Namao virus (NV) was associated with mortality in lake sturgeon Acipenser fulvescens reared as part of a conservation stocking program for this endangered species in Manitoba, Canada. The virus itself was large, doubly encapsidated and icosahedral-shaped. Phylogenetic analyses using the major capsid protein showed that NV and other epitheliotropic sturgeon nucleo-cytoplasmic large DNA viruses shared a common evolutionary past and formed a distinct evolutionary lineage within Megavirales. Three PCR tests were developed and their analytical performance was validated for detection of these viruses. Testing of wild sturgeon revealed that NV is endemic in the Nelson River water basin in Manitoba. Bath exposure resulted in transmission of NV to healthy sturgeon. The gills appeared to be the initial site of infection with virus persisting in the head skin tissue for up to 62 days. The molecular tests will be useful tools for disease management in sturgeon conservation stocking programs. / October 2015

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In this thesis the enriched stable isotope marking technique was examined to determine its validity and effectiveness in marking of Lake Sturgeon fin rays. The enriched stable isotope marking technique uses stable isotopes of elements that replace calcium in boney tissue, which are fixed in nature, however in laboratory settings can be easily manipulated. Manipulated ratios of naturally occurring isotopes can be determined from a small sample of the fin ray, thus allowing for the discrimination of fish stocks. Further, the thesis examined the underlying assumptions for strontium and barium into the Lake Sturgeon. For the marking technique to work, strontium and barium must be taken up from the environment and accumulated long-term in boney tissue. Net flux and tissue retention of strontium is reported and the research has demonstrated that enriched stable isotopes can be successfully used to mark the fin ray of Lake Sturgeon for long-term stock discrimination. / October 2015

Hatchery supplementation of declining fish populations is used for increasing year-class strength, particularly when fish are released with knowledge of local predators. The ability of young-of-the-year lake sturgeon (Acipenser fulvescens) to avoid predation, as well as their vulnerability to predation, remains undocumented. The objective of my thesis was to determine: 1) whether hatchery-reared, predator-naive juvenile sturgeon would respond to alarm cues from injured conspecific cues, a reliable indicator of predation risk in other fishes; and 2) if sturgeon would learn to identify unknown predators through a Pavlovian-like conditioning with conspecific alarm cues. Releaser-induced recognition learning is a variant of Pavlovian learning in which recognition of a previously neutral stimulus is acquired through the experience of pairing a behaviourally active releasing stimulus and a novel stimulus. Sturgeon were initially conditioned using a behaviourally active stimulus of sturgeon alarm cue, paired with a behaviourally neutral stimulus of novel northern pike (Esox lucius) odour, or were pseudo-conditioned with distilled water paired with pike odour. Following conditioning, sturgeon were tested for recognition of the predator odour 24 hours later. The first population of fish (Rainy River) showed a dramatic antipredator response to alarm cues from the skin of conspecifics, but failed to exhibit learning of a novel predator through conditioning with alarm cues obtained from the skin of conspecifics. However, when Rainy River fish were conditioned with alarm cues from the whole body of conspecifics, they showed strong learning of the predator. Conditioning Wolf River fish to recognize predators with whole body extract had no effect on response to predator odours. However, when the fish were conditioned multiple times there was evidence of predator learning. These results highlight potential opportunities and limitation to life-skill training of artificially reared sturgeon for future conservation initiatives.

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.