“We’re Mercer Island’s best-kept secret,” said the guy behind the counter at Freshy’s Seafood Market’s little walk-up window on the west side of Mercer Island (2411 76th Ave. SE; 206.232.3028; Facebook: “Freshy’s Seafood Market”). He must’ve noticed my surprised expression as I ordered a plate of three rockfish tacos ($10.99). Before stumbling upon it during a farmers market excursion, I’d never even heard of this former gas station, now transformed into a fish market and takeout fish ’n’ chips joint with a cute patio, picnic tables and flower pots in fishing nets. I sipped a Two Beers 20:20 Blonde (four local brews are on tap on any given day) and settled in with my tacos: grilled corn tortillas filled with softly cooked rockfish under a shredded cilantro-romaine salad with tomatoes; a dash of Tapatio made them just about perfect. Sorry, Islanders, but some secrets deserve to be shared.