What happened to the bass, in order
You will hear that the Susquehanna was sick, and it was. In 2005 PFBC biologists first documented disease-related deaths of young-of-year smallmouth, with sores and lesions turning up in late spring and early summer surveys year after year, and adult numbers fell hard between 2005 and 2012. Mike Heck of Precision Fly and Tackle, who guided the river through it, calls it a major fish kill that killed thousands of fish. Beginning in 2012 the PFBC petitioned the Department of Environmental Protection, without success, to list the river as impaired, passed board resolutions in 2010 and 2014, and in May 2015 announced that two independent labs had confirmed a malignant tumor on a single smallmouth caught near Duncannon in November 2014, the only such case documented in Pennsylvania. Since 2005 the agency has handled more than 22,000 adult bass in surveys without finding another obvious tumor.
The fish came back before the argument was settled. Surveys from 2013 to 2016 showed rising adult numbers, and in October 2018 nighttime electrofishing at Clemson Island, Rockville, the Dock Street Dam and the Turnpike bridge near Highspire produced the fifth-highest catch rate since standardized surveys began in 1990, with fish from 6 to 20 inches and record numbers of bass 18 inches and longer. The PFBC credits lower disease prevalence in young bass and the mandatory catch-and-release rule for better recruitment; Lancaster Online reported in 2018 that largemouth bass virus was the main killer, while the USGS paper on the die-offs finds no single cause, rather co-infections and stressors hitting fish at a vulnerable age. Wild East Outfitters, who guide it, say it is fishing as it did in its best years.
Sunbury to Clemson Island
The regulated reach begins at the inflatable dam near Sunbury, where the West Branch and North Branch have just joined, and the PFBC's channel catfish surveys treat Sunbury to York Haven as the middle river. Below Sunbury the river braids around islands past Selinsgrove, Liverpool and Millersburg, and Wild East runs floats from Sunbury down toward Harrisburg from July 5 into late fall. The Juniata enters at Duncannon and the river widens again.
This is boat water, drift boats and rafts covering ten or so miles a day, with wading at the ramps and around islands when the stage allows. Clemson Island, above Halifax, is one of the PFBC's four long-term survey sites.
Halifax to Harrisburg: the water trail and the dam below City Island
The original 24-mile Susquehanna River Trail runs from Halifax to Harrisburg with three PFBC trailheads, Halifax, Amity Hall at the Juniata mouth and Fort Hunter just above the city, plus municipal and private launches and 24 primitive island campsites under the Bureau of Forestry. A registered boat or launch permit is required at the PFBC ramps. Rockville, where the stone railroad bridge crosses, is another survey site, and the PFBC water trail guide calls this stretch's smallmouth fishing what it is, though its line about Big Bass regulations predates the current rule.
Below City Island in Harrisburg sits the Dock Street Dam, which the trail guide describes as the dangerous dam just south of City Island. Rivers Outdoor Adventures fishes the Duncannon to Marysville stretch above the city; the PFBC's Turnpike bridge survey site near Highspire is below it, on the way to Three Mile Island and York Haven.
Read the Harrisburg gauge in feet, then convert
Guides here talk in stage at USGS 01570500, not cfs. Rivers Outdoor Adventures publishes the clearest scale: 3.5 to 3.7 feet is perfect for a steady drift, 3.2 to 3.4 is low, below that is too low to drift, above 4 feet is too high and usually off-color, and wading is safe in most of the Duncannon to Marysville stretch below 3.25 feet, with caution. The live page on this site compares flow in cfs, so the band was converted using this summer's paired USGS readings at Harrisburg: 3.5 feet ran about 9,000 cfs, 3.7 feet about 11,500 and 4.0 feet about 15,800, which makes 9,000 to 11,500 cfs the float window. The lowest stage paired this summer was 3.39 feet at 7,730 cfs, so the 3.25-foot wading line sits somewhere below 7,500 cfs.
The long-term record explains the season. Median monthly means at Harrisburg since 1890 run about 21,400 cfs in June, 12,600 in July, 9,150 in August, 8,070 in September and 12,400 in October, then 24,800 in November. August and September are the months the river is reliably in the window, which is exactly when the White Fly comes off.
White Flies at dusk, hellgrammites all summer
The White Fly, Ephoron leukon, is the one hatch every shop mentions. Wild East puts prime time from late July through mid August and describes hundreds of smallmouth sipping them like trout; the Susquehanna Greenway and the Williamsport Sun-Gazette put the peak at dusk in late July and early August, starting below Wrightsville and spreading upriver, thick enough that some bridges turn off their lights. Fish it from 8 p.m. until you cannot see, with a white dry or a spinner in size 8 to 12.
The rest of the year is a streamer and popper game. Wild East fishes Clouser Minnows most days, the fly Bob Clouser designed for this river, plus the Drunk and Disorderly and Swinging D, and Boogle Bug poppers for the bigger fish; the Middle Susquehanna trail guide lists minnows and hellgrammites as the live baits, and rubber worms and plastic crayfish as the lures, which is a forage list. Seven and eight weights are standard for casting into wind on water this wide.
The 98-mile no-harvest rule and the tournament calendar
The 2026 PFBC summary lists smallmouth and largemouth bass as no harvest, catch and immediate release, from January 1 to December 31 on 98 miles of the Susquehanna from the inflatable dam near Sunbury downstream to Holtwood Dam, including all tributaries up to half a mile above their mouths, in Cumberland, Dauphin, Juniata, Lancaster, Northumberland and Perry counties. Casting repeatedly into a visible bass nest is unlawful. From April 11 to June 12 no tournaments are permitted; the rest of the year only catch-measure-immediate-release events may run, and no tournament on the North Branch, West Branch or main stem may allow a bass to be harvested. The spring closed season that the board kept in place in 2017 is no longer in the book.
Other rules worth knowing: for bass regulations the power and recreational dam pools on the Susquehanna count as rivers; American shad and river herring are closed year-round on the Susquehanna and its tributaries; and the summary's consumption advisory from the West Branch to the Maryland line is one meal a month for channel catfish over 20 inches because of PCBs, with smallmouth and fallfish advisories on the upper river. A trout permit is not required here; a Pennsylvania fishing license is.