[5] At the downstream limit of the stretch of Fidlers Run that is on the border of Lower Mahanoy Township, the stream's peak annual discharge has a 10 percent chance of reaching 1,130 cubic feet per second (32 m3/s).

The concentration of atrazine in the creek's unfiltered water was measured to be 300 nanograms per liter (3.0×10−7 oz/cu ft)[7] A National Pollutant Discharge Elimination System permit allowing a facility in Lower Mahanoy Township known as Former Hut Restaurant STP to discharge sewage into Fidlers Run at a point 1.58 miles (2.54 km) upstream of its mouth was issued; it will be effective from April 2015 to March 2020.

[14] Flooding was recorded on Fidlers Run, and numerous other streams in the Susquehanna River watershed, due to Tropical Storm Agnes in June 1972.

[10] The variant name "Fidlers Creek" appears in Israel C. White's 1883 book The geology of the North Branch Susquehanna River Region in the six counties of Wyoming, Lackawanna, Luzerne, Columbia, Montour and Northumberland.

[15] The variant name "Fiddlers Run" appears in the Stream Map of Pennsylvania, created by Howard William Higbee in 1965.

[16] The variant name "Fidler Run" appears in United States Geological Survey maps.

[16] In the early 1900s, the water supply for Herndon came from a 35,000-US-gallon (130 m3) reservoir at the headwaters of a tributary to Fidlers Run.

[3] In the late 1960s, civil engineer Stanley K. Sampsell was unable to find any written information on how to spell the name of Fidlers Run.

[11] However, the people he spoke to in the Herndon area all pronounced it with an "s" at the end, leading him to recommend that the stream's name be spelled "Fidlers Run".

[11] A two-span concrete slab bridge carrying Pennsylvania Route 225 was constructed across Fidlers Run in 1937 1 mile (1.6 km) south of Mandata and is 34.1 feet (10.4 m) long.

In 1960, a steel stringer/multi-beam or girder bridge carrying T-353 over the stream was built 0.5 miles (0.80 km) south of Herndon.

A concrete culvert bridge carrying Pennsylvania Route 225 over the stream in Mandata was built in 1995 and is 27.9 feet (8.5 m) long.

A concrete culvert bridge carrying State Route 3016 was constructed across Fidlers Run in 2003 in Mandata and is 26.9 feet (8.2 m) long.

[8] An unnamed tributary to Fidlers Run has experienced "excessive" aquatic plant growth due to nutrient pollution.