species’ present and historical ranges, habitat, and biology.

Along with the proposal to list the longsolid and round hickorynut, the Service also proposes designating critical habitat, or habitat critical to the recovery of the species. Designation of critical habitat does not affect land ownership, does not allow the government to take or manage private property, nor does it establish a refuge, reserve, preserve or other conservation area, and it does not allow government or public access to private land. Designating critical habitat on private land has no impact on landowner activities that do not require federal funding or federal permits. Critical habitat alerts federal agencies that they are required to make special conservation efforts when they work, fund or permit activities, including consulting with the Fish and Wildlife Service on the effects of their actions.

How much critical habitat is being considered for the longsolid and round hickorynut?

The proposed critical habitat for the longsolid is comprised of 12 units, along a total 1,115 river miles, in Alabama, Kentucky, Pennsylvania, Tennessee, Virginia, and West Virginia. Proposed critical habitat for round hickorynut is comprised of 14 units along a total of 921 river miles in Alabama, Indiana, Kentucky, Mississippi, Ohio, Pennsylvania, Tennessee, West Virginia. Eight of the proposed units overlap in part or whole. All proposed units are occupied by the species, and all are considered essential to the conservation of the longsolid or round hickorynut mussels because they provide the suitable habitat necessary for this species to survive and reproduce. Eleven of the units are home to either existing critical habitat and/or threatened or endangered species.

How did the Service come to this conclusion?

The Service compiled and analyzed data for these wide-ranging species. The Service reached out to species and habitat experts, including staff in its own field offices, state wildlife agencies for each of the states when the mussels occur, and university and agency researchers and staff who work with these species to compile a range-wide status of the species and it’s project status into the future. These status assessments subsequently went through a peer-review process. For each of these species, this represents the first time such a comprehensive, range-wide investigation into their status has been conducted. After examining historical, current, and projected future populations in light of the threats facing these mussels, the Service found that while all three have declined over time, only two, the longsolid and round hickorynut, currently warrant the protection of the ESA, something afforded our most imperiled species.

Is the Service proposing a 4(d) rule as the ESA allows?

Yes. According to these rules, certain actions with a minimal level of disturbance and no anticipated long-term negative impacts to the species would be excepted from prohibitions. Those actions are species restoration efforts by the Service or state wildlife agencies, and stream channel and bank restoration projects for creation of natural, physically stable, ecologically functioning streams, taking into consideration connectivity with floodplain and groundwater aquifers.

How do I provide comments on the proposed listing, 4(d) rules, and critical habitat?

For the longsolid and round hickorynut, we will accept comments received or postmarked on or before December 28, 2020. To submit comments electronically, go to In the search box, enter FWS–R4–ES–2020–0010, which is the docket number for this rulemaking. Then, click on the search button. On the resulting page, in the search panel on the left side of the screen, under the “Document Type” heading, check the proposed rule box to locate this document. You may submit a comment by clicking on “Comment Now!” Submit comments via mail or hand-delivery to Public Comments Processing, Attn: FWS–R4–ES–2020–0010, U.S. Fish and Wildlife Service, MS: JAO/1N, 5275 Leesburg Pike, Falls Church, VA 22041–3803. We request that you send comments only by the methods described above. We will post all comments on

Why should we care about mussels?

Although people are far more familiar with saltwater mussels commonly offered in restaurants, the United States is home to a tremendous diversity of freshwater mussels. There are more than 600 species worldwide, with North America being a global center of mussel diversity, with about 300 species. Despite the high amount of diversity, 65% of North American freshwater mussel species are imperiled. Sensitive to pollution, native mussels are indicators of broader stream health – vibrant mussel populations typically reflect a healthy stream. In addition to being indicators of stream health, mussels clean water as they feed, filtering their food from the water column, and with it, sediment and other pollutants.

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