Habitats essentiels des larves et des juvéniles de la nouvelle population de bar rayé du Saint-Laurent

La réintroduction du bar rayé dans l'estuaire du Saint-Laurent, suite à son extinction en 1966, soulève des questionnements et requiert l'acquisition de connaissances concernant la population. Entre autres, l'identification des habitats essentiels chez tous les stades de vie du bar rayé est une priorité. Cette étude vise à décrire les comportements migratoires des individus larvaires et juvéniles de bars rayés de l'estuaire du Saint-Laurent en utilisant la chimie des otolithes. Dans le but de cibler d'éventuels habitats essentiels, 118 bars rayés juvéniles (0+ et 1+ an) furent capturés dans le Saint-Laurent en 2011 et 2012. Les variations dans la composition chimique d'un tracé passant du coeur à la marge des otolithes furent analysées par spectrométrie de masse couplée à un plasma inductif avec ablation au laser (LA-ICP-MS). Les signaux élémentaires du noyau de l'otolithe ont aussi été analysés afin de définir une signature représentative de leur lieu de naissance. Trois comportements (contingents) migratoires récurrents (résident en eau douce, migrant oligohalin exploitant des eaux de 2 à 14 de salinité et migrant mésohalin exploitant des eaux de 11 à > 18 de salinité) furent identifiés par l'utilisation de l'analyse à fenêtre mobile (split-moving window). L'occupation des habitats d'eau douce par tous les contingents montre leur importance dans le développement des bars. Chez les deux cohortes, l'initiation de la migration s'est faite approximativement au milieu de la saison de croissance et, suivant l'atteinte des milieux oligohalins et mésohalins, les retours vers l'eau douce ont été peu fréquents. La classification des empreintes élémentaires du coeur de l'otolithe laisse croire qu'au moins deux sites de reproduction coexistent dans le Saint-Laurent. Un site situé en eau douce et l'autre ayant une signature élémentaire oligohaline. La spatialisation des comportements migratoires chez les juvéniles de bar rayé du Saint-Laurent cible les zones d'eau douce comme des habitats essentiels potentiels des jeunes bars rayés, en plus des zones oligohalines déjà identifiées (anse Sainte-Anne, La Pocatière). Cette étude augmente la compréhension de la dynamique de rétablissement et de colonisation de la nouvelle population de bar rayé. Le processus en cours dans le Saint-Laurent est un exemple probant de colonisation d'un milieu par une nouvelle espèce; il apporte une connaissance supplémentaire du point de vue écologique et évolutif. Les informations acquises soulignent aussi le haut niveau de plasticité du comportement migratoire du bar rayé, une contribution majeure à sa capacité de colonisation et d'adaptation à un nouvel environnement

Spatio-temporal changes in littoral fish community structure along the St. Lawrence River (Québec, Canada) following round goby (Neogobius melanostomus) invasion

The round goby (Neogobius melanostomus), a small Ponto-Caspian bottom-dwelling fish species, was first observed in the St. Lawrence River in 1997. After twenty years, it is now considered as one of the most successful invaders of the St. Lawrence River. Despite the elevated abundances observed throughout the river, little is known about its impacts on the littoral/mid-shore fish community. In this study, we used a large dataset obtained from an annual standardized fish survey held in the St. Lawrence River to analyze the impacts of round goby on littoral native fish community and native predator assemblages within five distinct segments of the river characterized by different round goby abundances. Throughout the system, the round goby negatively impacted the abundances of tessellated darter (Etheostoma olmstedi) likely as a consequence of competitive exclusion. In contrast, the small pelagic/demersal brook silverside (Labidesthes sicculus) and emerald shiner (Notropis atherinoides) increased in abundance. Indirect food web effects, such as predation pressure relaxation, are suspected. Native predator abundances exhibited contrasting trends in the different sectors analyzed, with the exception of smallmouth bass (Micropterus dolomieu) abundances that increased in all fluvial lakes. We hypothesize that trophic relationships between littoral fish and native predators are influencing the outcomes of the round goby invasion of the St. Lawrence River

Deciphering lifelong thermal niche using otolith δ18O thermometry within supplemented lake trout (Salvelinus namaycush) populations

1. The selection of thermal habitat by fish is strongly regulated by physiology and behaviour. However, delineation of a species lifelong thermal niche remains tech-nically challenging. Lake trout (Salvelinus namaycush) survival and productivity are recognised as being tightly linked to a somewhat restricted thermal habitat. The factors guiding temperature selection during each life stage remain poorly understood. 2. In this study, we tested the significant factors controlling the realised thermal niche of lake trout from two southern Quebec small boreal lakes that experienced supplementation stocking during the last 20 years. We used oxygen stable isotope (δ18O) thermometry of otolith calcium carbonates (aragonite) using secondary-ion mass spectrometry to estimate experienced lifelong temperatures. We investi-gated the thermal habitat of lake trout with known genotypes (local, hybrid, and stocked). 3. Ontogeny and genetic origin influenced temperature selection in both studied lake trout populations. Young-of-the-year consistently used warmer, shallower habitats (10.7 ± 2.6°C, 7.5 m depth) prior to a juvenile transition to colder and deeper waters (8.5 ± 3.3°C, 10 m depth). Stocked lake trout, originating from a genetically distinct ecotype, exhibited a more variable thermal niche, with some individuals consistently using warmer habitat (10.4 ± 1°C) than local fish. Their hybrid progeny also occupied a warmer thermal niche, intermediate to the paren-tal strains. We propose that increased fat content and genetic origin are potential explanatory factors for warmer temperature use. 4. This study reiterates that high-resolution otolith δ18O thermometry is a uniquely well-suited approach for unravelling the multiple factors that influence lifelong temperature selection in fish. Our results illustrate that the realised thermal niche is influenced by a genetic–environment interaction

Quantifying migratory capacity and dispersal of the invasive tench (Tinca tinca) in the St. Lawrence River using otolith chemistry

ABSTRACT The study of distribution and dispersal of invasive fishes is challenging during the early stages of invasion. Quantification of trace elements incorporated into fish hard parts represents an innovative technique for this task. Otolith chemistry has been used to describe fish stock structure, migratory behaviour and to support the management of several species. We used otolith chemistry to study the dispersal and population structure of tench (Tinca tinca), an invader in the St. Lawrence River. Tench movements throughout the invaded portion of the system were reconstructed using a Random Forests algorithm. The results showed that, despite the presumed limited dispersal capacity of the species, tench are capable of extensive migratory movements (up to 250 km). The variability in migratory patterns among individuals, including both short- and long-distance movements, supports a stratified diffusion. Such a strategy may explain the successful invasion of tench in the St. Lawrence River ecosystem. Our study represents a flexible framework for the study of tench ecology in its invaded and native range, as well as for other freshwater invasive fishes. RÉSUMÉ L’étude de la répartition et de la dispersion de poissons envahissants durant les premières étapes de l’envahissement n’est pas chose facile et, pour ce faire, la quantification d’éléments en traces incorporés dans les parties dures de poissons constitue une approche novatrice. La chimie des otolites a été utilisée pour décrire la structure de stocks et le comportement migratoire des poissons, ainsi que pour appuyer la gestion de plusieurs espèces. Nous avons utilisé la chimie des otolites pour étudier la dispersion et la structure de la population de tanche (Tinca tinca), une espèce envahissante dans le fleuve Saint-Laurent. Les déplacements des tanches dans toute la portion envahie du système ont été reconstitués à l’aide d’un algorithme de forêts aléatoires. Les résultats montrent que, malgré une capacité de dispersion limitée présumée pour cette espèce, les tanches sont capables d’effectuer de grands déplacements migratoires (jusqu’à 250 km). La variabilité des habitudes migratoires d’un individu à l’autre, qui comprend des déplacements tant sur de longues que sur de courtes distances appuie une stratégie de diffusion stratifiée. Une telle stratégie pourrait expliquer l’envahissement de l’écosystème du fleuve Saint-Laurent par la tanche. Notre étude offre un exemple d’approche polyvalente pour l’étude de l’écologie de la tanche dans ses aires de répartition indigène et envahis, mais aussi chez d’autres poissons d’eau douce envahissants

Fully equipped to succeed : migratory contingents seen as an intrinsic potential for striped bass to exploit a heterogeneous environment early in fife

Migratory contingents, groups of individuals belonging to the same population that adopt different migratory patterns, have been identified in numerous Striped Bass (Morone saxatilis) populations along North American East Coast. We tested the hypothesis that migratory contingents may develop early in life to maximize the exploitation of the variety of habitats faced by a recently introduced fish population. Using the discriminatory power provided by otolith chemistry, we studied early-life history stages of Striped Bass in a recently reintroduced population in the St. Lawrence Estuary. Migratory patterns were inferred using multivariate analysis of four otolith trace elements (Sr, Ba, Mn, and Mg) on juveniles (0+ and 1+). Three migratory contingents were identified during early-life history stages: freshwater residents, oligohaline migrants, and mesohaline migrants. This study demonstrates the rapid establishment, in less than 10 years since initial stocking, of three migratory contingents initiated early in life among the St. Lawrence Striped Bass population. We postulate that diversification provided by the establishment of distinct migratory contingents among early-life history stages promotes the rapid colonization of new environments through the exploration and exploitation of an increased number of nursery habitats

Past, present and future contributions of evolutionary biology to wildlife forensics, management and conservation

Successfully implementing fundamental concepts into concrete applications is challenging in any given field. It requires communication, collaboration and shared will between researchers and practitioners. We argue that evolutionary biology, through research work linked to conservation, management and forensics, had a significant impact on wildlife agencies and department practices, where new frameworks and applications have been implemented over the last decades. The Quebec government's Wildlife Department (MFFP: Ministère des Forêts, de la Faune et des Parcs) has been proactive in reducing the “research–implementation” gap, thanks to prolific collaborations with many academic researchers. Among these associations, our department's outstanding partnership with Dr. Louis Bernatchez yielded significant contributions to harvest management, stocking programmes, definition of conservation units, recovery of threatened species, management of invasive species and forensic applications. We discuss key evolutionary biology concepts and resulting concrete examples of their successful implementation that derives directly or indirectly from this successful partnership. While old and new threats to wildlife are bringing new challenges, we expect recent developments in eDNA and genomics to provide innovative solutions as long as the research–implementation bridge remains open

The role of ecotype‐environment interactions in intraspecific trophic niche partitioning subsequent to stocking

Worldwide, stocking of fish represents a valuable tool for conservation and maintenance of species exploited by recreational fishing. Releases of hatchery-reared fish are more and more recognized to have numerous demographic, ecological, and genetic impacts on wild populations. However, consequences on intraspecific trophic relationships have rarely been investigated. In this study, we assessed the impacts of supplementation stocking and resulting introgressive hybridization on the trophic niches occupied by stocked, local, and hybrid lake trout (Salvelinus namaycush) within populations of piscivorous and planktivorous ecotypes stocked from a wild piscivorous source population. We compared trophic niches using stable isotope analysis (δ13C and δ15N) and trophic position among the three genetic origins. Putative genetic effects were tested with phenotype–genotype association of “life history” ecological traits (body size, growth rate, condition index, and trophic niche) and genotypes (RADseq SNP markers) using redundant discriminant analysis (RDA). Results showed that sympatry resulting from the stocking of contrasting ecotypes is a risk factor for niche partitioning. Planktivorous populations are more susceptible to niche partitioning, by competitive exclusion of the local fish from a littoral niche to an alternative pelagic/profundal niche. Observed niche partitioning is probably a manifestation of competitive interactions between ecotypes. Our results emphasize that ecotypic variation should be considered for more efficient management and conservation practices and in order to mitigate negative impact of supplementation stocking

Supplementation stocking of Lake Trout (Salvelinus namaycush) in small boreal lakes : Ecotypes influence on growth and condition

Supplementation stocking is a commonly used management tool to sustain exploited fish populations. Possible negative consequences of supplementation on local stocks are a concern for the conservation of wild fish populations. However, the direct impacts of supplementation on life history traits of local populations have rarely been investigated. In addition, intraspecific hybridization between contrasting ecotypes (planktivorous and piscivorous) has been seldom considered in supplementation plans. Here, we combined genetic (genotype-by-sequencing analysis) and life history traits to document the effects of supplementation on maximum length, growth rates, body condition and genetic admixture in stocked populations of two Lake Trout ecotypes from small boreal lakes in Quebec and Ontario, Canada. In both ecotypes, the length of stocked individuals was greater than local individuals and, in planktivorous-stocked populations, most stocked fish exhibited a planktivorous-like growth while 20% of fish exhibited piscivorous-like growth. The body condition index was positively related to the proportion of local genetic background, but this pattern was only observed in stocked planktivorous populations. We conclude that interactions and hybridization between contrasting ecotypes is a risk that could result in deleterious impacts and possible outbreeding depression. We discuss the implications of these findings for supplementation stocking

The western tubenose goby (Proterorhinus semilunaris Heckel, 1837) is expanding its range into the St. Lawrence River: first record in Quebec

The invasive western tubenose goby (Proterorhinus semilunaris) was introduced in the Great Lakes in the 1990s. Since then, its range slowly expanded downstream into Ontario’s portion of the St. Lawrence River. This rapid communication reports on the first occurrence of a western tubenose goby found in Lake St. Francis (St. Lawrence River, Quebec) in August 2022. The specimen, the study area and the sampling methodology are described while hypotheses about its presence and expansion are explored