Otisco Lake is special among Finger Lakes. It was originally about 15' to 20' lower than it is now. The lake's level was first raised during the filling of the canal system - in effect flooding the original shoreline. Then it was raised again. I believe the same thing was done on Skaneateles Lake too (one time.) This lake also does not have a standard New York State launch on it (though one is currently being built,) so anglers with medium to large boats are forced to launch at one of two marinas at $9 a pop. Boat traffic is generally light on this lake, though weekends in the summer can be crowded here by midday. It's a great weekday option in the summer for bass/muskies.
Why go here? For me the main attraction is Tiger Muskies. This lake holds decent numbers of Tiger Muskies, including some 20lb.+ fish. This lake is the number #1 priority in NYS for Tiger Musky stocking - it receives the largest, healthiest tigers. I've done a lot of guiding here for Tigers over the past decade or more and my clients have landed fish to 46" long and in the 25lb+ range. They can be fly-fished here too. In 2016 my client Dave V. had a memorable day fly-fishing tigers here and I learned a lot. A lot of musky fishing (whether targeting pure-strain or hybrids) is about the conditions. Weather, water, moon phase et.al. Muskies are always challenging to fish for. Don't expect to nab a fish on your first time out though it is possible. Think of them more as a long term goal and you'll have the right mind-set.
The other big draw on this lake are walleyes - which get big here as well. Most walleyes are caught by anglers casting stickbaits at night from shore from the late spring through fall. I don't guide walleyes here. I rarely target them on my own either though I do enjoy it from time to time.
Brown trout are stocked here and from year to year their survival is variable. The lake is marginal brown trout water and they aren't a species I'll likely ever target here. Otisco also has some very nice largemouth and smallmouth bass. Other species found in the lake include both black and white crappies, yellow perch, white perch, bullheads and more and more channel catfish every year. This lake is loaded with suckers, redhorse and carp and it's hard not to notice them jumping around all day long.