IF YOU WANT to avoid the July heat, sunburn, the midday doldrums, water skiers, mothers-in- law and TV reruns, try night-fishing.

Since most fish are primarily nocturnal feeders, night-fishing is almost always more productive than daytime fishing. (More fish are caught during the day, but that's only because more people fish then.) And besides, night-fishing is particularly refreshing these sweltering days.

You can catch most any species at night on whatever bait works for you during the day. But we're going to focus on bass, because nighttime offers just about the only chance of catching them during the hot months. For some tips on what to do and what to avoid, we talked to parttime bass guide Jerry Liverman of Fredericksburg. Liverman fishes exclusively at night this time of the year, mostly on Lake Anna. Many of his recommendations apply to all night fishing, some just to bass fishing.

"First off, the most important thing to take along is mosquito repellent," Liverman says. "I've seen nights I would give $50 for some and consider it a bargain.

"But you have to be careful not to get any on your lures or your line. I have never seen a bass yet that was caught with mosquito repellent as bait, but I won't swear it absolutely will not work."

Here are some other recommendations:

* Go by yourself or with another experienced fisherman. "It's going to be deathly quiet out there, and the slightest noise, like a dropped lure in the boat, will spook the bass and ruin a hole," Liverman says. "If you have an emergency, it's good to have someone there you can depend on. Remember, there won't be anyone else around to hear your screams for help if something happens."

* "Always wear your life vest when night-fishing," he says. "If you fall out of the boat, you will be disoriented when you come up and it will take several minutes to figure out which way shore is. Meanwhile, without a life vest, you'll be spending all that energy just staying afloat until you locate the boat or the shore."

And if you're using a boat that has a large inboard or outboard motor, be sure to hook up your kill switch to yourself, so that if you do fall overboard the engine will stop, Liverman says.

* "Only fish waters that you are familiar with and know your way around very well," he says. (That's why most people don't recommend fishing the Bay or ocean at night.)

* "Make all of your preparations during the daytime," Liverman says. "Prepare your tackle and check your equipment and the condition of the boat while there is enough light to do a good job.

* "Plan your trip ahead of time, where you want to go and when you will be coming back. Tell someone where you are going and when you'll be back so that they will know to send out the rescue boats if you don't show up."

Now, as for the actual fishing, Liverman has a few pointers for bass fishermen, with particular regard to Lake Anna:

* "On Lake Anna you should be looking for points adjacent to deep water or dropoffs or for structure adjacent to deep water," he says. "That's where the bass will be -- not on the surface. Fish for them in the same places you would in the daytime. If they find a good place to feed, they will stay there, night or day."

* The best bait to use at night is an eight-inch-long black plastic worm, Liverman says. "And don't rig it Texas-style either (with the hook point imbedded in the worm), or you'll miss a lot of strikes," he says. "Rig it with a weedless hook, and as often as not the bass will hook himself when he picks it up."

It may not seem logical that black would be the best color to use at night, but Liverman is not alone in saying that.

According to Rob Gilford of The Rod Rack in Frederick, black and other dark-colored baits stand out better at night against a lighter background. Remember, the fish is looking up as the worm drops, and if the worm is black, then it is darker than the top of the water, even when the moon isn't out.

* Keep your line taut. Take up the slack as soon as you cast and then let the worm drop toward the bottom. A lot of the time, the bass will hit the worm as it falls, and you must be able to feel that first tap and set the hook immediately. Otherwise, the next thing you feel will be the bass spitting it out, Liverman says.

* Do not flash a light on the surface of the water. Keep all lights below the freeboard line. "Nothing will kill a hole faster than a light flashed across the surface. I won't even light a cigarette while I'm fishing at night," Liverman says.

So that's it. Stay cool. Fish at night. WHAT'S THE CATCH?

WASHINGTON AND VICINITY

"It is the dog days of summer, and that is the fishing report, too," says Ray Fletcher of Fletcher's Boat House. "It is too hot and nobody is catching anything. It's so hot, nobody is even out. And the river is cloudy from the rains. The only action is late at night when things are cool. A few catfish are being caught, but it is pretty slow."

Jose Calvino of Shepherd's Live Bait and Tackle in Alexandria says some of his customers have been catching a lot of stripers at night.

"It's a damn shame. A couple of guys I know caught and kept 47 stripers last night in D.C., where it's legal. There goes the future of rockfishing, if they keep the small ones," Calvino said.

He said some catfish are being caught, but the big ones are slow coming in. He said about four or five citation-size catfish (10 pounds in Virginia) are being brought into his store a week. He recommends frozen shrimp or clam snouts as the best baits. MARYLAND

UPPER POTOMAC -- "It's been kind of slow. A lot of catfish are being caught, but that's it. We've had a bunch of rain that has got the river up and muddy, and it has put a damper on things," says Rob Gilford of The Rod Rack in Frederick, Md.

"Plus, it is hazardous to be out on the river when it is like this. Enough people drown on the river every year without adding to it," he says. "It may settle down by the weekend if the rains let up. Then the fishing will be good. But now the only action is catfish."

And to catch these catfish, Gilford has two novel recommendations: Ivory soap and pureed chicken livers. But not together.

"Now this may sound kinda crazy, but some of the biggest catfish in the record books were caught on Ivory soap. You put a chunk of it on the hook and let it hang out in current and it sets up a chum line. The catfish will follow it right up to the hook," Gilford says.

Okay. But does a catfish that's been caught on Ivory soaphave lather on his whiskers? We forgot to ask. Actually, this is the third report we've heard this summer about the efficacy of Ivory soap as catfish bait. So we may try it and let you know how we do with it.

As for the pureed chicken livers, Gilford says some catfishermen he knows make a dough bait, usually using a carp dough recipe, and for flavor add to it chicken livers they have pureed in the blender. The advantage of this over regular chicken livers is that it stays on the hook better, he says.

Another way to get the livers to stay on the hook is to leave them spread out uncovered on a plate in the refrigerator overnight. This forms a tougher skin on them that holds the hook better.

LOWER POTOMAC -- "Things have slowed down considerably. The big perch have laid off. The jumbo spot are gone. Everyone is headed for the Bay to fish for trout and blues," says Bob Muscolino of Newburg Marine near the U.S. 301 Bridge. "Even the rockfishing has died off. They were here; now they are gone."

PATUXENT RIVER -- Anglers fishing for large white perch are also catching -- and releasing -- rockfish up to 15 pounds north of the Benedict Bridge, according to Calvino of Alexandria.

MAGOTHY RIVER -- The best perch fishing around now is near the mouth of the Magothy, just inside Gibson Island around the wrecks and oyster bars, says Marv Walls of Angler's in Annapolis. VIRGINIA

LAKE ANNA -- A few large bass and a lot of channel catfish are being caught now, according to Tom Goodwin of Sturgeon Creek Marina. The bass are being caught in the evening. Goodwin thinks that the bass fishing now is as good as it ever gets in July and August, which is to say, not great.

RAPPAHANNOCK -- "Well, there's not much to give you," says Karl Gentry of Chesley's Tackle Shop in Fredericksburg, when asked for a fishing report. "The river's muddy."

When the water clears up, go upriver from Fredericksburg and try for se smallmouth. "It should be excellent," Gentry says. "Smallmouth turn on in the hot weather." CHESAPEAKE BAY

UPPER BAY -- "It's kind of slow right now. We did have some small bluefish but they have scattered out," says Walls of Angler's. "There are still a few being taken on the eastern side off Kent Island and Bloody Point."

POINT LOOKOUT -- The head boats are bringing back plenty of blues and some trout, according to Capt. Bruce Scheible of Scheible's.

"It's a spinning tackle dream right now," Scheible says. "You can anchor in 20 feet of water and you can fight fish all day long. Most of them are running from four to six pounds. It is the best chumming that I've seen in about five years.

"It's kind of unfortunate, because most people figure the fishing is off because it is so hot and there aren't many out fishing now. Up until two weeks ago, the blues were breaking on the surface. But then the baitfish went down and the blues went down after them. It makes for good chumming when they are down."

As for trout, the best action is out near Buoy 54 in the Bay, according to Dave Watson of Dave's Sport Shop in Quantico, Md. "They are catching trout in the eight- pound range in about 90 feet of water," Watson says. ATLANTIC OCEAN

WACHAPREAGUE -- The flounder fishing has been good and is holding up well, according to Bob Fate of the Wachapreague Marina. A few croaker are starting to show up out by the bell buoy. Oceanside, the bluefin tuna are about gone, but the yellowfin tuna are hitting and the skipjack and marlin are very good, Fate says.

ACCOMAK -- The flounder fishing out of Accomak, just north of Wachapreague, is also good, according to Watson of Quantico, Md., who said he caught about 20 weighing from 13/4 to 3 pounds one morning this week. Watson said he used silver-sided minnows and squid for bait on a 2/0 hook with a white skirt.