Rinse crabs cold and drain well. Also drain mandarin oranges, collecting the juice. Clean and wash the salad and cut into thin strips. Mix yoghurt, mayonnaise and 2 tablespoons of mandarin juice.
Season to taste with salt, pepper and lemon juice. Rinse dill cold, dab dry and chop. Stir into the sauce. Mix the shrimps, mandarin oranges and salad with the dressing and divide between four cocktail glasses.
Garnish as desired with a lemon wedge and dill.