I hope Baitbucket doesn't mind me answering your question. Yes the only salmon in Quabbin reservoir are landlocked salmon. Either Baitbucket or one of the other guys here said they are naturally reproduced along with the lake trout. Pretty cool huh?
I've fished Quabbin reservoir a few times and not only was the fishing good but the scenery is magnificent. No houses on the 25,000 acre reservoir whatsoever. All protected. That said the reservoir has a required mandatory boat inspection and once you take your boat somewhere else (break a seal attached after inspection) you need to have it reinspected. They are trying to protect the reservoir from mussels and other exotics.
FYI, The LL salmon are not naturally reproducing in the Q any appreciable numbers they are stocked annually.
https://www.facebook.com/MassWildlife/videos/1515140681881393/Here is some info regarding the LL salmon and Atlantic's. Just thought you might want to know.
http://midcurrent.com/experts/the-difference-between-atlantic-and-landlocked-salmon/