Hey David, I’m not sure what software you’re using to map the data but I found CartoDB to be extremely efficient for this kind of work. If you take a look at my profile you can see some of the maps I’ve created. I chose to break up the data by AIS type, which is essentially the vessel classification (fishing, coast guard, etc).

I hope that’s helpful! In my previous research you’ll see that I was only looking in a specific area that I assumed the ghostboat would be in 24–48 hours after leaving port. I’m glad more people are looking into it. Perhaps you’ll come up with something I missed!