Simmer the crayfish in salted boiling water for 2 minutes. Drain, remove the shells and intestinal thread.
Put the crayfish shells, fish bones, onion, carrot, celery, pepper, thyme and bay leaf into a large saucepan and fry lightly in 1 tablespoon oil. Add the wine, cook until it has evaporated, then cover with water and simmer for 20 minutes.
Strain the "fumet" (fish stock) and add salt if necessary. Pour it into a saucepan with the julienned vegetables; cook them for less than a minute and remove them.
Cut the turbot fillets into pieces and season with salt. Sauté them in a dry nonstick pan. Arrange the crayfish in soup plates with the turbot fillets, cover with the vegetables, pour the fumet overtop and serve.