Taggish guy overcalls preflop after a fish and a tag utg open-raiser, he a rather large range. He would probably squeeze you with TT+ and AQ+, so we're looking at
22-99, Axs, suited connectors, broadways, maybe even connectors and some suited 1-gappers.
On that flop, he could do that with 77-99, 87, T9, 65, any 2 spades, 7x, maybe 8x for protection. A read on the BB would help, he looks fishy, i don't expect a tag to raise a paired board into a halfstacked loose passive fish and the preflop aggressor with a marginal hand or air, committing himself against him in the process, unless he knows you know it looks super strong.
So 99 is unlikely because you have it, 77 88 87 have the deck so crushed that i think he would slowplay them, a naked 8x would be pushing it but it's possible. He probably has an OESD, a FD, a combo of the two, all of that with or without overcards, or a 7x.
Bottom line is it looks strong and even if you're ahead now you're mostly flipping if the money goes in, and you won't like many turn cards : a spade, any overcard, even a 4 is sorta scary.
Unless you have a read on his him to suggest otherwise, i would just muck it out of position here, it's not worth the trouble.
Hope it helps.