What if guano hunters were really looking for black goo? Seriously... bird poop for fertilizer so much so that you are sailing fleets of ships to fetch it... and fill their holds with literal shit? I've heard some good ones before, but operating a ship to fetch poop as a viable long lasting industry...simply to augment soil...nope. It'd sure keep officials out of your ship though right? Think about it... 1800's and a ship full of poop. I don't wanna inspect it, do you? Nope... them let them through. Don't touch the poop boat, it's toxic... Through the port moves your clandestine load of "bird poop". I suppose better than penguin pineal glands... or whatever. Where was the Faukland War fought? Off the coast of what country? Black goo what? https://goodizen.com/why-did-the-state-dept-in-1973-purchase-frozen-penguin-pineal-glands-from-argentina/

wouldn't there be pics from the 1800s of ships full of poo? What kid wouldn't meme that back in the day? Yet little evidence I see. Could just be me... because I happen to know currently human poo is also used as fertilizer here in America, so if this practice was occuring in 2002, when I worked the turd grinding industry (now I just service it). I loaded the trucks with it with a giant front end loader. Lawrence Kansas baby. Rock Chalk Jayhawk...
https://www.audubon.org/news/holy-crap-trip-worlds-largest-guano-producing-islands