Western Pearlshell – Margaritifera falcata
Western Pearlshell shells can be dark brown to light brown in color, have an elongated kidney-like shape, and can grow over 180 mm in length. Western Pearlshell can be found in many subbasins in CTUIR ceded territory, including but not limited to the upper Umatilla, Walla Walla, Tucannon, Middle and North Fork John Day, Grande Ronde and Snake rivers. Development of glochidia in Western Pearlshell appears to be most sensitive to water temperature, among the western species. Gravid Western Pearlshell (e.g., female mussels holding glochidia – larval phase of a mussel) can be found when average daily water temperatures are 10-13°C. Reproductive timing in this species is often difficult to pinpoint because final development of glochidia often happens quickly and entire populations can release their glochidia in conglutinates (concentrated packets of glochidia) in a single day. Western Pearlshell glochidia are hookless, white, sub-round in shape and average 55 µm in size. Known host fishes seem to be limited to salmonid species, like the Rainbow Trout and Chinook Salmon. Life expectancy has been estimated as high as 100 years for closely related species; however, life span can be site dependent and has not been investigated for this species specifically.
Western Ridged Mussel – Gonidea angulata
Western Ridged Mussel shells can be greenish-brown to dark brown in color and grow over 150 mm in length. Western Ridged Mussels can be found in several subbasins on the CTUIR ceded territory, including, but not limited to the lower Umatilla, Middle and North Fork John Day, Grande Ronde and Snake rivers. They release glochidia in loose white rice-like conglutinates when daily water temperatures remain above 11°C and increase to 15°C. Their white glochidia are subtriangular and measure 172 µm in length. Host fish associations appear to only include sculpin spp. (Cottus spp.), though some research suggests the use of other fish species in certain populations. Analysis of shell rings estimated Western Ridged Mussels can live 50-60+ years, making this a long-lived species. Western Ridged Mussels are found in a variety of habitats including firm sand/mud, gravel, and sand, but not in ponds, lakes, or unconsolidated sediments.
The Floaters, Anodonta – Anodonta
The California Floater (Anodonta californiensis), the Oregon Floater (A. oregonensis) and the Winged Floater (A. nuttalliana).
Further genetic and taxonomic work is underway to better identify and understand this genus. Floater shells have a wide range of colors including greenish-brown, yellow-brown to dark brown in color. The size range varies with species and can be up to 150 mm in length for larger rivers. Floaters can be found in many subbasins on the CTUIR ceded territory, including, but not limited to the Walla Walla, Umatilla, Tucannon, Middle and North Fork John Day, Grande Ronde and Snake rivers. Based on related species found in the eastern US, it is possible western Floaters live 10 to 25 years. Floaters release their glochidia in sticky webs or strands when water temperatures are between 12 and 23°C. Floater mussels have larger (~300 µm), hooked glochidia that attach to fish fins and body. The mechanism for attachment has been identified as passive entanglement whereby the female mussel releases sticky web-like strands with entangled glochidia. When a fish swims near the sticky web the strand wraps around the fish allowing the glochidia to attach. Once attached, the glochidia take about two weeks to mature and fall off as juvenile mussels. Floaters are considered generalists when it comes to host fish usage, meaning they can use a variety of fish species as hosts. Currently Longnose Dace, Speckled Dace, Redside Shiner, sculpins, and some species of salmonids (Rainbow Trout) have been identified as host fishes for the Floaters, but they may use more species.
