Ulang or Giant Freshwater Shrimp (Macrobrachium rosenbergii) used to thrive in several rivers and waterways throughout the Philippines. They needed unsullied fresh water or somewhat brackish (part salt, part fresh water) conditions to thrive in the wild. In the last few decades they became rarer and rarer from natural sources as our rivers got more and more polluted. But we have now successfully domesticated the shrimp and raise them in shrimp ponds or together with rice crops in rice fields and nearby ponds. Large (compared to shrimp) and meaty, they are a more reasonably priced alternative to lobster and about the same price as prawns. The most common usage I have found is in a terrific ulang sinigang (shrimp with a sour broth). They differ from prawns in that their heads are unusually large and they have these long thin claws (not obvious in these pictures as I think the vendor removed them!). They have bright blue and sometimes yellow striped colored shells and legs.
Ulang can grow up to a foot long and weigh about 350 grams (or 3 pieces to a kilo). The ones I photographed here were about half that weight at 6 pieces to a kilo and they cost P380 a kilo. I suspect much of that potential length would include the long thin claws. Native to the Philippines, but related to dozens or hundreds of freshwater shrimp throughout the world, this is a food source that was unfamiliar to many Filipinos in the last two generations due to its disappearance from rivers and streams. However, aquaculture is bringing it back quite successfully. If you have never tasted ulang before, try it. Treat them like large prawns though I find the meat can be denser and dries out faster when it is roasted or grilled. Overcooking them makes them tough. For a first taste, try them in a sinigang made with sour tamarind or alternatively, kamias fruit.
In some material I came across doing research for this post, some local sources refer to ulang as freshwater shrimp or crayfish. They are not crayfish as the latter are small freshwater lobster and there are none of those in the tropics except in Papua New Guinea and Northern Australia. For the curious, ulang are also known as udang in Ilocos and Cagayan (also the word for shrimp in Malaysia and Indonesia); paje in Palawan; kalig in Leyte, kissing-kissing in Pangasinan, etc., according to an article by Rose De La Cruz on the Palawan.com website.