If you see thousands of tiny silver fish floating belly-up in the Chesapeake Bay over the next few weeks, don't be overly alarmed. Instead, grab your rod and reel.

That may sound like a rather cavalier attitude toward a massive fish kill, but the die-off of bunkers (menhaden) at this time of year on the Bay has become such an annual tradition that no one will be particular bereaved when you tell them of the dead fish. They've come to expect it.

"Anywhere from several thousand to several million menhaden die every year at this time," says Rudy Lukacovic, fish mortality investigator for the Maryland Department of Natural Resources. "It doesn't seem to harm the overall population at all."

The dead bunker were first noticed on May 14 this year; the three years previous the silver corpses were discovered on May 18. With minor variations, the same scenario has been repeated virtually every spring for the past 24 years, since 1955. In fact, there's evidence the die-offs have always occurred. Captain John Smith noted them when he first explored the Bay some 3 1/2 centuries ago.

Pollution and low dissolved oxygen have been ruled out as causes of the die-off. No concentrations of heavy metals or other polutants have been found in the dead fish.

Researchers with the National Marine Fisheries Service and the University of Maryland have isolated a virus in tissues of the diseased fish that they believe may cause the disorientation and death. According to Lukacovic, however, the virus seems to cause such massive fatalities only under stressful conditions, such as when the water is warming or after the fish have just completed their migration into the Bay waters. Almost predictably this means late May and early June.

But while biologist wrestle with the why of the die-off, a small group of astute anglers homes in on the where and when, believing that the sickly and vulnerable menhaden attract massive swarms of bluefish into the shallows where they find free and easy meals for the taking. It's an interesting theory. And if their catches are any gauge, an accurate one.

The mid- and upper-Bay areas are usually the scene of the severest die-offs. "From the Patapsco River or occasionally as far north as the Gunpowder, down to Herring Bay and sometimes even Cove Point. That's where the heaviest fish-kills occur," says Lukacovic.

One of the best places to intercept blues feeding on ailing menhaden is the Bay Bridge area. Most fishermen who work this vicinity troll in deep water with heavy weights, thick mono and massive boat rods.

But Joe Reynolds, editor of Maryland Angler, thinks these people are missing all the fun. He knows large blues are ripe for picking almost within casting distance of land in this area. He and his angling cronies take the fish on fly rods and light casting gear in water measuring less than six feet deep, where the blues have tracked down the hordes of virus-plagued menhaden.

The Sandy Point State Park boat ramp is located conveniently close to the prime fishing area, which can mean just about any of the coves and points along both the western and eastern shores of this part of the Bay during early June. Many fish have already been taken in these shallows, and most of them are running eight to 15 pounds.

Since the blues are found very close to shore, large boats aren't needed to reach them. The 16-foot fiberglass rental boats available at the State Park will do just fine on days with light winds, which is when the best fishing occurs. The boats and 6-up motors rent for $20 for the first four hours, $1 for each hour after that, with a $30 deposit required.

For throwing the big popping bugs required to bring up the blues, Reynolds uses a 10-weight fly line and long rod. The popper is worked with a fast, loud retrieve, and when a fish strikes, you'll be glad to have backing on your reel. Some very large blues can be found in these menhaden-rich shallows in June. Don Peters, of Baltimore, caught his fly-rod state-record blue is just such a thinwater spot in the Bay. It weighed over 14 pounds.

For spinning or casting, the Atom Popper and other surface lures draw solid strikes from blues feeding on the disoriented bunkers. Either a wire leader or heavy mono shock stippet should be used to avoid cut-offs by the needle-teethed fish.

For those who prefer live-bait fishing, there's yet another alternative. Simply pick up one of the disoriented bunkers swimming on the surface, impale it on a 4/3 hook, and toss it back out to thrash around and entice a hungry blue. It's a popular technique at this time, and quite effective.

Bluefish will be with us from now through November, and if you like trolling or chumming in deep water, there's no real urgency to tackling them now. But if the prospect of catching big blues with a popper in the shallows sounds exciting, don't let June's thinwater fishing slip by unsampled. CAPTION: Picture, A BLUEFISH COMES ABOARD. By Gerald Almy.