An effort to document fish in Pennsylvania streams has made useful findings for officials looking to manage trout populations in the state. It appears that stream temperature and acidity play an important role in predicting the presence of trout.
“The state’s interested in saving fish, and as a biologist, I’m interested in biodiversity,” said Steve Jordan, professor of biology at Bucknell University, and leader of the project that took place in summer 2014. He and students Miles Silva and Riley Schwengel made it out to more than 40 streams for the work. “About half of the streams we studied had no fish because they were too warm.”
In addition to temperature, Jordan and his students measured pH and conductivity of the streams with handheld meters. They used an acid titration method to measure alkalinity. All of those parameters are important in determining ideal trout habitat, says Jordan.
“In the streams with a pH near basic, they (trout) were good. But we didn’t have any fish in acidic springs due to acid rain,” said Jordan. No trout were found in streams with temperatures higher than 20 degrees Celsius. The ideal temperature seems to be just below 18 degrees, he says.
The study also confirmed what some anglers have known for a while: Trout can live near coldwater inputs flowing into the Susquehanna River. “A lot of trout are living at the intersection of the big river and small streams,” said Jordan. “That’s probably a very important habitat for them.”
Most of the support for the work came from the Mellon Foundation and Bucknell’s Department of Biology. The findings will go to help the Pennsylvania Fish & Boat Commission’s Unassessed Waters Initiative, which is looking to document all 86,000 miles of the state’s streams.
And while the findings are valuable for Pennsylvania trout, the work was also good for Jordan’s students.
“I must confess that a lot of this for me was driven by giving my students professional opportunities to get their hands dirty and to get them invested in the work,” said Jordan. “The state has invested lots of time and money, and people are interested in the data.”