The California floater (Anodonta californiensis) is a freshwater mussel, indigenous to parts of the western United States. Its shell is thinner than most other mussels and can range in color from yellowish-green to brown. They can grow up to five inches and live for up to 15 years. The California floater used to be found in many of Arizona’s river systems; however, due to the disappearance of native fish in rivers and lakes, California floater population numbers have declined. Currently, the only known population is found in the Black River.
At the Phoenix Zoo
In 2011, the Zoo developed the “Floater Float,” a suspended tray filled with suitable silt substrate to contain a small population of adult California floaters in the one of the lakes at the Zoo. The tray is suspended by floats that keep it about four feet below the water’s surface and about eight feet above the lakebed. The system can be raised out of the lake through the use of a pulley system.
The float project was initiated in collaboration with the Arizona Game and Fish Department. In April 2012, the Zoo placed six California floaters into the system. The main goal for this portion of the project was to determine if the group could remain alive in the suspended aquatic setting. After a year, the Zoo determined that the group of six mussels was thriving and that fish living in the lake were taking up residence within the float, providing an opportunity for glocidia (larvae) attachment and dispersal.
The Zoo now maintains California floaters at the Arthur L. and Elaine V. Johnson Foundation Conservation Center within one of the ranaria ponds. They are housed with longfin dace (Agosia chryogaster chryogaster), a native fish species that is a suitable host for the mussels’ glocidia. The California floater mussel is classified as vulnerable by the Xerces Society and faces other threats like predation from non-native fish and habitat loss. The Johnson Center hopes to develop a sustainable propagation program that will help to increase wild populations.