International rules that require ships to have ballast water management systems to stave off the spread of invasive species also require crew to maintain a ballast water record book.

But when vessels call at ports in different countries, officials inspecting the ship have different interpretations about what should be in the document.

As the International Maritime Organization gears up for a key meeting in June, member nations and shipping groups are urging the United Nations’ regulator to revise its rules to provide a more unified ballast water record book.