Peel shrimp; devein, if desired.
Arrange shrimp and grouper in a steamer basket over boiling water. Cover and steam 10 minutes or until grouper flakes easily with a fork. Cool and chop shrimp and grouper.
Combine onion and next 11 ingredients; stir in shrimp mixture, crabmeat, and 1 cup breadcrumbs.
Shape mixture into 12 patties;coat with remaining 2 cups breadcrumbs. Cover and chill 1 hour.
Melt 2 tablespoons butter in oil in a large skillet over medium heat; add patties, and cook 3 minutes on each side or until golden. Drain on paper towels, and serve with Jalapeno Tartar Sauce.
*1 (6-ounce) can lump crabmeat, drained, may be substituted for fresh crabmeat.