PNHP Project Profile:
The yellow lampmussel (Lampsilis cariosa) is a freshwater mussel that is found in many Atlantic-slope rivers and larger streams in Pennsylvania. It is quite rare throughout its range, which extends up and down the East Coast states and into two Canadian provinces.
Unfortunately, the yellow lampmussel suffers continued population declines or extirpations (once occurred but is now absent) in nearly all of the states and provinces in which it is found. Many populations of yellow lampmussels are isolated from one another and can no longer interbreed, decreasing the chances that their offspring will survive.
However, Pennsylvania supports some of the healthiest populations of yellow lampmussels throughout the species’ range. The rarity of this species on a global scale, coupled with Pennsylvania’s holding some of the best remaining habitats for the species, led the Pa. Fish and Boat Commission to declare the species an immediate priority for conservation. This helped spur a research study that is investigating the status of the yellow lampmussel in the state: where it exists, what its habitat needs are, and how we can most effectively preserve these habitats to ensure that this species is found in Pennsylvania for generations to come.
Mussels are unsung heroes of our waterways
Freshwater mussels are one of the most imperiled groups of animals in North America. In Pennsylvania, 17 species (representing about one-fourth of all mussel species ever found in the state) have been extirpated here, and another 24 species are considered threatened or endangered by the Pennsylvania Biological Survey (PABS) and the Pennsylvania Natural Heritage Program (PNHP). Too little information exists to accurately assign status designations to at least 16 other mussels in Pennsylvania, including the yellow lampmussel. This group of species is of significant and dire conservation need and accurate and up-to-date status surveys are vital to our understanding them.
North America is the worldwide epicenter of biological diversity for freshwater mussels, with approximately 300 native species. Unfortunately, more than two-thirds of these species are considered to be endangered, threatened, or of special conservation concern. There are numerous threats to mussels and their sensitive life cycle, including land development, mineral extraction from the land or substrate, water extraction, wastewater treatment plant discharges, pollution and siltation due to improper agriculture and timbering practices, dams and stream channel alteration, and invasive species, such as the Asian clam (Corbicula fluminea) and the zebra mussel (Dreissena polymorpha). All of these threats affect mussels in the rivers and streams of Pennsylvania.
Freshwater mussels are important, sensitive components of flowing water ecosystems in Pennsylvania. They are generally found in clean, medium to large-sized streams and rivers with good flow. Mussels live in waterways across Pennsylvania, but can be hard to see because they often bury themselves in the sand and gravel along the river bottom. When waters become polluted (possibly from poorly managed agricultural areas or urban effluent discharges), mussels will begin to disappear. Similarly, when flow is slowed or stopped by dams, the habitat changes and mussels can no longer survive there. Flow is important not only because it helps to shape their sandy, gravelly habitats, but it also provides them with a constant supply of oxygenated water, as well as the tiny organisms mussels filter out of the water for food. This feeding method is widely beneficial, as it can help to keep water clean and clear.
In fact, studies on the Delaware River have found that the resident mussels can filter all of the water in that river an incredible eight times each day! Additionally, through their feeding and movements in the stream bottom, freshwater mussels make nutrients more available for other aquatic animals. Studies have shown that higher densities of other aquatic animals, like fish and aquatic insects, are found in areas with higher densities of live mussels. However, when water has too many particles in it (sediments, algae, pollutants, etc.), the mussel’s siphons can become clogged, disrupting their feeding. Pollutants that are dissolved in the water may be held in the mussel tissue, potentially poisoning the mussel.
The unique way in which freshwater mussels reproduce makes them especially vulnerable. Each freshwater mussel species has a particular fish species (or group of species) that it depends on to distribute its larvae, called "glochidia." To attract their host fish, many mussels used fish-shaped "lures," which are fleshy parts of the mussel’s body tissue that have evolved to look like a fish (for more photos and videos of mussel lures, see: http://unionid.missouristate.edu).
Mussels have an amazing range of adaptations to ensure that their glochidia successfully attach to a fish. When the host fish are drawn near the lure of a fertilized female mussel (one that has taken in sperm from a male mussel, which the male simply releases into the water), the mussel releases its glochidia into the water, many of which attach themselves to the fish.
Glochidia look like microscopic mussels with teeth that latch onto the fish, usually on its gills. While the glochidia are technically parasitic, they generally do not harm the fish. After a period of time that can last days or weeks, the glochidia, which have now developed into juvenile mussels, release themselves from the fish and fall to the river bottom. It’s here that they grow into a full adult mussel, eventually to mate with other mussels and release their own glochidia to start this intricate life cycle all over again.
While the fish provide nourishment to help the glochidia develop, they also provide an essential dispersal system for the mostly immobile mussels. This is another reason why dams can be such a detriment to mussel populations. Not only do they restrict water flow, they can also impede the dispersal of fish up or down the river. Mussels count on this dispersal to spread their glochidia to other areas. With successful dispersal, they are able to breed with other mussel populations and maintain healthy, genetically diverse populations (for more information on the life cycle of freshwater mussels and to see an animation of the process: http://www.fws.gov/midwest/mussel/multimedia/life_cycle.html).
The Yellow Lampmussel Project at work
Aquatic ecologists from the Pennsylvania Natural Heritage Program are currently studying the yellow lampmussel in the Susquehanna River basin. The goals of the project include determining where populations of yellow lampmussel exist; where the healthiest populations and best habitat for the species are found; and determining the most effective methods for preserving the species in the commonwealth. Also, we have teamed up with a conservation geneticist, Dr. Curt Elderkin, from The College of New Jersey, to perform genetic tests on samples we collect from yellow lampmussels. This information will tell us which populations are the most genetically diverse, which ones are able to interbreed with other populations, and also where populations have become isolated.
To search for mussels, a team of ecologists dons wetsuits, diving masks and snorkels and carefully searches the river bottom (substrate) in measured sections of the river, for consistent amounts of time. Keeping track of area and time searched allows us to compare the size and characteristics of mussel populations across different areas and river systems. All mussels found during the timed search are placed in a mesh bag, which is kept underwater with the ecologists, while they are conducting the survey. Once the time is up, everyone meets back on shore to sort out the mussels by species and measure their length. Length is closely related to age in mussels, so this information is used to assess the variation in age within populations, and to see if populations are reproducing successfully. After all of the data are recorded, each mussel is placed back into the river substrate in the approximate area where it was found.
The work for this study has been separated into sub-basins of the Susquehanna watershed. In the summer of 2008, 60 river and stream locations in the Juniata River and its major tributaries were surveyed. The Juniata sub-basin includes sections of Bedford, Blair, Huntingdon, Mifflin, Juniata and Perry counties. In 2009, we will survey another 60 sites in the Middle Susquehanna watershed, which includes sections of Bradford, Susquehanna, Wyoming, Lackawanna, Luzerne, Columbia and Northumberland counties. In 2010, survey efforts will concentrate on the lower Susquehanna sub-basin, including portions of Centre, Snyder, Northumberland, Schuylkill, Dauphin, Perry, Lebanon, Cumberland, Lancaster, Adams and York counties. See the sub-basins online: http://www.srbc.net/subbasin/subbasin.htm.
We found 10 different species of mussels throughout the entire Juniata watershed during the 2008 field season. In addition to yellow lampmussels, other species commonly encountered were the eastern elliptio (Elliptio complanata), creeper (Strophitus undulatus), elktoe (Alasmidonta undulata), and the rainbow mussel (Villosa iris). The eastern elliptio was the most common mussel species in the Juniata River basin, found at 46 sites. Interestingly, the yellow lampmussel was the second-most-common species, found at 30 sites.
By piecing together information from the sub-basins, we will be able to accurately describe the status of this species across Pennsylvania. With this knowledge, we can determine actions necessary to preserve the habitats on which this sensitive species depends.
This project is jointly funded through the Wild Resource Conservation Program and State Wildlife Grants, which are administered through the Pennsylvania Fish and Boat Commission.
For more about mussels
The Pennsylvania Natural Heritage Program (PNHP) is a member of NatureServe, an international network of natural heritage programs that gather and provide information on the location and status of important ecological resources (plants, vertebrates, invertebrates, natural communities and geologic features). Its purpose is to provide current, reliable, objective information to help inform environmental decisions. PNHP information can be used to guide conservation work and land-use planning, ensuring the maximum conservation benefit with the minimum cost.