In a bowl, soak shiitake mushrooms in warm water for about 30 minutes or until softened. Remove from water and squeeze excess liquid. Finely chop and set aside.
In a pot over medium heat, combine fish, soy sauce, and enough water to cover fish. Bring to a boil, removing any scum that floats on top. Cook for about 5 to 7 minutes or just until fish can be easily flaked from the bones.
Remove fish, discarding liquid. Let cool to touch and flake flesh, discarding bones.
In a wide skillet over medium heat, heat about 1 tablespoon of oil. Add onions and garlic and cook softened.
Add water chestnuts and shiitake mushrooms. Cook for about 1 to 2 minutes or until heated.
Add flaked fish and cook until just heated through.
and Chinese celery and continue to cook until celery is just wilted. Season with salt and pepper to taste. Remove from pan and drain excess liquid, if any.
Separate spring roll wrappers into individual sheets. On a flat working surface, lay wrapper like a diamond.
Spoon about 1 1/2 to 2 tablespoons of fish mixture on the middle of the wrapper. Fold the bottom pointed end of wrapper over filling. Fold side ends of the sheet inward and roll into a log. Wet the pointed edge of the wrapper with water to completely seal. Repeat with the remaining mixture.
In a skillet over medium heat, heat about 1 inch deep of oil. Add spring rolls in a single layer and deep fry, turning once or twice, for about 3 to 5 minutes or until golden brown and crisp.
Drain on a wire rack. Serve immediately with spiced vinegar.