Towards a functional understanding of the effects of sediment aggradation on stream fish condition

Abstract

AbstractUsing both field and laboratory experiments, we evaluated mechanistic links among sediment aggradation, embeddedness and fish condition. In the field, we measured fish condition in three common stream and river species representing unique feeding guilds [creek chubs (surface and water column feeders), pumpkinseeds (omnivores) and white suckers (benthic invertivores)] over time across varying sedimentation levels. We continued this work in the laboratory with white suckers (benthic invertivores) and common shiners (surface and water column feeders), standardizing food amounts across degrees of sediment aggradation. In the field, pumpkinseeds – the species with the greatest foraging plasticity – showed no significant difference in condition across levels of sediment aggradation or time. Creek chubs and white suckers were affected by sediment level and time. White suckers – the most specialized forager – were most strongly affected, but exhibited the greatest loss of condition in least aggraded conditions. Laboratory data suggested that sedimentation and time spent in aggraded conditions were significant factors affecting common shiners, in spite of consistent food availability. Results varied across feeding guilds, indicating that opportunistic species that feed across the water column may be more resilient to sedimentation than more specialized trophic groups. However, all fish in the study experienced a loss of condition in aggraded environments over time, indicating that streams and rivers with extensive sediment aggradation are unlikely to support healthy fish assemblages. Copyright © 2009 John Wiley & Sons, Ltd.