Besides the usual flounder, perch, cod and halibut, what's here, what's hot and what's coming in Washington seafood?

For one, say some seers of our fish future, we should be receiving more fish imported from all over the globe, as long as the strength of the dollar continues abroad.

Look for new species, particularly from New Zealand, where, according to Lee Weddig, executive vice president of the National Fisheries Institute, the government has taken aggressive control over the country's fishing grounds.

Now that the monkfish phase has peaked, also watch for heavy promotions of other underutilized species. The latest word from fish sources is that pollack may be next on the list. What's Here

Orange Roughy. This pearly white, medium-firm fish, also known as deep sea perch by the New Zealand Embassy, has been making its appearance in area supermarkets. It is shipped frozen, where it is sometimes defrosted and placed in service counters or else sold in the frozen seafood section.

Previously fished primarily by the Japanese and Russians before New Zealand declared its 200-mile fishing limit, orange roughy has been the focus of a lot of time and technology by New Zealanders trying to develop it into a commercial fish. It is caught via deep sea trawling and skinned and filleted mechanically. Prepare it as you would other white fish such as cod, flounder or perch.

Shrimp from all over. Argentina, Panama, Taiwan and Bangladesh shrimp are being caught and shipped to Washington markets. They are different colors, live in different-temperature waters and are slightly different species, according to Chuck Anderson, Georgetown Safeway fish manager, who added that they are also often less expensive than domestic shrimp.

According to Anderson, Argentinian shrimp are pink, lobster-like in taste and are very tender. Panamanian and Equadorian shrimp, which are often farm raised, are similiar to Gulf Coast shrimp. From Taiwan come black tiger shrimp, which Anderson thinks are tough, require minimal cooking and which are better relegated to salads or casseroles. The big prawns arriving from Bangladesh are good for barbecuing, says Anderson.

Farm-raised catfish. It's selling "like gangbusters," says Wedding, referring to the marketing success of southern catfish farms. It's still regionally based; you won't get people in Boston to eat catfish, says John Farquahar, director of technical services at the Food Marketing Institute. And in Washington, some fish wholesalers say the same. Nevertheless, it's available, and Church's Fried Chicken has started marketing a fried catfish if you don't want to cook it yourself. (Mini-review: It's a heavily breaded rendition, but the fish retained its sweet, moist flavor.) What's Hot

Tuna. Demand for canned tuna has dropped and demand for fresh tuna has soared, says Steve Himmelfarb, president of U.S. Fish wholesalers in Kensington, Md. Himmelfarb and other local fish sources report that fresh tuna is selling strong. It'll be "the most popular fish for 1986," predicts Himmelfarb, who added that his tuna sales are already up about "500 percent from last year."

Redfish. You might not see it in your neighborhood supermarket, or even in your local fish shop, but every restaurant short of Arthur Treacher's is blackening this sweet white fish, which, according to Darryl Derk, manager of Cannon's Seafood, is really a drum fish. Derk says it's an expensive fish to sell retail because its yield is small (out of whole fish, you only get about 40 percent edible flesh).

Annette Nalevanko, fresh-seafood buyer for Washington Fish, says its success in a retail market may be limited because of the difficulty in reproducing the blackened dish at home, although there's no reason why it can't be prepared any other way. According to Roger Anderson of Cox's Wholesale Seafood, a Tampa, Fla., company that wholesales redfish nationally, it does well mesquite-grilled and is becoming popular along the Gulf Coast as redfish beignets, a kind of seafood Chicken McNugget version of the Louisiana deep-fried, confectioners' sugar-coated doughnut, the beignet. The redfish are cut into the size of a small doughnut and then batter fried, says Anderson.

The probable reason it hasn't infiltrated the retail market is that the demand here isn't great enough, says Anderson of Safeway. At least not until Paul Prudhomme ever brings his traveling Cajun restaurant show to D.C.

Sea Legs. Also appearing as imitation crab, ocean pieces or seafood sections, these bright white sticks that are coated in iridescent orange are actually a combination of pollack and/or cod and croaker. The fish are mixed with crab paste and/or extract, coated with artificial food coloring and extruded into sticks. Retailers say they are selling well, as they are much less expensive than real crab meat. But beware: they are not crab meat and can't be called such, according to local truth-in-menu regulations. We've spotted the offense in more than one area carryout selling "crab meat" salads. What's Coming

John Dory. It's a firm, delicate-fleshed white fish that looks like a pompano, according to Weddig. Another import from New Zealand, it's also fished in Europe where it's called St. Peter's. It's already being imported from New Zealand (as John Dory), where it has hit West Coast markets, according to Weddig.

Corvina. Himmelfarb predicts that South American species such as the corvina, a fish similar to a giant sea bass, will be entering the Washington market by fall.

Butterfish. These round silvery fish are nothing new, but we may be seeing lots more of them, according to Weddig, and this is why: There are more American shrimp boats in the Gulf of Mexico than there are shrimp. In order to make their treks worthwhile, shrimpers are exploring the waters for other species. What they found was a large resource of butterfish, says Weddig. The success of butterfish domestically, of course, depends on the export market.

Red talapia. Nalevanko says this "gorgeous" fish is being farmed in Idaho. She's supplied several area restaurants with the fish and although it didn't do that well, she feels that it is a perfect fish for retail operations because of its goldfish look-alike appearance.

End note from Nalevanko: She's even imported green mussels from New Zealand. The punks of mussels, they have lime green shells and pink meat.