I lived in the far east for many years so I can draw a few conclusions that might possibly shed some light:
Not knowing exactly what ethnicity the older men may have been, I can only answer in general terms however.
Having fished in the orient, I've found that any fish that is caught is kept. There is always a use for it, and seldom is anything wasted. Unlike many western cultures, asian cultures utilize most all parts of the catch. (We've all seen the infamous fish head soup portrayed in the movies) Fish oil is a multi use product. Used for lubrication to medicinal purposes.
The meat of less desirable fish is often dried and ground into powder and used for seasoning. I've even noticed here, in the US, that these traditions continue even when the fishermen catches fish that they have never encountered in their native country. So, I'm not surprised to read about the strange look, but I think it was more of (why wouldn't you keep it) kinda look! My 2 cents worth...
Forgiveness is between them and God. My job is to arrange the meeting!
US Army 1st SGT (Ret)