Assessing the ecological importance of coastal habitats to Great Lakes ecosystems requires an understanding of the ecological linkages between coastal and offshore waters. Elemental analysis of fish otoliths has emerged as a powerful technique that can provide a natural tag for determining nursery area affiliation, population structure, and movement of individual fish. Since the elemental composition of fish otoliths reflects some of the environmental conditions under which a fish was reared, otolith chemistry can record differences in ambient water conditions specific to habitats used during a fish's life history. Although few studies have been conducted in freshwaters, trace element analysis of marine fish otoliths has proven useful in identifying the chemical signatures unique to particular spawning and nursery habitats. To examine the utility of this method in freshwater, sagittae were removed from 275 young‐of‐the‐year yellow perch Perca flavescens captured from eight wetlands in western Lake Superior during August 2001. They were analyzed for Ca and 13 minor and trace elements using inductively coupled plasma mass spectrometry (ICPMS) and inductively coupled atomic emission mass spectrometry (ICPAES). Otolith concentrations of Ba, K, Mg, Mn, Na, and Sr differed significantly among wetlands (ANOVA, P < 0.001). Interwetland differences were also pronounced when analyzed as a multivariate fingerprint (MANOVA, P < 0.001). Discriminant function analysis revealed relatively distinct chemical fingerprints associated with each wetland. Wetland classification accuracy based on a five‐element model (Sr, Mn, K, Ba, and Mg) ranged from 62% to 100% and averaged 76%. Differences in fingerprints between wetland types (river‐influenced versus lagoon) were also distinct (MANOVA, P < 0.001). Classification accuracy for wetland type was 81% based on a five‐element model that included Ba, Mg, Mn, Na, and Sr. Our results suggest that otolith elemental fingerprints may be useful for quantifying the relative contributions of different wetland nursery areas to recruitment in adjacent lake populations.

We analyzed data from coastal wetlands across the Laurentian Great Lakes to identify fish assemblage patterns and relationships to habitat, watershed condition, and regional setting. Nonmetric multidimensional scaling (NMDS) ordination of electrofishing catch-per-effort data revealed an overriding geographic and anthropogenic stressor gradient that appeared to structure fish composition via impacts on water clarity and vegetation structure. Wetlands in Lakes Erie and Michigan with agricultural watersheds, turbid water, little submerged vegetation, and a preponderance of generalist, tolerant fishes occupied one end of this gradient, while wetlands in Lake Superior with largely natural watersheds, clear water, abundant submerged vegetation, and diverse fishes occupied the other. Fish composition was also related to wetland morphology, hydrology, exposure, and substrate, but this was only evident within low-disturbance wetlands. Anthropogenic stress appears to homogenize fish composition among wetlands and mask other fish-habitat associations. Because land use is strongly spatially patterned across the Great Lakes and aquatic vegetation is a key habitat element that responds to both biogeography and disturbance, it is difficult to disentangle natural from anthropogenic drivers of coastal wetland fish composition.Résumé : Nous analysons des données provenant de terres humides riveraines réparties sur l'ensemble des Grands Lacs laurentiens afin d'identifier les patrons d'associations de poissons et leurs relations avec les habitats, les conditions du bassin versant et l'environnement régional. Une ordination de cadrage non métrique multidimensionnel (NMDS) de données de captures par unité d'effort de pêche électrique révèle l'existence d'un gradient prédominant de facteurs de stress géo-graphiques et anthropiques qui semble structurer la composition des peuplements de poissons par son impact sur la clarté de l'eau et la structure de la végétation. Les terres humides aux lacs É rié et Michigan avec des bassins versants agricoles, de l'eau turbide, une végétation submergée rare et une prépondérance de poissons généralistes et tolérants, occupent une extrémité de ce gradient; en revanche, les terres humides du lac Supérieur avec des bassins versants en grande partie naturels, de l'eau claire, une végétation submergée abondante et une diversité de poissons, occupent l'autre extrémité. La composition des peuplements de poissons est aussi en relation avec la morphologie des terres humides, l'hydrologie, l'exposition et le substrat, mais la relation n'est évidente que dans les terres humides peu perturbées. Le stress anthropique semble homogénéiser la composition des peuplements de poissons dans les différentes terres humides et masquer les autres associations poissons-habitats. Parce que l'utilisation des terres dans la région des Grands Lacs forme un patron spatial bien marqué et que la végétation est un élément essentiel de l'habitat qui réagit à la fois à la biogéographie et aux perturbations, il est difficile de démêler...

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The relative importance of regional, watershed, and in-stream environmental factors on fish assemblage structure and function was investigated in western Lake Superior tributaries. We selected 48 second- and third-order watersheds from two hydrogeomorphic regions to examine fish assemblage response to differences in forest fragmentation, watershed storage, and a number of other watershed, riparian, and in-stream habitat conditions. Although a variety of regional, fragmentation, and storage-related factors had significant influences on the fish assemblages, water temperature appeared to be the single most important environmental factor. We found lower water temperatures and trout–sculpin assemblages at lower fragmentation sites and higher temperatures and minnow–sucker–darter assemblages as storage increased. Factors related to riparian shading and flow separated brook trout streams from brown trout (Salmo trutta) – rainbow trout (Oncorhynchus mykiss) streams. Functionally, fish assemblages at lower fragmentation sites were dominated by cold-water fishes that had low silt tolerance and preferred moderate current speeds, while fishes with higher silt tolerances, warmer temperature preferences, and weaker sustained swimming capabilities were most common at higher storage sites. Our results suggest that site-specific environmental conditions are highly dependent on regional- and watershed-scale characters and that a combination of these factors operates in concert to influence the structure and function of stream fish assemblages.