Cooperative Freshwater Mussel Propagation/Culture Project
One of the goals of the Service is to stabilize and recover populations of depleted aquatic species, including mussels, and reduce the need for listing species under the Endangered Species Act. One of the strategies that is being undertaken to fulfill this goal is to develop propagation and culture procedures for threatened and endangered species indirectly, through the use of surrogate species. Hatchery personnel have recently completed a three-year research project designed to transfer mussel propagation/culture technology from the Tennessee Cooperative Fishery Research Unit (Unit) located at Tennessee Technological University, Cookeville, Tennessee, to the National Fish Hatchery System (NFHS). The project was funded with U.S. Army Corps of Engineer's Olmsted Lock and Dam mitigation monies. A total of $10,000 was provided to both the Unit and to the NFHS (i.e. Dale Hollow NFH, TN and Wolf Creek NFH, KY) in FY 2000. The NFHS was provided with an additional $10,000 in FY 2001 and FY 2002. In support of this project, hatchery and Unit personnel worked together to collect, propagate, and culture the wavy-rayed lampmussel (Lampsilis fasciola) and painted creekshell (Villosa taeniata) which are found in both the Tennessee and Cumberland River drainages. These species are surrogates for the endangered Cumberland bean (Villosa trabalis), an endangered mussel species also occurring in the Tennessee and Cumberland River drainages. Hatchery personnel were responsible for most aspects of culturing the juveniles with Unit personnel providing technical assistance as needed.
Mussels have a complex reproductive cycle. Sperm is released into the water by the males. This sperm is then drawn into the female were fertilization of the eggs takes place. These eggs develop into larval mussels called glochidia. When the glochidia mature, they must attach to the gills or fins of fish in order to continue their development. Some species of mussels expel large numbers of glochidia into the water where a few usually find a suitable host fish. Other species of mussels attract host fish through the use of a modified part of the mantle - a soft part of the body located at the outer edge of the shell - which mimics small forage fish. Large numbers of glochidia are then released into the water, increasing the chances that the glochidia will find a suitable place to attach. Once the glochidia attach to a host fish, they transform into juvenile mussels and drop off onto the bottom of the body of water.
Propagation is accomplished a bit differently at the hatchery. Hatchery and Unit personnel collect gravid female mussels from the wild. The female mussels are transported to the hatchery where the glochidia are flushed out of the mussels into a glass dish. Host fish, being maintained in aquaria at the hatchery, are then infested with these glochidia. Once the glochidia transform into juvenile mussels, they are siphoned off of the bottom of the aquariums and placed into culture systems.
As have other mussel holding facilities, Dale Hollow NFH and Wolf Creek NFH are experiencing problems keeping juvenile mussels alive for prolonged periods. The problem with growing some species of mussels is being able to meet their nutritional requirements. Survival after 60 days usually indicates that these organisms are utilizing the nutrients being supplied to them and are not solely dependent on energy derived from glycogen stored in the body. Developing techniques to enable long term survival and growth is important because the larger we can rear juvenile mussels, the better chance they have to survive when they are reintroduced into the wild.
One might ask, "Why bother? Why worry about an organism that most people never even see?" Freshwater mussels live on the bottom of streams, rivers, or lakes and are an important part of the food web. They are filter feeders, removing algae, bacteria and other organic material from the water, thereby helping to improve water quality. Mussels are, in turn, eaten by predators such as fish and racoons. These important roles support the cycle of life in the aquatic ecosystems in which these animals occur. Mussels are an important indicator species. They are easily affected by pollution and habitat alteration. Declining mussel populations are an indication that something is not right and corrective action is necessary. The specific goal of imperiled aquatic species recovery is part of the overall charge of ensuring fishable, swimable waters in sufficient quantity to meet the reasonable needs of Americans.