Doctor of Philosophy (PhD)


Biological Sciences

Document Type



Unionoids (freshwater mussels) are important in aquatic ecosystems, yet despite their continued decline in diversity, little is known about their distribution and ecology. To study Louisiana mussel species richness, abundance, and distribution I sampled 65 sites within six major watersheds in the Pine Hill region, Louisiana. Second through sixth order streams were surveyed for local instream variables, land use, hydrology, and co-occurring fish assemblage. To evaluate mussel species richness and abundance a structural equation model was created that suggested two major variables were important: 1) habitat stability, influenced by benthic shear stress, percent of silt substrate, and stream order and 2) anthropogenic disturbance influenced by agricultural land use in riparian corridors and water quality. Mussel species’ distribution in various stream sizes has been associated with hydrologic disturbance and their obligatory host fishes’ distribution. Few studies have looked at life history variation between mussel species to help explain their distributions. I contrasted the life history strategies, behavioral adaptations, and shell functional morphological of nine mussel species from the Amite River, Louisiana. The set of life history traits demonstrated two distinct groups of mussels: cosmopolitan species found through range of stream sizes and a set of large river specialist. The traits associated with cosmopolitan species includes: fast growth rates, early maturity, use of visual displays for host fish attraction, thin shells, and higher mobility. The traits of the large river species were: long lived, late to maturity, relatively sessile, none displaying methods of host attraction, and with thick sculptured shells. The sampled assemblages of mussels and fishes from the Pine Hill region were used to develop a Tiered Aquatic Life Unit (TALU) framework. The TALU is an efficient bioassessment tool, with conservation goals that are based on practical, systematic sampling of stream attributes. The developed TALU was created from metrics that are sensitive to anthropogenic disturbance. The model demonstrated to be quite conservative, resulting in only a 4% error rate in site allocation. Our framework is broadly applicable and easily modified to fit other eco-regions, and should prove useful for resource managers to monitor the health of rivers.



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