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Substratum Size (substratum + size)
Selected AbstractsSpatial and ontogenetic variability in the microhabitat use of stream-dwelling spined loach (Cobitis taenia) and stone loach (Barbatula barbatula)JOURNAL OF APPLIED ICHTHYOLOGY, Issue 6 2004G. H. Copp Summary Ontogenetic and spatial variability in microhabitat use of spined loach Cobitis taenia (Linnaeus), considered as one species for the purposes of this study, and stone loach Barbatula barbatula (Linnaeus) were examined in the River Great Ouse basin, England, using multivariate and habitat suitability methods, including a technique for handling spatial variation in collections of preference curves. Distinct ordinations of spined age classes and stone loach developmental stages, respectively, in canonical correspondence analysis of species × variables × samples relationships suggest that the two species occupy completely different microhabitats; however, young-of-the-year spined loach occurred more often than expected with all developmental stages of stone loach except young larvae. Water velocity and filamentous algae were the most influential microhabitat variables, the latter decreasing in importance with increasing age of both fish species. Preferred water velocities generally decreased with age in spined loach and increased in stone loach, with substratum size generally increasing with fish age in both species. Spatial variation in microhabitat preferences was great in both species but less so in the spined loach, suggesting that limited plasticity in habitat use could account, at least in part, for the latter species' limited distribution and abundance in the catchment. Preference curves for a species, if generated and verified for all life intervals and all seasons, could be used as a management tool for a given stream or sector of river basin. But preference curves should be generated for each location to ensure that river management decisions with regard habitat and species conservation consider local-level species requirements. Thus, a multi-(eco)species and multi-scale approach is required in habitat suitability assessments. [source] Habitat selection by juvenile Atlantic salmon: the interaction between physical habitat and abundanceJOURNAL OF FISH BIOLOGY, Issue 4 2005R. D. Hedger The effect of physical river habitat variables on the distribution of juvenile Atlantic salmon Salmo salar L. in the Rivière de la Trinité, Québec, Canada, was examined using generalized additive modelling. A survey of Atlantic salmon fry and parr densities and habitat variables (flow velocity, water column depth and substratum size) was conducted in the summer months from 1984 to 1992. Clear patterns of habitat use existed: specific ranges of habitat variables were selected, with parr preferring greater velocities, depths and substratum sizes than fry. There was a large variation, however, in juvenile densities for given velocities, depths or substratum sizes, with this variation being greatest in optimal habitats. On examination of an individual year, interaction between the variables was found to explain some of the variation. On a year-to-year basis the juvenile Atlantic salmon population was found to exhibit an ,Ideal Free Distribution', which resulted in greatest variation in optimal habitats with year-to-year changes in population abundance. [source] Suitability criteria for spawning habitat of riverine European graylingJOURNAL OF FISH BIOLOGY, Issue 5 2002M. Nykänen Generalized suitability curves, developed for the spawning habitat of grayling Thymallus thymallus by combining new preference data with information available in the literature, provided optimal ranges for dominant substratum size, water depth and mean water velocity. These were 16,32 mm, 30,40 cm, and 50,60 cm s,1, respectively. [source] Habitat selection by juvenile Atlantic salmon: the interaction between physical habitat and abundanceJOURNAL OF FISH BIOLOGY, Issue 4 2005R. D. Hedger The effect of physical river habitat variables on the distribution of juvenile Atlantic salmon Salmo salar L. in the Rivière de la Trinité, Québec, Canada, was examined using generalized additive modelling. A survey of Atlantic salmon fry and parr densities and habitat variables (flow velocity, water column depth and substratum size) was conducted in the summer months from 1984 to 1992. Clear patterns of habitat use existed: specific ranges of habitat variables were selected, with parr preferring greater velocities, depths and substratum sizes than fry. There was a large variation, however, in juvenile densities for given velocities, depths or substratum sizes, with this variation being greatest in optimal habitats. On examination of an individual year, interaction between the variables was found to explain some of the variation. On a year-to-year basis the juvenile Atlantic salmon population was found to exhibit an ,Ideal Free Distribution', which resulted in greatest variation in optimal habitats with year-to-year changes in population abundance. [source] | ||||||||||