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Diss. (sammanfattning) Göteborg : Göteborgs universitet, 2009. / Härtill 4 uppsatser.

Current riparian management objectives in the Pacific Northwest promote both retention of existing conifers and conversion of hardwood-dominated areas to conifers. Although understanding of relationships between riparian vegetation and salmonid prey availability is growing, temporal variation in these relationships is poorly understood. Seasonal fluxes in availability of aquatic and terrestrial invertebrate prey for coastal cutthroat trout (Oncorhynchus clarki clarki) were investigated by estimating invertebrate biomass from aquatic (benthos and drift) and allochthonous (terrestrial) sources in three watersheds in the Oregon Coast Range. To investigate the influence of vegetation type on food sources, samples were collected in each watershed from stream sections dominated by deciduous, conifer, and mixed vegetation. During each sample period, diet was assessed by examining gut contents of captured trout. Stream discharge appeared to be an influential factor regulating seasonal fluxes of aquatic invertebrate biomass in the benthos and drift. Total allochthonous invertebrate biomass at deciduous and mixed vegetation sites (64 and 61 mg·m⁻²·day⁻¹, respectively) was almost 30% higher than at coniferous sites (45 mg·m⁻²·day⁻¹). Although aquatic insects dominated the total gut contents during this study, prey from terrestrial origin was more common during summer and fall. These results suggest that systematic removal of deciduous vegetation in riparian zones to promote conifers may have unintended consequences on the food resources of coastal cutthroat trout and the productivity of aquatic food webs in the Pacific Northwest. / Graduation date: 2004

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The gravel environment of 30 brown trout (Salmo trutta) redds and adjacent nonredd sites in two western North Carolina streams were studied during the incubation period in 1979-1980 and 1980-1981. Intragravel water temperature, dissolved oxygen concentration, and percent oxygen saturation were highly correlated with surface water measurements, indicating that intragravel water is of surface origin. Permeability ranged from 250 to 149,350 cm/hr and averaged 6,150 cm/hr. Apparent velocity varied from 0 to 1,000 cm/hr and averaged 30 cm/hr. Permeability in redds was significantly greater than at nonredd sites. No significant differences in apparent velocity were found between redd and nonredd sites. No consistent differences in permeability or apparent velocity were found between streams or over time. Permeability and apparent velocity decreased significantly with depth. Freeze cores were collected from redd and nonredd sites and divided into three 10-cm layers for analysis. Geometric mean diameter, sorting coefficient, fredle index, percent fines <2.00 mm, and percent porosity were highly variable and averaged 11.8 mm, 2.8, 4.2, 17.0 percent, and 19.0 percent, respectively. No significant differences were found among factors tested. Correlations between these gravel indices and permeability and apparent velocity were low. The gravel and intragravel environments appeared to be adequate for larval survival. Measurements did not reveal any clear trends during the incubation period. Brown trout did not by choice or redd construction appear to select or create (by redd construction) a subsurface environment different from the surrounding stream bed. / M.S.