A river that lost three dams
Start with what changed. In 2018 the 18-foot Columbia Lake Dam in Knowlton came out, in 2022 the 4-foot County Line Dam in Stillwater followed, and in 2024 the Paulina Dam in Blairstown went too, reconnecting about 45 river miles to the Delaware. South Branch Outfitters counts four removals between 2018 and 2024, says summer water now runs 3 to 5 degrees cooler, and credits The Nature Conservancy with planting more than 58,000 trees along 10 miles of bank. The old impoundments at Columbia and Paulina are now moving water, so if you last fished here a decade ago, forget the lake at the bottom.
None of that makes it a wild trout river. The Paulins Kill runs 41.6 miles out of the marshes around Newton, north and then southwest down a limestone valley to the Delaware just below the Water Gap, and in summer it gets shallow and warm. Most of the trout you catch were put there by the state; holdovers exist, helped by limestone seeps, but plan around the stocking calendar.
Limecrest to Columbia: the Thursday rule
New Jersey stocks the Paulinskill, as the digest spells it, from the Limecrest railroad spur bridge on the East Branch in Sparta and from Warbasse Junction Road (Route 663) on the West Branch in Lafayette all the way to the Delaware. Trout streams close from March 23 until opening day, April 11, 2026 at 8 a.m. After that the river and its East and West branches are closed 5 a.m. to 5 p.m. on Thursdays through the spring stocking run, which in 2026 meant April 16, 23 and 30 and May 7, 14, 21 and 28, and the closure extends 100 feet up every tributary. There are no fall closures, and the river gets fall fish.
No special trout regulation area applies. Statewide stream rules cover it: 9-inch minimum, a daily limit of two trout from January 1 to March 22, six from opening day through May 31, and two from June 1 to December 31. The shop's page still says four after Memorial Day, which is out of date. The river is in the Brook Trout Conservation Zone, so brook trout must be released at once.
Blairstown, the rail trail and the viaduct
Access is easier than on most New Jersey streams because the old New York, Susquehanna and Western grade follows the river. The Paulinskill Valley Trail runs 27 miles from Sparta Junction to Columbia, and the shop names the Blairstown area off Route 94 as the best place to start. Downstream near Hainesburg the river passes the Paulinskill Viaduct, built between 1908 and 1911 to carry the Lackawanna Cut-Off across the valley, and in the same area a creek draining the Yards Creek reservoir in Blairstown joins. Four wildlife management areas sit in the valley: Bear Swamp, Trout Brook, White Lake and Columbia Lake.
Much of the bank between those points is private. Use the trail and WMA land, and ask before crossing a field.
What 90 to 300 cfs at Blairstown means
No local shop publishes a wading range for the Blairstown gauge, so the band on this page comes from the USGS record there. Monthly means peak at about 369 cfs in March and 336 in April, fall to 230 in May and 163 in June, and bottom out near 111 to 122 cfs from August through September. Wikipedia's figure for long-term median flow is 76 cfs. Between about 90 and 300 cfs the river is wadeable and carries enough water to hold stocked fish in the runs; above 300 in April it is pushy and colored, and below 90 in a dry summer the trout crowd into the few deep holes and warm by afternoon.
In the three weeks to September 23, 2026 the gauge read 68 to 157 cfs and sat near 72 at the end, low but not unusual for September.
Spring mayflies, then bass
South Branch Outfitters lists Hendricksons, a heavy sulphur hatch, March Browns, caddis and blue-winged olives as the main events. Nobody publishes a dated chart for this river, so the table below borrows the timing from the same shop's South Branch chart 30 miles south: Hendricksons in April and early May, March Browns in May, sulphurs from May into early July, caddis through the summer evenings, and olives in spring and again in fall.
Once the water warms in July the shop suggests switching to smallmouth bass, which hold in the lower river through the summer. Trout fishing picks back up with the fall stocking and cooler nights in October.