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Deakin University (2018)

Water level & habitat affect small-bodied fish in semi-arid lakes

Halliday Bryce

Titre : Water level & habitat affect small-bodied fish in semi-arid lakes

Auteur : Halliday Bryce

Université de soutenance : Deakin University

Grade : Master of Science (Ecology & Environment) 2018

Résumé partiel
The freshwater lakes at the terminus of the Murray-Darling Basin, Lakes Alexandrina andAlbert (Lower Lakes)in southern Australia, are ecologically important as is recognised by the region’s Ramsar listing. In such lakes, changes in water level are likely a key driver of functional connectivity (the integration of physical connection with species-specific traits, e.g. dispersal ability)by altering the presence, complexity, distribution andphysical connectivity among habitat patches. For example, water level variation changes access among, andability to move between, habitats for small-bodied fish (adult length <200mm). Drought also acts to significantly shift the mix of the fish assemblage present in the Lower Lakes. The consequences of drought for fish often include the decline of ecologicalspecialists andthe predominance of generalist species. The restructuring of the littoral fish assemblages following prolonged drought is poorly understood. By combining factors such as physical habitat, water levels, food resources andfunctional connectivity, a more holistic view of how animals utilise habitat is generated. This research quantified the relationship between water level andhabitat use for small-bodied fish in three inter-connected studies. The first studycompared lake-edge small-bodied fish assemblages between the two lakes, examining the shift in the littoral fish assemblage and assessing the fish assemblage’s recovery over a five-year, post-drought period. The second studyaimed to quantify the small-bodied fish assemblages within four lakeshore habitat types focusing on how lake water levels influence the availability of the habitat used at inter-and intra-lake scales. The final studyis an assessment of the food andfeeding habits of four common fish species within the Lower Lakes, based on stomach content andprey item data. The overall aim of the research was to gain a more comprehensive picture of the habitat association, differential use of, andfunctional connectivity among, a range of habitat types, including emergent vegetation, submerged vegetation, bare sediments andartificial structures for small-bodied native fish.


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