by John McPhee
From the perspective of a shad, nothing shoots forth light quite as much as white water on a bright day—one more reason to stop and think twice about a rapid. “They don’t see in the way that we see,” Kynard continued. “They make a chemical called rhodopsin that is sensitive to light. The more light, the more rhodopsin is used up.” Shad normally, and successfully, avoid bright light. They stay deep enough in the ocean. They stay low in the river. “But when they want to come up rapids they have to come into shallow water, where they have this bright bright bright light—of fifty, sixty thousand lux. That’s what it is! I think so much light is coming in there that it uses up all the rhodopsin, and now they’re essentially blind. And now it’s exactly the way it was at night. They cannot stay in fast water. I think that’s why they have difficulty going up long rapids in the middle of the day.”
They move upstream at first light—an optimal time, when muscles are rested. And resolutely they move in the afternoon. Kynard guesses that the falling light reminds them that another day is ending and they’ve got to get on with their mission. “That drive to get upstream is strong. It must be particularly forceful when they sense that they are losing light.”
This reminds me of what I do all day (nothing). I sharpen imaginary pencils and look out real windows. The light of a computer screen seems far too bright to me. I kill hours, hoping for distraction, and complain bitterly when distraction occurs. Three, four, five P.M. Nothing whatever accomplished. The day coiling like a spring. Nothing is worse than a lost day. Panic rises, takes over, and I write until I go home at seven, thinking like a shad.
When daylight drops in the evening, the fish turn and retreat from rapids, because they can’t maintain orientation. “They go back down, but not far. They find the very first deep slow-water area. That’s where they stay. They just kind of settle down to the bottom. Get down to a lower velocity. Get in the current, where they can just maintain position. Let the lateral line take care of keeping them up, and not moving downstream.” As if they were treading water, they wait out the night.
“Do they sleep?”
“They rest. That’s as close as they come to sleep. Some fish settle to the bottom, and you can come up to them at night. You can hit ’em. They’re out of it. Shad are never out of it. Even at night. We’ve looked at them with infrared. Their eyes are moving.”
“Those fish you can go up to and touch—would you say that they are sleeping?”
“Yes. They’re out. If you’re a predator, they’re toast.”
“For example.”
“Yellow perch. Sticklebacks. All the centrarchids—basses, crappies. Their eyes and brains are not connected with the outside world. There’s probably a better word for it, but it’s certainly sleep. They’re resting on the bottom—two fins and the tail.”
If night comes upon a school of shad in a long and quiet reach of the river, they will, sometimes, continue to migrate upstream. “Telemetry studies have found that these guys do move at night, on the bottoms of rivers. In the first place, velocities down there are low. The shad are orienting with their lateral lines. They can do that. They have incredible lateral-line senses. That’s how they move upstream at night.”
These generalizations about the behavior of American shad are valid only to the point where they give way to individual characteristics, he suggested. “Shad vary. They’re as individual as people. If you had fifty people in a room and asked them to do something, there would be fifty different ways of doing it. It’s the same with fish. Some shad fight harder than others—wherever they are in the river. I’m a behaviorist. To tease out the variation in behavior, you tag twenty or thirty fish and see what they do.” He once tagged “a bunch of shad” below Holyoke Dam, with its controlled tailrace, its elevators—its high-tech methods of manipulating nature. He wanted to see what the bunch would do. Some individuals figured it out quickly and went on upstream. Others took many days. Others hung around for weeks, never figured it out, and went back downriver to spawn.
“We see that in the Delaware,” I remarked. “Some fish quit at the first riffle. Others go on and on.”
“Oh, you’ve got to know it,” Kynard said. “Some phenotypes are just better at doing that sort of thing than others.”
“So they’re not particularly clever or smart?”
“I don’t know if they’re clever. I’m not sure they’re smart. They’re persistent. With a few exceptions, they’re persistent. They never give up.”
“What are they living on?” I asked him. “I’ve looked in hundreds of shad stomachs. I like to slit open the stomach and look inside. Usually, it’s clean as a whistle. I’ve never seen anything of any size in a shad’s stomach.”
“Neither have I.”
“Once in a while, I find something like little bits of grass or algae.”
“I’ve never interpreted that as food.”
“How does it get in there?”
“Incidentally.”
“Oh.”
“When a shad comes into a river, after living on zooplankton in the ocean, it has fixed storage reserves—fat reserves, muscle mass. Those are at a peak for that fish, because a shad never eats on the spawning run. In April, there are essentially no zooplankton in the river. A shad loses up to forty per cent of its somatic body weight. In mass, it’s half the fish that entered the river.”
Shad that come out of the Gulf of St. Lawrence go upriver past Quebec City and through the Lachine Rapids at Montreal and on to the Ottawa River, a distance of four hundred and fifty miles. Some shad do that—but not all shad that enter the St. Lawrence River. Shad out of the Gulf of Maine—before being occluded by dams a couple of centuries ago—went a hundred and seventy miles up the Penobscot River to Millinocket, where they encountered the natural dam called Grand Falls. Less than two miles below Grand Falls is a broad pool in the river that is still known as Shad Pond. The historic range of shad in the Connecticut—something over two hundred river miles, including a hundred of the border miles of Vermont and New Hampshire—is inconvenienced and ultimately shut down by five dams, of which Holyoke is the first. The free-flowing Delaware is the only main-stem major river in the forty-eight contiguous American states that is not blocked by a dam. A large proportion of the spring migration seems to prefer to spawn between the Delaware Water Gap and Minisink Island—a piece of river two hundred and ten to two hundred and forty-five miles from the sea buoy. Considerable numbers, though, continue. Those that reach the head of the river, at Hancock, New York, have ascended three hundred and thirty miles, yet many of them keep on going. They go up the Delaware’s tributary branches and swim on into a dendritic shrine—the streams of sacred origin of American fly fishing. They go up the Beaver Kill to the Willowemoc and sail through the trout at the Junction Pool. What an experience it must be for a trout to see these argent zeppelins go by. Shad have been known to go on up the Willowemoc to the Little Beaver Kill, passing the Catskill Fly Fishing Center and Museum, at Livingston Manor. According to Ed Van Put, a regional fisheries technician, shad have been seen a mile up the Little Beaver Kill, four hundred miles from the ocean, where they were stopped by a ten-foot waterfall.
I told that story to Boyd Kynard.
He said, “These guys are the Olympic fish. It has to do with swimming abilities, with response to new environments. This is your athlete fish.”
Shad vary, right enough. I thought of my own Olympic fish—two and a half hours on the line at Lambertville. Had I not interfered, she would have gone up to the Little Beaver Kill, jumped that waterfall, jumped the Catskill divide, swum up the Hudson to Lake Champlain and down the Richelieu River to Montreal, gone up the Ottawa to Lake Nipissing and down the French River into Lake Huron and on across Superior and up the Pigeon River and on to the Lake of the Woods and Lake Winnipeg and Reindeer Lake and Lake Athabasca and the Great Slave Lake (doing the Methye Portage in a heavy rain) and down the Mackenzie to the Rat, and up the Rat to the Porcupine, and down the Porcupine to the
Yukon River, and down the Yukon River to the Bering Sea. It’s a shame I ate her.
I asked Kynard why shad would go all the way from the Atlantic Ocean to a Catskill mountain brook when they could copulate in New Jersey. Why would shad in the Connecticut River, which could have their sex in Hartford, fight their way into an elevator car, ignore the creature comforts of the Holyoke Pool, and—at Turners Falls and Vernon—scale a couple of fish ladders to get to Bellows Falls?
He said, “I think I know the answer. I have a hypothesis, anyway. This is what, to me, seems to drive the whole migration. There must be a big selective advantage in going upstream, and in putting your offspring upstream, or you wouldn’t do it, would you? The farther up you go, the less energy you have, the more obstacles you encounter. So what’s the advantage to the offspring? We have a little bit of data on this. I think they’re putting their offspring at the head of the chow line.”
Tributaries bring zooplankton into rivers. Plankton are what fingerling and juvenile shad eat. Plankton, for that matter, are what shad eat in all their adult years. They are ram ventilators—swimming with their mouths open, using the force of swimming to pull water across their gills. The gills remove oxygen from the water. Meanwhile, plankton are trapped in the long tines of the gill rakers. One September, when large numbers of juvenile shad were in the Holyoke Pool—the thirty-odd miles of impounded water between Holyoke Dam and Turners Falls—Kynard and a graduate student monitored the plankton that came into the pool from upriver. (The spawning run, at that time, was stopped at Turners Falls.) The study showed a whole lot of plankton in the river at Turners Falls, of which nothing was left at Holyoke. “The zooplankton had been grazed by all those shad in the Holyoke Pool. So my hypothesis is that what keeps these guys going farther and farther, when there are clear disadvantages to doing so, has to be an advantage for progeny. And the one advantage to progeny that we have documented is that there’s more food—zooplankton—upstream for concentrations of juvenile shad than there is downstream. So, put your offspring at the head of the chow line. This hypothesis relies on the very well documented fact that the larger you are as a prey species the better off you are. Even one extra millimetre will confer a survival advantage to you in the face of predation. When juvenile shad move down the river, they’re subject to all sorts of riverine predators that eat them—smallmouth bass in particular.”
“What else eats them?”
“Walleyes. White perch. Stripers. These guys—the juvenile shad—are coming down by the hundreds of millions, and they’re all very tender and bite size.”
In spring, sexually mature shad begin to enter their home rivers when the water temperature rises through six degrees Celsius, and they spawn when the temperature is between sixteen and twenty-two (sixty to seventy Fahrenheit). So, in effect, they have brackets around them. In the Connecticut River, they have, on average, forty-five days to make their run and complete the ritual sexing of their eggs.
In Kynard’s words, “When they enter a river, the clock is ticking. They have varying degrees of energy, varying degrees of swimming ability. They’re not feeding, so they have an unrenewable energy reserve that will take them only so far up the river, depending also on delays, water velocity (how hard they have to swim to get there), and water temperature. It is fairly well established that when water temperature gets to twenty-one they slow down, and by twenty-two they stop. They look for a suitable place to spawn. It’s a race against time. If you’re a shad, you take every opportunity to get as far upstream as you can, past every obstacle, before the water temperature reaches twenty-one degrees. The joker is that you never know what the environment is going to throw at you. You can have the fifty-year flood. You can have low water. Through it all, you have to keep going, and go as fast and as far upstream as you can, because that’s the only way your offspring have any chance to have an advantage.”
When the Delaware River is just honkin’, I told him, I have discovered that I can catch shad on people’s lawns. After extreme and sustained rains—water over the banks—the center of the stream is a lethal rage of gray rolling waves. A couple of hundred miles above Philadelphia, I’m standing on somebody’s lawn, in fairly calm but turbid water three feet deep. This is not quixotic. The fish—completely frustrated, anxious to go as far as possible—are up on the lawn, too. Kynard explains: “Come a big rain, the whole migration will stop for two weeks. Trying to save energy in slow water, they aren’t doing anything—they’re just hanging on. Out in the river, not only is the current heavy but turbidity is such that the shad can’t go to the low slow water, because there’s not enough light down there. They have no choice. They have to hang out way over to the side, maintain position, and just hope like hell it doesn’t keep raining.”
Out of our waders and into Kynard’s office, we had been through a fair amount of this dialogue at the S. O. Conte Anadromous Fish Research Center, in Turners Falls, a small community in northern Massachusetts enabled by a dam built in 1798 at a natural pitch of the Connecticut River. Built to intercept logs, it also blocked the migration of fish, setting a fateful precedent as the first main-stem dam on a major river in North America. Thomas & Thomas bamboo fly rods are made at the intake end of the power canal there, and the Conte lab, two miles down, is not far from a generating station where the canal water spills through turbines and back to the river. Below Thomas & Thomas, a modest cluster of antique industrial structures soon gives way to open ground, forested at the edges, in which the swift current of the canal slows and spreads into something like a lake, flanked by a road but—in the better part of a mile—only a low pair of buildings, the seventeen-milliondollar Conte lab, nestled into the canal’s right bank. Named in part for Silvio Conte, the Massachusetts congressman who made it happen, the lab was Boyd Kynard’s idea. It was built by the Department of the Interior and modelled on a lab on the Columbia River that is now a parking lot. It was also named for anadromous fish, which live in oceans and spawn in fresh water. Nimbly, all other possibilities have been covered in language that would entertain W. S. Gilbert. If you live in fresh water but go out into the ocean to spawn, you are catadromous. Anadromous means “running up.” Catadromous means “running down.” If you are anadromous or catadromous, you are also diadromous. And if you’re a fish that goes from fresh water to salt water, or salt water to fresh water, to eat or to survive drought but not to procreate, you are amphidromous.
Ordinarily, ichthyologists visit fish. At the Conte lab, it’s the other way around. “Without a lab, we could not do experimental work; all we could do was field work,” Kynard explained. After shad arrive at Turners Falls, a selected number might go into one of three long concrete flumes that suggest the containment chambers in a nuclear-fuel reprocessing plant. The fish hop uphill and upcurrent in pool-and-weir fishways built of wood and jigsawed into experimental geometries—open Vs, inviting trapezoids. Above each pool—each step of the ladder—is an antenna. The shad are wired and are broadcasting to the antennae, which are related to a computer. Using fly-tying vises, Dr. Alex Haro and Ted Castro-Santos, a graduate student, have bound No. 8 fishhooks to small cylindrical microchip tags in exactly the way you bind bucktail to a shad dart. The microchip rigs resemble shad darts. Haro and Castro-Santos hook them into the back end of the shad’s dorsal fins. The shad don’t seem to mind, possibly because they are each and all veterans of Holyoke Dam, showing raw spots and missing scales from the thrashing ride in the elevator.
The Ph.D.s on the lab’s staff are also adjunct professors at the University of Massachusetts, in Amherst. Alex Haro wrote his doctoral dissertation on American eels, which are not ignored in the anadromous-fish lab, the fact notwithstanding that they are catadromous. Dr. Steve McCormick and Dr. Joe Zydlewski study salt-excreting cells in gills, and the rest of the complex physiology in transitions between river and sea. As one of McCormick’s Ph.D. candidates intent on learning how much energy migrating shad burn away as they swim, Jill Leonard developed the laboratory’
s swimming respirometer—a vertical toroid tube about the size and shape of a truck tire, in which water flows around like river current and can be sped up or slowed down. Built into the respirometer’s uppermost arc is a clear-plastic horizontal chamber, sized for one shad, in which the incumbent specimen swims in place under eyeball-to-eyeball scrutiny, taking on whatever current Leonard chooses. She measures, among other things, oxygen depletion—the oxygen requirements of shad at different swimming speeds.
In the natural Connecticut, down through steep woods from the power canal, some of these people fish for shad, in a place they described as uncommon. Site unseen, I made a date to go with Steve McCormick at six-thirty one morning in late May. From my fishing diaries, this is the entry for that day: “Their place is called the Rock Dam, an imposing diabase ledge between the left bank and a large island. In the ledge close to the bank is a narrow gap, like an open door. You can cast a fly line across the confined river as it comes through that slot and drops into a twenty-foot pool. Beyond the pool is a pond eddy. Steve McCormick had to leave at eight. Having caught salmon smolts in Turners Falls and equipped them with acoustic tags, he went off to listen to the salmon in Hartford and beyond. Others from the Conte lab fishing at the Rock Dam this morning were Joe Zydlewski, Joe Kunkel, and Gabe Gries. At one point, as many as nine fishermen were clustered there. Gries is an ecologist who works on juvenile salmon. He caught a shad. Joe Zydlewski took it—he wanted the gills. Joe Kunkel is doing a study with McCormick and Zydlewski to see how gill morphology changes as shad come into the river. I used a fly rod and a spinning rod. I used a flutter spoon. I used darts. I used lead-core leader. I used my brain, to the extent that it was working, and once again I could not get a shad out of the Connecticut River. It’s as if I were a rejectee, an alien. The Rock Dam is as tight and intimate as it is natural and beautiful. Everybody else was fishing from dry ground in sneakers, while I was dressed up in neoprene stocking waders, sand guards, L.L. Bean felt-soled boots, and an Orvis vest bearing the orange-and-green emblem of the Delaware River Shad Fishermen’s Association. I looked like a hapless astronaut, while these scientists stood on the ledge in their bluejeans, catching shad.”
