Translate the following English sentence to French:
"In many cases, the port services - both with regard to the ship and the goods - are faced with no effective competition or with very limited competition and this means that there is often abuse of dominant positions, such as the imposition of obligatory services which are not necessary or are not even used, for example, piloting, towing, mooring and port handling, as well as the payment of very high tariffs."
Dans bien des cas, les services portuaires - concernant le navire et les marchandises - sont fournis sans concurrence réelle ou avec une concurrence très limitée, ce qui entraîne souvent des abus de position dominante, comme l' imposition de services obligatoires inutiles et même inutilisés comme, par exemple, le pilotage, le remorquage, l' amarrage ou la manutention portuaire, ainsi que le paiement de tarifs très élevés.