The historic range – Mexico to Alaska – of
freshwater mussels has declined by 18 percent, according to a recent study that
surveyed over 700 watersheds in western states.
Surveying 708 watersheds, thought to have at
one time hosted a variety of mussel species as far back as 1834, the study
found that just 580 of the watersheds still contain some species of mussel. In
addition, mussel richness, or diversity of types of mussels found, declined by
“When watersheds with higher past mussel
richness (containing three or four species or clades) were considered
independently, 48 percent of these historic ‘hot spots’ have declined in
richness in the recent time period,” the study says.
“The results from this work are depressing,”
said Emilie Blevins, conservation biologist with the Xerces Society and lead
author on the new study. “But until now there wasn’t a solid foundation for
planning conservation efforts. With this information we can now get on with
There are more than 300 species of freshwater
mussels in North America, mostly east of the Rocky Mountains, but 74 percent of
those are considered imperiled, according to Xerxes Society information. That
means that they either have disappeared from some areas, persist in only small
population or are extinct.
Western species, such as western pearlshell,
western ridged and several species of floater mussels are fewer in number and
receive less attention than eastern mussels or other aquatic species that share
the same waters with mussels.
“Freshwater mussels are profoundly important
to creek health, filtering the water as they feed and keeping it clean and
clear for people as well as fish and other wildlife,” said Matthew Shephard of
the Xerces Society.
Researchers compiled a comprehensive database
of mussel records from research and museum collections, historical
publications, and public agency and personal records dating as far back as
1834, allowing scientists for the first time to understand the true picture of
mussel distribution in western North America.
The scientists also assessed the health of
individual species, finding that the western ridged mussel and winged floater
are “vulnerable” to extinction; they have disappeared from more than 30 percent
of their range.
The western pearlshell is “near threatened,”
having disappeared from more than 15 percent of its range and suffered large
declines in abundance elsewhere.
The Oregon floater and western floater appear
to be suffering the least, and are together classified as of “least concern,”
the report concludes.
“This was a joint project of the Xerces
Society and Confederated Tribes of the Umatilla Indian Reservation Mussel
Project,” said Sarina Jepsen, director of aquatic programs for the Xerces
Society. “The project took nearly ten years and the Confederated Tribes’
continued engagement has been essential to its long-term success.”
More than 160 people and nearly 100
institutions provided their observations or collection information to the
Western Freshwater Mussel Database (https://xerces.org/western-freshwater-mussels/).
The database is a project of the Xerces Society and the Confederated Tribes of
the Umatilla Indian Reservation’s mussel project.
Members of the Pacific Northwest Native
Freshwater Mussel Group (https://pnwmussels.org/) contributed thousands of
records to the database, often revisiting mussel populations repeatedly over
the ten-year study to document their observations. In some cases, the project
used crowdsourcing to gather information.
The study, Extinction risk of Western North
American freshwater mussels: Anodonta Nuttalliana, The Anodonta
Oregonensis/KennerlyI Clade, Gonidea Angulata, and Margaritifera Falcata, was
published online October 27 in Freshwater Mussel Biology and Conservation,
In addition to Blevins and Jepsen, co-authors
are Jayne Brim Box, Donna Nez and Alexa Maine with the Department of Natural
Resources Fisheries Program, Freshwater Mussel Project of the Confederated
Tribes of the Umatilla Indian Reservation; Jeanette Howard of the Nature
Conservancy; and Christine O’Brien of Browns River Consultants.
“Many conservation and research priorities
identified in the Freshwater Mollusk Conservation Society’s national strategy
(2016) would benefit western freshwater mussels,” the study concludes. “These
strategies include improving understanding and increasing accessibility of
taxonomy and distribution information, addressing past, ongoing, and emerging
stressors and their impacts, improving understanding of habitat and conserving
habitat, improving understanding of mussel population ecology, and restoring
abundant mussel populations.”
Established in 1971, the Xerces Society is a
nonprofit organization that protects wildlife through the conservation of
invertebrates and their habitat (www.xerces.org).
--CBB, September 4, 2015, “Umatilla Tribes Use
BPA Funds To Acquire Acreage To Improve Spawning, Rearing For Endangered