Woodcock Creek has good numbers of em. My son likes to go there a couple times a summer and catch them on his fly rod.
The tribs have decent numbers of em the couple times I have fished them in June. Not sure how long they stick around though.
Never fished this spot myself but I’ve heard a few times near where they dock the Brig Niagara is good, but not sure how easy it would be to use a fly rod there.