Secrets of Steelhead Biology Essential to Study Planning September 2008 This is meant to be a living document. I will be periodically revising and adding to it as I achieve new insights. You can help. Whether you are an angler, biologist or other professional knowledgeable about the species, if you have a contribution, send it to me. If it is within purview of the title, I’ll work it into the discussion. And don’t hesitate to send me your opposing arguments to what I have presented, if you have any. The initial presentation here is designed especially for new or inexperienced biologists (or other professionals). Nevertheless, “old salts” to the steelhead game may discover useful new insights, too. My views represent coalescing of my: (a) 4 decades of angling and scientific-study experience with salmonids; (b) some “fireside” conversations with two former poachers who plied their trade on north-coast (California) rivers for over 6 decades; and (c) nearly 700 miles of adult steelhead spawning surveys (and 3 years of associated snorkeling surveys for juvenile steelhead) logged on the Gualala since 2001. In some of the discussions I have considered available literature. However, literature searches were limited and discussions are not meant to be exhaustive, scientific, citation-based treatises. I am simply offering my “two cents worth” as “food for thought” and basis for further discussions. Be aware, however, that certain issues likely pertain very specifically and uniquely to the Gualala River. Applicability outside of this watershed may be limited. Thus, keep the Gualala River’s unique setting in mind. It is a mid-sized northern California coastal stream. It is unregulated and free-flowing. It has an estuary which remains closed to the sea much of the time, blocked by wave-generated sandbars. Estuary breaching occurs from rainfall-induced elevated stream flows and high impoundment stages, which eventually overtop and then wash through the sandbars. In the past, artificial breaching, from digging by anglers, was also a fairly common practice. And finally, the Gualala’s steelhead run is composed of wild, free-spawning fish. As a result, a number of the issues I discuss will almost certainly not be applicable to larger streams, watersheds some distance away, streams with highly regulated flows, and streams with hatchery-derived steelhead populations. To take advantage of the html indexing capabilities of the world wide web, the questions are listed below, linking to their answers. You should read this document from beginning to end to get an understanding of all of the information presented here. This index of questions is offered as a reference tool, should you need to return to the web site for answers offered on this page. How soon after breach of the river’s mouth do adult steehead start entering the river? Do adults enter the river mouth in one large “school?” What is the diel pattern for upstream immigration of adults? What is the rate of daily travel for upstream immigration of adults? At what season and age do juvenile steelhead (JSH) typically migrate to sea? What is the diel pattern for downstream emigration of JSH? At what rate do JSH migrate downstream? Why are adult steelhead rarely observed spawning or even at the vicinity of their redds? With redds being quite conspicuous, isn’t counting them a straightforward task that anyone can master? Does adult spawning occur uniformly along the same stream reaches each year? What is “stacking” and when does it occur? If the flow drops below the “stacking” thresholds and remains there for a prolonged period, due to lack of rainfall, what happens to the adult fish? How are steelhead kelts identified? What percentage of kelts survive to become repeat spawners? How are adult steelhead accurately counted from a boat, or while snorkeling, if they remain hidden within cover? How accurate are counts of JSH made while snorkeling? What are the characteristics of the “favored” pools and runs most frequently used by adults for resting and holding? What constitutes a “barrier” to adult movements? Is it true that steelhead of various ages “love company of their kind?" How do adult steelhead leave “tracks?" What dynamics do adult steelhead follow when moving upstream through very shallow riffle areas? Do they always tend to ascend in a group? Do fish in a group all follow the same route? What is their rate of movement? How quickly and easily do they pass the shallowest obstacles? ? How should The Steelhead Population of a river such as the Gualala be described? Which environmental parameters are the most critical “drivers” of population size?" Are there any specific flow criteria that predict the strength of a future spawning return? What is the phenomenon known as “skying?" When do “half-pounders” typically appear in the river? Why are coho salmon essentially extirpated from the river, while steelhead continue to persist? In sum, what does the steelhead’s biology and behavior suggest as an appropriate philosophical strategy for steelhead population studies on the river? Q1: How soon after breach of the river’s mouth do adult steehead start entering the river? A: It varies between and within seasons, but remarkably, it can occur within minutes. I recall one incident during 1977, the second year of a record drought. It was late February and we were staying at the Surf Motel just above the river’s mouth; I was there to angle for steelhead. But the river mouth had been closed for days and anglers were lamenting the poor fishing success, when three local men literally took matters into their own hands. As I stood amongst an ever-growing “support crew” on the bluff next to the motel, the three men climbed down to the sandbar blocking the river’s mouth and began digging, using just garden shovels. Two hours later, a small rivulet began flowing seaward and it quickly expanded to a torrent, carrying both water and sand into the sea. “They’re coming up!” one of the diggers soon yelled up to my group. I was skeptical and among several who did not reach for a fishing rod–not just yet, anyway. But sure enough, torpedo-like wakes could be seen coming up-current through the shallow water pouring to sea. And even more amazing (to me, at least), within minutes, the first fish–a chrome-bright 10-pound steelhead–had been caught and was flopping in the sand. Fifteen minutes later three more had been taken, all by anglers using Little Cleo spoons. But the real “catch” if you will, was that the fish had not been illegally snagged; each had been “fair-hooked”–right in the mouth! That memorable day failed to deliver me a lucky fish. But I gained new respect for the steelhead’s adaptability, i.e., being able to swim straight in from salt- to fresh-water, and despite the physiological rigors this entails, aggressively pouncing on a small silver spoon held wobbling in the path upstream! A few years later I watched a similar event unfold on the Russian River, California. I was parked on the high bluff above the mouth of the river. With binoculars, I watched as a bulldozer hired by the County worked to breach the mouth to reduce upstream flooding. Just as on the Gualala, torpedo wakes began appearing in the outflow soon after the mouth began flowing seaward. One such “torpedo” make a wrong turn. It swam hell-bent into a very shallow braid and ended up flopping in 2-inch-deep water next to the bulldozer. The operator quickly stopped the machine, jumped down, and pounced atop a mint-bright 7-pound steelhead. Both of these incidents occurred relatively late in the season, when the river mouth had been closed for several weeks. Such a rapid ascent of the river does not necessarily occur every time the mouth breaches during the 5-6-month-long steelhead spawning season. [ Click Here to Return to Q Index ] Q2: Do adults enter the river mouth in one large “school?” A: No, under average precipitation and flows, adults tend to ascend through the river mouth in small-to-moderate-sized groups of up to a few dozen individuals. This occurs through the spawning season. Exceptions occur during prolonged droughts, when the mouth may remain closed for weeks or months; this can result in larger “waves” of fish entering the river all at once, when the mouth does finally breach. More typically, groups of fish leave the sea and traverse the mouth on every high tide for days, if the mouth remains open and surf conditions are mild. A chaotic, high, pounding surf reduces or halts immigration. If the mouth is open but the flow is very low and clear, fish often begin “stacking up” in the largest, deepest pools in the tidal-estuary portion of the river. And fresh fish moving upstream often telegraph their presence by “rolling” and “boiling,” especially during the ebb tide. The presence of fish that are “stacked” in pools can be determined by floating over them by boat (or snorkeling) or watching for their occasional boils. Planning for population studies at this time is governed by the premise that steelhead “go with the flow.” [ Click Here to Return to Q Index ] Q3: What is the diel pattern for upstream immigration of adults? A: Upstream movements are most pronounced when the stream’s hydrograph is declining after rainfall. During this period, if cover in the form of turbidity or surface turbulence (i.e., from high flows) is present, movements can occur day and night. As the flow recedes and clears, however, movements gradually shift to nighttime. With nighttime movements, adults are often found early the next morning resting in very shallow edge-water areas only a few inches deep. Once, I nearly stepped on an 18-pounder whose back was fully out of the water early one morning on the Mattole River, California. And I have experienced many similar events (albeit involving smaller fish) on the Gualala River. [ Click Here to Return to Q Index ] Q4: What is the rate of daily travel for upstream immigration of adults? A: A detailed answer would be lengthy and involve many variables and caveats. However, for large, controlled and uncontrolled rivers in general, a “ballpark range” (supported by telemetry and trapping studies) for actively migrating fish is from a low of about 3-5 miles/day to a high of about 20-24 miles/day. On the Gualala, a lower range–of perhaps 3-12 miles/day when adults are actively migrating–appears to be normal. Adult migration rate is inversely related to gradient and flow, which determine average river velocity (and thus the swimming effort fish must expend going upstream). And both very low and very high flows can greatly reduce or halt migrations. In addition, migration rate slows as fish ascending the main stem reach the vicinity of their spawning tributary. Effective study planning thus requires understanding just how adult steelhead migrating upstream “go with the flow” in the stream being studied. This in turn requires understanding the dynamics of the river’s hydrograph, including the flow thresholds which trigger movements. [ Click Here to Return to Q Index ] Q5: At what season and age do juvenile steelhead (JSH) typically migrate to sea? A: Again, the theme that steelhead “go with the flow” applies. And I would thus argue that today, there is not much that is “typical” about JSH emigration in the Gualala River–except that of wide annual variation. “Rules of thumb” appear to apply only infrequently, at best, especially given the river’s highly disturbed conditions. Steelhead are adapted to employing numerous emigration strategies to enhance survival. And this is also why long-term studies and putting each population estimate into its proper context are important steps to understanding population status and trend. [ Click Here to Return to Q Index ] Q6. What is the diel pattern for downstream emigration of JSH? A: Movements tend to occur at night and during twilight hours. One exception occurs in summer when large schools of fish move, seeking refuge from potentially lethal (high) daytime water temperatures. Such schools are sometimes observed moving en masse–both in upstream and downstream directions–during daylight hours, especially early morning. [ Click Here to Return to Q Index ] Q7: At what rate do JSH migrate downstream? A: Two issues are involved: (1) the downstream emigration rate of smolts bound for the sea; and (2) the movement rate of pre-smolts and younger JSH as they redistribute themselves within the stream system in response to extremes of water temperature or flow. Empirical data (from telemetry and trapping studies) exist for only the former value. Results show that travel rate is a function of stream size and average water velocity. For streams the size of the Gualala River, a “ballpark rate” of up to about 1/2-mile per hour is probably reasonable. Under certain conditions, the rate of JSH movement may exceed the average flow rate. And JSH migration rates are yet another way in which the species has adapted to “go with the flow.” [ Click Here to Return to Q Index ] Q8: Why are adult steelhead rarely observed spawning or even at the vicinity of their redds? A: Steelhead investigators under constraint of 8-to-5 work schedules are generally out looking for spawning activity at the wrong times. Most spawning occurs in the twilight hours of morning and evening, and at night–especially on moonlit nights. [ Click Here to Return to Q Index ] Q9: With redds being quite conspicuous, isn’t counting them a straightforward task that anyone can master? A: Accurate counts of redds using minimally-trained observers is most likely to be accomplished on small rivers, with low sediment and bedload movement characteristics, and highly regulated flows. The Gualala River is not such a stream. It presents unique exceptions and challenges to obtaining accurate counts of redds. For example, redd color contrast, due to adults displacing sediment and periphyton from the cobble and gravel that is moved about, is often quickly masked by new depositions of sediment, even at relatively low flows. Bedload movement, which can quickly “level” redd pots and tail-spill areas, occurs relatively frequently and at fairly low flows, due in part to the poor condition of the stream. Lamprey and steelhead redds are sometimes superimposed atop each other and present unique identification challenges. Numerous hydraulic features are present in certain reaches which can create substrate patterns resembling redds. And finally, “test” digging by adults increases dramatically under certain conditions, necessitating additional observer training and experience. With such an array of potential errors, new observers need to conduct surveys under guidance of a highly-trained observer until proficiency is achieved. Otherwise, counts may have a low level of accuracy. [ Click Here to Return to Q Index ] Q10: Does adult spawning occur uniformly along the same stream reaches each year? A: No, spatial distribution of spawning can and does vary widely between years and even within the same year. The controlling mechanism appears to be flow, with adult steelhead very definitely “going with the flow.” For example, in overall high-flow years (e.g., 2006), spawning is focused in uppermost stream reaches that fish are able to access, including areas only rarely utilized. In overall low-flow years, much more spawning occurs in higher-order downstream reaches, including the main stem of the river. However, within any given season, a shift to more spawning downstream can and does occur when the river hydrograph is in rapid decline, or the end of the spawning season (i.e., roughly mid-April to mid-May) is nearing. [ Click Here to Return to Q Index ] Q11: What is “stacking” and when does it occur? A: Adult steelhead movements are most rapid and uniform when the hydrograph is either falling or rising. However, as a declining hydrograph drops to certain low levels, there are distinct thresholds at which adult movements begin to slow and then eventually stop altogether. As these thresholds are crossed, more and more fish end up “stacking” in certain “favored” pools and runs. On the Gualala, stacking generally beings when the flow declines (following rainfall) to about 150 cfs (Wheatfield Fork [WF] gage–or Navarro River gage, as an index, when WF inoperable) and it peaks when the flow drops to about 75 cfs (and below)–when most adult steelhead stop moving. [ Click Here to Return to Q Index ] Q12: If the flow drops below the “stacking” thresholds and remains there for a prolonged period, due to lack of rainfall, what happens to the adult fish? A: During the majority of the spawning season, from roughly December through March, a single stacking and holding event, due to low flows, may last weeks or even months. Invariably, a freshet will occur, however, sending fish on their way up- and down-stream. However, in April and May at the end of the spawning and rainfall seasons, there is a “tipping point” during prolonged low-flow periods, beyond which adults leave places where they are stacked and begin moving out of the river system; this occurs despite the difficulties (i.e., physical barriers) and risks (due to increased predation). The tipping point phenomenon likely occurs in response to increasing day length and water temperatures, and is why very few adult steelhead become trapped in the river over summertime in most years. Nevertheless, every few years (roughly 7-10, on average) just the right combination of low rainfall and declining flows occur during springtime, setting up conditions in which significant oversummer stranding of adult fish can occur. Fish can become standed both upstream (in deeper pools) and in the estuary (when the river mouth becomes blocked by sandbars). The last year this phenomenon occurred on the Gualala River was 2008; at one point, several hundred adult fish were stranded in the estuary for weeks and could easily be seen from the bluff above the river. After a few weeks, the river mouth finally broke open, releasing these fish to swim back to sea. [ Click Here to Return to Q Index ] Q13: How are steelhead kelts identified? A: Kelts are post-spawn, or “spent,” adult steelhead. Anglers refer to them as “snakes” or “downstreamers.” And experienced anglers and biologists generally share the believe that kelt identification, based on the fish’s abdominal appearance, is straightforward and reliable. The “rule of thumb” is that steelhead with fat, rounded abdomens are pre-spawners, whereas kelts have thin, imploded abdomens. In addition, kelts often have paler, more drab coloration than fresh-run fish. Moreover, in my experience, kelts (i.e., with great anthropomorphic wisdom, what I believe to be kelts) observed from a boat during surveys tend to occur as individuals or pairs of fish instead of the small groups more typical of pre-spawners. Also, I have found kelts to generally be less wary than pre-spawners, often not even moving as the boat floats past them. If and when they do finally become startled and move, it tends to be in a downstream direction rather than the upstream movements typical of pre-spawners when they become startled (again, assuming that anthropomorphism reigns). But here’s the need for caution: Several studies comparing accuracy of such visual estimates of adult steelhead spawner status (i.e., kelts vs pre-spawners) versus actual status, as verified by ultrasound imagery of viseral anatomy, show that the visual estimates of even experienced biologists are often highly inaccurate. Thus, if study goals necessitate an accurate determination of spawner status, an approach utilizing ultrasound or some other confirmation method may be necessary. It also means that unless I am correct in my perceptions about kelts (i.e., occurring mostly as singles and pairs which do not startle easily and tend to move downstream when startled), spawner determinations made from a boat or while snorkeling may have low accuracy. [ Click Here to Return to Q Index ] Q14: What percentage of kelts survive to become repeat spawners? A: This is clearly a number that varies widely from year-to-year. An interesting side note, however, is that kelts which do become repeat spawners are likely to migrate up river at about the same time during each successive spawning season. [ Click Here to Return to Q Index ] Q15: How are adult steelhead accurately counted from a boat, or while snorkeling, if they remain hidden within cover? A: Start with the premise that winter-run steelhead behave quite differently than summer-run steelhead. In particular, on Wolly Creek, California (Salmon/Klamath rivers tributary) and upper reaches of the Eel River, California, I have found adult summer-run steelhead often already well-hidden in crevices, holes, woody debris and other structure as the boater or snorkeler first approaches. This is rarely true with much less wary winter-run fish. I almost exclusively find them resting and holding in open, exposed locations, even when there is abundant cover and hiding places nearby. They tend to move into such cover only if repeatedly harassed, such as by a second boater or snorkeler, or by an observer attempting repeated “passes” over their resting/holding site. Intense angling pressure also makes them seek cover. In addition, once adult steelhead reach uppermost stream reaches, they may remain mostly hidden within cover, especially during low-flow conditions. [ Click Here to Return to Q Index ] Q16: How accurate are counts of JSH made while snorkeling? A: Biologists like to believe that their counts of JSH made while snorkeling are accurate and reliable, especially when corroborated by similar results of their colleagues snorkeling through the same waters. This may be true if observer training and experience are adequate, and water temperatures are at the high end of the scale. But as water temperatures fall, JSH behavior changes and resulting accuracy of snorkeling counts declines dramatically. At the low end of the water temperature scale, snorkelers may observe and count only a small fraction of the fish actually present. In addition, accuracy often declines dramatically for large schools of fish, schools of mixed ages or species, small (<100 mm FL) fish in shallow (<6-inch) water, and other unique situations. Before embarking on snorkeling as a technique for assessing JSH populations, biologists need to understand how these various factors may influence their snorkeling results. With adequate conditions, snorkeling can be a quick and inexpensive technique to estimate population numbers. But under marginal conditions, snorkeling may be best-suited for measuring simple presence/absence or generating coarse trend data within seasons or over years. In any case, a distinct advantage in accuracy may come from having the same observer(s) involved throughout the study period. [ Click Here to Return to Q Index ] Q17: What are the characteristics of the “favored” pools and runs most frequently used by adults for resting and holding? A: There are clearly some “special” pools and runs that are highly favored by adults. Along my 18-mile index reach on the river, about a dozen such areas exist where the majority of all adult steelheaed are counted every season. In fact, the type of population indexing of adults I am doing could be accomplished by surveys of just a few (four to eight) of these favored sites, if only they were more readily accessible. Except for relatively large size and great depth (which alone are not consistent identifiers), favored areas do not share any visually apparent common threads, such as amount and type of cover, shape, bottom substrate, or vicinity to fish-passage obstacles. Moreover, there are at least an equal number of other very similar pools and runs which adults rarely, if ever, utilize. Identifying the key attraction attributes of important holding and resting sites will thus necessitate intensive physical, chemical, and geomorphic measurements of the sites, coupled with appropriate statistical analyses. Meanwhile, identifying favored holding and resting sites along any given stream reach is best accomplished through multiple surveys, either by boat or snorkeling, over several seasons. I do believe, however, that one attraction issue in some cases may be the relative ability of adults to safely elude a key predator–the river otter. I am seeing that river otters are a fairly common predator of adults, especially kelts. [ Click Here to Return to Q Index ] Q18: What constitutes a “barrier” to adult movements? A: The literature is replete with barrier criteria, including what constitutes impassable waterfalls, jumps and shallow water. However, I have observed every such “rule of thumb” broken numerous times. Adult steelhead can ascend impressive obstacles simply by waiting for the right flow conditions (i.e., “going with the flow”). Another controlling factor seems to be the absolute number of so-called barriers which must be passed. For example, on my lower index reach, there is one extremely wide, shallow (2-3-inch-deep) riffle, which at even moderate flows necessitates adults swimming 100 feet or more with their backs exposed. Yet this site does not appear to slow or delay adult migrations under most conditions, and they are not observed holding above or below it. It is only when the stream drops so low that numerous such shallow obstacles develop do movements cease and the fish begin to “stack up” in favored pools and runs. [ Click Here to Return to Q Index ] Q19: Is it true that steelhead of various ages “love company of their kind?” A: At most life-stages from juvenile to adult, steelhead are clearly quite gregarious. Such “schooling” behavior provides numerous adaptive advantages to survival. Adults migrating upstream are usually in small schools of from a few to a few dozen fish. Size of adult schools tends to be proportional to the overall size of the population in the river at the time. An exception is when adults “stack up” in favored pools and runs during low-flow periods; schools may then be disproportionately larger. JSH are equally as gregarious. For example, even in summer, when water temperatures begin reaching lethally-high levels, JSH still tend to be found in small schools in fast-moving water. [ Click Here to Return to Q Index ] Q20: How do adult steelhead leave “tracks?” A: I was skeptical of this concept before observing it myself. Here’s what happens: In low-flow years, particularly near the end of the spawning season when air temperatures are warmest, periphyton often begins to flourish on gravel and cobble substrates. At night, as adults ascend upstream through the shallowest riffles, periphyton is rubbed off, leaving clear “trails” or “tracks” which are readily visible the following morning. In addition, both former poachers swear that they can lie in bed at night next to the river and hear the fish splashing upstream through the shallowest riffles. [ Click Here to Return to Q Index ] Q21: What dynamics do adult steelhead follow when moving upstream through very shallow riffle areas? Do they always tend to ascend in a group? Do fish in a group all follow the same route? What is their rate of movement? How quickly and easily do they pass the shallowest obstacles? A: During nearly 4 decades of angling for them, I have gotten glimpses of some answers when observing “torpedo wakes” moving upstream across shallow areas, including riffles. But most such observations were during periods of moderate-to-high turbidity, when it was difficult to ascertain just how many fish were present and how they were moving upstream. This changed during a survey of the Index Reach I conducted on March 23-24, 2008. I had two very exciting “moments” with adult steelhead observed moving upstream through shallow riffle areas. The first event occurred along the upper survey reach at mid-day–1208 hours to be exact–when about 75 yards downstream, I spotted fish splashing upstream through a shallow riffle. I knew they hadn’t seen me yet, so I quickly jumped out of the boat, shoved it towards the shoreline, and kneeled down in the water (about 1-ft deep), where I remained motionless. The 20 adults in the group ascended the next riffle, just below me, as a group, with about half following up one “braid” while the rest came up an adjacent one about 12 feet away. At the top of the farthest braid, three of the largest fish took a “wrong” left turn into very shallow water and nearly beached themselves. Two-thirds of their upper bodies were exposed. Then, all of the fish quickly regrouped and continued swimming rapidly upstream directly in front of me; all twenty of the group passed by me within about 10 seconds. As they did, I snapped off some underwater photos (see File Memo #86 with the 2008 annual report). The second event occurred the following day at 1042 hours along the lower survey reach. This time 13 adult fish were seen coming upstream–before they had spotted me. I rowed to shore, stayed motionless in the boat, and watched. Their ascent mirrored that of the group the day before, except that they all came up the same exact places in the successive riffles. Average movement rate along the 150-yard reach where I watched them was about the same as that of a person walking normally–just as I had observed the day before. [ Click Here to Return to Q Index ] Q22: How should The Steelhead Population of a river such as the Gualala be described? A: Today, partly due to the high cost of scientific studies and competition for available funding, steelhead populations are often studied over relatively short time frames of one or two seasons or years. Nevertheless, we often see rather broad conclusions drawn from such time-limited data. Part of the impetus for this is the species’ Federally-listed status (and thus the urgent need to address population size and trend) and part is a failure of many investigators to recognize and consider the dynamic nature of steelhead populations–especially wild populations. Such populations naturally ebb and flow rather dramatically over time in response to many variables. However, primary controlling factors are rainfall, resulting streamflows and ocean conditions. Steelhead populations thus need to be examined over a representative range of year-types, and not for just a single season or year (or two). And each season or year of data should be fully described and documented within its context–i.e., the environmental parameters under which it occurred. The context of a population estimate (e.g., for adult spawning escapement or JSH production) can be developed by answering key questions. Did it occur under good, bad or average environmental conditions? What were these, specifically? Were environmental extremes, such as severe drought or well-above-average rainfall and flows, involved? Was ocean survival or growth (as “indexed” by conditions recorded for local salmon populations) likely impaired? Did drought conditions prevent spawning in one year which provided a rare “boost” to the following year’s population? Was there a positive population response to dramatically improved environmental conditions? How did environmental variables coalesce to drive population size or to influence the very accuracy of the population estimate? How does the indicated population (and related environmental parameters) compare to historical values. With such comprehensive questioning addressed, we then have a firmer basis for answering the overarching question: How is the population doing at this window in time? [ Click Here to Return to Q Index ] Q23: Which environmental parameters are the most critical “drivers” of population size? A: Rainfall and resulting flows are the most basic population drivers. Populations nearly always show dramatic, positive association with (1) above-average annual rainfall and flows; (2) above-average springtime rainfall and flows; and (3) below-average summertime water temperatures. Under the converses of these variables, populations show negative responses. [ Click Here to Return to Q Index ] Q24: Are there any specific flow criteria that predict the strength of a future spawning return” A: In time, and with enough years of data, I may be able to establish some useful predictors. However, one that has clearly emerged already is the “50 cfs rule.” On May 1st, if the flow on the river (Wheatfield Fork [WF] gage–or Navarro River gage, as an index, when WF inoperable) is 50 cfs or less, summertime rearing conditions for juvenile steelhead are invariably poor. This in turn means that one or more future spawning runs, usually 2-3 years later, will be significantly reduced. [ Click Here to Return to Q Index ] Q25: What is the phenomenon known as “skying?” A: As discussed earlier, adults initially entering the river from the ocean are often observed “rolling” or “boiling.” Once arriving upstream at the first (and successive) branch in the river (where a stream enters or two forks join), their migration slows and “skying” may be observed. Skying tends to be more prevalent during a low or rapidly declining hydrograph. Skying is when an adult holds near the surface in the current of the confluence area and periodically breaches above the surface with head and nose. Most veteran steelhead anglers have observed this phenomenon, which is likely related to the process of “homing” back to the natal stream. [ Click Here to Return to Q Index ] Q26: When do “half-pounders” typically appear in the river? A: Half-pounders are the relatively small, immature steelhead that enter the river after just a few months at sea. During the decades-long “Era of Hatchery Madness” (my connotation; i.e., when hatchery supplementation, from often distant stocks, was quite common) for the Gualala, halfpounders were not uncommon and generally appeared in early winter or winter. Today, with the run sustained by wild fish, half-pounders are much more uncommon. However, relatively small (3-5 lbs) mature steelhead, often referred to as “bluebacks” are seen in the river in some years; they usually arrive in April or May near the end of the spawning season. [ Click Here to Return to Q Index ] Q27: Why are coho salmon essentially extirpated from the river, while steelhead continue to persist? A: The two species exhibit different adaptations developed through evolution. Steelhead appear to have developed greater diversity of behavioral and physiological traits, allowing them to better adapt to present-day rapid environmental changes. Some of the differences, which have likely worked against the coho’s survival, especially as the health of the river has dramatically declined over recent decades, are: coho adults spawn relatively early and over relatively short time spans, whereas steelhead can spawn throughout the 5- to-6-month-long rainy season; coho adults die after spawning, whereas steelhead may return for repeat spawnings; coho juveniles are relatively intolerant of warm water, whereas juvenile steelhead are more broadly adapted to it; and coho juveniles’ seaward migration is compressed in time and more age-dependent, whereas steelhead juveniles are more flexible, emigrating at multiple ages and time frames, including leaving the stream earlier (or staying longer) to adapt to conditions. In addition, for the Gualala River, the undesirable genetic effects to wild coho from several decades of planting coho of hatchery origin in the river–often from distant stocks–cannot be discounted. [ Click Here to Return to Q Index ] Q28: In sum, what does the steelhead’s biology and behavior suggest as an appropriate philosophical strategy for steelhead population studies on the river? A: One guiding principal should be to avoid broad conclusions about the population based on short-term studies–such as over just one or two seasons or years. Steelhead are well-adapted to widely varying environmental conditions (i.e., rainfall, flows, turbidity, temperatures, etc.), but their populations still vary widely and need to be examined over a representative sub-set of conditions. Only then can population status and trend be adequately judged (and reasonably compared to historical data). Long-term studies are also more effective for identifying key population-limiting factors and the best approaches to population enhancement. A second guiding principal is that numerous aspects of steelhead behavior and biology involve “going with the flow.” Investigators need to thus be prepared to set aside their “day planners” and detailed projections of survey dates and times. Weather, rainfall, and stream flows invariably dictate the best times for surveys on uncontrolled small rivers and streams, and indeed, whether survey on any given date is even prudent. Adopting a “survey only when the time is right” philosophy clearly presents challenges for many steelhead investigators, since many are either government employees or consultants–in either case, hampered by a structured work schedule. Investigators must also develop a thorough working knowledge of the hydrodynamics of the river they are working on, including rainfall-flow relationships under different conditions and the particular thresholds of flow which trigger the “go” behavior in adult and juvenile steelhead. “Investigators studying wild steelhead populations on small, uncontrolled rivers should put aside their day planners. Steelhead ‘go with the flow,’ and biologists must be prepared to adopt schedules which ‘go with the fish.’” [ Click Here to Return to Q Index ]