The default RTP for the original Fishin' Frenzy is 96.12%. That's the figure Blueprint Gaming publishes, and it's the one you'll see on most reputable operators. It isn't the only number in play, though.
Operators are allowed to run officially certified lower builds of the same game. The common ones are 94%, 93%, 92% and 90%. Same reels, same Fisherman collect, same art. The only thing that changes is the long-run payout. And you can't tell which build you're on from the spinning reels.
The paytable is where it's written. Open the in-game info screen before you stake real money, find the "return to player" or "theoretical RTP" line, and read the actual percentage for that specific casino. If it doesn't say 96.12%, you're on a trimmed build.