The life history of Fusconaia edgariana, the endangered shiny pigtoe pearly mussel, was determined in a two-year study at North Holston Ford, North Fork Holston River (NEHRM 86.9) above Saltville, Virginia. Sixty 0.5m² Quadrats indicated a mean density of 10.6 mussels/m², representing 1 species. Six additional species were collect handpicking or in muskrat middens. The density edgariana was 1 adult/2 m². Distribution of the pigtoe was restricted to shallow areas of mixed gravel, and pebble substrate in low to moderate velocities. Drift nets (130um mesh) indicated glochidia edgariana were released into the water column from 23 June to 18 August, 1981 and 24 June to 28 August, 1982. Of the 4,800 fish examined from June 1981 to June 1982, 1.5% carried shiny pigtoe glochidia. The telescope, common, warpaint, and whitetail shiners were found naturally encysted by 1 to 3 glochidia of F. edgariana. Laboratory induced infestations were conducted on twenty two species of fish, and all but two species sloughed the glochidia within 4 to 14 days. The whitetail and common shiners retained glochidia for 38 days, indicating these two fish species to be probable hosts for the shiny pigtoe. / Master of Science

Recent efforts to restore depressed or extirpated populations of freshwater mussels have focused on artificial propagation as an effective and practical conservation strategy. Although artificially cultured juveniles have been produced and released to the wild, no study has investigated the best time of year or the best developmental stage to release these juveniles. Several experiments were conducted to gain knowledge of appropriate culture and release techniques. Juvenile wavyrayed lampmussels (<I>Lampsilis fasciola</I>) were artificially propagated in the laboratory and subsequently release into a fish hatchery raceway during June, September and March. Juveniles released in June experienced a gradual decline in survival rate, with 50% survival after 72 days and stable survival thereafter until 200 days. Juveniles released in September and March experienced high mortality within the first month, and were unsuccessful in surviving the cold water conditions typical of those seasons. Temperature was strongly associated with growth; thus, juveniles released in June exhibited considerably greater growth than those released in September and March. Survival was positively correlated with shell length in the first 32 days post-metamorphosis. Fall and spring survival values, shell length-frequency data, and a significant increase in overwinter mean shell length (p = 0.045) suggest that overwinter survival is size-dependent. Survival rates of juveniles released in June exceed those of previous culture studies reported in the literature. From these results, I suggest that the best time for release of propagated juvenile freshwater mussels should be at the beginning of the growing season in late spring, when water temperatures exceed 15 degrees C (plus/minus 1°C). Offspring of four, gravid female <I>L. fasciola</I> were tested to evaluate the extent of variability in growth and survival among brood stock. Comparison of growth and survival of progeny showed significantly lower performance of only one female (p < 0.05). Although results indicate variability in growth and survival among broods, it is not known whether heritabilities or physiological fitness caused this variability. Infested fish (IF), newly metamorphosed juveniles (NMJ) and juveniles cultured for 1 month (CJ) were released to a fish hatchery raceway in order to determine the most appropriate developmental stage to release juveniles. Significant differences were recorded among the three release methods, with CJ attaining the greatest growth (2.47 mm plus/minus 0.02), NMJ with the next best growth (1.86 mm plus/minus 0.02), and IF exhibiting the least growth (1.34 mm plus/minus 0.02) (p < 0.0001). Survival among release methods was not statistically different because of high variability within each release method. High mortality from predacious fish was presumably the cause of this variability. With minimal predation, L. fasciola experienced 82.2% (plus/minus 3.6) survival at 90 days. Survival of hatchery-reared juveniles was comparably higher than laboratory-reared juveniles, suggesting that culturing freshwater mussels in a hatchery raceway is a preferable alternative to laboratory culture. An experiment was conducted to compare growth of confined and unconfined juvenile L. fasciola released to a fish hatchery raceway. After 72 days, juveniles confined to small open dishes within the raceway (1.04 mm plus/minus 0.08) exhibited significantly less growth than juveniles released to the raceway that were not held in containers (2.15 mm plus/minus 0.07) (p < 0.0001). Results of additional comparisons with compiled growth data suggest that juvenile growth is retarded when cultured in small dishes. / Master of Science

The immunological aspects of the interaction between fish and glochidia were studied using glochidia of the Alabama rainbow mussel (Villosa iris). Tested host species was the rock bass (Ambloplites rupestris) and non-host fishes were common carp (Cyprinus carpio) and goldfish (Carassius auratus). Ouchterlony double-diffusion tests showed that both the host and non-host species expressed a specific humoral response to glochidial antigens after being artificially infested with the parasites. Further microagglutination tests were completed to compare titers of host and non-host fishes which were either uninfested, infested, or reinfested with glochidia. These tests showed that host and non-host species exhibit humoral responses of similar strengths (similar titers) to glochidia. In addition, fishes infested with glochidia had higher titers than uninfested fishes, and reinfested fishes had titers higher than both uninfested and infested fishes. Results indicate that fishes express anamnestic responses to glochidia. Because many host-specific parasites mimic their host’s antigens to avoid full immune attack, I tested for antigen mimicry in glochidia. Goldfish were injected with host (rock bass) and non-host (carp) antigens, in the form of sera, and then re-exposed to glochidial antigens at a later time. This test and other experimental results show no evidence of mimicry of host antigens by glochidia before attachment to host fish. Immunoelectrophoresis (IEP) was used to compare precipitation patterns of host and non-host fishes and to determine whether IEP can be used for identifying suitable hosts for a species of mussel. Although there were subtle differences observed between the precipitation bands of host and non-host fishes using IEP, successful molecular host identification will require more precise electrophoretic methods. The precipitation patterns of glochidial antigens and transformed juvenile antigens (reacted with anti-glochidia fish anti-sera) were compared to determine whether glochidia develop new antigens to avoid a full immune attack during glochidiosis. No precipitation occurred in trials using transformed juvenile antigens; therefore, pre-infestation glochidia and post-infestation juvenile mussels are antigenically different. / Master of Science

There is a great deal of concern about the declining freshwater mussel fauna of North America. Although deteriorating water quality and habitat degradation may account for much of the decline, it has been suggested that the exotic Asian clam, Corbicula fluminea, may be having an effect on native unionids. Negative impacts may result directly from competition or indirectly, because of Corbicula population crashes that release ammonia and reduce dissolved oxygen in the sediment. Laboratory tests were conducted to determine the relative sensitivity of native mussel and Asian clam life stages to unionized ammonia, and mussel glochidia were the most sensitive (24-hr LC50 of 0.11 mg/L NH₃-N). Juvenile and adult mussels were similarly sensitivity, with average 96-hr LC50's of 0.49 and 0.52 mg/L NH₃-N, respectively. Adult C. fluminea were the least sensitive, having an average LC50 of 0.80 mg/L NH₃-N. The EPA standard test organism, Ceriodaphnia dubia, had one of the lowest LC50's (0.07 mg/L NH₃-N) of the five species, and the fathead minnow, Pimephales promelas, had the highest (1.18 mg/L). The differing sensitivities of the various life stages are important when trying to determine the impact of an Asian clam dieoff. If a dieoff occurs at a time of year when the more sensitive life stages, such as glochidia are present, then the impact on mussel recruitment may be greater. Two miniature artificial stream tests were used to determine the effect of clam density on dieoff rate, ammonia production and dissolved oxygen levels. Only clams at the highest density of 10,000/m2 experienced 100% mortality. Unionized ammonia levels exceeded 4.0 mg/L, and dissolved oxygen levels dropped below 1.0 mg/L during the dieoff. The amount of unionized ammonia produced was twofold greater than the concentration that produced an LC50 in adult C. fluminea and ~40 times greater than the LC50 for V. iris glochidia. Factors thought to have contributed to the C. fluminea dieoff were flow rate, low dissolved oxygen levels, temperature and perhaps ammonia. A complete dieoff did not occur until flow was stopped and dissolved oxygen concentrations began to drop. One-hundred percent mortality occurred in 38 days for the first test, and 21 days in the second test. Higher water temperatures in the first test (26° C) compared to the second test (average = 21.7°C) are thought to have resulted in the faster dieoff. / Master of Science

The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on October 20, 2009). Thesis advisor: Dr. Charles Rabeni. Includes bibliographical references.

Thesis (M.Sc.)--Memorial University of Newfoundland, 2003. / Bibliography: leaves 101-113. Also available online.

Growth of mussels under laboratory conditions was examined under various food regimes in different water types and temperatures. Growth was less than would be useful as an indicator and comparisons with field exposures were of minimal value. The effects of organophosphates on bivalves were examined via toxicity tests, tissue concentration, and by controlling exposure through the use of physical constraints. Upper temperature tolerance of both bivalve species was examined with respect to different acclimation temperatures and organophosphate exposures. Deviations from control exposures occurred at some temperatures. Copper effectively lowered the mean heat coma temperatures of C. fluminea at some concentrations, however, chlorine exposures did not alter heat coma temperature.

Over 100 species of freshwater mussels (Unionidae) are endangered or threatened in the United States, and another dozen species support a declining commercial harvest of shells for the cultured pearl industry in Asia. Because of these Significant declines in abundance, a study was undertaken to develop a diet for rearing juvenile mussels, with the goal of long-term propagation of rare species. Three trials were conducted to test various tri-algal and commercial diets and to determine the influence of silt in survival and growth of the rainbow mussel (Villosa iris) and giant floater (Pyganodon grandis). After 45 days post-metamorphosis, juvenile V. iris fed algae with silt exhibited a two-fold increase in shell length (532 μm), and 63.5% survival. Juvenile P. grandis exhibited similar results at 45 days post-metamorphosis. In comparison, all juvenile mussels fed algae without the presence of silt exhibited no increase in shell length after 45 days post-metamorphosis. However, survival varied between species. Survival after 45 days was 5.0% for V. iris and 43.3% for P. grandis. P. grandis is probably more tolerant of a variety of environmental conditions. Analysis of covariance showed that growth rate over time (120 days) of P. grandis was significantly greater than that of V. iris. Shell lengths of P. grandis juveniles fed algae in the substrates kaolin, sterilized silt, sterilized silt plus Aqua Bacta-Aid, and bacteria-colonized silt were Similar, indicating that bacteria were not essential to juvenile digestion or nutrition. Shell lengths of V. iris juveniles fed algae in kaolin or algae in bacteria-colonized silt also were similar after 60 days. Juvenile mussels appear to be pedal-feeding for approximately 120 ± 30 days, depending on the species; hence, silt probably serves as a physical substratum for pedal-feeding mussels to collect food particles. Subsequent tests indicated that growth was significantly correlated with algae high in oils which contain polyunsaturated fatty acids (PUFA). V. iris juveniles fed a tri-algal diet, consisting of Neoehloris oleoabundans~ Phaeodactylum tricornutum, and Bracteacoccus grandis (NPB), with silt substratum showed the best growth over time. Individuals achieved a mean shell length of 1747 μm and had 30.0% survival after 140 days postmetamorphosis. All other tri-algal diets tested enhanced growth over the commonly used green tri-algal mix of Chlorella, Ankistrodesmus, and Chlamydomonas (CAC), and all algae diets enhanced growth over a silt-only diet. Commercial yeast diets did not support growth. After 272 days post-metamorphosis, V. iris fed CAC in silt achieved a maximum shell length of 4520 μm (17-fold increase in length), with a mean length of 2968 μm and approximately 5% survival. After 195 days postmetamorphosis, P. grandis achieved a maximum shell length of 7846 μm (22- fold increase in length), with a mean of 4877 μm and approximately 12% survival. Results of all feeding trials indicate that algae are a suitable food source for rearing early juvenile freshwater mussels. A tri-a1gal diet high in oils resulted in greater growth than all other diets tested. Resident bacteria in riverine sediments were not essential to growth and survival of juvenile mussels. Silt provided some nutritional value, but primarily served as a physical substratum for pedal-feeding juveniles. / Master of Science

The reproductive cycle, population dynamics, and habitat use of the dwarf wedgemussel (Alasmidonta heterodon) were studied in populations from the Tar River, North Carolina and Aquia Creek, Virginia during 1991 and 1992. This mussel is a long-term brooder, spawning in late summer and becoming gravid in September with glochidia maturing in November. Drift net sampling at sites with this species in both rivers during spring and fall of 1991 and spring of 1992 yielded no A. heterodon glochidia, indicating poor or no reproduction at both sites in 1991. Laboratory infestation experiments testing 15 fish species found three hosts for A. heterodon. The tessellated darter (Etheostoma olmstedi), the Johnny darter (EE. nigrum), and the mottled sculpin (Cottus bairdi) all supported glochidial development to the juvenile phase. Six species of sunfishes, four minnows, one sucker, and one catfish species tested in the laboratory did not serve as hosts. Because of seemingly poor reproductive success in 1991, natural infestations of fishes with glochidia were not documented. Age and growth characteristics were calculated using a thin-sectioning technique on valves collected from the Tar River, Aquia Creek, and the Neversink River, New York. As computed by the von Bertalanffy equation, the dwarf wedgemussel reaches a maximum length of 38.70 mm, 45.26 mm, and 45.84 mm in the Tar River, Aquia Creek, and Neversink River, respectively. There were significant differences among the growth curves of A. heterodon from the Tar River and Aquia Creek, and between those of the Neversink River and Aquia Creek. There was no significant difference between the growth curves of dwarf wedge mussels from the Tar and Neversink rivers. Microhabitat parameters including depth, roughness, velocity, turbulence, distance from shore, distance from obstructions, canopy cover, presence or absence of macrophytes, and substratum size were collected for dwarf wedge mussels at the Tar River and Aquia Creek. Microhabitat use differed between the sites, most significantly described by the following variables: distance from shore; turbulence; and velocity. Laboratory preference studies designed to determine preferred substratum size and water velocity were conducted. Dwarf wedge mussels always preferred the finer substratum offered; little preference was exhibited by the mussels for lotic versus lentic flow regimes in the laboratory. / Master of Science

Mussels play an important supplementary role in the diet of local communities on the Transkei coast in the Eastern Cape province of South Africa. The exploitation of mussels date back to about 1350 years ago, but in the last 3 decades, exploitation of the brown mussel Perna perna has become unsustainable with mussels collected as small as 30-40mm when they are only just sexually mature. Dye and Dyantyi (2002) developed a technique to rehabilitate areas denuded of adult mussels. The government sponsored Mussel Rehabilitation Project (MRP) to use this technique but only some sites have been successfully rehabilitated, reaching c. 80 % cover within a year whilst others only reach about 5%. At an unexploited site (Riet River), I tested the effects of mussel size and wave strength on the effectiveness of the rehabilitation technique, hypothesizing that different size classes may respond differently due to differences in their energy allocation (growth vs reproduction), while wave action determines food supply. Small (1-2cm) and large mussels (3-4cm) were deployed for rehabilitation at 2 exposed and 2 sheltered sites, separated by 100s m. A similar study was repeated in Coffee Bay where shores are exploited. Six sites were selected, 3 sites that had been successfully rehabilitated and 3 that were unsuccessful according to the MRP. Again, two size classes were used but these differed from the first experiment. Mussels of 3-4cm size were now rated as small and 5-6cm as large. Two methods were used to re-attach mussels, the original and the same method with the addition of mesh bags during mussel deployment. Treatments were examined on three occasions at approximately one month intervals. At Riet River, the sites chosen did not show differences in wave strength (measured using dynamometers) or water flux (measured using erosion of cement balls) so that water motion was excluded from the analyses. Small mussels grew faster and had weaker attachment than large mussels. There was no difference in condition index between small and large mussels, or in the numbers of recruits settling among the byssus threads of deployed mussels of the two size classes. In Coffee Bay, there was no relationship between rehabilitation success and maximum wave force, and no difference in bulk water flux among sites. Small mussels deployed using mesh bags survived better than non-meshed or large mussels of either treatment. There was no difference in condition index (CI) between mesh and no-mesh, or between small and large mussels. As in the case of Riet River, small mussels grew faster than large mussels, but large mussels attached stronger than small mussels, with no effect of mesh. Although the factors that improve reseeding of mussels can be identified (use of mesh, use of small mussels, choice of sites with high recruitment rates), successful long-term rehabilitation requires appropriate subsequent management of re-seeded sites.