Currently working in this space on orbital sensor systems, there are about to be a lot of fun ways to hunt these dark vessels and ID them/track them back to their ports. For instance, there are already small satellite constellations that can geo-locate and profile them based on their other RF emissions aside from AIS. The space is also heating up rapidly as this is becoming a national defense priority for a number of different countries that don't want to deal with illegal fishing among a host of other issues that anonymous vessels near their shores present.