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Despite the widespread occurrence of microsporidian parasites in vertebrates and many invertebrates, research regarding their effects on wild populations remains uncommon. We used several metrics of individual growth, condition, and population characteristics to evaluate the effects of a microsporidian infection (Glugea) on six infected populations of mottled sculpin (Cottus bairdii) compared with 10 nearby uninfected populations. Infected individuals (n = 129) were significantly heavier in each age class when compared with uninfected fish (n = 331), yet other measures of growth and condition indicated little influence of the parasite. No significant parasite-associated effects were found when comparing mortality rates, mean age, sex ratios, and history of population genetic bottleneck between infected and uninfected populations. Additionally, we did not detect significant differences in environmental variables or fish assemblages between streams with and without the parasite. Given the disfiguring nature of infection and the strong effects of microsporidian parasites on other hosts, the lack of significant effects caused by parasitism was unexpected and is likely attributed to strong host density-dependent population dynamics or relatively low host infection intensities. Bien que les microsporidies parasites soient repandues chez les vertebres et de nombreux invertebres, les travaux sur leurs effets sur les populations sauvages demeurent assez rares. Nous avons utilise plusieurs mesures de la croissance et de l'etat individuels et des caracteristiques de la population pour evaluer les effets d'une infection a microsporidie (Glugea) sur six populations infectees de chabot tachete (Cottus bairdii) par rapport a 10 populations non infectees voisines. Si les individus infectes (n = 129) etaient significativement plus lourds dans chaque categorie d'ages comparativement aux poissons non infectes (n = 331), d'autres mesures de la croissance et de l'etat indiquaient peu d'influence du parasite. Aucun effet significatif associe au parasite n'a ete note sur le plan des taux de mortalite, de l'age moyen, du rapport des sexes et de l'historique de goulots d'etranglement genetiques entre les populations infectees et non infectees. En outre, nous n'avons decele aucune difference significative des variables du milieu ou des assemblages de poissons entre les cours d'eau avec et sans parasites. Etant donne l'effet defigurant de l'infection et les effets importants de microsporidies parasites sur d'autres hotes, l'absence d'effets significatifs causes par le parasitisme etait inattendue et serait vraisemblablement attribuable a une dynamique de la population fortement dependante de la densite des hotes ou des intensites d'infection relativement faibles des hotes. [Traduit par la Redaction], Introduction Infectious disease can have profound effects on host species in natural ecosystems, such as regulating abundance (Hudson et al. 1998), shaping genetic variation (Burdon and Shattock 1980), and limiting [...]

We monitored 94 mottled sculpins (Cottus bairdii) marked with passive integrated transponder (PIT) tags to examine seasonal movement patterns. High detection efficiency (mean [+ or -] standard error = 0.76 [+ or -] 0.03) of PIT-tagged fish was obtained with a portable antenna. Nighttime searches were more effective than daytime relocations in summer, and smaller fish ( Nous avons suivi 94 chabots tachetes (Cottus bairdii) porteurs de transpondeurs integres passifs (PIT) afin d'etudier leurs patrons de deplacements saisonniers. Nous avons obtenu une efficacite elevee de detection (moyenne [+ or -] ecart type = 0,76 [+ or -] 0,03) des poissons marques de PIT au moyen d'une antenne portative. Les recherches de nuit sont plus efficaces que les relocalisations de jour en ete et les poissons plus petits (100 m sur une annee avec un deplacement maximal de 511 m et les poissons mobiles montrent typiquement une preference pour l'amont. Bien que la plupart des chabots tachetes dans notre systeme soient relativement sedentaires, un petit pourcentage d'individus se deplace sur des distances plus grandes qu'il n'a ete observe dans d'autres systemes. [Traduit par la Redaction], Introduction Information on the movements of stream fishes provides valuable insight into a variety of population processes in streams (Skalski and Gilliam 2000; Rashleigh and Grossman 2005; Roberts and Angermeier [...]

1. Rapidly advancing geographical information systems (GIS) technologies are forcing a careful evaluation of the roles and biases of landscape and traditional site-based perspectives on assessments of aquatic communities. Viewing the world at very different scales can lead to seeming contradictions about the nature of specific ecological systems. In the case of Michigan trout streams, landscape analyses suggest a predictable community shaped by large-scale patterns in hydrologyand geology. Most site-based studies, however, suggest these corranunities are highly variable in structure over time, and are strongly shaped by site-specific physical and biological dynamics. As the real world is comprised of processes operating both at local and landscapescales, an analytical framework for integrating these paradigms is desirable. 2. Decomposition of variances by factorial ANOVA into time,space and fime-space interaction terms can provide a conceptual and analytical model for integrating processes operating at landscape andlocal scales. Using this approach, long-term data sets were examinedfor three insects and two fishes common in Michigan trout streams. Each taxon had a unique variance structure, and the observed variance structure was highly dependent upon sample size. 3. Both spatially extensive designs with little sampling over time (typical of many GIS studies) and temporally extensive designs with little or no spatial sampling (typical of population and community studies), are biased in terms of their view of the relative importance of local and landscape factors. The necessary, but in many cases costly, solution is to develop and analyse data sets that are both spatially and temporally extensive. [ABSTRACT FROM AUTHOR]

Microsporidian infections are common in many fish species, yet detailed studies of these parasites in ecologically important wild populations are rare. Phylogenetic analysis using rDNA sequence data and parasite morphology indicate that mottled sculpin Cottus bairdii and slimy sculpin C. cognatus are hosts for Glugea sp. microsporidia in the northern USA. Glugea sp. is common in the Michigan populations sampled for this study, and prevalence was ≥ 70% in 4 of 6 infected populations (range -4 to 80%). Glugea sp. infection causes the formation of xenomas associated with the body wall, fat body, gonads, and kidneys. Infections range from mild to very heavy, with variable xenoma numbers and sizes. Female sculpin experience heavier infections and more frequent infection of the gonads relative to males. Glugea sp. is transmitted horizontally between hosts through ingestion of spores. Vertical transmission may also be possible, either by spores infecting eggs directly or by spores contaminating the surface of eggs in the ovary or in the nest. The frequency and route of vertical transmission requires further study, but if it occurs, it may partly explain the high prevalence of infection. Our study combined with previous research suggests that additional molecular data and cross-infection experiments should be conducted to clarify species designations in the genus Glugea.