The greenies have arrived and the horses are close behind.

Whole generations of salt-water anglers are growing up under the impression that the Chesapeake bay exists principally to support hordes of oversized summer visitors from the ocean.

In the last 10 years, bluefish have burst upon the beautific Bay scene. With every passing summer they have squeezed tighter and tighter, until today only a few diehards test the water for anything else.

Regular Bay anglers are so tired of saying "bluefish" that this year they started calling them "greenies." Blues are, after all, almost as green as they are blue, particularly early in the season.

Then there are the horses.

Over the years there have been occasional estuarine visits from sea trout, another open-water species that from time to time finds Bay circumstances to its liking.

But for the last years it's been a burgeoning sea trout bonanza.

Chesapeake folks wouldn't feel like a fish was their own unless they had a special name for it. Hence "horses," in honor of the six- to 10-pound average size of these latest Bay invaders.

If the Chesapeake Bay is dying, as some occasional analysts contend, somebody forgot to tell the blues and sea trout about it.

Oddly, the blitz of the '70s appears to be duplicating one that happened four decades ago.

"This marks the first time in my experience for this widespread sea trout phenomenon," said Dr. John Merriner, head of the Virginia Institute of Marine Sciences. "We do have records of a similar peak in the mid-30s, but they petered off after that."

Giant blues also staged a massive incursion into Chesapeake waters in the '30s, and while schools of smaller blues have been pursued off and on here every since, it wasn't until the last 10 years that the big mean greenies arrived in abundance again.

According to Merriner, "There are indications of a major change in behavior patterns among bluefish. They are traditionally an open-water fish. It wasn't until the late '60s that we began to find them hitting the shallow beaches and moving into the inshore waters. This behavior change appears to be related to food sources."

Dr. Gene Cronin, Merriner's counterpart at the Chesapeake Research Consortium, regards the bluefish Bay presence over the last several years as "unprecedented I can't remember any time in the last 40 years when we've had the large numbers of large fish that we have now."

Both blues and big sea trout are responding in large part to the abundance of the Bay's swimming feedbag-the menhaden population. Menhaden are small, oily, silver fish that also arrive from the deep each spring to use the Bay as a nursery and summering grounds.

As Merriner put it, when menhaden are running "the blues can't be far behind."

The result should be another mobile smorgasbord for blues and trout. Fishermen already are hauling in blues from six to 15 pounds from the mouth of the Chesapeake north to the Bay Bridge off Annapolis. The first few sea trout were caught by hook and liners in the lower and middle Bay last week, and netters say the horses already are running afoul of their nets in substantial numbers. It's only a matter of time before the water warms and the trout begin smashing anglers' baits.

The bad news is that while these offshore species are going boom, some of the Bay's traditional inshore residents are going bust.

Striped bass, long the royalty of the Chesapeake, are on the worst slide. White shad are failing. River herring finally are beginning to rebound after a dropoff.

The offshore fish that are doing so well reproduce in the ocean, where there is a stable environment that changes little from year to year.

Bluefish and trout have a spawning period that may last as long as three months. In that time, appropriate conditions are almost certain to develop for a good spawn.

But stripers, which once ruled the Bay, and shad and herring must depend on rivers for their reproductive cycle. The going has not been good.

"They go through hell to get to the spawning beds," said Merriner. "They are subject to all the vagaries of nature. They are in confined areas where the fishing pressure can be great. And they have a much shorter spawning season, perhaps only a month."

Most long-term Bay watchers like Merriner and Cronin are taking a broad view of the latest developments-the rise of ocean species and the decline of traditional Bay residents.