[Madhu Pabda (Bangladesh); Ompok pabda of family Siluridae (Sheatfishes)]
This fish is found in rivers of Afghanistan, Pakistan, India, Bangladesh and Burma, and is particularly popular in the cuisines of West Bengal and Bangladesh. It can grow to 11 inches, but is more commonly around 6 inches. IUCN Red listed NT (Near Threatened). Photo by Balaram Mahaider distributed under license Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International Attribution Required..
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While popular in West Bengal and Bangladesh (formerly East Bengal) Pabda is not available in North America. Since it is a Sheatfish, a different sheatfish would seem a natural substitute - but not easy to find outside Los Angeles. If you can not find sheatfish, I suggest using the now very common Vietnamese Catfish (Basa, Swai). American Channel Cat has a different shape and more assertive flavor, so would not be as good a substitute.
Most Bengali recipes call for cooking Pabda whole, certainly possible with other Sheatfish, but not with Vietnamese catfish. On the other hand, most Americans aren't thrilled with fish staring back at them from the plate, never mind dealing with fins, so fillets would be just fine. While small Swai fillets can sometimes be found, larger ones could be cut into chunks, perhaps about 2 inches by 5 inches.
One of my Bengali cookbooks, written by a real Bengali, suggests "Whiting" which she describes as a "close cousin" to Pabda, which would certainly not be true of any whiting listed on Fishbase. Most whiting are hake, of the cod family, except in Southeast Asia and Australia where they are Sillago, no closer to Pabda than Hake, and unlikely to be widely available in New York where she lives. The weight she gives by count of whole fish would be only 5 ounces each, rather small for Hake Whiting - so I really don't know what it is they're selling as "whiting" in New York.