Authors: John McPhee
The Founding Fish (13 page)
“SLS? Begging your pardon, what is that?”
Dadswell says, “Shit-like substanceâbrown, squishy, no smell.” Ebbing tides carry the SLS into the waters of the bay,
where it nourishes phytoplankton that are eaten by copepods that are eaten by shad, moving the carbon up the food chain. And this biological richness of the Bay of Fundy is one reason why the shad are there, in Dadswell's conception.
where it nourishes phytoplankton that are eaten by copepods that are eaten by shad, moving the carbon up the food chain. And this biological richness of the Bay of Fundy is one reason why the shad are there, in Dadswell's conception.
Spartina grassâcordgrassâis a dominant plant of the tidal marshes, growing along the U.S. Atlantic coast in sometimes vast prairies, five, ten miles wide. Its roots reach down into the ooze and mine nutrients. When the grass dies and crumbles, it becomes high-protein detritus. The marsh is a soup of microscopic animals and plants. Reaching northward, spartina grass seems to stop at Cape Cod. It is everywhere down the coast but nowhere up the coast, with one exception. It leaps from Cape Cod four hundred miles to the shores of the Minas Basin, where spartina grows in a vast isolated colony. Water temperature rises as you go from the open to the closed end of Fundy. The sun, baking on the mudflats at low tide, warms the ecosystem there, warms the water, and allows the grass to flourish at the edges. Spartina, like the rockweed, breaks off, breaks apart, and ultimately nourishes invertebrates and phytoplankton.
In the ocean in daytime, other things equal, shad will generally prefer depths between a hundred and fifty and seven hundred feetâfar enough down for them to find their level of “preferred light intensity.” They come up the Bay of Fundy into progressively shallower and increasingly cloudy water. When they ride the flood tides into the northern basinsâopaque with suspended mudâthey can comfortably rise near the surface within the same range of light. They are thus vulnerable to anything human beings might do to them, but take the human factor away and they are left with an edge over most other swimmers. As ram ventilators, swimming with their mouths open and water washing through their gill rakers as if through long-toothed fine-toothed combs, they can eat with no difficulty in the dark, even if the darkness is caused by mud. Turbidity seems to be a large reason why shad go into the north-Fundy
basins. The turbid waters are rich in zooplankton. “A filterfeeding planktivore such as a shad could prey on this food source while sight-oriented planktivores would be less able,” Dadswell and his colleagues wrote in their initial paper, in 1981. “Our studies indicate virtually no other large pelagic fish utilize Cumberland Basin, suggesting that turbidity may provide shad with a competitive advantage.”
basins. The turbid waters are rich in zooplankton. “A filterfeeding planktivore such as a shad could prey on this food source while sight-oriented planktivores would be less able,” Dadswell and his colleagues wrote in their initial paper, in 1981. “Our studies indicate virtually no other large pelagic fish utilize Cumberland Basin, suggesting that turbidity may provide shad with a competitive advantage.”
Dadswell and his colleagues said it was possible that shad had been coming there in all the six thousand years since the turbid habitat developed in the wake of receding ice. Evidently, what Talbot and Sykes discerned in 1958 as schools summering in the Gulf of Maine were actually shad travelling in and out of the Bay of Fundy.
The question remained: Where do they go for the winter? By 1987âall tag returns in and analyzedâDadswell and company decided that “three distinct aggregations” occur in the winter Atlantic: a modest one on the Scotia Shelf (which is an area of comparatively warm water off Maine and Nova Scotia that is accommodating to shad from far-northern rivers), a major one in the mid-Atlantic bight (shad from the Delaware, Hudson, and Connecticut congregating with others off the Virginia Capes), and the third off Florida. They also concluded and proposed that shad move through their geographic cycles drawn and guided not only by thermal sensitivity but also by a sophisticated complexity of other instruments. Their 1987 scientific paperâ“Influences of Origin, Life History, and Chance on the Atlantic Coast Migration of American Shad”âarrives at this intriguing sentence: “Evidence also suggests that American shad alternate between extrinsic and intrinsic cues to direct migration, depending on their physiological state, and at times may use a bicoordinate navigation system with map, compass, and clock.”
“Extrinsic?”
“Temperature, light intensity.”
“Intrinsic?”
“Sexually reproductive. Ready to spawn.”
“Physiological state?
“Ripe or not ripe.”
“Bicoordinate?”
“They're offshore. There are no real cues. They seem to know the way. They must have a genetic map in their heads that tells them where to go.”
South to north at the end of winter, the migrations approach the rivers. In the mid-Atlantic bight, they part like lines of graduating seniors, going left or right to their rivers, homing on olfactory clues. Having been out in the ocean three to six years, they need keen olfactory memories, and some of them miss. In studies of wild Pacific salmon, as many as six and a half per cent have missed their ancestral rivers and gone to novel streams. Striped bass are less erratic, but one in a hundred straysâor goes astray, as the case may be. Nearly all shad are faithful to their home rivers, but not a hundred per cent. A shad Dadswell once tagged in a Nova Scotia river was found spawned out in Chesapeake Bay. Another was captured in a different Nova Scotia river. The numbers are low but not unremarkable, like the divorce rate among pheasants.
In the ocean, after the spawning migrations disappear into the continent, the young and otherwise nonspawning shad, in their vast numbers, are left with nothing much to do. They just make their way toward the Bay of Fundy, easily averaging fifteen miles a day, ram ventilating, and sucking up plankton. Survivors of the spawning runs will follow. Some shad bypass Fundy and make their destination the north coast of Labrador or the upper estuary of the St. Lawrence. In the latter, tide-stirred turbidities and regional oceanographic conditions are much like those in the upper end of Fundy. “In Labrador, there's no turbid water,” Dadswell
says. “They don't go shallow. In Labrador and Newfoundland, incidentally, shad are known as king herring.” The numbers suggest that for every visit they make to Labrador or the St. Lawrence estuary, they go in two summers to the Bay of Fundy. “There's no way to sort them out easily,” he comments. “But virtually every American shad born on the East Coast of North America goes to the upper Bay of Fundy at some point in its life cycle.”
says. “They don't go shallow. In Labrador and Newfoundland, incidentally, shad are known as king herring.” The numbers suggest that for every visit they make to Labrador or the St. Lawrence estuary, they go in two summers to the Bay of Fundy. “There's no way to sort them out easily,” he comments. “But virtually every American shad born on the East Coast of North America goes to the upper Bay of Fundy at some point in its life cycle.”
The migration will linger there as much as four monthsâmid-June to mid-October. As many as a million shad may be in the Minas Basin on a summer high tide. The Bay of Fundy as a whole will contain in summer eighty per cent of the total number of eastern American shad. Mike Dadswell figures that number to be about thirty million shad.
I
had been given the name of James Webb, a commercial shad fisherman in the Minas Basin, and had called him from my home in New Jersey to ask if I could arrange to watch him at work. He was a weir fisherman, meaning that he trapped shad. I had no idea how he did it. As the date he suggested drew near, I began to worry about seasickness, which had severely threatened me now and again on small fishing boats. A few miles east of Atlantic City, while working on an earlier story, I became so queasy on the heaving swells that my pencil couldn't find my notebook. All my life I had heard stories of the tidal whirls and chopping seas of the Bay of Fundy. What would happen to my pencil there? I confided this worry to George Hackl, in New Hampshire, who is a lifetime friend and a pharmaceutical savant. In his bottomless empathy, he express mailed to me a pair of Sea-Bandsâtight elastic bracelets (“The Only Clinically Tested Wristband”) manufactured in England. On the inside surface of each bracelet was a hard-plastic hemisphere a half-inch in diameter. If you positioned the plastic
pressure point a short way up your inner wrist and between the two central tendonsâand did so on both armsâyou could ride the bowsprit of the Hesperus in the winter North Atlantic.
had been given the name of James Webb, a commercial shad fisherman in the Minas Basin, and had called him from my home in New Jersey to ask if I could arrange to watch him at work. He was a weir fisherman, meaning that he trapped shad. I had no idea how he did it. As the date he suggested drew near, I began to worry about seasickness, which had severely threatened me now and again on small fishing boats. A few miles east of Atlantic City, while working on an earlier story, I became so queasy on the heaving swells that my pencil couldn't find my notebook. All my life I had heard stories of the tidal whirls and chopping seas of the Bay of Fundy. What would happen to my pencil there? I confided this worry to George Hackl, in New Hampshire, who is a lifetime friend and a pharmaceutical savant. In his bottomless empathy, he express mailed to me a pair of Sea-Bandsâtight elastic bracelets (“The Only Clinically Tested Wristband”) manufactured in England. On the inside surface of each bracelet was a hard-plastic hemisphere a half-inch in diameter. If you positioned the plastic
pressure point a short way up your inner wrist and between the two central tendonsâand did so on both armsâyou could ride the bowsprit of the Hesperus in the winter North Atlantic.
At Cove Road and Trunk Highway 2 in Upper Economy, Nova Scotia, was Webb's neat, yellow frame house, and a small wooden sign: FRESH FISH. He told me it was about time to go check the “ware,” as he pronounced it, and I should get up behind him on his Honda three-wheeler. Hooked to it was a small cart. We went south on Cove Road and through woods to the top of a steep and cobbled slope that afforded us an aerial view over Cobequid Bay, the innermost finger of the Minas Basin. Five miles across, it was reddish-brown with turbidity, and rapidly dropping. This was not as apparent at first as it was a short time later, when a very long thin black lineâthe top of the weirâpreternaturally appeared all at once at the surface. Before long, a vertical foot of the weir was exposed. Soon, three feet, four feet. And presently the vast mudded plainâthe brick-red flatsâmaterialized as the water drained away. The weir, more than a hundred yards distant, appeared to be a solid fence. Webb remarked that it was seven feet high at its center, and gradually diminished to five feet at its ends. As if the scene had been painted by Salvador Dali, the fence stood there incongruously on the naked floor of an arm of the ocean. It was three thousand feet long.
Generally parallel to the shoreline, it was, geometrically, a wide-open chevronâa V whose two sides had been bent all but flat.
The ends were nearer shore than the point of the Vâthe bend in the fenceâwhich aimed away from us, toward the middle of the basin. To deflect currents and improve the efficacity of the trap,
the two ends curled a little, so that the shoreline and the three-thousand-foot weir looked something like this:
the two ends curled a little, so that the shoreline and the three-thousand-foot weir looked something like this:
You could straighten up that slash a little, but for government work the image will do.
The Minas Basin tapers east and heads near Truro. Upper Economy is about halfway along the north shore. The incoming tide floods east, and carries the shad with it. As the basin tops up, as much as forty-five feet of water will rise around James Webb's fence. When the tide reverses, the shad turn and go with it, moving in a westerly directionâparticularly toward the last of the ebbing, when time is growing short. The weir is so strategically placedâwith respect to the currents, to the bathymetry, to the tidal channelâthat shad swim between it and the shore. But the shoreline now is moving steadily toward the weir. The shad try to swim past its western end, but the dropping water has closed the western end. It's a three-thousand-foot sprint back to the eastern end, but that would be futile. The dropping water has simultaneously closed the eastern end. The water's edge moves ever closer to the V until only a shallow pocket contains the captured fish.
Webb started up the Honda and got ready to go out to the weir. The long cobbled slope that had given us our aerial view was actually an inclined beach. The Honda had stopped just short of a black line of rockweed wrack, where water had been lapping only
hours before. Our high lookoff was at the top of the intertidal zone, the edge of the absent bay.
hours before. Our high lookoff was at the top of the intertidal zone, the edge of the absent bay.
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