Effects of Anthropogenic Stream Alteration on Brown Trout Behavior and Physiology: A Multifaceted Approach

The Upper Esopus Creek in the Catskill Mountains of New York supports a popular brown trout fishery; however, the stream is impacted by cold and occasionally turbid-water releases from an aqueduct originating in a nearby reservoir.  Although turbidity has been shown to negatively affect trout, cold water provides thermal benefits to trout during warm periods and may offset effects of turbidity.  The actual effects of the aqueduct’s releases on brown trout in the Esopus Creek are unknown and a point of contention between anglers and stream managers.  The objective of this research is to understand relationships between aqueduct releases and brown trout populations.  We quantified differences in the physical and chemical habitat upstream and downstream from the aqueduct and assessed behavioral and physiological responses of trout occupying these two segments.  Although we found differences in stream habitat, we did not detect expected differences in trout behavior or physiology; however, our assessment of trout clinical chemistry and water content revealed both populations to be stressed and in relatively poor condition.  Research is ongoing into how the aqueduct releases are affecting the growth and condition of individual trout and other characteristics of the trout populations occupying these two segments of the Upper Esopus Creek.