Although young male elk sometimes wander through the Tarboo watershed after they’ve been weaned, we don’t have anything like the resident herd that the Elwha managers have to contend with. The Dead Zone has been a challenge, but we consider ourselves lucky in comparison.
So our tree order changes each year as we learn more about our soils and site, and as saplings planted in earlier years thrive or die. The Dead Zone doesn’t fool us anymore—when we’re planning for that area now, we order things like Sitka spruce instead of the usual array of upland species. We’ve gone so far as to try western cottonwood—a classic river-bottom tree—and willows. And when we order for areas where the early plantings of trees are doing well, we load up on shrubs so we can get an understory layer started. The only constant is change. Each year we watch, learn from the land, and try new things.
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Tree orders get mailed off in October, but we usually wait to take delivery until early January. By then the holidays are over, temperatures are cool and steady, and the soils are well wetted.
Between ordering time and planting time, then, we have a couple of months to wait. And as we’re waiting, the fish come.
Salmon
There is poetry in a salmon run. When a big year is peaking, the creek is a frenzy of flashing red skin, fighting, splashing, and sex. It is a bacchanal, a primal rite passed down from the ancients. But when a run fails, there is a void. The landscape is changed, for its soul is missing. You stare at the water flowing by, wondering if its life, and your life, will always be this empty.
There is mystery in a salmon run, too. These are large creatures; even in tiny streams like Tarboo Creek, many are 2 feet long and 7 pounds or more. But they appear from nowhere. Days and weeks and months go quietly by; then suddenly the stream is alive with great beasts, thrashing their way upstream. And there are so many questions: Why are they abundant enough in some years to crowd each other, and almost nonexistent in others? When you see them migrating in the open water of Puget Sound, before they sort themselves out by natal stream and thus final destination, they throw themselves up and out of the water: one, then another, flashing like silver coins flipped in sunshine. Why do they do this? Then how do they find their way to their fryhood home and adjust to living in freshwater, after years in the salt?
Finally, there is beauty in a salmon run. When the fish approach the stream of their birth, their bodies change. The males acquire great hooked jaws—cartilaginous extensions to their normal bony jaws—lined with triangular teeth that are useless for hunting prey but efficient in combat. They have morphed into fighting machines, brandishing spiked war clubs that they wield in fights over females. Both males and females color, their silver bodies darkening as salmon-colored pigment molecules migrate from their muscular sides to concentrate in their skin. Females also load these pigments into their eggs.
The orange-red pigments that color breeding salmon and their eggs are members of a molecular family called the carotenoids; they make egg yolks an orangey yellow and northern cardinals a bright red. Carotenoids are synthesized by photosynthetic organisms—the plants and algae and bacteria that do most of the planet’s interesting biochemistry—and are passed up the food chain to herbivores and their predators. Because the pigments are acquired in the diet, only well-fed individuals can have good carotenoid supplies. The pigments boost immune system function in both birds and fish—individuals subsisting on a carotenoid-poor diet are not only more dully colored but also tend to be sicker. So colorful salmon are healthy, well-fed salmon. Both males and females actively prefer redder mates.
The sockeye and pink salmon found in larger streams in the Pacific Northwest flush scarlet from nose to tail when they move into rivers to breed. Tarboo Creek’s coho dress in a deep emerald green above and a brilliant red below; the chum salmon are olive streaked with ruby-red gashes, like lightning strikes.
Along with changing their jaws and body color before spawning, salmon remake their gonads. The males load long tubes with milky-white milt, brimming with tens of millions of sperm, and the females ripen great sacs of eggs, numbering up to seventy-five hundred in large species like Chinook. The load typically represents a fifth of a female’s body weight; imagine a 140-pound woman carrying a 28-pound baby in utero and swimming upstream—in some cases, hundreds of miles; in many cases, through boulder-filled rapids and up and over waterfalls.
The salmon of Tarboo Creek are large, sleek, and strong, but ephemeral. They arrive a fire-engine red and bristling with vigor but are dead in less than two weeks. The females beat the skin and muscle right off of their tails as they dig a nest for their eggs; it’s common to see exposed bone in the tails of spawned-out coho. Even before spawning is over, a mother’s eyes may begin to dim. Soon they whiten and begin staring out at the world haunted and ghostlike. Her brilliant breeding coloration fades quickly, and patches of infected skin appear—fuzzy with growing white strands of the funguslike decomposers called oomycetes. Her body has started to rot before death. Within days, you will find her carcass lying on the shallows, often next to her nest. She has given everything to the young. Nearby, dying males will lie on sandbars, slowly being covered with sediment, even as their gills still open and shut. Brief floods may carry the bodies away a short distance, only to be snagged on the branches of low-lying trees, where they hang, limp. Newly arrived salmon, fresh and brightly colored, swim by the carcasses—passing the dead on their way to the front.
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At the start of a run, when they are moving in storm-driven water, the salmon are quicksilver. If you get too close to the stream they flash away; all you see are the ripples of their splash. The fish themselves have disappeared into the shadows or raced upstream—heading to a promised land of deep gravel and many mates. But if you are lucky enough to spot a female who has already committed hours to excavating a particular site, she will not flee. She will ignore you. So will the males who have come to love her, biding their time nearby. If you sit quietly, you can watch a nest taking shape, at your leisure.
We did this, one afternoon on a Thanksgiving weekend. Susan found a female digging a redd in the gravel directly above a riffle, where the water was bubbling rapidly over a cobbled incline. This is a prime location for salmon eggs to develop: the gravel is deep and well oxygenated. It also happened to be in one of the first meanders Tom and Peter had engineered and Bob had dug. The female was nesting in newly restored habitat.
Susan was joined by our boys and a cousin; some friends and I came and went throughout the afternoon as we did stream-maintenance chores or walked other sections of creek looking for redds. The new nest was in a section of the stream that wasn’t more than 6 or 7 feet across; the water was shallow enough to see the bottom clearly. Sitting on the bank with the toes of their boots in the water, Susan and the boys could almost reach out and touch the fish.
Susan named the female Cassandra, inspired by her sleek, exotic looks and—once we’d counted the courting males nearby—her powerful allure.
When we first started the watch, there were three males in attendance. Closest to Cassandra—currently in pole position—was a beautiful hunk of a male, clearly fresh from the ocean. The boys called him Fabio, to reflect his classic European styling and flair. He was the type of big, flamboyant fish that makes all the girls stop and stare. Nearby was Tony Bennett, who may have achieved greatness in the past but by now had seen better days. His coloration was a shadow of its former self; he was in the game, but out. The third gentleman-in-waiting was Red-cheeks. When the males jostled for position near Cassandra, Tony Bennett was sometimes displaced by the fresher Red-cheeks and always by Fabio.
Although it got difficult to keep track, Susan eventually counted at least six males who were following Cassandra’s progress. Fabio, Red-cheeks, and Tony Bennett tended to stay nearby; the other salmon-boys would check in for a few minutes and then head back upstream—presumably to other riffles where other females were preparing their nuptial beds. Those mal
es were making the rounds, keeping tabs on the action. They had to weigh their prospects with various females, assessing their odds against the other suitors at each redd. But sooner or later, they all came back to Cassandra.
As the afternoon wore on, Susan noticed a fourth fish staying close to the redd. He was small and secretive, staying well away from Fabio, Red-cheeks, and the other big boys. He was probably a jack—a sneaker. Jacks occur in several salmon species, including coho. They are males that only stay out in the ocean for a single year instead of the multiyear residence—two or three or four, depending on the species—of normal males. Because jacks are younger, they don’t get big enough to compete directly for females. Instead, they loiter on the street corners near redds, waiting. When a female finally begins to spawn and the dominant male aligns with her, the jack will dash to the female’s opposite side, spray sperm at the eggs, and bolt for cover before the attending male can bite him.
Jacks can play a winning hand if two conditions are met. First, predation pressure in the ocean, from orcas and fishermen, has to be intense—making life dangerous for males who stay out multiple years. The big boys may get bigger each year, but they may also get eaten. The key insight here is that jacks are making a trade-off between higher survival and lower success at fertilizing eggs. They are less likely to be eaten by orcas, but they also can’t hope to best the big males in fights over females. So for the jack way of life to pencil out, a lot of salmon have to get eaten in their second (or third or fourth) year out in the ocean. But there is another issue: other jacks have to be relatively rare. If the creek is full of sneakers, the jacks start competing with each other as well as the big boys. The dominant males also get more wary of them—meaning that jacks have a greater chance of getting killed in flagrante delicto by a jealous husband.
Breeding experiments have shown that the “decision” to be a jack is at least partially determined by an individual’s genetic makeup. That is, some males have a predisposition to leave the ocean early and pursue what biologists like to call an alternative mating strategy. The frequency of these sneaker alleles—an allele is a version of a gene—goes up and down over time, as jacks do better or worse in the game of fertilizing eggs.
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All of these little dramas involving males, though, were nothing compared to what Cassandra was going through. We would watch her float above the redd placidly for five minutes or more, then suddenly roll to one side, arch herself into a U, and beat her tail like a hoe against the rocks—making four or five quick, forceful thrusts. It was over in a flash and a splash. Then she would float again, peacefully. It was like watching an Olympic champion still himself, clean and jerk two huge iron disks with a great roar of effort, drop the barbell with a crash, and then stand there, dazed and rocking slightly. The males—who swam aside each time Cassandra pitched herself into a bout of digging—would sidle back toward her.
At first we wondered how long she could keep this up. But then we realized that the answer was simple: as long as it takes. The depression Cassandra was carving had to be deep enough for her eggs to settle into—out of the current—until they were fertilized and she could cover them back up. It also had to be deep enough that the eggs wouldn’t be exposed by scouring currents—to prevent them from being swept downstream when winter storms brought the creek to flood stage. But too deep, and the tiny fry, still carrying their yolk sacs, would have trouble wriggling up to the surface after hatching. Redd making is a Goldilocks problem: not too deep, not too shallow—juuust right.
Susan and the boys spent most of the afternoon by the reddside, sitting shoulder to shoulder. They marked Cassandra’s progress, commented on the comings and goings of the salmon boys, listened for the bald eagle calling downstream, and watched flocks of chickadees and kinglets as they went foraging by.
And always, they watched the water. A creek is flowing rain: water that rose into the air somewhere in the wilds of the North Pacific before being transported south by a swirling storm front that smashed into the Olympic Mountains and dropped its load of moisture. The water in the creek right now could be fresh drippings from the forests of the upper watershed, or fossils that had been sitting in the ground for years, slowly seeping their way downhill.
The salmon also follow this cycle, from ocean to forest to river and back. As they move through the open ocean, the growing fish store nutrients that have welled up from the depths of the sea. The nitrogen, potassium, and calcium atoms in their bodies were passed from photosynthetic bacteria to microscopic crustaceans to herring and candlefish to them. When they’ve grown stout enough to carry the load, the salmon swim these nutrients back to the land. As they spawn and die, the nutrients may be snatched up by the bacteria that coat the gravels and fill the muds in the creek, only to be passed to a caddis fly nymph and a tiny salmon fry. In this way, the young fish are nourished by the bodies of their mothers and fathers. Or the parents’ bodies can be hauled away from the creek by a river otter, bald eagle, bear, cougar, raccoon, or raven. The scavenger’s feces, along with the remains of the salmon carcass, fertilize the trees. In this way, the forest is fed by the fish.
Experiments that trace the path of nitrogen atoms in forests have documented that a tree will quickly take up more than a third of the nitrogen in a salmon carcass deposited under it; an observational study in southeast Alaska showed that Sitka spruce near salmon streams grow three times as fast as Sitkas on similar but salmonless sites nearby. The 20 million sockeye salmon that run into rivers feeding Alaska’s Bristol Bay can deposit 54,000,000 kg of biomass in the adjacent watersheds. Salmon are a swimming fertilizer. They represent a massive transfer of nutrients from the open ocean back onto land.
Eventually, the Sitka spruce and other trees along salmon streams drop their needles and leaves back into the creek, where the leaching nutrients are absorbed by bacteria and algae and passed back up the aquatic food chain. One way or another, the atoms that make up the older generation are passed on to the new.
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If you watch a creek flow by long enough, you will find yourself thinking about things: like how long this cycle of water and salmon has been going on without us, or how much you love the people sitting next to you, or how long it’s been since you just sat somewhere. And you begin to wonder about things: like what this spot was like during the last ice age, when there was a mile of ice above you, and whether fish feel weather. A salmon can’t possibly understand humidity or wind or rain or snow. It can only know that the water around it is cold or warm, fast or slow, deep or shallow, fresh or salty.
But salmon can feel things we can’t. Along with other fish and aquatic amphibians, they have a lateral line—a sensing system that runs the length of their bodies on either side. The core of the system is a row of sensory cells similar to the ones found in your inner ear. These cells have tiny hairlike projections that bend in response to changes in pressure. The bending movement causes a minuscule electrical current to flow inside the sensory cell, which triggers a stronger electrical signal from adjacent nerve cells to the brain. The brain integrates the signals sent by all of the cells in the system and sends a pulse of messages back down motor neurons to the muscles that control swimming. In response, salmon face into water currents. They detect rocks and other objects nearby and avoid smashing into them; they sense and turn toward passing prey.
Salmon feel their way, and not only with the lateral line system. The leading hypothesis for how they navigate hundreds of miles of open ocean back to the region of their natal stream is magnetosensing. The idea is that they construct a map based on perceiving and recording changes in the intensity and angle of Earth’s magnetic field. It’s an ability that humans can only imagine—or replicate with sensitive instruments.
Once the fish have followed this magnetic map back to their old neighborhood, they use their sophisticated olfactory bulbs to smell their way home. It’s like my parents navigating to my father’s hometown in Indiana using a highway map and then f
ollowing landmarks to get to my grandparents’ house. My grandmother always baked cookies in anticipation of our arrival; my brothers and sisters and I would jump out of the car and home to her kitchen, following the smell.
In the Columbia River, some salmon follow their noses like this for 600 miles, making an elevation gain of 2,000 feet, to get to the same stretch of the same tributary where their parents spawned. It’s hard to exaggerate just how specific this homing can be. Tagging experiments in southwest Alaska have shown that salmon eggs buried in lake gravel, versus the gravel in nearby streams, give rise to adults that return to the lake—not the streams a stone’s throw away.
A salmon’s sense of smell does much more than guide it, though. Salmon can smell danger. Experiments have shown that they avoid water that has been washed across the skins of bears or otters. They can smell food nearby, too—both as fry in streams and as adults in the open ocean.
Salmon also see the world differently from us. With eyes positioned on either side of their head, they get a much wider perspective on things than we can. The trade-off is that they lack some of the depth perception we’re capable of. Further, inside the receptor cells that line their retinas, color-detecting pigments can monitor the angle at which light is scattered or polarized—another sense we lack. These eye pigments are also particularly good at distinguishing wavelengths of light in the ultraviolet (uv) and red part of the spectrum. The red sensitivity is probably an evolutionary response to the importance of red coloration in mating and other aspects of salmon social life; the best hypothesis we have to explain the uv sensitivity focuses on seeing well enough to feed near the water surface. As sunburn victims know all too well, bright sunlight is packed with ultraviolet wavelengths; uv is also abundant in the first few centimeters below a water surface. Pigment molecules that detect uv are present in the eyes of newly hatched fry, which feed at or near the stream surface, and are thought to help the fry feed and grow efficiently in freshwater. The uv-detecting molecules are lost, however, when juvenile salmon undergo smoltification—the drastic physiological remodeling that allows a freshwater fish to move into salt water and thrive. Instead, young salmon that are making the freshwater-to-salt-water transition acquire an extra sensitivity to blue wavelengths, which are abundant in the deeper ocean water they’ll soon call home. The ability to detect uv is regained when adults return to freshwater to breed—a change that helps their eyes cope with the light available in shallow water. It’s no wonder that Darwin referred to the vertebrate eye as an organ of extreme perfection.
Saving Tarboo Creek Page 5