Boil a sterlet in lightly salted boiling water, turn into a coarse sieve to cool, then cut into pieces. Meanwhile, boil vinegar with bay leaves, pepper, cloves, cinnamon, and 1 tablespoon prepared mustard. In another saucepan, place several dried figs, dates, raisins, and several skinned and seeded lemon and orange slices. Add the cut-off citrus zest, shredded into strips, and 2–3 quartered Crimean apples. Strain the spiced vinegar over the fruit, bring it all to a boil twice, and cool. Arrange pieces of sterlet in a jar, interspersing them with the boiled fruit, cover with the almost cooled vinegar, and pour a spoon of olive oil on top. Set the jar aside for 4 hours, tie it up with waxed paper and then with ordinary paper. Store in a cold place.