Without spoiling me too much, can you tell me if there is anything of interest or at least fun to get from spreading blemmingans? I don’t know, but from the various messages, warnings and red lights I gathered from Sunless Sea, it seems these critters are mean and nasty. Why would I want to spread them, unless I hate the inhabitants of an island?
Well, perhaps I answered my own question :)
Don’t put them on Mangrove College unless you hate yourself. I haven’t found anywhere else where they have a significant effect. edited by Olorin on 2/14/2015
They can also be troublesome if you put them on at the Empire of Hands, depending on what interactions you’re planning to have there. There are a few places where I don’t feel the least bad dropping them off, generally because the locals are more than a match for them - Polythreme, the Iron Republic, Godfall, the Fathomking’s Hold, places like that.
As for rewards, well, you get a choice - one is a brightly-coloured item of interest to a few different parties, and another is useful for the Father’s Bones ambition.