Xavier Bordeleau

• Ph.D.
• Research Scientist at Fisheries and Oceans Canada

Juvenile survival, a fundamental parameter in the population dynamics of long-lived species, is often tightly linked to early-life body growth. Here, based on repeated mass measurements on 555 harbour seal Phoca vitulina pups marked between 1998 and 2023 in the St. Lawrence Estuary, we first characterized the shape of neonatal growth patterns of th...

This study presents the first systematic assessment of trends in white shark Carcharodon carcharias presence in Atlantic Canadian waters (ACWs) using 2 standardized acoustic monitoring arrays—the Halifax and Cabot Strait lines—deployed by the Ocean Tracking Network between 2014 and 2023. We evaluated annual changes in the probability that acoustica...

Fine‐scale age estimation of animals can provide insight into important biological processes but can be logistically difficult to measure in wild populations. We evaluated the accuracy and precision of an umbilical‐based method for fine‐scale age and birthdate estimation in a wild population of harbour seal pups (Phoca vitulina) in the St. Lawrence...

Most marine ecosystems are experiencing increasing cumulative impacts from climate change, fishing, shipping and land-based pollution. The resulting ecosystem responses are challenging to monitor. Studying the space use of top marine predators may provide insight into how these ecosystems react to these impacts. However, natural populations are com...

Stable carbon (δ ¹³ C) and nitrogen (δ ¹⁵ N) isotope ratios are widely used in marine food web and habitat use studies. However, lipids are naturally depleted in ¹³ C relative to proteins and are variable in content, biasing δ ¹³ C of bulk samples, with consequences for the accuracy of conclusions. This issue can be resolved either by extracting li...

Many Atlantic salmon (Salmo salar) populations have experienced significant declines for decades throughout North America and Europe. Mortality due to marine mammal predation during their early marine life could be an important factor contributing to these declines and limiting their population recoveries. However, quantifying predation events, and...

Beluga (Delphinapterus leucas) from the St. Lawrence Estuary, Canada, have been declining since the early 2000s, suggesting recruitment issues as a result of low fecundity, abnormal abortion rates or poor calf or juvenile survival. Pregnancy is difficult to observe in cetaceans, making the ground truthing of pregnancy estimates in wild individuals...

Marine mammal populations worldwide greatly benefitted from conservation measures put in place since the 1970s following overexploitation, and many pinniped populations have recovered. However, threats due to bycatch, interspecific interactions or climate change remain, and detailed knowledge on vital rates, population dynamics, and their responses...

Iteroparity occurs when organisms reproduce more than once, and is seen as a bet-hedging reproductive strategy. Despite a wealth of research on iteroparous Atlantic salmon, steelhead, brown trout, and Arctic charr, the determinants of reproductive investment, the intra- and interspecific differences in the degree of iteroparity, the drivers of repe...

In 1954, brown trout were introduced to the Kerguelen archipelago (49°S, 70°E), a pristine, sub-Antarctic environment previously devoid of native freshwater fishes. Trout began spreading rapidly via coastal waters to colonize adjacent watersheds, however, recent and unexpectedly the spread has slowed. To better understand the ecology of the brown t...

Salmonids are some of the most widely studied species of fish worldwide. They span freshwater rivers and lakes to fjords and oceans; they include short‐ and long‐distance anadromous migrants, as well as partially migratory and non‐migratory populations; and exhibit both semelparous and iteroparous reproduction. Salmonid life‐history strategies repr...

The sea trout (anadromous brown trout Salmo trutta ) displays extensive among-individual variation in marine migration behaviour. We studied the migration behaviour of 286 sea trout (27-89 cm) tagged with acoustic transmitters in the spring, in 7 populations located in 2 distinct marine fjord systems in Norway. We examined whether individual nutrit...

Iteroparity is a bet-hedging strategy where individuals spread the risk of reproductive failure over time. The occurrence of iteroparity (i.e. proportion of repeat spawners in annual returns) varies among Atlantic salmon (Salmo salar) populations, yet information on its ecological importance is limited. We compiled multi-decadal time series on the...

Despite the importance of iteroparity (i.e. repeated spawning) for the viability of Atlantic salmon populations, little is known about the factors influencing the migratory behaviour and survival prospect of post-spawned individuals (kelts). To test the hypothesis that post-spawning nutritional condition underlies differences in spatiotemporal aspe...

Despite that the study of individual repeatability is a common topic in behavioral ecology, virtually nothing is known about inter-annual variability in the marine migratory behavior of iteroparous salmonids that can complete multiple feeding migrations in their lifespan. Behavioral data from 38 anadromous brown trout (Salmo trutta), tracked by aco...

The overarching objective of my thesis is to shed light on a poorly understood life history stage of salmonid fish species, by quantifying spatio-temporal variation in the ecological importance of iteroparity (i.e. repeated breeding), as well as the factors influencing the movement ecology and survival of post-spawners, in freshwater, estuaries, an...

The marine migration and habitat use of 340 anadromous brown trout Salmo trutta (often termed sea trout, total length 135-730 mm) and 14 Arctic Charr Salvelinus alpinus (350-480 mm) from four watercourses drain-ing to the marine fjords Tosenfjorden and Bindalsfjorden were studied from 2015 – 2017. The fish were tagged with acoustic transmitters and...

The timing of the juvenile Atlantic salmon ocean-entry is considered a critical stage in the species’ life-history. Entry into the ocean at suboptimal times can have negative survival impacts on entire smolt cohorts. Previous studies have identified smolt residency time in the Bras d’Or Lakes as highly variable and correlated with body condition. T...

Broodstock collection and enhancement programs are a widely-used management practice within the Atlantic salmon’s (Salmo salar) native range. Wild-origin adult salmon captured as part of these programs experience multiple stressors during their time in hatcheries. However, no studies have assessed the potential consequences of hatchery practices on...

The brown trout (Salmo trutta) is an iteroparous, anadromous salmonid that exhibits a complex continuum of feeding migration tactics, ranging from freshwater residency, to potamodromy, to estuarine migration, as well as short- to long-distance coastal migrations. While anadromous migrants are believed to play an important role in the species’ popul...

Atlantic Coastal Plain Flora (ACPF) are a group of plants mostly inhabiting lakeshores along the Atlantic coast of the United States, with disjunct populations in Nova Scotia and Ontario. To better define their ecological requirements, the main objective of this study was to determine the factors (biotic and abiotic habitat components) influencing...

We investigated the physiology of two closely related albatross species relative to their breeding strategy: black-browed albatrosses ( Thalassarche melanophris ) breed annually, while grey-headed albatrosses ( T. chrysostoma ) breed biennially. From observations of breeding fate and blood samples collected at the end of breeding in one season and...