Assessment of Fish Habitat Impairment in Large U.S. Reservoirs

Degradation of reservoir fish habitat has become a serious concern in the U.S.  Habitat issues—such as sedimentation, excessive nutrient loadings, and lack of submerged structure—may emerge and worsen as reservoirs age, and are accompanied by undesirable shifts in the fish community and fishery.  To prioritize habitat rehabilitation efforts in reservoirs, we developed an index of reservoir habitat impairment based on an extensive habitat survey of large reservoirs in the conterminous U.S.  Oblique principal components analysis was used to identify major sources of habitat impairment, wherein each impairment class contained several indicator (observed) variables.  Scores from each habitat impairment class were then combined to create a composite index of reservoir habitat impairment (IRHI).  The IRHI was calculated for surveyed reservoirs and compared to descriptors of the fish community, recreational fishery, reservoir morphology, and watershed characteristics.  This method of assessment provides a nationally-applicable method for comparing and prioritizing reservoirs for habitat improvement.