Really, measurements are the single way. We suggested that the on-board observers from our service-providing company could offer a bit of that service, as well, in C and P's absence. Primarily, it's just measuring with calipers.
Evidence of meeting #28 for Fisheries and Oceans in the 43rd Parliament, 2nd Session. (The original version is on Parliament’s site, as are the minutes.) The winning word was prawns.
A video is available from Parliament.