I just ran across this "Mike" post from December 2023 about the fall stocking program which I saved like the other stuff he has explained over the years.
While the OP was talking about a Dec 1 stocking date versus the typical Fall Stocking commencement, it still is good stuff as usual and has implications as to the "whys:"
The original fall stocking program was only for lakes…lakes with good angler use. Years later, streams were initially added in two counties where there weren’t any lakes near-by and where angler use was expected to be high. Those counties were Philly and Delaware, both with high population densities that were expected to produce good fall angler use.
Based on measured high angler use at the time on the Wissahickon the program (stream) was expanded to other regions. Unfortunately, years later it was learned that angler use was low on a number of these streams and measurements of use confirmed that. Low use streams were removed from the fall program with fish allocated to the fall program generally being returned to the spring program in the streams.
A key point is that the fall stocking program for a given stream acquires its fish from the spring stocking program for that stream. Many streams don’t receive enough fish in spring to be suitable for allocating fish to a fall program and generally speaking, spring use is usually higher than fall use, so AFM’s need to use good judgement in selecting streams for the fall program…ones that 1) can afford to lose some fish without substantially depleting the spring program and 2) those that are expected to receive good fall use and typically have adequate fall flows despite the fall period often being a time of low flow. Low use isn’t good because the fall program carries extra expense. Holding fish from spring until fall is not a one to one proposition, as there is mortality over the summer.
As for lakes, an advantage is that even if fall use is only low or moderate, the fish apparently survive fairly well based on spring creel surveys that have detected marked fall stocked fish. Likewise, early spring electrofishing surveys for warmwater/coolwater species have at times detected good numbers of fall or late fall stocked fish. Such survival provides the opportunity for not only fall anglers to catch these fish, but also ice anglers and some early spring anglers as well. Survival in streams is generally not very good based on other past studies in northcentral PA. - Mike Kaufmann