Date of Award


Document Type


Degree Name

Master of Science (MS) in Biology




"The introduction of non-native fishes can cause trophic cascades in freshwater habitats; these effects may be amplified in ephemeral/temporary habitats. Non-native brook stickleback fishes (Culaea inconstans) were first documented on the Turnbull National Wildlife Refuge (WA) in 1999 and are now present in many portions of the refuge. The consequences of their presence on the refuge's perennial/permanent and temporary habitats are poorly understood. Therefore, the purpose of my project was to determine if brook stickleback are affecting habitat characteristics that are important for waterfowl nesting success. From April-August 2015, I compared the macro invertebrate and macrophyte community characteristics, fingernail clam population and stress metrics, and water quality parameters in twelve lentic systems on the refuge; those that contain brook stickleback or are fish free, and are either temporary or permanent. The fish free, permanent lentic systems had more macroinvertebrate and macrophyte taxonomic/species variety, more macroinvertebrates and macrophyte dried biomass (abundance), the highest fingernail clam condition index, and the highest clam brood sizes. Macroinvertebrate taxonomic assemblages were additionally influenced by lentic system category and size. The macrophyte abundance and diversity was influenced more by the permanent or temporary status. Fingernail clam condition index, clam length, chlorophyll, transparency, nitrate, and pH were influenced by the compounding effects of brook stickleback presence and permanent or temporary status. Overall, it appears that the presence of brook stickleback most likely affects habitat quality characteristics in the lentic systems that are temporary, especially those that also are smaller in size. This is of particular concern for the refuge because these changes, if they persist, may impact waterfowl nesting success"--Leaf 4.