@rana sb
Yaar I'm just a student of this 'shouq'...:). However,If u have any queries i'll be glad to answer them or provide answers from my other sources if u didn't knew the answers.As for a separate thread I think someone already did so,but it didn't went well donno y.
@gypsy_acumen
Sorry bro,I posted my reply and then closed my system for the day..So didn't knew u replied and require more info.But i guess u have already searched it on net and now know the difference and know how to distinguish between china and mahseer..
For kantaye,v have to go abit indepth at the life style of fish and i don't wanna bore u with the details..:). So in short,china has big and less kantaye (that's one of the main reason for it's selection for aqua-farming) then catla,rahu and last mahseer (highest number of kantaye).
As for your observation regarding theil (catla), yes it's not pure theil it's a cross between rahu and theil ,most likely reason for that is to introduce taste and lessen the amount of fat as compared to theil, locally name is hybrid or hybreed.
The most distinctive feature of a pure rahu is a self-texture horizontal line which runs in the middle of body till end.A freshly caught rahu will be light grey from top and pinkish white color from bottom,and as the time pass by the grey becomes darker and pinkish turns to very light yellow or off-white.Body will be cylindrical and proportionate.
You are somewhat right about their diet.BUT it's the ratio of these things which develops taste in fish.For common man the preference would be like this,
1 - Rahu
2 - Narain (mori,mrigil), it's of same shape as of rahu but of golden color
3 - Theil
4 - China
Please note that i have mentioned only scaled (chan-naye wali) commonly available fish.
otherwise there are other species as well..which have more taste and are scaled too.
Then there are non-scaled fish (maali,singharah,baam etc), unki eik alag story hai ..