Effects of Different Riparian Timber Harvest Intensities on Brook Trout Bioenergetics

Studies in which we manipulated the timber harvest rates in riparian areas from 50 to 90% basal area removals provided a template in which to assess potential effects on the bioenergetics of eastern brook trout.  These treatments opened canopies allowing increased summer warming in affected sections, but were accompanied by increases in aquatic invertebrates and terrestrial subsidy delivery in the 90% treatments.  A bioenergetics model for brook trout showed that maintenance ration increased 15-18% in the 90% and 7-10% in the 50% harvest treatments due to increases in temperature.  Effects were stronger on younger cohorts and decreased with size.  Consumption must increase 6-15% to compensate for increased metabolic demands.  Concurrent in situ consumption estimates showed no such increases in consumption relative to reference reaches.  Higher densities of trout in the cut areas led to a reduced per capita consumption making stream sections with harvests that open canopies effectively production sinks.