Though they do not have much meat, they are caught and fermented in salt water, making a briny crab sauce for seasoning. These small freshwater crabs are found in great numbers in and around ricefields and flatlands turned into wetlands during the rainy season. Stir in vinaigrette; season with 1/4 cup rice vinegar (not seasoned) 3 tablespoons sugar; 2 tablespoons water; 4 teaspoons Asian fish sauce; 1/2 teaspoon Salted Crab in Green Papaya Salad (Click on an image to see a larger version.) Ingredients. Add peas and onion and stir to combine.