Thesis (M.S.)--Oregon State University, 2006. / Printout. Includes bibliographical references (leaves 26-28). Also available on the World Wide Web.

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Thesis (Ph.D.)--Memorial University of Newfoundland, 2005. / Bibliography: leaves 129-148.

Thesis (M.Sc.)--Memorial University of Newfoundland, 2002. / Bibliography: leaves 78-89.

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Thesis (M.S.)--Virginia Polytechnic Institute and State University, 2003. / Title from PDF t.p. (viewed on Dec. 9, 2005). Vita. Includes bibliographical references.

Thesis (Ph.D.)--University of Waikato, 2006. / Includes bibliographical references (leaves 135-150)

The principal aim of this study was to establish the biological and environmental parameters governing the successful and sustainable cultivation of mussels in Saldanha Bay. The environmental study investigated seston, chlorophyll-a and particulate organic matter (POM) levels, water temperature dissolved oxygen and salinity levels in the bay and water flow in and around the rafts. The biological part of the study investigated the efficiency of food extraction, growth rates, mussel condition, fouling and production and yield on a rope, raft and farm scale. Saldanha Bay is well suited for the culture of mussels, particularly Mytilus galloprovincialis and Choromytilus meridionalis. Water temperature and salinity in Saldanha Bay were found to be near optimal for mussel culture. POM and chlorophyll-a levels were found to be high due to primary production resulting from the nutrient rich upwelled water outside Saldanha Bay. The mean levels of chlorophyll-a (8,6μg/l) represent 6%, by mass, of the total POM. On a bay scale the POM remained above the mussels maximum requirements (pseudofaeces threshold) during the study period. Mussels showed a preference for the phytoplankton portion of the POM. Approximately 40% of the chlorophyll-a was extracted from the water by the mussel farm. The efficiency of food extraction increased with mussel age. Rafts with seed mussels younger than 2 months, 3 to 4 months, 5 to 6 months and older than 6 months extracted 32%, 55%, 85% and 92% of the available chlorophyll-a respectively. An increase of rope spacing on the rafts resulted in 37% more chlorophyll-a and 30% more particle volume reaching the lee of the raft. Ambient water currents in the bay show flow rates of up to 22cm per second. However, on entering a raft with a rope spacing of 60cm, the water flow is attenuated by 90%. Increasing the rope spacing to 90cm resulted in a water flow attenuation of 72%. The increase in rope spacing ensures that the mussels in the centre of the raft are feeding on food levels close to, or above, the pseudofaeces level. Mussel growth rate at a rope spacing of 90cm is significantly improved as a result of the increased food delivery. There are other factors, however that effect mussel growth. Growth rates were found to be better in summer than in winter. The reduced winter growth rate is possibly due to competition with the maturing fouling organisms which settle in mid to late summer. Fouling by mussel spat and Ciona intestinalis is seasonal, occurring from December to May. C.intestinalis is prevalent in the centre of the farm and rafts as low energy waters are preferred by this species. Mussel spat settles mainly on the periphery of the farm and the rafts. Competition with fouling organisms reduces growth and increases mortality of the cultured mussels. Results indicate that the present spacing of rafts, (1 raft per hectare) is adequate under existing conditions. Any new farms should maintain batches of 50 rafts with channels between them to ensure water current penetration into the furthest reaches of the farm. Rope spacing on the rafts should be increased to between 60cm and 90cm. Mussel density should be regulated according to mussel size and fouling should be controlled to maintain yields.

A flow-through pond at White Sulphur Springs National Fish Hatchery was evaluated as culture environment for juvenile freshwater mussels of Villosa iris and Lampsilis fasciola. Survival did not differ significantly (p = 0.1910) over 93 d for V. iris cultured with silt (mean 49.8% ± SD 14.5) and without (mean 32.9% ± SD 11.7). Survival differed significantly (p <0.0001) between juveniles of V. iris (mean 49.8% ± SD 14.5 at age 93 d) and L. fasciola (mean 6.3% ± SD 4.5 at age 86 d). This may indicate that the pond failed to meet requirements of L. fasciola, or may have resulted from microhabitat variables. Growth did not differ significantly between species (p = 0.1315). Villosa iris reached a mean length of 1.81 mm ± SD 0.67, and L. fasciola 1.78 mm ± SD 0.78. Water quality parameters remained within suitable ranges, and planktonic algal densities were between 2850 - 6892 cells/mL. Survival of V. iris and growth of both species compares favorably to previous culture attempts. Juveniles of V. iris and L. fasciola were exposed to ammonium chloride solutions for 96 h in static renewal conditions at 12°C and 20°C. Calculating LC50 values with the Trimmed Spearman-Karber method, juveniles of L. fasciola (mean 96 h LC50 of 0.26 mg/L NH3-N) were significantly more tolerant of unionized ammonia than juveniles of V. iris (mean 96 h LC50 of 0.11 mg/L NH3-N). The only organisms with reported LC50 values lower than those seen for V. iris juveniles were Ceriodaphnia dubia and Hyella azteca. / Master of Science

Shellfish aquaculture is growing rapidly with the expanding human population, offering high-quality animal protein as well as economic benefits to producing areas. Cultivation relies on coastal and estuarine habitats, dynamic ecosystems where marine organisms including mussels are exposed to natural environmental variability, and which will be affected by climate change (e.g. ocean warming, acidification, desalination etc.). This thesis investigated the variability in blue mussel, Mytilus edulis, performances under suspended rope-culture in a stratified Scottish sea loch, Loch Leven. Environmental conditions were monitored over one year and at different culture depths and related to the mussel's product quality (meat yield, condition index), genetic composition (genotype, extent of hybridisation) and shell phenotype (shell strength and shape). Environmental conditions varied over time (seasonal cycles and short-term fluctuations) but also across depth, generating different microhabitats for mussels depending on their position on the rope. Conditions varied most at shallow culture depths, for salinity in particular, but presented warmer temperature and higher food availability compared to greater depths and promoted mussel growth and abundance. Meat yield and condition index followed a seasonal cycle, with maximum values in early summer and minimum values in winter, associated with environmental (nutritional) and reproductive cycles. The genetic composition and shell morphology of cultured mussels differed across depth. On average, every sixth mussel carried alleles of Mytilus trossulus, but the level of introgression was overall low. However, highly introgressed mussels (≥ 75 %) presented distinct shell morphology (significantly lower shell strength, elongated shell shape) and originated mainly from shallow culture depths. This phenotype distinguished them from their congeners and allowed for their identification based on shell characters. This thesis presents the variability in suspended mussel culture in a heterogeneous environment, highlighting the complex relationships between habitat conditions and the genetic and phenotypic make-up in naturally occurring mixed-species stocks. The knowledge gained offers guidance for the farm operators to optimise production (site selection, spat collection etc.) and provides better predictions for the industry on the possible effects associated with climate change on future mussel production.