Seasonal shifts in the microhabitats used by feeding brown troutSalmo truttain a northern Spanish river were related to changes in habitat availability. At higher flows, mean water column velocities, focal velocities, and depths occupied by brown trout were greater and focal elevations above the substratum were less, but no changes in substratum use were detected. Cover use differed between dates, apparently according to the presence of suitable materials. In May, a lower proportion of the observed fish were holding feeding positions than in July, October, or January. Total metabolic costs associated with holding feeding stations were primarily determined by swimming costs, and both costs varied substantially between dates, mainly as a consequence of the different swimming speeds of brown trout on the different dates. Standard metabolism was less important than swimming cost in total energy expenditure and showed no obvious relationship with total metabolic rate. Brown trout exhibited considerable individual variation in swimming costs, which seemed not to be related to fish size.