Pacific Northwest Native Freshwater Mussel Workgroup
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Caged Mussel (abstract)
2003 Mussel Surveys (abstract)
Pacific Northwest Native Freshwater Mussel Workgroup (Poster abstract)
Status of Smith-Bybee Lakes Mussel Populations in 2000-2001 (Project completed in 2001)
Distribution, abundance, and habitat use of freshwater mussels in four urban streams of Clark County, Washington (Project beginning in 2004)
abundance, and habitat use of freshwater mussels in four urban streams of
Clark County, Washington.
Distribution and Habitat Use of the Western Pearlshell Mussel (Margaritifera
falcata) in a Western Washington Stream
Authors: Cynthia K. Tait*, Bureau of Land Management, 100 Oregon St, Vale, OR, 97918; 541-473-6246; email@example.com; Allan K. Smith, Pacific Northwest Native Freshwater Mussel Workgroup, Hillsboro, OR
Abstract: Beginning in 2001, freshwater mussels have been inventoried and systematically sampled on drainages in the Owyhee River Basin, including 10 remote sites on the Owyhee River. Only one mussel species, Gonidea angulata, was encountered, but the species was widespread and multiple age-classes were present. However, mussel shells found in prehistoric Indian middens located on the main river and on a tributary included shell fragments of Margaritifera falcata as well as G. angulata, indicating that both species were present and accessible for harvest ca. 2000 years b.p. Because M. falcata relies on salmon and trout for hosts, its absence or scarcity in the Owyhee could be related to historic extirpation of anadromous salmonids and the subsequent introduction of unsuitable hosts such as nonnative smallmouth bass (Micropterus dolomieui). Declines in some European Margaritifera populations have been linked to trout host densities that drop below a critical threshold. G. angulata’s fish host preferences are unknown, although this species is likely to be less host specific than M. falcata and, therefore, less vulnerable to changes in fish assemblages.
Presenter: Al Smith, Hillsboro, Oregon;
Contact: Phone: 503-628-7825, Email: firstname.lastname@example.org
Abstract: Native freshwater mussels in the Greater Portland area receive very little attention from biologists, much less the public. Yet they are very interesting and ecologically important animals. They filter huge amounts of water over their long lives, provide food for predators such as raccoons, river otters and muskrats, are an indicator of stream health and have a fascinating life history. Three species of mussels currently occur in the area: Anodonta oregonensis (Oregon floater), A. californiensis (California floater) and A. wahlamatensis (Willametter floater). Shells have been found for two other species that likely also live here: Margaritifera falcata (western pearlshell) and Gonidea angulata (western ridgemussel). Depending on the species, they occur in the area’s rivers, streams, sloughs and lakes. Two examples, Fanno and Rock creeks, both tributaries of the Tualatin River, in the southwest and west parts, respectively, of the area support populations of A. oregonensis with juvenile mussels found in both streams. This is a good sign because it means the habitat in these somewhat degraded streams meets their survival and reproductive needs. Smith-Bybee lakes in North Portland, on the other hand, probably lost their populations of mussels in the drought of 2001. An interesting historical note is that A. oregonensis and A. wahlamatensis were first scientifically described as species by Isaac Lea in 1839 from the “Wahlamat near its confluence with the Columbia River”.
Presenters: : Jen Stone, Al Smith
Contact: Phone: 360-696-7605, Fax: 360-696-7968, Email: email@example.com
Abstract: On February 19, 2003, a workshop on freshwater mussels was held in Vancouver, Washington that consisted of presented papers, a panel discussion and discussion of future activities. The workshop was attended by 91 participants of very diverse backgrounds. Out of this meeting the Pacific Northwest Native Freshwater Mussel Workgroup was founded. The goal of the Workgroup (including eight objectives) is to ”Ensure that freshwater mussel research, management, and educational activities are coordinated, prioritized and are consistent with identified information needs”. The Workgroup is divided into two committees; an outreach and education group and a research, monitoring and management activities group. The Workgroup meets at least four times annually. Accomplishments so far are establishment of a website (website here), two mussel classes scheduled for next year in Portland and Ellensburg, Washington and the annual workshop. The workshop will be held in western Washington with the theme of a review of the status of freshwater mussel research, management and education. The annual workshop will rotate around the Northwest. The status of the seven species of freshwater mussels in the Northwest has received very little attention from biologists, let alone the public. The Workgroup intends to raise the awareness of the status of freshwater mussels and assure that the knowledge base about these mollusks continues to build.
Presenter: Al Smith
Contact: Phone: 503-628-7825, Email: firstname.lastname@example.org
Abstract: I surveyed the shores of Smith-Bybee lakes in North Portland, Oregon five times in August and September 2000 and 2001 for freshwater mussel shells when the lakes were very low or dry from drought. I found shells from recently dead native mussels of three species: Anodonta oregonensis (Oregon floater), A. californiensis (California floater) and A. wahlamatensis (Willamette floater). The mussels were likely scavenged by birds after dying from desiccation or high temperature. I found shells from 39 individual mussels, all very large adults. The percentage species composition at Smith-Bybee lakes was nearly the same as the species composition from Prescott Slough on the Columbia River near Rainier for the same years. Prescott Slough was also very low in 2000-2001. However the mean sizes of A. oregonensis and A. californiensis were significantly larger at Smith-Bybee lakes than at Prescott Slough. In addition, the size range for both species was greater at Prescott Slough due to multiple year classes in the populations. No successful mussel reproduction has occurred at Smith-Bybee lakes for many years. The reason is unknown. Since both lakes went virtually dry in 2001, the old, declining mussel populations are likely gone. All three species depend on attachment to fish gills at the larval stage (glochidia) for nurturing, protection, growth and dispersion. The mussel populations should eventually return to the lakes as long as fish from outside the lakes have access and as long as there is perennial standing water in parts of the lakes.
Investigator: Washington Trout
Abstract: The purpose of this study was to determine the spatial distribution, in the upper Bear Creek Watershed, of chemicals that are bioaccumulated by the freshwater mussel Margaritifera falcata. The M. falcata population of Bear Creek has declined greatly over the last 40 years; it is unknown what proportion of this decline is due to exposure to toxic chemicals from anthropogenic sources. As filter feeders, freshwater mussels have a great deal of direct contact between their body tissues and any chemicals dissolved or suspended in the water. By placing caged mussels in strategic locations throughout the Bear Creek watershed, we will be able to determine the spatial distribution of the chemicals which are being bioaccumulated by M. falcata. Cage location will be chosen to specifically examine the relationship between upstream landuse and accumulated chemicals.
Investigator: Washingon Trout
Abstract: Western pearlshell freshwater mussels (Margaritifera falcata) inhabit Bear Creek in King County, Washington. In 2002 Washington Trout determined M. falcata bed size, density, and population age structure at a sub-sample of ten known freshwater mussel beds on Bear Creek. In 2003 five of the ten beds were resampled in order to elucidate changes in mussel bed density and population age structure. In order to make certain that population age structure estimates were accurate, a detailed search for juvenile mussels was conducted using a methodology designed explicitly for the location of smaller individuals. The results of this study provide the beginnings of a documented population trajectory for the Bear Creek mussel population. The number of live mussels sampled increased in two beds between 2002 and 2003 and decreased in three beds, indicating that the mussel population in upper Bear Creek is likely stable on a year-to-year basis. In order to make certain that population age structure estimates were accurate, a detailed search for juvenile mussels was conducted using a methodology designed explicitly for the location of smaller individuals. No live mussels < 30 mm were identified in this study, indicating a lack of detectable juvenile recruitment in Bear Creek.
Principal Investigators: Sacha Johnson, Jake Jacobson, Kathy Thornburgh
Organizations/Partners involved: Barry Dreher, citizen volunteer
Funding Source: Snohomish County Surface Water Management
Project Duration: summer 2003
Abstract: The survey was performed between July 16, 2003 and August 1, 2003 on Church Creek, a small stream running through northern Snohomish County and a tributary to the larger Stillaguamish River. Approximately 7,300 feet of stream were surveyed through a wide variety of riparian habitats such as city parks, pasture lands, and mature forests. Our objective was to develop an efficient method to obtain baseline mussel distribution and abundance information throughout a watershed using individuals with a moderate level of training and a minimum amount of equipment. We used the following equipment in our surveys: GPS, hip chain, Aquascope viewing scope, polarized glasses, field forms, clipboard, pencil, measuring rod, Ziploc bags, and hip waders. The mussel count for a stream reach five channel widths long was estimated each time a mussel was sighted. The estimated mussel count was recorded using the following classifications: 0.3 for 1-3 mussels, 1 for 4-10 mussels, 2 for 11 to 50 mussels, and 3 for more than 50 mussels. Other information recorded included stream habitat type (pool, riffle, or glide), wetted channel width, channel depth, sediment type, and GPS location of mussel sightings. Percent of dead shells was noted for each reach surveyed. The only mussel species seen during the survey was the Western pearlshell, Margartifera falcata. Using our protocol, a preliminary survey of mussel densities in a reach of about 1.5 miles of a small creek was completed by two individuals in 8-10 working days. The individuals needed no rigorous science background, only good eyesight and basic measurement skills. Our citizen volunteer, Barry Dreher, provided local knowledge about the watershed and introductions to many streamside landowners. The survey is an opportunity to involve community residents in learning about their watershed and local water issues.
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