I honestly can't find any relationship between Samurai and fishing anywhere. In fact the word 'fish' isn't mentioned once in the lengthy Samurai Wikipedia article. Even if its improves Japan a little (and it really is a little) its horribly a-historical. Why not just give them half price work boat, or give this ability to workers instead. The Legion improvement building and Conquistador settling has a historical basis, so why give us this rubbish? Its like giving Panzers the ability to roll around building plantations. There was so many good ideas for a new Japan UA such as buffing domestic trade routes, and instead we get this. Feels lazy and poorly thought out to me. I'm sure many of you agree. Its a real shame as I'm quite happy with the rest of the patch, this is such a disappointment. 
