(CN) – Following the extinction of seven others, the last native mussel species in New Mexico finally has federal protection under the Endangered Species Act after the U.S. Fish and Wildlife Service said Thursday it has listed the Texas hornshell mussel as endangered.
An endangered listing indicates the species is in imminent danger of extinction throughout its range.
First identified as a listing candidate in 1989, “higher listing priorities” prevented the agency from further action, according to the listing rule. In 2011, the Center for Biological Diversity and other conservation groups settled combined lawsuits with the agency, resulting in a six-year workplan for Fish and Wildlife Service to address its backlog of hundreds of species that had been waiting for protection – some, like the hornshell, for decades.
“This mussel now has an excellent chance for survival in the face of would-be dam-builders and polluters thanks to the Endangered Species Act,” said Michael Robinson, conservation advocate for the Center for Biological Diversity. “That’s good news for the hornshell and for all of us who rely on clean water and love free-flowing rivers.”
The Texas hornshell is a freshwater mussel that was once easily found in free-flowing rivers and streams in southern New Mexico and the Rio Grande river basin in Texas. The agency estimates that it can only be found now in 15 percent of his historical range.
The mussels are threatened by water impoundments and poor water quality from the oil and gas industry, agricultural runoff, and grazing, in addition to fragmentation of their habitat, drought, loss of native species and invasion by exotic species. Many freshwater mussels are dependent on native fish species for their reproduction. Fish eat the mussel larvae, which then form cysts in the fish’s gills, face or fins until they grow into the juvenile form and are released.
The agency says that climate change is likely to exacerbate threats to the hornshells due to factors such as increased sedimentation from a decrease in cleansing flows, and reduced water levels that create a higher concentration of contaminants, higher water temperatures and unsuitable oxygen levels.
Juggling the needs for the species’ survival with the demands of industry and landowners is a challenging path for the service, which has entered into Candidate Conservation Agreements with Assurances with gas and oil companies and landowners, and formed partnerships with other agencies “to provide conservation benefits for the hornshell and regulatory certainty for landowners and industry,” the agency said in its announcement.
“The Endangered Species Act is a tool used to help species recover to healthy populations. Going forward, the service will work with state and local stakeholders to enhance conservation of the hornshell while also respecting local voices,” said Amy Lueders, the service’s Southwest regional director.
Candidate Conservation Agreements with Assurances – voluntary agreements with landowners and developers – ask for cooperation with conservation practices in exchange for assurances that there will be no additional requirements once a species is listed under the act.
“Landowners, oil and gas companies, irrigation districts and others enrolled in the CCAA will not be required to do more than they have agreed to do under the agreements,” the agency said.
Section 9 of the act prohibits certain activities that may harm or kill individual members of a protected species. Harm is termed “take” under the act. Examples of activities that may cause harm in this case include unauthorized handling or collecting of the mussels, modifying water flow of streams, grazing that destroys stream habitat, and discharge of chemicals into waters where hornshells are known to live.
When asked if the conservation agreements would allow higher levels of take than would normally be allowed, Fish and Wildlife’s spokesperson Lesli Gray said, “For CCAAs, in the event that take occurred as a result of the activities being carried out under the CCAA, the participant would be covered; however, CCAAs do not identify take levels and the agreements are built to conserve the species and limit impacts while providing landowners the ability to continue managing their lands.”
The agency finalized a Candidate Conservation Agreement and a Candidate Conservation Agreement with Assurances in October last year. The listing proposal for the hornshell was published in October 2016, with the final listing expected to be published in October 2017. However, the agency reopened the comment period on the proposal twice and extended the listing determination for an additional six months at the end of June 2017.
“Interested landowners or industry can enroll in the CCA or CCAA until March 12, 2018, the effective date of the listing,” the agency said.
In addition to the conservation agreements, partnerships with other agencies also play a part in recovery for the species.
One example involves a project launched by the New Mexico Department of Game and Fish in 2013, reintroducing the mussels into the Delaware River. It takes many years to determine success, “because the size of the juvenile mussel prevents detecting natural reintroduction for at least three years or more. As a positive sign, NMDGF biologists captured two gray redhorse [native host fish] from the Delaware River that appeared to be infested with Texas hornshell glochidia [larvae],” the agency said, but the project will not be considered a success until progeny from the reintroduced adults have been found in the river.
Fish and Wildlife says that a critical habitat determination is appropriate for the hornshells, but that it is not determinable at this time. The agency indicated that it anticipates publishing a proposed critical habitat rule in the near future.
The final listing for the Texas hornshell mussel is effective March 12.