For the blueberry sauce:
Wet the skewer sticks before assembling.
Clean the mushrooms and cut the pineapple into 16 pieces. Peel and devein the shrimp. Set aside.
Dice the salmon filet into 1×1-inch pieces and marinate in lemon juice, pepper, salt and dill.
For the blueberry sauce: cook the onion with oil and butter in a pan over medium heat for 2 minutes and then add red wine and balsamic vinegar. Reduce for 3 minutes and add blueberries, once they boil, cook over low heat for 10 minutes and add salt and pepper to taste. Allow to cool and blend. Then put in the pot again until it has a sauce consistency.
To assemble the skewers, layer a piece of pineapple, salmon, mushroom, shrimp, pineapple, and repeat in the same order. In a hot pan, brown the skewers 2 minutes per side.
Spread the sauce over the salmon skewers and serve.