Behavioural ecology of foraging and predator avoidance trade-offs in Lake Sturgeon (Acipenser fulvescens)

Abstract

I investigated Lake Sturgeon (Acipenser fulvescens) foraging and anti-predator behaviour. My goals were to understand: (1) The role of environmental change on foraging and anti-predator behaviour trade-offs. (2) The relative cost/benefit trade-off between escape behaviour and cover-seeking behaviour. (3) How development of several independent morphological traits affects anti-predator behaviours. I used simulated river mesocosms to study Lake Sturgeon behavioural ecology under controlled conditions. I found: (1) Foraging intensity was significantly higher during the night than the day as well as in turbid environments versus clear environments, indicating that decreased turbidity alone, may in part drive anti-predator behaviour and constrain foraging activity. (2) In high-risk clear-water environments, Lake Sturgeon responded to danger by evoking an escape response and seeking cover in rocky microhabitats. However, in low-risk turbid environments, Lake Sturgeon responded to danger by seeking cover in rocky microhabitats, but not fleeing to a significant degree. Cover-seeking behaviour may therefore be a relatively low-cost/high-benefit anti-predator strategy. (3) Strong evidence for trait co-dependence between escape responses and body size, where larger fish were able to elicit stronger escape responses. I also found that cover-seeking behaviour exhibited a complex multi-tiered relationship, representing a mixture of trait compensation and trait co-specialization that is dependent on specific combinations of morphological traits. These findings are important because they help us understand: (1) The degree to which anti-predator behaviour can be influenced by changing environmental conditions. (2) The relative cost/benefit trade-off between two common anti-predator behaviours. (3) How behaviour and morphology interact in species with a complex anti-predator phenotype.