(12)Where Member States grant exemptions from the obligation to carry a Union certificate of qualification, they should recognise Union certificates of qualification for persons who operate on their national inland waterways that are not linked to the navigable network of another Member State where the exemption is applied. Those Member States should also ensure that, regarding those inland waterways, the data regarding navigation time and journeys carried out are validated in the service record books of persons who hold a Union certificate of qualification, if the crew member so requests. Furthermore, those Member States should take and enforce appropriate measures and penalties to prevent fraud and other unlawful practises that involve Union certificates of qualification and service record books on those non-linked inland waterways.