Or as the kids today might call it, sushi rice.
Perhaps something you could have with your mackerel?
From a box sold in Martinez, California.
Osushi Rice
5 c. water and 5 c. rice–cook
Vinegar Syrup
1 c. sugar
1 c. white vinegar
1-1/2 T. salt
juice of 1 lemon
1/2 tsp. Ajinomoto