I think that just means that reports to the database are old, with no recent confirmed sightings. It does not mean the fish is no longer present. Fish listed as "historical" I would think are more likely no longer present than fish listed as "current", but either could be now present or now absent.
I suppose but Atlantic salmon are fished for quite often over here. There is also a hatchery that rears and stocks them so I doubt in this case it is due to no recent sightings, just an error on their part.
They also fail to list green sunfish in the watershed I live in (Seneca) and two other nearby watersheds. Now, while they are uncommon in NYS they do live here and in my watershed, I caught two of them last year. One is in my avatar. My point is that while the site is useful I would take it with a grain of salt, the same for most other online sources.