Importance of Un-Named Tributary Streams to Brook Trout Populations

Pennsylvania contains over 64,000 streams, however biological data exists on only 12% of these streams, which are actively managed for water quality and biotic standards. The other streams are considered unassessed. In Pennsylvania almost 54,000 un-named tributaries remain unassessed, thus there is need to obtain biological data on these waterways. In 2013-2014 as part of the Pennsylvania Fish and Boat Commissions Unassessed Waters Initiative we surveyed over 300 unassessed Un-named tributaries throughout Pennsylvania to determine their status as possible wild trout streams. We found brook trout in greater than 50% of these streams. Many streams supported robust populations of brook trout and serve as valuable source populations to their named tributaries. We sought to create a predictive model utiziling data from two watersheds to determine the presence of brook trout in un-named tributaries in order to better target future assessment efforts. Tributaries were delineated, and characterized by soil, landuse, and terrain variables. Multiple regression was used to determine the 4 most significant factors related to presence of brook trout populations: percent of soil area containing carbonate bedrock, landuse/land cover area developed, watershed size, and watershed slope. To improve the methods predictive capability, we intend to add climate and mining/drilling measures of habitat stress.