[Rehu (India); Ctenopharyngodon idella]
A silver bodied fresh water fish imported from Asia, the grass carp can grow to 59 inches and nearly 100 pounds, but the photo specimen was 27 inches and 8.4 pounds. Grass carp are voracious eaters of underwater vegetation and are an important food fish in Asia, both farmed and caught wild.
Use of triploid (sterile) grass carp to control invasive aquatic weeds was pioneered in the Imperial Valley of California. Triploids are created by slightly damaging eggs immediately after fertilization. They grow to only 40 pounds in the irrigation channels and live half as long as diploid carp but they eat about 90% as much and won't establish wild populations where they are not wanted. The California hatchery has been studied by teams from many states and countries.
More on Carp Family.
Warning: In the state of California, transporting a live grass carp without valid permits, or failing to release one caught in the irrigation systems, carries a penalty of $5000 and/or a year in jail. Many other states also have stringent regulations.
The flesh of Grass Carp is white, tender, smooth in texture and mild with practically no "fishy" taste. Just about anyone should find it enjoyable - but, Grass Carp does, like all carp, have a "spine problem" similar to Milkfish (Bangus), a fish in a related order. Some find the spines rather annoying, but unlike those of the milkfish they are impossible to remove before cooking. To enjoy delicious carp Americans just have to learn to deal with the spines at the table like the rest of the world does. If you don't want to deal with them, use catfish instead (unless you're an observant Jew or Muslim - catfish isn't kosher or halal).
Personally I don't have a problem with the spines. As with most fish I eat carp with chopsticks, breaking it up as I go along. The spines are large and are easy to find that way. In any case, do provide a small bowl or some other way for your guests to dispose of the spines. Even in formal Victorian society it was permissible to remove fish bones from the mouth (but nothing else).
There's no need to skin grass carp, but some picky eaters just won't eat skin, so you may want to serve filets skin side down so such people can leave it on the plate easily, or you can easily peel it off after cooking.
Buying: Grass Carp can often be found in markets serving a Southeast Asian or Chinese community, at least here in California it can. I haven't seen it in the Philippine markets, though, which do stock Common Carp. As with Bighead Carp, Grass Carp is usually cut into cross sections because the fish is so large, but 8 to 10 pounders can sometimes be found whole. If you see pieces and want a whole fish ask the fish guy (if he speaks any English) what he has in back.
Cooking: Most cooking methods suitable for a large fish can be used for Grass Carp. It remains firm enough to steam and pan fries just fine with a light dusting of rice flour. It is tender, so while simmering for 10 to 15 minutes is fine, a rapid boil or much longer cooking is likely to break it up.
Do Not cut carp into pieces smaller than about 2 inches on a side. Doing so makes the spines nearly impossible to deal with.
Scales: Grass Carp is completely covered with very large scales, about 3/4 inch square for an 8 pounder. Adhesion is moderate so they're not hard to scrape off, but they are springy so they'll fly around a bit. They curl as they dry so they're not difficult to clean up, but make sure they don't get into your drains, they could cause a clog.
Cleaning: This fish is fairly easy to clean, just cut from the vent right up to the underside of the jaw (you'll need kitchen shears from the pelvic fins forward) and pull stuff out. There's a big two chamber swim bladder but it comes out easily and the gills are fairly easy to pull out. The one obstacle is the throat which contains a massive grinding mechanism that's not real easy to pull out.
Skin: Grass Carp skin does not shrink badly when cooked, in fact you can take a hunk of skin and pan fry it and it'll stay pretty flat. It has no strong or objectional flavors, so it hardly seems worth the bother to remove it. If you insist, Grass Carp fillets can be skinned fairly easily using the standard long knife and cutting board Method.
Fillet: This fish is easy to fillet with plenty of bones to follow. It is one fish where I fillet the flesh off the ribs rather than cut them loose and deal with them on the fillet. They're easy to follow and carp bones are stuck in hard and difficult to pull.
Yield: The photo specimen, 27 inches long and 8.4 pounds, yielded 4.5 pounds of skin-on fillet (54%). I don't have an exact skinless weight because I never bother to skin it. The filets were 1 inch thick at the thickest part. The specimen was sold at 2009 US $1.39 per pound in Alhambra, CA, so it's pretty economical compared to many fish.
Stock: I've found stock made from Grass Carp heads, fins and bones a bit too bitter and with a flavor not to my liking.