Feeding ecology and niche overlap of Lake Ontario offshore forage fish assessed with stable isotopes

The forage fish communities of the Laurentian Great Lakes continue to experience changes that have altered ecosystem structure, yet little is known about how they partition resources. Seasonal, spatial, and body size variation in [delta][sup.13]C and [delta][sup.15]N was used to assess isotopic niche overlap and resource and habitat partitioning among the five common offshore Lake Ontario forage fish species (n = 2037; alewife (Alosa pseudoharengus), rainbow smelt (Osmerus mordax), round goby (Neogobius melanostomus), and deepwater (Myoxocephalus thompsonii) and slimy (Cottus cognatus) sculpins). Round goby had the largest isotopic niche (6.1[[per thousand].sup.2], standard ellipse area), followed by alewife (3.4[[per thousand].sup.2]), while rainbow smelt, slimy sculpin, and deepwater sculpin had the smallest and similar niche size (1.7[[per thousand].sup.2]-1.8[[per thousand].sup.2]), with only the sculpin species showing significant isotopic niche overlap (>63%). Stable isotopes in alewife, round goby, and rainbow smelt varied with location, season, and size, but did not vary in the sculpin species. Lake Ontario forage fish species have partitioned food and habitat resources, and non-native alewife and round goby have the largest isotopic niche, suggestive of a boarder ecological niche, and may contribute to their current high abundance. Si les communautes de poissons-fourrage des Grands Lacs laurentiens continuent de subir des changements qui ont modifie la structure des ecosystemes, les connaissances sur le partage des ressources dans ces communautes sont limitees. Les variations saisonnieres, spatiales et associees a la taille du corps du [delta][sup.13]C et du [delta][sup.15]N ont ete utilisees pour evaluer le chevauchement des niches isotopiques et le partage des ressources et des habitats entre cinq especes de poissons-fourrage pelagiques repandues du lac Ontario (n = 2037; le gaspareau (Alosa pseudoharengus), l'eperlan arc-en-ciel (Osmerus mordax), le gobie a taches noires (Neogobius melanostomus), le chabot de profondeur (Myoxocephalus thompsonii) et le chabot visqueux (Cottus cognatus)). Le gobie a taches noires presente la plus grande niche isotopique (6,1[[per thousand].sup.2], aire de l'ellipse standard), suivi du gaspareau (3,4[[per thousand].sup.2]), alors que l'eperlan arc-en-ciel, le chabot visqueux et le chabot de profondeur ont les plus petites niches, de tailles semblables (1,7-1,8[[per thousand].sup.2]), seuls les chabots presentant un chevauchement significatif de leurs niches isotopiques (>63 %). Les isotopes stables des gaspareaux, gobies a taches noires et eperlans arc-en-ciel varient selon le lieu, la saison et la taille, contrairement a ceux des chabots. Les especes de poissons-fourrage du lac Ontario presentent un partage des ressources alimentaires et des habitats, le gaspareau et le gobie a taches noires, des especes non indigenes, etant caracterises par les plus grandes niches isotopiques, ce qui indiquerait une niche ecologique plus large et pourrait contribuer a expliquer leur forte abondance actuelle. [Traduit par la Redaction]
Introduction In the Laurentian Great Lakes (hereinafter Great Lakes), consumption by the offshore prey fish community transfers production from the lower trophic level to higher trophic levels and can influence [...]