Peel and finely dice the onions. Heat the oil in a pot and sauté the onions for about 5 minutes until golden brown. In the meantime, wash, clean and quarter the tomatoes. Add the tomatoes to the onions and sweat for about 1 minute.
Add tomato paste, stir in and fill up with white wine and stock. Wash and clean the fennel and put the green aside for garnishing. Cut the fennel into about 12 corners and add to the tomato stock.
Let simmer for about 15 minutes. In the meantime wash, clean and halve the sugar snap peas. Wash the salmon and loach fillets, dab dry and cut into medium-sized pieces. Season with salt and pepper.
Let the fish pieces and sugar snap peas simmer for about 6 minutes in the boiling tomato-fennel broth. Wash the shrimps, dab dry and add them about 2 minutes before the end of the cooking time. Arrange bouillabaise in soup plates and garnish with fennel greens.