In a medium glass bowl, combine vinegar, sugar and salt and stir until almost fully dissolved.
Prepare the fish (this process works best if you have a fillet knife -- if not, just use the sharpest knife you can find). Remove any pin bones and cut very thin strips into 2” pieces.
Add fish, onion, ginger, bay, lemons and lemon/lime juice to the vinegar mixture; stir to combine. Be sure the fish is fully covered -- if not, add a bit more vinegar and lemon or lime juice and stir again.
Cover with plastic wrap and refrigerate at least 8 hours. Mid-way, stir to mix up the fish.
Before serving, add a squeeze of lemon or lime juice and parsley. Add a little salt, to taste.
Serve on crostini or crackers.
Recipe by My Delicious Blog at https://www.mydeliciousblog.com/pickled-mahi-mahi/