First the coronavirus epidemic trapped on-duty crews at work without relief. Then it kept off-duty crews cut off from their ships.

Now — with China holding a near monopoly on crew changes at times during the pandemic — it has driven some managers and owners to reconsider the sourcing of their workforce.

Asia's shipmanagers are adjusting their businesses to cope with a shifting set of constraints to keep their vessels running as crews are held back whether by law, by fear of disease, or by the lack of airline services.