J.S.
The practice of having separate ownership for each vessel owned, in order to absolve the parent company from responsibility should one of their vessels cause a major environmental (or otherwise) tragedy (think Exxon Valdez) was one of the main driving forces behind the mandatory introduction of ISM, brought about on the insistence of the marine insurance business.
The main thrust of ISM is traceability whereby there is always one named person in any ship owning/ship management company that can be held to account in the event of any marine disaster. This person is the designated person who forms the link between the ship board management team and has access to the highest level of management (board of directors/owners) ashore.
This supposedly eliminates the owners of a number of vessels hiding behind single ship registered companies, think of all those shipping company offices in one street in Monrovia.
rgds
JA