This is from the PFBC web site, notice any connection with the postponed stocking events. Maybe the concern is bringing NZ mud snails back to the Hatchery, or distributing them from stream to stream as they stock.
Until recently, New Zealand Mudsnails were known to occur only in Lake Erie, Erie County; Spring Creek and Bald Eagle Creek, Centre County; and the Little Lehigh Creek in Lehigh and Berks counties. Surveys during 2020 revealed populations of snails in Trindle Spring Run, Cumberland County; Codorus Creek, York County; and Valley Creek, Chester County; prompting expanded surveys.
During 2021 surveys, 16 streams and rivers were found to host populations of New Zealand Mudsnails, including Fishing Creek, Clinton County; Jordan Creek, Lehigh County; Trout Creek, Lehigh County; Bushkill Creek, Northampton County; Saucon Creek, Northampton County; Monocacy Creek, Northampton County; Perkiomen Creek, Montgomery County; Tulpehocken Creek, Berks County; Wyomissing Creek, Berks County; Wissahickon Creek, Philadelphia County; Big Spring Creek, Cumberland County; Letort Spring Run, Cumberland County; Pohopoco Creek, Carbon County; East Branch Brandywine Creek, Chester County; the Schuylkill River, Berks/Montgomery/Philadelphia counties; and the Lehigh River, Lehigh/Northampton counties.