Caveat: Post some of the comments I must put a disclaimer that the piece and size preferences are mine. Perceptions on cholesterol and fat are relative and are based on what my mom and grandmom told me
I got some nice rohu and ilish (hilsa) from the Khar fish market at Mumbai today.
I was Live tweeting at @finelychopped on what I was looking for as I shopped. Then Roma Abraham asked me on the Finely Chopped Facebook page on tips to buy good Bengali fish.
Here’s my answer:
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Roma Abraham will do…. usually my Dad loves going to buy the fish himself, but I usually like to buy the Bengali fish and love cooking Bong food too. maybe you can give me some tips on how the Bengalis choose their fish… So far I’ve relied mostly on the fisherman or woman’s advise.about an hour ago · -
Finely ChoppedI was actually tweeting from the market on buying fish today @finelychopped basically find fish sellers that are crowded. ask them to choose. say you will return if not good. Rohu/ kaatla should be at least 3 kilos plus. If buying part buy the upper half. Ask for square not round pieces. Ilish should be at least 1.5 kg. Without egg is better for any fish. Tastier. You can press fish and see if it bounces back. Flesh shouldn’t be yellow. But above all a trustworthy fish seller http://finelychopped-k.blogspot.com/2010/10/harem-in trigues-khar-fish-market-s quid.htm 
Hilsa: 1.5 kg plus will have less bones. Go for separate gaada (back, bony), peti (stomach, less bones) pieces. If you have a fish which is 1.3 kg like this then go for ’round’ pieces with both gaada and peti
Rohu: If you are buying a part (cut) of fish then go for the upper half. Less bones, more fleshy. Cut fish is more expensive than the whole one where you take the head and lower half too 
Rohu: Peti or belly pieces. More fat and cholesterol. Less bones. tastier. If the fish is bad then first sign is bitter peti 
Rohu: gaada or back pieces. More bones. Less fat. There are two types of cuts. Round – which pi@#*s me off. I have changed fish sellers who cut it round despite my asking them not to. Or rectangular which is my choice
Hi! The peti that u've mentioned as fat and cholesterol seems misleading… because of the terms 'fat and cholesterol'.. It contains HDL which lowers LDL and is very good for the skin. Makes it glowy and blemish free.. And never makes u fat or clog the arteries.
Well good to know that Shriti… my mom and grandmother would tell me that petis are fattening and have cholesterol. ditto the mudo and the head. so i make the odd effort to avoid them
thanks for sharing so much information.
Maam…I have only recently started buying fish..I get confused as to which is what fish..I cannot tell a rui from katla..can you please tell me??
Dear anon, I am a guy 🙂 katla has a bigger head than Rui and is broader on the sides while Rui is more sleek. The latter is more fatty
Dear Sir, I am a school teacher from Tamil Nadu. Thanks for a clear-cut guid on Fish selection. Your FB page is cool and updated. Rogu and Katla are favourite among us. During evening on the Road Side, the Rogu, Katla fry will be available. Vanjerem, Pamfret, Nandu are high priority in our community. I appreciate your intension to share your knowledge on “food and health “.
Vanjerem is between Rs 800 and Rs 1300 per k.g. Rogu and Katla between Rs. 180 to Also one piece of Fried Vanjerem is around Rs. 180 to Rs. 220. [ Dec 2015 ]
I request you to consider the following as my suggestions
# label the images
# Give Point by Point tips on Fish Selection
# Give "Dos" and "Don'ts"
# Tips for Vanjerem and Pamfret
They all look the same to me. Can you give me more differences.