Hybrid stripers are a cross between a striper and a white bass. I don't know of any white bass in Ct. As above, probably brought in from Pa. or Jersey where you have access to hybrid fingerlings or do a catch and release into Candlewood of a larger specimen.
The DEEP electro-shocks Candlewood most years for bass and trout and every once in a while for walleye. Both stripers and hybrids are "pelagic" meaning they orient in open water feeding on alewife herring so they are not in the shore line zone where electro-shocking takes place.
The drop off in trout is due to the drought conditions that led to massive trout kills in Candlewood a few years ago. With that, the DEEP cut the stocking of trout in Candlewood in half from up to 20,000 per year to something around 10,000 a year. The left over fish were dumped in Squantz increasing that water's allocation and probably the expanded trout parks got more.