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Rainbow trout is an exotic fish species that has been introduced in Quebec (Canada) since 1893–1894. Despite spatially-restricted stocking for recreational fishing, the species has spread throughout the Saint Lawrence River. In this study, the relationship between rainbow trout occurrence (presence or absence) and abiotic variables (river geomorphology and climate) was examined for 91 coastal rivers throughout Eastern Quebec in order to determine which variables promote or impede the ongoing invasion process. Results revealed that rainbow trout presence in Eastern Quebec was primarily determined by geomorphological parameters. The invader’s presence was strongly related to the presence of tributaries (especially larger ones). To a lesser extent, the presence of rainbow trout was positively related to warm spring and summer temperatures and negatively related to the peak flood date occurring during the egg deposition period (May). This study proposes a parsimonious modelling approach to identify which environmental parameters favour the spreading of an invader, even when a limited dataset is available due to the incomplete invasion process.

Metamorphosis is a critical developmental stage that presents particular challenges in fish aquaculture. The sharp increase in mortality that accompanies this transformation has often been attributed to nutritional deficiencies. Providing live feed (the rotifer Brachionus plicatilis Muller, 1786 and the brine shrimp Artemia salina (Linnaeus, 1758)) during the larval stages is costly and labour intensive, which explains why much effort has been put on early weaning. However, previous observations in winter flounder (Pseudopleuronectes americanus (Walbaum, 1792)) indicate that juveniles weaned after settlement had better survival than those weaned at the larval stage. In this study, we tested whether late weaning (at settlement (W0) and groups maintained on co-feeding for 1 month (W1), two months (W2), or 3 months (W3) after settlement) could improve juvenile survival and lipid composition. Our results demonstrated that maintaining co-feeding beyond the larval stage was essential for after-settlement survival. Juveniles co-fed until 90 days after settlement were 32.5% heavier. Analyses of fatty acid trophic markers suggested that juveniles preferentially fed on enriched rotifers rather than inert food. No pigmentation or fin erosion problems were observed in any of the weaning treatments, which indicates good rearing conditions.Key words: winter flounder, Pseudopleuronectes americanus, weaning, live prey, lipid classes, fatty acids, aquaculture.La metamorphose est une etape critique du developpement qui presente des defis particuliers en aquaculture. La forte hausse de mortalite associee a cette etape a souvent ete attribuee a des carences nutritionnelles. Fournir de la nourriture vivante (le rotifere Brachionus plicatilis Muller, 1786 et l'artemie Artemia salina (Linnaeus, 1758)) au cours des premiers stades de vie est couteux et exige beaucoup d'efforts ce qui explique l'interet pour un sevrage rapide. Cependant, des observations precedentes chez les juveniles de plie rouge (Pseudopleuronectes americanus (Walbaum, 1792)) indiquent que des juveniles sevres au moment du passage a l'habitat benthique ont une meilleure survie que ceux sevres au stade larvaire. Dans cette etude, nous avons verifie si un sevrage tardif (au moment du passage a la phase benthique (W0) et chez des groupes maintenus en alimentation mixte pour 1 mois (W1), 2 mois (W2), ou 3 mois (W3) suivant le debut de la phase benthique) pouvait accroitre la survie et ameliorer les teneurs en lipides. Nos resultats indiquent que le maintien de l'alimentation mixte au-dela du stade larvaire est necessaire pour ameliorer la survie apres le passage a la phase benthique. Les juveniles nourris d'un regime mixte jusqu'a 90 jours suivant le passage a la phase benthique avaient une masse de 32,5 % plus elevee. L'analyse de marqueurs trophiques parmi les acides gras donne a penser que les juveniles se nourrissent preferentiellement de rotiferes. L'absence de problemes de pigmentation ou d'erosion de nageoire au cours des differents traitements indique la presence de conditions d'elevage adequates.Mots-cles: plie rouge, Pseudopleuronectes americanus, sevrage, proie vivante, classes de lipides, acides gras, aquaculture., IntroductionWinter flounder (Pseudopleuronectes americanus (Walbaum, 1792)) is a common flatfish that inhabits coastal waters of the northwest Atlantic, from Georgia, USA (33[degrees]N), to Newfoundland and southern Labrador, Canada (53[degrees]N) (Buckley [...]

Flounders (Pleuronectiformes) from eastern North America have been extensively studied over the last few decades, and most of that work has been oriented towards different aspects related to fish production, i.e., aquaculture. However, aquaculture production has not progressed as it might have been expected. Flounders are omnivorous, euryhaline, inhabit shore habitats, and offer good potential for aquaculture diversification. They are found all along the eastern coast of Canada and the US, and different species occupy coastal habitats with some species overlapping in certain areas. Despite specific biological and ecological requirements for each species, the accumulated knowledge on breeding, larval rearing, juveniles, and stock enhancement creates a frame of reference that is often underestimated but that indicates a promising future for the production of these fishes. Les poissons plats (Pleuronectiformes) de type << plie >> ou << limande >> de l'est de l'Amerique du nord ont ete tres etudies au cours des dernieres decennies et une large part de ces etudes ont ete orientees vers la production piscicole. Cependant la production aquacole de ces especes n'a pas progresse comme on aurait pu s'y attendre. Ces animaux sont omnivores et euryhalins; ils utilisent les habitats cotiers et ont ete identifies comme de bons candidats pour la diversification de la production aquacole. On les trouve tout le long des cotes canadienne et americaine et differentes especes utilisent ces habitats cotiers avec des chevauchements entre les zones d'occupation. Meme si chacune de ces especes possede ses propres caracteristiques biologiques et ecologiques, la somme des connaissances acquises au niveau de la reproduction, de l'elevage larvaire, du stade juvenile et du repeuplement en zone cotiere forme un cadre de reference souvent sous-estime et qui pourtant s'avere un puissant outil pour le developpement futur de ces productions., Introduction Production of flounder (Pleuronectiformes) in eastern North America still has a very small economic impact (e.g., Bengtson and Nardi 2010; Daniels et al. 2010; Fairchild et al. 2010) even [...]

Brook trout (Salvelinus fontinalis (Mitchill, 1814)) supports a lucrative fish aquaculture industry in Quebec and production of this species is mainly oriented to stock enhancement supporting sport fisheries. The aim of this study was to verify the expression of interstrain heterosis, i.e., increased performance of first generation hybrid progeny, during the first stages of development in brook trout. Two wild populations that were recently introduced to fish production in Quebec, the Laval (L) and the Rupert (R) strains, and a domestic strain (D) that is present in most Quebec fish farms were used in this study. The growth of 72 full-sibling families, representing three pure (♀D x ♂D, ♀L x ♂L, ♀R x ♂R) and five hybrid (♀D x ♂L, ♀D x ♂R, ♀L x ♂D, ♀L x ♂R, ♀R x ♂L) cross types, were surveyed from hatching to 2136 degree-days. Both heterosis and outbreeding depression were observed, depending on the hybrid cross type. The occurrence of heterosis was dependent on the developmental stage, and growth advantage at a very early developmental stage did not necessarily translate into bigger size later on. Outbreeding depression in growth (mass or length) was much less common than heterosis, and when occurring, it varied from 9.2% to 33.3% compared with 9.0% to 88.2% improvement in growth traits for heterosis. The results indicate that in early development, there was higher occurrence of heterosis relative to fish mass than to fish length and that, overall, the occurrence of heterosis was unpredictable. L'omble de fontaine (Salvelinus fontinalis (Mitchill, 1814)) est une espece tres importante au Quebec, aussi bien dans le domaine de la peeche que dans celui de l'aquaculture et la production aquacole est principalement axee vers l'ensemencement. L'objectif de notre etude etait de verifier la presence d'heterosis, soit une augmentation de performance durant les premiers stades du developpement chez les hybrides de premiere generation, lors de croisements inter-souche d'ombles de fontaine. Trois souches ont ete utilisees, soit une souche domestique (D), largement utilisee dans les piscicultures quebecoises et deux populations sauvages recemment introduites dans le cheptel aquacole, soit la Laval (L) et la Rupert (R). Nous avons etudie la croissance de 72 familles de type plein-frere, representant 3 croisements purs (♀D x ♂D, ♀L x ♂L, ♀R x ♂R) et 5 croisements hybrides (♀D x ♂L, ♀D x ♂R, ♀L x ♂D, ♀L x ♂R, ♀R x ♂L), de l'eclosion jusqu'a 2136 degrees-jours. De l'heeterosis et de la depression de croisement ont ete observees chez differents croisements hybrides. La presence d'heterosis etait dependante du stade de developpement et une bonne croissance a un jeune stade de developpement ne se traduisait pas neecessairement par une taille plus importante lors des stades suivants. Lorsque presente, la depression de croisement se traduisait par des baisses de croissance (masse ou longueur) entre 9,2 % et 33,3 %, alors que dans le cas d'heterosis, des ameliorations des traits de croissance variant de 9,0 % a 88,2 % ont ete observees. Ces resultats montrent une presence accrue d'heterosis durant les premiers stades du developpement en fonction de la masse plutot que de la longueur des poissons et ils illustrent dans leur ensemble l'imprevisibilite de l'occurrence de l'heeteerosis chez cette espece., Introduction Brook trout (Salvelinus fontinalis (Mitchill, 1814)) is a salmonid species that is widely present in eastern North America's rivers where it supports an important sport fishing industry. In Quebec, [...]

Researchers fed a single dose of methylmercury to immature arctic charr to examine the biological actions of mercury within fish metabolism. Data about the adsorption of mercury from the food to the gut, and then into tissues was gathered. Mercury concentrations within internal organs were examined separately to show that some tissues are more likely to adsorb and retain mercury, while other tissues are more likely to eliminate mercury. Researchers also developed a mathematical model based upon the data to predict levels of mercury contamination.

Intraspecific hybridisation may result in hybrid offspring exhibiting superior (heterosis) or inferior (outbreeding depression) fitness relative to their parental populations. As both have been demonstrated in salmonids, consequences of interbreeding between divergent populations are relevant to their conservation. Atlantic salmon Salmo salar L. were extirpated from Lake Ontario by the late 19th Century due to anthropogenic causes. Multiple allopatric populations of hatchery-reared Atlantic salmon are being stocked in an effort to re-establish a self-sustaining population. This study evaluated whether interbreeding between Sebago Lake (Maine) and LaHave River (Nova Scotia) individuals will result in heterosis or outbreeding depression in juveniles. This was accomplished through full-factorial 2 × 2 mating crosses between the strains and comparing multiple fitness-related traits between the cross types. Hybrid juveniles displayed no signs of outbreeding depression nor heterosis. Further studies on comparative fitness of backcross and F2 hybrids are recommended to assess potential consequences for this and similar restoration efforts. [ABSTRACT FROM AUTHOR]