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The diet of juvenile and adult female California sea lions (Zalophus californianus (Lesson, 1828)) at San Miguel Island, California, was estimated and compared using fecal and stable isotope analyses to determine dietary differences by age. Fecal samples were collected during 2002-2006 and prey remains were identified. Stable carbon δ[sup.13]C) and stable nitrogen (δ[sup.15]N) isotope values were determined from plasma and fur obtained from yearlings, 2- to 3-year-old juveniles, and adult females during 2005 and 2006. Juveniles ate more than 15 prey taxa, whereas adult females consumed more than 33 taxa. Relative importance of prey was determined using percent frequency of occurrence (%FO). Engraulis mordax Girard, 1854, Sardinops sagax (Jenyns, 1842), Merluccius productus (Ayres, 1855), genus Sebastes Cuvier, 1829, and Loligo opalescens Berry, 1911 were the most frequently occurring (%FO > 10%) prey in the feces of both juvenile and adult female sea lions, although their importance varied between age groups. Only yearlings had significantly different isotopic values than older conspecifics, indicating that older juveniles were feeding at a similar trophic level and in similar habitats as adult females. Whereas each method had biases, combining the two provided a better understanding of the diet of California sea lions and intraspecific differences. Des analyses fecales et des analyses d'isotopes stables nous ont permis d'estimer le regime alimentaire de jeunes et de femelles adultes du lion de mer de Californie (Zalopus californianus (Lesson, 1828)) a l'ile San Miguel, Californie, et de comparer les differences alimentaires en fonction de l'age. Nous avons preleve des echantillons de feces en 2002-2006 et identifie les restes de proies. Nous avons determine les valeurs des isotopes stables de carbone (δ[sup.13]C) et d'azote (δ[sup.15]N) dans le plasma et la fourrure provenant d'individus de l'anneee, d'individus de 2-3 ans et de femelles adultes en 2005 et 2006. Les jeunes consomment plus de 15 taxons de proies, alors que les femelles adultes en utilisent plus de 33. L'importance relative des proies est representee par la frequence d'occurrence en pourcentage (%FO). Engraulis mordax Girard, 1854, Sardinops sagax (Jenyns, 1842), Merluccius productus (Ayres, 1855), le genre Sebastes Cuvier, 1829 et Loligo opalescens Berry, 1911 sont les proies qui apparaissent le plus frequemment (%FO > 10 %) dans les feces des jeunes lions de mer et des femelles adultes, bien que leur importance varie selon les groupes d'age. Seuls les individus de l'anneee presentent des valeurs isotopiques differentes de celles de leurs congeneres plus ages, ce qui indique que les jeunes plus ages se nourrissent au meme niveau trophique et dans des habitats de meme type que les femelles adultes. Bien que chaque methode ait ses sources d'erreurs, la combinaison des deux permet une meilleure comprehension du regime alimentaire des lions de mer de Californie et de ses differences intraspecifiques. [Traduit par la Redaction], Introduction Energy is essential for all animals, and many actively search, pursue, and handle several types of prey to survive and reproduce. Although it has been assumed that individuals seek [...]

Abstract: We compared the nonbreeding-season foraging behavior of lactating California sea lions (Zalophus californianus californianus (Lesson, 1828)) at San Miguel Island, California, during El Nino conditions in 1993 and non-El [...]

The relationship between forest stand composition in southern interior British Columbia and fluorescent pseudomonad bacteria populations was investigated using seedling bioassays. The objectives of this study were to (i) compare the relative population sizes of fluorescent pseudomonads baited from soils in pure paper birch (Betula papyrifera Marsh.), pure Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), and mixed stands of the two species and (ii) determine if fluorescent pseudomonads from these soils have inhibitory effects against the root pathogen Armillaria ostoyae (Romagn.) Herink in vitro. Soil from birch stands supported four times more pseudomonads on seedling baits than soil from Douglas-fir stands, with the mixed stands intermediate. Soil from young stands yielded twice as many rhizosphere pseudomonads as soil from mature stands. Pseudomonad population size was positively correlated with percent cover and density of birch, and negatively correlated with basal area of Douglas-fir, percent cover of Douglas-fir, and carbon/nitrogen ratio of the soil. Greater than 50% of the fluorescent isolates reduced radial growth of A. ostoyae by more than 20% and greater than 90% reduced biomass of the fungus in dual culture tests. Cell-free bacterial culture filtrates added to the growth medium also reduced growth of A. ostoyae. This study provides evidence that paper birch provides a more favorable environment for fluorescent pseudomonads than Douglas-fir and suggests a mechanism by which paper birch can positively influence the susceptibility of managed forest stands to Armillaria root disease. [ABSTRACT FROM AUTHOR]