my first encounter with fish sauce (back in groningen via a vietnamese neighbour) might have been a bit rocky. i still remember him pouring the stuff on a hot wok and the unbelievable stench it would leave on the corridor as it evaporated… which sounds funny to me now, because i have to say, ten years later, it has kind of grown on me.
in these stone tanks that are still around in quite a few places in portugal, fish bowels would be mixed with salt water and left to ferment and dry for several months. the resulting paste would be rich in protein and minerals — and probably just as stinky as it was umami. it was prized in roman cuisine where there are numerous records of its usage — poets even make jokes about its smell!
today, all that is left are these decaying tanks by the water… and some geek curiosity! :)