Without a doubt, the flathead catfish has more aliases than any other fish, probably beating out even the infamous choupique.

Two of the more common names are yellow catfish and Opelousas catfish, with the latter often being shortened to just "op." In Cajun country, the creature is known as a goujon. In parts of North Louisiana and the Florida Parishes of Louisiana, tabby cat is hung on it.

Less common names include pied cat, Mississippi cat, shovelhead cat and even mud cat. The fish's scientific name is Pylodictis olivaris, which is part Greek and part Latin and means "olive-colored mud fish."

The op is one of those peculiar fish that is ugly enough that it can be considered beautiful. The head is so flattened that it appears to have been run over by a cement truck that backed up to see what it hit. Tiny, beady eyes are spaced wide apart on the flat head. The huge gaping mouth has a strongly projecting lower jaw that looks like the landing ramp of an LST.

True to its scientific name, the fish can generally be called olive-colored, but a lot of variation exists, some but not all of which is due to the color and clarity of the water from which the fish came. A number of ops, especially smaller ones, are so dark as to be approaching a mottled black color. Others are very yellow. A few are almost silvery-green. Small fish usually have white tips on the tops of their tail fins.

The native range of flathead catfish is the entire Mississippi-Missouri-Ohio River drainage and the smaller rivers that drain into the Gulf of Mexico from western Alabama to northern Mexico, including the whole length of the Rio Grande. Wherever the species is found, it is the most esteemed catfish for table fare, easily beating out channel and blue catfish.

Its flesh is somewhat soft, but very white in color and mild and sweet-tasting. Knowledgeable catfish fishermen covet the "belly meat" of the fish above all else. This big, thick slab of meat, found between the ends of the ribs, has a unique texture, almost being grained like well-marbled fillet mignon.

The succulent taste of its flesh is often attributed to its diet. Unlike other North American freshwater catfish species, which will scavenge as well as hunt live prey, the op is almost a strict piscivore, meaning that it lives entirely on live fish.

It is a predator. Very small fish consume insects, freshwater shrimp and crawfish. But as soon as they get big enough to wrap their cavernous mouths around small fish, they begin preying on fish. As they get bigger, they eat bigger fish. A study in North Carolina showed that it was not uncommon to find 12 to 19-inch largemouth bass in the stomachs of 29- to 40-inch flatheads.

While bass are a favored food item for ops, their most common prey is often one of the many species of sunfish, commonly called bream or perch in the South. But they are not fussy and will eat almost anything that swims, including other catfish, even of their own species.

Their preference for eating other fish has landed them in trouble when they are introduced into places where they are not native. This is particularly true for the rivers east of the Appalachian Mountains, which drain directly into the Atlantic.

In the Cape Fear River in North Carolina, flathead catfish were introduced as an exotic for trophy fishing in 1966. Blue catfish, also an exotic, were introduced into the river in the 1970s. The two invasive species severely impacted native catfish species. By 1992, no yellow or brown bullhead catfish were left. By 1997, the white catfish was wiped out.

A similar story exists for the Altamaha River in Georgia. Flatheads were introduced in the 1980s. In 10 years, native bullhead catfish were almost exterminated, and angler catches of redbreast sunfish were down by 90 percent.

On their high-protein fish diet, flatheads grow fast and they grow big. Ops have been recorded that weighed 77 pounds, but were only 13 years old, although most probably grow a little slower. They have a life expectancy of at least 20 years.

The IGFA all-tackle world record for the species is 123 pounds, and was caught in Elk City Reservoir near Independence, Ks., in 1998. The official Louisiana record is a 95-pounder caught by Roland Lasseigne from Wax Lake in July 2007. Larger fish than the world record have certainly been caught many times in the commercial fishery.

Ops tend to be loners and travel very little once they establish residence in a spot, preferably one with shelter such as a brushpile or an overturned tree-root wad.

This desire for shelter can be the source of substantial mortality for young flatheads. Aluminum drink cans carelessly discarded by boaters seem to offer perfect shelter for young flatheads. Protected in their lair from larger fish, the young ops happily dine on any living food item that ventures into the can, eventually growing large enough that they can no longer escape through the small hole that they entered.

Jerald Horst is author of four books on fish and seafood, including the acclaimed Trout Masters: How Louisiana's Best Anglers Catch the Lunkers. His latest book, co-authored with his wife Glenda, is The Louisiana Seafood Bible: Crawfish.