Mighty humpback now surprising fixture in bay

ON THE BAY

April 01, 1995|By TOM HORTON

In mild Atlantic swells, the charter boat drifts, a mile or so off the Chesapeake's mouth. A hundred passengers crowd the rail, every eye focused on an opaque, greenish patch of ocean.

Something gigantic hunts 60 feet below, blowing clouds of bubbles as it encircles frantic bait fish, weaving a fine, fizzy "net" to herd and pack them.

Then, with an agility belying its 30 tons, the hunter lunges through the dense swirls of anchovies, mouth several feet agape, to feed its 3,000-pound-a-day appetite.

And then the humpback whale, one of perhaps 12,000 of its kind remaining worldwide, rises to breathe.

Just the brief, glistening arc of its massive black back, and

departing flip of broad flukes, brings cries of joy and excitement, and applause, from us humans.

It is an awe-inspiring contact with a species that, next to us -- or perhaps along with us -- has the most highly evolved brain on the planet.

Such encounters are becoming, quite unexpectedly and delightfully, a regular fixture of the lower Chesapeake Bay from January through March.

Since 1991 the humpbacks have begun routinely to feed here -- as many as 19 in a winter -- in the food-rich plume of water debouching from the bay, fed by runoff from the bay watershed.

The Virginia Marine Science Museum in Virginia Beach has taken more than 20,000 people on two-hour whale watches. Feeding whales were seen this year on 92 percent of all cruises.

There is perhaps no way to compare minds, cetacean and human, that took radically different evolutionary paths some 80 million years ago. But what we can tell, from studies of whale and dolphin brains, makes you wonder if the whale below us is not at least as richly conscious of us as we are of it.

When researchers look at the excess of brain development beyond what is needed for survival and body control, they must place humans in a set including dolphins, orcas and quite possibly the great whales.

No other tissue in the body, except muscles involved in heavy exercise, comes close to brain tissue in its demand on metabolic energy.

Thus, evolution does not lightly underwrite such luxuriant expansions as these species show in the neocortex, the part of the brain that in us, at least, enables higher thought and consciousness.

In other words, where such brains exist, they must be doing a lot of complex and unusual things. And while the explosion of those large, frontal lobes in our brains that made us human happened just 300,000 years ago, the cetaceans have enjoyed it for some 20 million years.

The humpbacks are famous for their eerie, moving and complex songs, lasting up to half an hour, repeated for hours at a time, and constantly changing over the years.

Different populations of humpbacks have their distinctive "dialects," or ways of vocalizing; and as their songs change, every individual in a population appears to learn the changes.

Many of the great whales also "talk" to one another, in low tones that carry across hundreds of miles of ocean, perhaps signaling identity, position and reproductive status.

We can only wonder at much of what is going on, and the naturalist Henry Beston perhaps had the proper approach when he wrote: "They are not brethren, nor are they underlings. They are other nations."

No field guide to the Chesapeake will list great whales like the humpback as creatures of the estuary; but a couple decades ago, we did not consider Pennsylvanians and New Yorkers as bay dwellers either. Since then, our view of the bay had to expand to include the lands of a watershed, encompassing peoples of six states.

And so have we also begun to appreciate a multitude of interactions between the lower bay and the coastal ocean.

The computer program used to model various environmental scenarios for the bay and its watershed soon will be revised to encompass the ocean, from Assateague Island to North Carolina, and out some 35 miles.

Oceanographers talk about the "Hoover effect" at the Chesapeake's mouth. The action, a product of the bay's layered flow of water, goes like this: Light, fresh river water slides seaward on the surface, and heavy, salty water constantly slips beneath it, up the bay.

This creates a vacuuming action, sucking into the bay everything from sediment and nutrients to algae and the eggs and larvae of fishes, drawn from miles out on the continental shelf. The bay, we are learning, "imports" surprising quantities of phosphorus, a pollutant we are trying to control on farms and in sewage. How this oceanic import offsets our best control efforts is a critical research item.

Virginia scientists are keenly interested in how the bay-ocean interaction affects population fluctuations in fishes like croakers, spot, drum, summer flounder and menhaden.

Those and other important bay species spawn in the ocean; then their young are sucked into the bay, where they grow up. Blue crabs are a fascinating variation of this; the eggs drift miles out to sea, then are drawn back into the bay.

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