Katz, Harvey, Aquatic Ecologist, katzhm@verizon.net.
Rock Run is one of the most popular trout streams in Pennsylvania and helps, along with other trout waters to bring just under a half billion dollars to the state annually. While PA has more than one stream named Rock Run, this Rock Run starts in the southwest corner of Sullivan County and its waters flow into Lycoming Creek at Ralston, PA. The run flows for about 20 river miles, initially through private property and then through the public lands of Loyalsock State Forest.
Starting around 2012 indications of warmer temperatures in PA were becoming evident, but subtile. As a result, water temperatures at 13 locations along Rock Run and its tributaries were measured in 2021 and 2022 from April through November. The results of these water temperature measurements were then matched to upper temperatures limits for Rainbow, Brook and Brown Trout.
In addition, Rock Run water temperatures were matched to the National Aeronautics and Space Administration (NASA) Annual Global Surface Temperature (AGST) data in order to determine if Rock Run water temperatures, in the summer, will become too warm for these trout to survive. Some attention to the rate of temperature change in the AGST was determined through the use of an exponential regression. This predictive regression is then used to determine which year Rock Run water temperatures, in the summer, will likely prohibit trout survival. Attention to the fact that over 100 bogs are present within the drainage, and that these bogs contribute warmer waters then otherwise would be expected is included. Opposed to these warm waters are cooler ground waters that enter the length of the Run. This complex water temperature system tends to influence how trout use the Run.