A TEMPORARY REFUGE
Natural History of a
Wild Summer Steelhead Refuge Pool
in the Western Cascades of Oregon
© Lee Spencer
The North Umpqua Foundation
All rights reserved
LATE WINTER AND EARLY SPRING
During the late winter and the early spring, Sis and I are still settled in our winter quarters wherever they are and I am immersed in the natural history data from the previous season and equally immersed in the process of transcribing notes, making tables, analyzing, and comparing creatures and circumstances observed from previous seasons at the pool. We are also continuing to take our long walks, weather permitting, and reading, visiting, and catching up on recent movies. If we are wintering close enough, we will generally make a few visits to the pool during this time.
During a visit in late March of 2000, Sis and I saw what appeared to be a piece of dirty-white cloth crumpled on the far bank rocks. A closer look with binoculars showed it to be the largely eaten carcass of a steelhead. I got my waders from the truck, put them on, and crossed the creek to take a closer look.
The carcass was that of a large male steelhead and it had been turned inside out behind the head and every bit of meat and small bone consumed between the area of the anal fin and the gills. Even the inside of the skin was uniformly white and picked clean of flesh. The eye on the upper side of the head had been eaten too, as well as the meat behind the eye.
Otters had harvested this steelhead, however, I don’t know whether the fish was dead or close to death when it was collected. If it was alive when taken, it had not been in tiptop form as was shown when I turned the outside of the fish back to the outside again. The ventral and pectoral fins had been worn to stubs no more than half-an-inch long by contact with the substrate in the shallow waters of some spawning reach. This amount of wear at this time of year showed this fish to have been a summer steelhead. Whether killed by an otter or by the vicissitudes of its own life habits, this steelhead had not been dead long, at most a day or two; the flesh remained moist and didn’t smell at all strongly.
As interesting as this evidence of otter feeding was, it was equally interesting that these particular summer steelhead nutrients were immediately serving other species which were active at that time around the pool. A water strider, flies, and butterflies were on the carcass when I came carefully up to it in the chest-deep water off the rock.
A single loose copious scat had been voided by the otter at the top of the rock. This scat was covered with butterflies too, tortoise shells for the most part, but also a mourning cloak, a small blue one, and another butterfly or day-flying moth unknown to me. The scat contained crawdad shell and leg fragments, dark sediment—steelhead blood?—and sections of bone from a large fish.
On this same visit there were what appeared to be summer steelhead spawning at the head of a riffle just below the pool.
By late winter and early spring, most of those summer steelhead that will be ascending the North Umpqua River during the coming season are gathering instinctually —some perhaps serendipitously—in the ocean off the mouth of the Umpqua River. These steelhead have traveled in great gyres past the Aleutian Chain and back again at least once. The straight-line distance from the mouth of the Umpqua River to the near side of this chain of islands is 1,600 miles. This journey is further than if I drove from Istanbul to Mecca or from Portland, Oregon, to Fargo, North Dakota, a town I used to live across the Red River of the North from when I was a kid. I am unsure the 1962 Chevy pickup I drive—green and blue with steelhead painted on it—would make it there and back again without some part or system giving up the ghost, but the mechanic-less steelhead populations native to the Umpqua Basin have been doing this every year since before the retreat of the last continental glacier more than fourteen thousand years ago.
Many of these fish are spending much of the daylight hours swimming into and out of the surface plume of Umpqua River water floating on the ocean off the mouth of the river. Freshwater is lighter than saltwater and so these river waters float on the surface, carrying their messages with them while they drift away, merging gradually with the sea.
In the southern part of the Pacific Northwest, the summer steelhead populations of the North Umpqua River begin their ascent into the freshwater basin containing their ultimate home stream reach during a time when these streams are generally brimming with the addition of melted snow. The start of their migration corresponds with the regional arrival of the warming temperatures which are beginning to thaw the snow that has been in storage at elevations above three thousand feet in the Cascades since sometime in the previous fall. By mid-April, this melt water is beginning to swell the North Umpqua River and color it a rich malachite, the distinctive color produced by water that originally fell as snow. This snow-melt peak invigorates the rivers and creeks, sending the trace-element messages of whole drainage basins copiously out across the ocean.
The more swollen these streams are with snowmelt, the easier it is for steelhead to locate the right one because the further this stream spreads out into the immensity of the marine environment. As an example of this, the plume of current from the Colombia River, a very large river, at certain times travels hundreds of miles down along the Pacific coast of North America.
Having entered the drainage basin containing their natal stream in middle and late spring during a time when flows are bank full, these summer steelhead populations have up to ten months of freshwater traveling and waiting to accomplish before they make their nests in the gravel and deposit their fertilized eggs into them. Because the Umpqua River is a moderate length stream, the summer steelhead having at most two hundred miles to cover during this ten months, these populations spend the largest portion of this time not traveling, but waiting. Even a lazy steelhead can travel this distance in less than six weeks under normal circumstances. The individuals of a given population of summer steelhead wait at different times in many different places in a given drainage basin.
If so much waiting is necessary, why then do summer steelhead enter their home stream so early?
There are only guesses in answer to this question and there are a variety of them. One of my favorites is that what we now accept as normal in the way of climate may have changed drastically and often over the last several million years that the present species of Pacific salmon have been swimming to and from the waters of the North Pacific. For instance, during the balance of these eons, significantly greater amounts of ice than are now present have been advancing or retreating from the Pacific Northwest and the rest of the earth. When this was so—when these glaciers have been stable or advancing or retreating—the highest annual flows have been during the summer rather than the winter.
Whatever else this long wait of the summer steelhead is, however, it is undoubtedly adaptive. The presence of wild summer steelhead populations makes this clear. This wait is a positive response to the flux of environmental conditions—freshwater and marine—met with during the life histories of the ancestors of these fish, conditions which obviously still pertain to a certain degree.
Another oddity of this long freshwater wait, however, amazes me. It is that this early entry into their native rivers and creeks has summer steelhead populations of at least the Umpqua River leaving the ocean prior to the period of high productivity brought about by the summer upwelling events. During these events, the near shore waters are commonly several times as productive as they are at any other time of the year.
As an example of what they are giving up, winter steelhead that are the same age at summer fish are on average about four-pounds heavier, so long as they spent the same amount of time in freshwater as juveniles. This increased body mass is the difference between staying and feeding in the ocean an average of six months longer, as opposed to leaving the ocean in the spring to fast for those same six months. The productivity of the seasonal upwelling events allows four-year-old (two-salt) North Umpqua winter steelhead to average twelve pounds, versus the eight pound average of the four-year-old (two-salt) North Umpqua summer steelhead. Summer upwellings make possible a 50% increase in body mass for these two-salt winter steelhead.
As with all anadromous Pacific salmon, the summer steelhead return to that stream which initially carried them as eggs nested in its gravels. The various Pacific salmon species—other than some populations of the pink (Oncorhynchus gorbuscha), the sockeye (Oncorhynchus nerka), and the chum (Oncorhynchus keta)—are characterized as headwater spawners. These species commonly travel well up into the basins of rivers and creeks to spawn, places that are cold, nutrient poor, and oxygen rich and where the flows are potentially only inches deep and a few feet wide, areas of streams that may be dry in the summer and early fall. Furthermore, Pacific salmon have imprinted not only on the stream that gave them birth, but potentially on a small portion of the head waters of that stream, above or below certain tributaries, above or below certain rapids or falls or other obstructions, down to an area as small as a mile or a few hundred yards of stream. With the exception of the populations of relatively small cutthroat trout and the non-anadromous populations of rainbow trout, summer steelhead populations appear to spawn further up in smaller streams than do the other Pacific salmon.
Now, if a given steelhead population summers over in the flows of a relatively large mountain stream that are kept cool directly or indirectly by the melting of permanent snow packs, where this deme spends its summer and fall is less critical. The affects of the earth’s close proximity to the sun and the longer days will be ameliorated by these cooler larger flows. If a population of steelhead ascends a smaller natal stream that is more subject to heating during the summer, it may be necessary for that population to seek out much more circumscribed refuges from warm and low flows during critical times. As noted above, if such a stream harbors populations of steelhead in the summer, and if its temperatures rise above the middle sixties for even part of the day, this stream will contain refuges somewhere in its basin. It has to, and the wild summer steelhead, as well as people who poach them, key to these cool refuge pools.
Late winter and early spring is approximately the time summer steelhead populations that went up the river the previous year complete their spawning in the numerous headwater reaches of the North Umpqua Basin. A very small proportion of these fish will survive the spawning process and some of these early survivors may now be re-entering the ocean. These lucky summer steelhead that have lived past reproduction—mostly females—are acclimating themselves again to life in saltwater and are substantially feeding for the first time since they left the ocean nearly a year before.
After a few months of feeding near the mouth of the river, when they have their muscle tone and fat reserves back and their eggs or milt are once more beginning to grow inside them, these spawned-out steelhead will turn around and ascend their home streams once more. Since these are summer steelhead, the repeat spawners will not be any larger than they were during their first spawning run. In the few months available to them before they re-enter their home river, even the much greater productivity of the marine environment is not capable of doing more than return these fish to fitness after their effectively foodless sojourn of ten to twelve months in freshwater.
Sixteen years ago now, I stood on a high bank of the Navarro River in northern California looking into a large transparently clear tidal pool that was more than a hundred yards long and thirty yards wide. The distant boom of waves collapsing on a beach was audible. I was stretching and getting the kinks out of my shoulders from a drive over the Coast Range in the old truck.
As I watched with my friend Deborah, a large male steelhead fresh from the ocean entered the lower end of the pool. It may have been a repeat spawner because its snout was already lengthened and I could see a kype at the tip of its lower jaw. This was in late December, so the fish was probably part of the Navarro’s winter run of steelhead. The fish was swimming in what seems now to my memory to be a preternaturally clear flow.
Oddly, this steelhead swam at the surface, moving more slowly than my dog of the time, Muchacho, could swim. Every minute or so, it raised its head so high above the surface that the whole of its body showed ahead of its dorsal fin. When the steelhead had swum in its slow and head-raising fashion to the center of the pool, it turned and swam to the shore directly beneath where the three of us were standing on that high bank. Thoroughly amazed, I watched the fish push itself up onto and into the mud of the bank so that it was in no more than a couple inches of water and its body was exposed to below its lateral line. The fish fell to its side a few times as it lazily thrashed its body there in the sediments it was stirring up. After about a minute of wallowing, the steelhead backed away from the bank and off into deeper water and swam out to the center of the pool, where it turned upstream again. This steelhead then swam to the head of the pool and was gone from sight, still moving in a leisurely way and occasionally lifting its head above the surface.
Not surprisingly, this serendipitous window into steelhead behavior baffled me. After a couple of years of extensive reading, I figured out what I think was happening. This steelhead was taking its time about determining whether the stream of freshwater it was swimming into was the one it had been born to and that it had spent its first year or so foraging, establishing territories, and escaping predators in. I had learned that the ubiquitous coriolus force, an inertial force brought about by our world spinning eastward at 1,037.6 miles an hour—more or less—on it axis, caused the lighter freshwater to float as a wedge on the salt water in estuaries. In the northern hemisphere this wedge is thickest on the right, or northern, bank of these estuaries in the Pacific Northwest and thinnest on the left bank. It was on the Navarro’s north bank that the steelhead had thrashed in the mud. The sediments that this fish was bathing itself in were those that carried the strongest particulate and trace-element signature from the drainage basin above that tidal pool.
Steelhead and other Pacific salmon that are about to venture into a river or creek on a spawning run want to be as certain as they can that this drainage basin is the one which they are native to. Is it this one that, through their genes, these populations have closely adapted to, genes that are held in common with and inherited from ancestral generations? This is part of the reason why adult salmon that are going to be entering streams spend most of their time in the upper few meters of water while in the ocean or an estuary. Another part of the reason Pacific salmon focus on the least saline layer and regularly move into and out of it, is because they are acclimating themselves once again to the freshwater that will support them for what will probably be an energetic and variable length journey and a stay by summer steelhead that will last the best part of a year before they even begin to reproduce. It is a journey from which few of these wild summer steelhead will be returning.
While summer steelhead do not necessarily die after spawning—none of the various varieties of rainbow trout do—most of them here in Oregon will not make it back to the ocean. This is ok. Nature takes advantage of this common death by allowing the marine nutrients carried in the bodies of the parental generation to fertilize their home stream, and thus these nutrients will ease their offspring more gently into the beginning of their own journeyings.