Recherche | Research

Ph.D | Des individus aux populations: liens entre comportement, métabolisme et sélection d’habitat

Understanding the distribution of organisms in nature is one of the key challenges in ecology and is critical for effective conservation efforts. Modelling approaches have been developed to quantify the relationships between abundance metrics and environmental variables describing the habitat. Habitat use models correlate abundance metrics in a series of habitat patches to environmental conditions observed in these patches. However, assuming organisms select habitats that will allow them to maximize their fitness, a mechanistic understanding of how species relate to their environment, from physiological processes to behavioural response, is necessary to better predict the impacts of environmental and anthropogenic changes on species distribution.

SMBtaggedThe general goal of this project is to explore the relationships between habitat selection and physiology for fish, and whether these relationships are context dependent. The project implies a combination of field (sampling of fish abundance and environmental conditions, and tracking of fish movement) and laboratory (measurement of metabolic traits) studies.

Freshwater ecosystems are subjected to many threats and stressors, but habitat loss has been identified as the principal threat to freshwater fish populations . By studying the determinants of fish habitat selection, the ultimate goal of our project is to improve our ability to develop valid models, and therefore to guide conservation of critical habitat for freshwater fish.

M.Sc. | Thermal stress in a tropical freshwater fish IMG_0148

Environmental temperature is a key predictor of species distribution that can affect fitness and performance of individuals. Assuming organisms are adapted to the thermal regime of their environment, their temperature limits and optimum should fall with the thermal range of their natural habitat. The effect of water temperature on aerobic performance is key in determining persistence of fish populations faced with rising water temperatures. However, there is a paucity of empirical data on thermal sensitivity of tropical fishes, many of which contribute to food security. In Africa alone, about half of the human population relies on fish for more than 20% of its animal protein intake; and in some countries such as Uganda, East Africa, fish is critical, comprising an estimated 50% of per capita protein consumption. Lake Victoria is home to Africa’s largest inland fishery fueled by the large piscivorous, non-native Nile perch (Lates niloticus).

The general goal of my M.Sc. research was to evaluate the effects of body size and habitat conditions on thermal tolerance of Nile perch. In fishes, resting metabolic rate is known to increase with body size, and it is predicted that thermal sensitivity is also greater in larger individuals. Habitat specificity may also be an important predictor of thermal sensitivity, particularly when populations show habitat-related ecological divergence, as is the case with Nile perch. In Lake Nabugabo (Uganda), juvenile Nile perch captured near wetlands show larger gill size, a different body shape, and a more piscivorous diet than their conspecifics captured in well-oxygenated waters suggesting habitat-specific phenotypes. I conducted respirometry and critical thermal maximum (CTmax) trials on juvenile perches (5-20 cm TL) from these distinct habitats of Lake Nabugabo acclimated for a minimum of three days to ambient (25.5 oC) and elevated water temperatures (27.5 oC, 29.5 oC, 31.5 oC).

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