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to PCFFA Home Page Endangered Species Petition: Coho Salmon
(Oncorhyncus kisutch)
California Endangered Species Act
Submitted July, 2000
to the
California Fish and Game Commission
EXECUTIVE SUMMARY
The Salmon and Steehead Recovery Coalition (SSRC) is formally petitioning the California Fish and Game Commission to list coho salmon populations as an endangered species, pursuant to the California Code of Regulations. Coho salmon living in California’s coastal streams are specially adapted to each stream and best suited to its conditions by genetics, behavior and physical adaptability. This adaptability has enabled coho salmon to survive for many thousand of years in the presence of man.
The coho salmon populations in California have declined at an alarming rate in the last 40 years. In this period, over 40% of the streams have completely lost their historic coho runs; 25 streams have intermittent runs of very few fish and only a few streams still retain self sustaining runs of this once abundant salmon species.
This petition is warranted because the populations of coho salmon (North of San Francisco Bay) that have not been listed, have declined by an estimated 90% in the last 30 years, and now stand at 1% of their estimated historical populations. The SSRC believes that efforts taken by the State of California must be quickly expanded to the entire range of California’s stocks of coho salmon, as soon as possible, if we are to have a chance of saving important coho genetics and restoring native runs of coho salmon.
Some of the present threats that must be dealt with are habitat degradation, migration barriers, water diversion, and disease. Commercial and recreational harvests have been curtailed with little effect on the species. This evidence points to freshwater and ocean habitat as the primary factors restricting coho recovery. The SSRC petitions the State of California to use the special protections afforded by the California Endangered Species Act to protect and restore our streams and watersheds. Habitat recovery for coho salmon will benefit many vanishing aquatic species, restore an important coastal economy, and improve drinking water quality and recreational opportunities for the citizens of the State.
SPECIES DESCRIPTION AND BIOLOGY
COHO SALMON – Oncorhynchus kisutch
Coho Salmon are widely distributed in steams along the California coast and are important to sport and commercial fisheries. Their life history is well known from numerous studies that have been conducted over the years, including the classic life history study by Shapovalov and Taft, 1954. They have adapted to the unpredictable conditions present in most California coastal streams. Coho salmon, nevertheless, have demanding habitat requirements and are most abundant in least disturbed, heavily forested watersheds. They move upstream in response to an increase in stream flows caused by fall storms, especially in small streams when water temperatures are 39-57 degrees F. Spawning sites are typically at the head of riffles or tail of pools where there ideally are beds of loose, silt free gravel and where cover exists nearby for adults. Optimal temperatures for development of the embryos in the gravel are 43-50 degrees F. Juveniles prefer deep (greater than 3 feet) well shaded pools with plenty of overhead cover. Juveniles prefer water temperatures of 50-59 degrees F and demand high oxygen and food (invertebrates) levels. High turbidity is detrimental to emergence, feeding and growth of young coho.
Description: Coho are fairly large salmon, with spawning adults typically attaining 22 to 28 inches in length and weighing 6.5-13.2 pounds. They have 9-12 dorsal fin rays, 12-17 anal fin rays, and 9-11 pelvic fin rays. Lateral line scales number from 121-148 and the scales are pored. There are 11-15 branchiostegal rays on either side of the jaw. Gill rakers are rough and widely spaced, with 12-16 in the lower half of the first arch (Moyle 1976).
Spawning adults are dark and drab. The head and back are dark green, the sides are dull maroon to brown, and the belly is gray to black. Females are paler than males. Spawning males are characterized by a bright red lateral stripe, hooked jaw, and a slightly, humped back. Both sexes have small black spots on the back, dorsal fin, and upper lobe of the caudal fin. The gums of the lower jaw are gray, except the upper are at the base of the teeth which is generally whitish (Fry, 1973). Parr have 8-12 narrow parr marks centered along the lateral line. The marks are narrow and widely spaced. The adipose fin is finely speckled, imparting to it a gray color, but the other fins lack spots and is tinted orange.
Taxonomic Relationships
Coho salmon are one of five species of Pacific salmon (Oncorhynchus) found in California. They do not appear to have the genetically distinct, temporally segregated runs that characterize the more abundant chinook salmon and steelhead trout. However, the strong homing abilities of coho salmon make it likely that each coastal stream has a distinctive strain of coho adapted to local environmental conditions. For the purposes of this section, the coho populations are divided into big-river coho salmon and short-run coho salmon. Big-river coho are those that migrate up large river systems 65-130 miles or more to spawn in the river tributaries. They typically start entering the streams in September or October, somewhat earlier than short-run coho. In the Klamath River and some other systems, much of the production of the big-river fish takes place in hatcheries.
Short-run coho salmon occupy the smaller coastal streams and the tributaries of the lower reaches of the big rivers and rarely migrate more than 65 miles upstream. These populations in any one stream system are typically small and highly dependent on natural reproduction. Overall, coho populations in California are the southernmost for the species and have adapted to the extreme conditions (for salmon) of many coastal streams. From Mendocino County south, the conditions in California are even more extreme. The physical, climatic, and hydrologic factors make coho salmon survival in the southern end of the range even more rigorous.
Life History
The life history of the coho salmon in California has been well documented by Shapovalov and Taft (1954) and Hassler (1987). Most coho salmon return to their parent streams after spending two years in the ocean (up to three years in Alaska). Jack males may, however, return after one growing season in the ocean (at age 2 years), but most fish in California return after two growing seasons in the ocean (age 2 years). In California, spawning migrations begin after heavy late fall or winter rains breach the sand bars to the mouths of coastal streams, allowing the fish to move into the streams. However, migration typically occurs when stream flows are either rising or falling, not necessarily when streams are in full flood.
In the Klamath River, the coho will run between September and late-December, with peak runs occurring during October and November. Spawning itself occurs mainly in November and December (U.S. Fish and Wildlife Service, 1979). In Waddell Creek, peak spawning is between January 15 and February 15 and spawning migrations often do not begin until late November or December (Shapovalov and Taft, 1954). In Oregon and south of San Francisco streams, spawning can occur as late as March, if drought conditions delay rains or runoff (Sandercock, 1991, Smith, 1991).
Coho salmon migrate and spawn mainly in small coastal streams that flow directly into the ocean or in the tributaries of large rivers. Females choose the spawning sites (redds), usually near the head of a riffle (at the tail of a pool) at, or slightly upstream of the hydraulic control, where the water changes from smooth to turbulent flow and there is a medium to small gravel substrate (1/2” to 4.4”). The flow characteristics at the location of the redd usually ensure good aeration, and the circulation facilitates fry emergence from the gravel. Each female builds a series of redds, moving upstream as she does so she deposits a few hundred eggs in each. Thus, spawning may take about a week to complete and a female can lay between 1,400 to 7,000 eggs. There is a positive correlation between fecundity and size of females. Both males and females die soon after spawning.
Eggs hatch after 8-12 weeks of incubation, the time being inversely related to water temperature. Hatchlings remain in the gravel until their yolk sacs have been absorbed, 4-10 weeks after hatching. Upon emerging, they seek out swallow water along the stream margins. Initially they form schools, but as they grow bigger the schools break up and the juveniles (parr) set up individual territories. The larger parr tend to occupy the heads of pools (Chapman and Bjornn, 1969). As the fish continue to grow, they move into deeper water and expand their territories until, by July and August, they are in deep pools. Territory size for coho is inversely related to the amount of food available.
Between December and February, winter rains results in increased stream flows and by March, following peak flows, fish again feed heavily on insects and crustaceans and grow rapidly. Toward the end of March and the beginning of April they begin to migrate downstream and into the ocean. Out-migration in small California streams typically peaks from mid-April to mid-May, if conditions are favorable. Migratory behavior is related to rising or falling water levels, size of fish, day length, water temperature, food densities and dissolved oxygen levels. At this point, the outmigrants are about one year old and 10-13 centimeters in length. The fish migrate in small schools of about 10-50 individuals. Parr marks are still prominent in the early migrants, but later migrants are silvery, having transformed into smolts.
After entering the ocean, the immature salmon initially remain in near-shore waters close to their natal stream. They gradually move northward staying over the continental shelf. Coho salmon can range widely in the north Pacific. The movements of California fish were poorly known until the Pacific States Marine Fisheries Commission’s (PSMFC 1994) Regional Mark Information System. It appears that recent coded wire tag data indicates that at least 65-92% of Californias’ coho salmon feed in the oceans off our coast. This is also true of Oregon’s coho as most coho caught off the California coast in ocean fisheries were reared in Oregon streams (natural and hatchery). In 1990 for instance, commercial and recreational fisheries caught 112,600 coho, a number that greatly exceeds the present production capabilities of California populations alone. (A. Baracco, California Department of Fish and Game, personal communication.)
Oceanic coho tend to school together. Although it is not known if the schools are mixed, consisting of fish from different streams, fish from different regions are found in the same general areas. Adult coho salmon are primarily piscivores, but shrimp, crabs and other pelagic invertebrates can be important foods in some areas.
HABITAT REQUIREMENTS
Spawning sites are typically at the head of riffles or tail of pools where there are beds of loose, silt free, course gravel and where cover exists nearby for adults. Unlike other salmon species, coho salmon redds can be situated in substrates composed of up to 10% fines (Emmett, et al, 1991), but in general, spawning success and fry survival are favored by very clean gravel consisting of less then 5% fines (California Department of Fish and Game 1991). Spawning depths are 4-21 inches, with water velocities of 6.5 to 26.2 feet per second (Hassler1987). Optimal temperatures for development of embryos in the gravel are 43-50 degrees F, although eggs and alevins can be found in 40-70 degree F water. Dissolved oxygen levels should be above 8 mg/l for juveniles (Emmett, et al. 1991).
Juveniles prefer deep (greater than 3 feet), well shaded pools with plenty of overhead cover; highest densities are typically associated with logs and other woody debris in the pools or runs. Juveniles require water temperatures that do not exceed 71-77 degrees F for extended time and oxygen and food (invertebrates) levels remain high. Preferred temperatures are 50-59 degrees F (Hassler, 1987); preferred water velocities for juveniles are .25 to 1.5 feet per second depending on habitat. High turbidity is detrimental to emergence, feeding and growth of young coho (Emmett, et al, 1991). Young and adult coho salmon are found over a wide range of substrates, from silt to bedrock.
SETTING
California rivers having coho salmon, from Redwood Creek (in Humbolt County) southward, drain 1,500’- 3000’ high Coast Range, an area underlain by easily eroded sedimentary rocks of the Franciscan Formation (California State Lands Commission 1993). To the north, the Smith and Klamath River Basins cut through the Coast Range to drain the Cascade Mountains as well. Maximum elevations in this area are typically 3,000’-6, 000’. Rivers from the Smith River south to the Mattole River exhibit peak flow in late January or early February, while rivers farther south have peak flows in late February (Figure 2). Duration of peak flows in rivers south of the Mattole are much shorter than those farther north (Figure 3), although both areas experience relatively low flows during the summer and early fall figure 4. Annual precipitation levels are also much higher along the west side of the Coast Range in northern California (60” to 80”) than they are farther south (25” to 60”), or the dry interior along the east slope of the coast range (25” to 60”) (figure 9). Central California has a relatively short rainy season compared to regions farther north. Annual snowfall in the southern Mattole River basin averages 2 feet, while the Klamath Mountains average 2 feet to above 10 feet. Maximum summer stream temperatures (18 to 26 degrees C), average maximum summer temperatures (Figure 7), and winter minimum temperatures (Figure 8) are similar along the California coast from the San Lorenzo River to the California/Oregon border. Winter stream temperatures in central California are generally warmer by an average of 10 degrees F, while differences in average annual sunshine in central California are higher by 200 to 600 hours per year.
The California coastal area is dominated mostly by (Sequoia Sempervirons) redwood forests, giving way to Douglas fir/hardwood forests farther inland. This forest type forms the dominant coastal vegetation in coho dominated landscapes south to Monterey, at elevations between 100’ to 2500’.
Vegetation in the upper basins in northern California rivers is adapted to a more arid climate than basins closer to the coast. Other vegetation types that exist in some upper river basins are Klamath montane, coastal montane, Blue oak-digger pine, and chaparral. South of the Mattole River, upper basins are not as arid, and the vegetation is primarily redwood with patches of mixed evergreens and mixed hardwoods, and coastal prairie-scrub around the San Francisco Bay area.
HISTORIC AND CURRENT DISTRIBUTION
Coho salmon are a widespread species of pacific salmon, occurring in most major river basins around the Pacific Rim from central California to Korea and northern Hokkaido, Japan. In the United States distribution is from Point Hope, Alaska to the San Lorenzo River in Santa Cruz County. Recently published investigations have reported that a number of local populations of coho salmon in Washington, Oregon, Idaho, and California have become extinct and that abundance of many others is depressed (e.g., Brown and Moyle1991, Frissel 1993, Nehlsen et al. 1991 ).
California
In California, coho salmon were distributed in all accessible streams on the coast north of Big Sur. Some inland populations still occur on the Eel and Klamath River systems (Hassler 1987). Principal populations are located in the Smith, Klamath, Trinity, Mad, Noyo, and Eel rivers, with smaller populations in coastal streams south to the San Lorenzo River. In the Eel River system, coho formerly ascended 390 kilometer (246 miles) of stream in 60 tributaries (Mills, 1983) of the South Fork Eel, the lower main stem Eel River, and the Van Duzen River (Brown, 1987). Annual runs on the Eel River in the early years have been estimated at over 40,000 fish; current runs are probably less than 1000 fish (Brown and Moyle, 1991). Brown and Moyle (1991) found historical records of occurrence of coho in 582 California streams, ranging from the Smith River near the Oregon border to the Big Sur River on the Central Coast. More recent surveys available for 42% of these streams indicate that 46% have lost their populations (Brown and Moyle, 1991). The Wilderness Society estimates in California, that coho salmon are extinct in 26% of their range, endangered in 22%, and threatened in the remaining 52% of the historic range.
Generally, the further south a stream is located on the California coast, the more likely it is to have lost its coho population (Brown and Moyle, 1991). Coho Salmon are rare in the Sacramento River even though several attempts have been made to establish runs (Hallock and Fry, 1967). It is likely that runs occurred at one time at least in tributaries to San Francisco Bay, if not in more interior streams. In the 1960s coho salmon were also widely distributed on the central coast surveys in the 1970s showed 12 streams from San Mateo to Monterey County, had documented runs of coho salmon (Hassler, Sullivan, Stern 1991). By the 1980s these populations had been extirpated in 8 streams, and with reestablishment of coho in Gazos Creek, there are now coho in 5 streams with small populations (Dave Hope personal communication).
EVOLUTIONARY SIGNIFICANT UNIT
“The existence of stocks, as defined by Ricker (1972), is no longer in doubt. The subdivision of a species into local populations which posses genetic differences that are adaptive is the fundamental basis of the stock concept, and it is this concept that must be incorporated into management if fishery reserves are to be restored and maintained.” (MacLean and Evans, 1981.) “We recognize that many instances will arise were there is doubt. In those cases, we believe the prudent manager will recognize the stock in question until such time that enough evidence is collected to show otherwise. Since the loss of a stock is an irreversible loss, its existence should be given the benefit of any doubt.” (Nehlsen, Williams and Lichatowich, 1991.)
The best biological science of the day and the Federal Endangered Species Act recognize the importance of listing “distinct population segments” of vertebrates. In the “Definition of a Species” paper (Waples 1991), salmon populations will be considered “distinct” for listing purposes if they represent an evolutionary significant unit (ESU) of a biological species. An ESU is defined as a population that 1) is substantially reproductively isolated from conspecific populations, and 2) represents an important component of the evolutionary legacy of the species.
The term “evolutionary legacy” is used in the sense of “inheritance” and is something received from the past and carried into the future. The evolutionary legacy of a species is the genetic variability that is a product of past evolutionary events and that represents the reservoir upon which future evolutionary potential depends. Conservation biology recognizes that these genetic resources will help ensure that the dynamic process known as evolution will not be constrained in the future if a species maintains this reservoir of its evolutionary past. DNA analysis has advanced enough in the last few years that it can now analyze gene flow that has occurred over evolutionary time scales, and therefore determine the lineage of a population of salmon.
The most important question to answer is, will the loss of population significantly affect the genetic diversity of a species? This too must be evaluated by looking at many types of information. Life history traits, size, migration patterns, fecundity, and timing of the spawning run age, all of which can represent a local adaptation to a local environment. Unfortunately, adaptive genetics is not well differentiated by past genetic studies. It is likely that future genetic studies with higher resolution may prove that habitat differences not only create local adaptation but also impart a genetic variation over time.
Many types of evidence should be considered when making a species determination. Isolation does not have to be absolute, but it must be at least significant enough to impart genetic differences that can be maintained in an evolutionary unit. Isolation must be considered in the backdrop of natural straying, recolonization, evaluations of natural barriers, and shear measurement of genetic differences between populations.
The National Marine Fisheries Service evaluated the stocks of coho salmon in California and the West Coast. They determined that at least two ESUs could be established in California, Central California coast (Map 1) and the Southern Oregon/Northern California ESU (Map2). The State of California has recognized the distinct stocks of coho salmon south of San Francisco as an ESU, it is likely that future studies and a better understanding of adaptive genetics will likely support this listing decision.
HISTORIC AND CURRENT ABUNDANCE
Historical information on state-wide coho salmon abundance are estimates made by fisheries managers, based on limited catch data, hatchery records and personal observations of runs in various streams. Estimates for the number of coho spawning in the state in the 1940’s range from 200,000 – 500,000 (Brown et al. 1994) to close to 1 million (California Advisory Committee on Salmon Steelhead and Trout, 1988). According to some researchers (Brown and Moyle, 1991), coho populations held at about 100,00 in the 1960’s and dropped to an average of 33,500 during the 1980’s (Brown and Moyle, 1991). The reliability of these estimates is uncertain, and they must be viewed only as “order-of magnitude” approximations.
The total number of adult coho salmon entering California Streams in 1988-90 averaged about 31,000 fish per year. However, hatchery fish made up 57% of this total, and many main stem populations contain at least some fish of recent hatchery ancestry. The hatchery stocks, without exception, have in their ancestry fish from other river systems and often from outside California (Brown and Moyle, 1991). This may explain the overall lack of genetic differentiation of coho salmon from different California streams that have been extensively planted (Bartly, 1991). Recent studies of spawning escapement showed that 63 populations showed significant decline and only 2 showed increases. This data is similar to that found in Washington. ( Konkel and McInyre 1987). In 1890 Sacramento River summer and fall runs of coho salmon were noted in the press, but by 1950, no viable populations could be found (Hallock and Fry 1967).
The upper Klamath River had runs of 1,600 coho before the 1920s; these coho are now extinct (Klamath River Task Force). The California Department of Fish and Game summarized recent data and determined that most remaining coho salmon were hatchery fish although some wild coho may still remain in small tributaries. This same report concluded “ coho salmon in California, including hatchery stocks, could be less than 6% of their abundance in the 1940’s, and have experienced at least a 70 % decline in numbers since the 1960’s,” and many populations have been eliminated and others have runs only 1 out of 3 years, indicating two brood years have been lost and extinction is imminent.
In 1993, Pacific Rivers Council, Brown and Moyle (1991) estimated that naturally spawned adult coho salmon (regardless of origin) returning to California streams were less than 1% of their abundance at mid-century, and indigenous, wild coho salmon populations in California were a probably 1,000 individuals. Brown and Moyle (1991) also found that 46% of the California streams that historically supported coho salmon no longer supported runs. Brown et al. (1994) found in central California that the proportion of streams with coho salmon present was higher in recent surveys (1995-96), moving from 47% to 57%, but northern California streams with coho present, fell from 63% to 52%.
Brown and Moyle (1991, Brown et al. 1994) estimated average coho salmon spawning escapement in the central California coast ESU as 6,160 naturally spawning coho salmon and 332 hatchery spawned coho salmon from the period from 1987 to 1991 (Table 7). Of the naturally spawning coho salmon, 3,880 were from tributaries in which supplementation occurs (Noyo River and coastal streams south of San Francisco). Only 160 fish in the range of this range ESU (all in Ten Mile River) were identified as “native” stock (lacking a history of supplementation with non-native hatchery stocks).
Populations south of San Francisco were estimated at around 10,000 returning adults in the late 1800s, these populations had fallen to 100 or fewer in 1990 (Hope 1993). These populations have rebounded due to efforts enhance survival through curing populations of Bacterial Kidney Disease and careful propagation and release of fry. The returning adults are now estimated to be between 500- 1000 on good brood years (D. Hope pers. com.). Evaluation of these streams by Nehlsen in 1991 identified stocks in small coastal streams north of San Francisco as at moderate risk of extinction, and those small streams south of San Francisco at high risk of extinction. Higgins et al. (1992) looking closely at streams in Sonoma County north identified the Gualala River at high risk of extinction.
Historic data on adult coho salmon runs are available for 186 streams. Recent data for 133 of those 186 streams show 71 no longer have runs of coho salmon, while 62 still maintained runs of adult coho salmon (Brown et al. 1994).
NATURE OF THE THREAT
In reviewing the following description of the factors that threaten the continued existence of coho salmon in California, it should be noted that this decline has been continuing for over 50 years. The cumulative effects of all human induced impacts has so depressed the populations that even factors such as natural predation have taken on critical significance. Human development and its associated impacts are primarily responsible for the decline of coho salmon populations. Habitat loss in both freshwater and ocean, overexploitation, disease and a host of other human related influences has created a critical situation for the continued viability of coho salmon in California.
Loss and Fragmentation of Historic Range
The coho salmon consists of a highly organized network of dynamically connected, locally adapted populations. Each population is locally adapted due to the unique effects of a stream environment and particular natural selection that is therefore unique to each population. Each population has accumulated a unique combination of adaptive traits that cannot be duplicated or replaced in the span of a human lifetime. Inbreeding depression and speciation were historically minimized or prevented by the infrequent but periodic exchange of individuals between neighboring populations. Since suitable habitats and thus coho populations are often small and relatively isolated, the occasional exchange of individuals is beneficial because geographically nearby streams have similar habitats and are thus likely to reproduce successfully. The maintenance of such a dynamic metapopulation structure, and the interpopulation diversity associated with it, is necessary to ensure the future of the species and its role in ecosystems. This means that each breeding population is geographically, evolutionarily, and ecologically distinct, perhaps at as fine a scale as individual spawning tributary streams and major river reaches. Either the cumulative depletion or extinction of many populations or the fragmentation and severing of natural linkages between populations can precipitate rapid extinction of the species across large portions of the its range (Frissell 1993). These types of impacts immediately threaten coho salmon.
Complex metapopulation structure is adaptive in a region subject to frequent catastrophic disturbance, such as volcanism, earthquakes, sea level change, large landslides, flooding, and wildfire (Frisell 1993). When such disturbances cause localized extinctions, coho from adjacent populations colonize and eventually re-establish populations. Natural colonists of local origin, unlike hatchery fish or foreign stocks transferred from distant locations, are likely to be relatively well adapted to the empty habitat by virtue of geographic proximity and environmental similarity. Given sufficient time they can successfully restore the former range of the species. Because the life span of a single population is likely to be less than a few thousand years or perhaps centuries, maintenance of a broad distributional range and an expansive network of such population is critical for the long-term survival of the species as a whole. Large-scale fragmentation and collapses of range, such as coho have exhibited in California and the Columbia Basin this century, indicate that metapopulation structure and function is breaking down catastrophically, and that remaining populations face greatly increased risk of extinction (Frissell 1993).
Southern populations of coho salmon may be unusually well adapted to future, warmer and intensively human-altered environments. This indicates that the populations of coho salmon disappearing most rapidly are those which may be of greatest utility to ecosystems, fish managers, and fish harvesters in the future.
The loss of the coho salmon over significant portions of its range curtails or eliminates the functional role of the species in the ecosystem. In freshwater, coho and other salmon species are prey items for numerous aquatic and terrestrial predator and scavenger species and may contribute significantly to the nutrient budget of aquatic and riparian ecosystems (Houston 1983, Cederholm et al. 1989). At sea, and in freshwater, coho salmon function as a significant, if not primary food resource for a incredible array of predatory animals. Thus the loss of coho salmon is felt throughout the full range of the aquatic and terrestrial ecosystem.
For the present, our lack of understanding of how subtle natural genetic signatures create success or failure in a specific stream, makes it imperative that we save all existing runs of coho salmon to preserve the genetics for future conservation efforts. Loss of any population causes an irreversible blow to the genetic pool of a species and will jeopardize the recovery of the species forever. The present large-scale collapse of coho salmon and the fragmentation of this species range clearly demonstrates that conservation biology must take precedence immediately if we are to save this and other collapsing salmonid populations.
It is exactly the progressive decline, attrition, and lack of genetic diversity in all of our coho salmon populations over their entire range that threaten the future of this species. The loss of single population hinders the entire species ability to survive environmental change, and reduces the ability to evolve and persist into the future.
Artificial Propagation and Loss of Between-Population Diversity
Hatchery-origin fish have not been used to successfully re-build or re-establish coho salmon populations in the region. In general, there are very few (if any) examples of hatchery programs that led to successful re-building of wild populations of Pacific salmon within their native range ( Miller et al. 1990). Despite this history, some hatchery proponents continue to make optimistic projections of the future benefits of fish culture, with little or no scientific evidence to back up their claims. When successful in terms of producing hatchery fish, artificial propagation breeding tends to reduce, rather than increase, diversity of wild populations.
The potential and demonstrated adverse genetic effects of artificial propagation of salmonid populations have been discussed in several recent reviews (Hindar et al. 1991, Waples 1991). The capture of brood stock itself can be destructive of small or declining wild populations. Due to small broodstock populations, pre-spawning mortality during capture or transport, unnatural mating combinations, differential viability of gametes in artificial situations, disease, and artificial selection, wild brood stock typically contribute little genetic diversity to subsequent generations of hatchery fish (Bartley et al. 1992). The taking of larger numbers of wild fish for broodstock in an attempt to overcome these problems in hatchery stocks merely increases the risks for wild populations.
Large or repeated introductions of hatchery fish (foreign stock, hybrid stock, or local-origin stock altered by artificial selection) pose additional risks for wild fish (Steward and Bjornn 1990, Waples 1991, Hindar et al. 1991). Introduction of hatchery fish can adversely affect wild fish through competition and other processes. Maladaptive phenotypes can be introduced (Nickelson et al. 1986) and may temporarily persist in the population, particularly where wild population densities are low or habit has been altered (Campton 1987).
The failure of hatchery programs to boost or re-establish wild populations of coho salmon has been repeatedly demonstrated. Nickelson et al. (1986) documented the net negative effects of stocking coho pre-smolts in coastal Oregon streams, a practice still widespread in Washington and California. The effects of hatchbox programs and fry releases, widespread in all three states, have never been adequately evaluated. Hallock and Fry (1967) reported that numerous introductions of coho salmon had failed to re-establish a self-sustaining run in the Sacramento River. Hope (1993) documented in detail the many failed efforts to restore northern California coastal coho with artificial propagation, starting in the 1940’s and continuing through the present. Many if not most coho streams in the region have a similar, long history of introductions of hatchery-origin coho salmon. In many cases no fish return; in others first-generation returns are followed by failure of the second generation to reproduce successfully. Little monitoring of these programs occurs.
The litany of repeated failure in attempts to rebuild or re-establish self-sustaining wild populations with diverse kinds of artificial propagation argues that conservation of wild, indigenous populations of coho salmon in their native habitat is the only prudent and defensible course of action. The many potential side effects of small-scale and large-scale artificial propagation activities, led the Klamath River Basin Fishery Task Force (1991) to stress the overriding importance of habitat protection and restoration. Although recent successes in Scott Creek have been reported, this emergency propagation was combined with Bacterial Kidney Disease treatment (a disease likely introduced by past hatchery programs). A long term study of the success is necessary to determine the efficacy of this program for other streams (Dave Hope personal communication).
Deterioration of Freshwater Habitat
The long-term decline of coho salmon populations parallels the deterioration of freshwater habitat caused by human disturbances (Lawson 1993). Coho are especially vulnerable to loss or degradation of spawning, summer rearing, and winter rearing habitats (Pearcy et al. 1992). Pearcy et al. (1992) pointed to degradation of freshwater habitat as perhaps the largest contributor to long-term declines of coho productivity and recent shortfalls in escapement. Loss of woody debris and habitat complexity in estuaries may reduce survival of outmigrating smolts and winter migrants (McMahon and Holtby 1992). Coho habitat is lost when large woody debris and the stable, complex channels and wetlands associated with floodplain forests are damaged or destroyed by logging, grazing, channelization, cropland agriculture, or urbanization. Flow diversions for irrigation and hydropower generation poses serious problems for coho salmon throughout California. Sedimentation, debris flows, loss of channel stability and complexity, and increases in turbidity or summer stream temperature often result from disturbance of small headwater slopes and stream channels by logging roads and timber harvest. These impacts alone may be sufficient to damage or destroy coho populations even where buffer zones are left along larger, fish-bearing streams. Clearcutting of entire basins has the effect of increasing ambient air temperature and decreasing humidity. Instream water temperatures show direct response to this increase in ambient air temperature and decrease in humidity. The potential environmental effects of the myriad of chemicals applied or discharged into watersheds supporting coho salmon and the complex breakdown products of those chemicals, have been insufficiently investigated and regulated.
Coho salmon spend their first 15-20 months in streams and rivers and are therefore particularly vulnerable to adverse impacts of past and current land use practices. Reeves et al. (1989) defined physical habitat requirements for coho salmon at each freshwater life history stage. Spawning habitat is best carried out in small streams with stabile gravels, summer and winter freshwater habitats most preferred by coho salmon consist of quiet areas with low flow, such as backwater pools, dam pools and side channels. Habitats used during the winter generally have greater water depth, and have large amounts of large woody debris (LWD). Studies by Nickelson et al. (1992), show coho salmon smolt production is probably limited by the lack of adequate winter cover. Nutrients and food sources do limit production of juvenile coho salmon but procedures for identifying these limitations is not well developed at this time.
The role that LWD plays in creating and maintaining coho salmon spawning and rearing habitat is critical in all sizes of streams, but has only been recognized in the last two decades.
Historical Conditions
Descriptions of the pre-development conditions of river with abundant salmon suggest that all these rivers had large amounts of LWD, which in some cases blocked navagation, but in all cases stored sediment and nutrients, impounding and slowing waters, and creating many side channels and sloughs. (Sedell and Frogatt 1984, Sedell and Luchessa 1982) Many streams were so filled with logs and snags they could not be ascended by the early explorers. In California many smaller streams were “splash dammed to facilitate log drives”. These practices scoured, widened, and flushed gravels and essentially cleaned the streams bare. Stream cleaning continued through the mid-1970s, in an attempt to reduce flooding and improve fish migration.
Habitat Modification
The National Marine Fisheries Service (NMFS) reviewed the past destruction, modification and curtailment of freshwater habitat in 1996. NMFS found that the factors for decline of habitat on the west coast were due to dams (blocking juvenile and adult passage), water withdrawal (stranding fish entraining juveniles and increasing temperatures), flood control (stream channelization and simplification), logging and agriculture (loss of LWD, sedimentation, loss of riparian vegetation, habitat simplification), mining (gravel removal dredging and pollution) and urbanization (vegetation removal pollution channelization increased runoff, habitat simplification). Lichatowich (1989) confirms that habitat loss is a significant contributor to stock declines in coastal coho salmon streams.
Gregory and Bisson (1997) showed that habitat degradation has been associated with 90% of documented extinctions or declines of pacific salmon stocks. California has reportedly lost 89% of the states riparian woodlands due to various land use practices (Kreissman1991). Fisk et al. (1966) showed a loss of over 1,600-km of stream had been destroyed or damaged by 1966.
Large deep pool habitat, critical for coho salmon survival has declined on the West Coast by 58% on National Forest Lands, and by 80% in surveyed Oregon coastal streams (FEMAT 1993, Murphy 1995). Logging, agriculture, urbanization, grazing, and mining have led to large reductions in essential summer and winter rearing habitat for coho salmon. Habitats essential for coho survival are now rare in many streams i.e. backwater pools, side channels, off-channels, deep lateral sour pools, dam pools, and stream margins where LWD and boulders form deep cold water pools. In California loss of deep water pool habitat leaves coho salmon vulnerable to high instream summer water temperatures, winter flood events and predation by birds and mammals, due to lack of cover.
Habitat protection is the key to conservation and recovery of wild coho salmon, because the technological ability to restore habitats once they are damaged is severely limited, mostly due to our lack of understanding of how to best provide for coho salmon and the need for improvements in the technology. Although millions of dollars have been invested in artificial habitat alterations in attempts to improve habitat for coho and other fish, there have been few examples of successful large-scale recovery of coho populations attributable to man made habitat improvements. Unfortunately the cost of restoring a significant portion of altered streams using these technologies is prohibitive (Pearcy et al. 1992). In many streams in the Pacific Northwest existing technology for channel restoration has failed to treat the causes of habitat degradation (e.g., Klamath Basin Fisheries Task Force 1991). Furthermore, because the largest share of coho habitat is surrounded by private land (The Wilderness Society, report in preparation), recently proposed reforms in federal forest management (FEMAT 1993), will not be sufficient to safeguard this species from further decline and widespread extinction across a significant portion of its range.
Adverse Ocean Conditions
Ocean conditions have generally been deteriorating for coho in the lower 48 states during the past two decades (Lawson 1993), and there is little indication that favorable conditions will return in the near future. Most variation in ocean mortality of coho salmon apparently occurs during the first few weeks of ocean life (Pearcy and Fisher 1988), so that near-shore conditions during late spring and early summer along the coasts of Washington, Oregon, and California dramatically affect year-class strength. Evidence that upwelling along the Pacific Coast of North America is driven by 40-60-year cycles in wind patterns. Following an interval of generally favorable conditions in 1945-1975, upwelling declined along the Oregon coast and marine survival of coho salmon declined at a similar rate (Pearcy et al. 1992). Coho along the Oregon and California coasts may be especially sensitive to upwelling patterns, because these regions lack extensive bays, straits, and estuaries to buffer oceanographic effects. Assuming Ware and Thompson’s hypothesis is correct, ocean conditions are likely to remain generally unfavorable at least through the next two decades.
Evidence suggests there have been extensive changes in marine food webs during this century, and these changes may reduce survival of coho salmon at sea. The abundance of two species comprising a large share of the pelagic biomass of the Northeast Pacific Ocean, Pacific sardines and hake, have collapsed during this century, and failed to recover during the most recent period of favorable ocean conditions. Overfishing of these species during low-productivity periods may have contributed to their collapse and failure to recover, and resulting changes in the marine food web (i.e., predation shifts from pelagic to near-shore and migratory species) could adversely affect coho and other anadromous fishes.
Assuming oceanographic and atmospheric relationships of recent centuries hold in the future, anticipated climate warming during the next several decades is likely to cause continued adversity, or perhaps progressive deterioration of marine habitat for coho salmon. This could forestall or curtail the future recovery of ocean conditions postulated by Lawson (1993).
Given that manipulation of ocean and atmospheric behavior is beyond human capability, the deterioration of ocean conditions clearly makes the quality of freshwater habitat more critical for short-term productivity and long-term survival of the species (Lawson 1993).
Overfishing
Overfishing is often cited as a principle factor causing decline of salmon runs. However, there are few historical or recent records to indicate that curtailment of fishing has lead to increased spawning abundance of coho salmon. For example, curtailment of fishing seasons has been thought to have reduces harvest-related mortality rates on Oregon coastal coho substantially during the past decade. However, there has been no evidence of increased spawner escapement during this period, suggesting that fishing curtailment is at best merely keeping pace with rapid habitat deterioration and declining productivity of coho populations (Pearcy et al. 1992). In other words, environmental change is likely driving sustainable harvest rates downwards as fast as, or perhaps faster than, catch has been reduced. Unfortunately, the lack of adequate monitoring of habitat precluded certainty in assessing the relative roles of environmental deterioration and overfishing (Pearcy et al 1992).
Current methods of forecasting and in-season adjustment of fishing are insufficient to ensure sustainable harvest rates and wild fish escapement. Greater factors of safety for escapement numbers and better indicators of determining freshwater and marine survival and distribution factored with a clear understanding of habitat loss may give a more accurate model for determining harvest.
Annual catch of coho salmon in California ocean and troll fisheries ranged from 100,000 to more than 650,000 fish in the late 1960s and 1970s (PFMC 1978). Fishing effort in this region is directed primarily toward hatchery coho and to the much more abundant chinook salmon. Aside from this very large landed harvest of coho, which includes a mixture of hatchery and wild fish, heavy incidental coho mortality may occur during the chinook season. Additional mortality of wild coho is incurred in freshwater fisheries. Spawning escapement of wild coho in California and southern Oregon is not monitored or calculated in Pacific Fishery Management Council (PFMC) harvest decisions, and fishery mortality on viability and distribution coho salmon populations throughout the southern portion of their range. Although California and southern Oregon populations of coho salmon are lumped with Oregon coastal populations by PFMC for purposes of harvest management, these southern populations were not considered in PFMC’s assessment of overfishing of Oregon coastal coho (Pearcy et al. 1992).
The current and past policy of attempting to conserve coho salmon by focusing primarily on the regulation of harvest has failed. Curtailment of fishing can do little than temporarily delay extinctions that are ultimately caused by deterioration of habitat (Lawson 1993).
On the other hand, given that freshwater and marine habitats apparently continue to decline, it is difficult to establish sustainable levels of a coho fishery. In view of critically low escapement levels and signs of extensive local extinction of populations in recent years, as well as little indications of recovery of freshwater habitats in the near future, severe curtailment on fishing appears to be a prudent temporary measure.
Interspecific Hybridization
As a formerly abundant species becomes fragmented and dwindles in abundance, it becomes vulnerable to the impacts of genetic introgression and hybridization. Hybridization can be aggravated by habitat change or barriers to movement that reduce the opportunity for isolation between coexisting species, or by introduction of hatchery-origin or non-native fish whose life history patterns, behaviors, or distribution are unlike those of the fisheries indigenous to the site. Hybridization causes the loss of inter-population diversity, possibly jeopardizing the evolutionary future of the species.
Bartley et al. (1990) and Bartley (1990) have reported hybridization between coho and fall-run chinook salmon in the Klamath River basin. Hybrid individuals were detected by electrophoretic techniques. In one case coho and chinook salmon adults were apparently inadvertently crossed by fish culturists at the Irongate hatchery and the offspring released. In another case hybridization was likely a result of artificial blockage and crowding of large numbers of adult salmon in a tributary just below Lewiston Dam and hatchery in the Trinity River (Bartley et al. 1990). Two hybrid salmon were recovered in the ocean fishery, so at least some hybrids survive and grow to large size (Bartley et al. 1990). Their ability to mature and produce viable offspring remains unknown.
If first generation hybrids fail to produce viable offspring, at a minimum they can function to dilute the reproductive effectiveness of coho salmon that mate with them, as well as potentially competing with viable coho salmon individuals for food and space (Hindar et al. 1991). Transfer of genes from chinook to coho salmon via hybridization in Trinity River could underlie a detected increase in the susceptibility of (putative) coho salmon to infectious hematopietic necrosis virus (IHNV). Until recently coho salmon were considered resistant to this disease.
Monitoring has been insufficient to determine the possible incidence and long-range effects of hybridization problems. This is especially important given the widespread and increasing occurrence of situations where wild coho salmon populations are closely intermingled with hatchery salmon or artificially induced concentrations of salmon of multiple species on spawning grounds.
Failure to Adequately Monitor Wild Populations and Habitat
The failure of state and federal agencies to adequately monitor wild populations of coho salmon is a serious problem for protection and management of salmonids. In California, there is virtually no systematic monitoring of wild coho escapement by state or federal agencies. Wild coho in California are included in ocean harvests, but there has been no attempt to ascertain the effects of these harvests and mitigate their potential effects on wild populations.
No adequate monitoring of freshwater or ocean habitat, or yearly survival of coho in artificial propagation programs has been done to date. There are a variety of propagated fish species that may directly or indirectly impact coho salmon. In California there are only rudimentary monitoring and regulation of artificial propagation programs for a variety of fish species that directly or indirectly impact coho salmon. These programs are conducted by both large and small hatcheries throughout the state, by wide variety of volunteer and semi-official organizations and individuals. Although stock transfers, extensive trapping and broodstock collection efforts, and loosely regulated breeding, rearing, transportation, and stocking may pose a treat, there is little to no monitoring or regulation of such effects.
The coho salmon migratory and anadromous life history leads it through a diverse array of regulatory jurisdictions. The majority of the coho salmon life stages (egg, larval, juvenile and spawning adult) occur in freshwater and are thus affected by laws and policies designed or supposed to regulate inland watersheds and riparian zones.
DISEASE
Bacterial Kidney Disease (BKD) is a very debilitating disease that effects coho salmon in many stages of its life. Studies conducted in 1993 by Dr. Bill Cox showed all of coho salmon sampled in Scott Creek (Santa Cruz County) tested positive for BKD. One of the serious side effects of this disease is first demonstrated in low survival of eggs. Infected coho salmon females had only a 40% survival rate for eggs incubated at the hatchery. While females treated with erythromycin had egg survival rates of 80% (Dr. William Cox, California Department of Fish and Game). While living in fresh or saltwater life stages, the growth of BKD lesions on the kidneys can weaken and kill juvenile and adult fish. But it is theorized that serious losses occur when coho salmon transition as smolts from freshwater smolts to salt water and again as sea run adults transitioning back from salt water to freshwater. During this life stage the kidneys play a major role in this amazing adaptation that in fresh water allows coho to absorb salts and conversely in salt water, expel salts from the body. This transition is difficult for healthy fish, and it is theorized that a large percentage of coho salmon infected with BKD, are lost at both of these migration phases.
Ceratomyxa shasta, a parasite is present in the Colombia River system and is increasing (Ratliff 1983), and may be spreading to other areas. Some stocks of coho salmon may be resistant, but present methods of detecting the parasite are lacking and previous data on resistance may be confounded due a detection error. No information has been found to indicate the presence of C. shasta in California. This parasite as well as any other disease should be carefully monitored for, diligence by the State of California is this arena may be the best assurance against a set back in future restorations efforts.
EXISTING PROGRAMS
The State Fish and Game Commission has listed coho salmon south of San Francisco as “Endangered” under the California Endangered Species Act. A “Draft Recovery Plan has been developed and the Department of Fish and Game has taken some immediate action to protect and recover this important stock of coho salmon. The treatment of disease and emergency propagation of the few returning adults , has proven to be a very effective in greatly increasing spawning runs and reestablishing coho in neighboring streams that had completely lost their runs of coho salmon. Populations of coho salmon in streams with similar problems, await this same quick and decisive action.
The California Environmental Quality Act (CEQA), and the National Environmental Protection Act require a finding of significant impact (and mitigation applied) if a project will; 1) interfere substantially with the movement of any resident or migratory fish… 2) “ Substantially degrade water quality or 3) cause substantial flooding, erosion or sedimentation. However these protections can only be triggered if the public identifies the problem and it is deemed to meet the threshold of “Substantial”. The most onerous part of the process is when politics and economics cause the best alternatives to be rejected, in favor of watered down mitigations or alternatives that damage coho habitat. The failure of this system of regulations is evident when the cataloging of habitat destruction and population declines has continued unabated under this system of regulations. Further, the money spent on EIR and EIS documentation clearly exceeds by more than a 1000%, any money spent to protect or recover coho salmon habitat.
Recent studies by the Scientific Review Panel (SRP), set up by the Board of Forestry, determined that the existing Forest Practice Rules were not adequate to protect salmonids. Attempts to adopt new rules have been limited to modest protections for Class I watercourses, and they will automatically expire on December 31, 2000. The majority of rules suggested by the SRP were not adopted even though they were backed by the Department of Forestry, Department of Fish and Game and considered a good “first step” by the National Marine Fisheries Service. The Board of Forestry is attempting to adopt new rules to address Cumulative Effects and watershed analysis, but as mentioned previously the process of politics and economics will probably cause the best alternatives to be rejected.
The lack of habitat protection, and inability of existing regulations to affect watersheds and bring about aquatic ecosystem recovery, is at the core of why the process needs to be coordinated and upgraded. Despite all of the consistent and clear evidence provided by scientist, that damage to key environments has lead to losses in all salmonid populations, state and local governments have failed improve regulation of activities that are known to destroy and cause damage to aquatic ecosystems and watershed function.
For many decades salmon declines have been hidden behind a mask of hatchery produced fish. Hatchery production of non-native coho salmon inflates both the marine and freshwater populations, allowing losses to go unnoticed by the public. The worst effect of this practice is that hatcheries are also directly responsible for declines in coho salmon (Lichatowich and Nicholas, 1991). Some extinctions have been documented by NMFS, due to “extensive” introgression or mixing of non-native hatchery stocks with wild stocks. The existing program of hatchery operations must be evaluated by the Fish and Game Commission to determine the proper use a regulation of this management activity.
Ocean regulatory control is set for the near coastal water by the State of California, and from that zone out to 200 miles offshore by the Pacific Fisheries Management Council (PFMC). While the PFMC tries to regulate the coho fishery to provide optimum yealds on a sustainable basis, they do so by attempting to prevent “overfishing”. The process of regulation does not take into account the highly migratory nature of coho salmon, and in the past has tended to deal with authorizing fishing as a combined total, rather than acknowledging weak stocks. There have been attempts by the PFMC to change the practice of agglomeration, in and effort to protect endangered runs of salmon. Ocean migratory ranges have been determined by coded wire tagging, and fishing has been restricted to areas outside the range of these weak stocks. Recent protections afforded coho salmon by the PFMC has lead to fishing regulations and gear restrictions that have almost eliminated commercial and recreational catch of coho salmon in the ocean.
For recovery to succeed it is critical the protect important populations of locally adapted and geographically distinct stocks. At this time there is only one program (south of San Francisco) to manage coho salmon populations to maintain genetic diversity. More immediate actions must be taken. The loss of coho stocks that migrate over 200 miles from Eureka to Willits, (Eel River) is almost certain at this time, due to the small number of returning adults. This extinction will doom efforts to recover coho salmon in these and many other headwater streams throughout the Eel River basin. The future of coho salmon, its role as a natural resource, its ability to adapt in the future and survive by evolving are in jeopardy if we lose more of the runs that are now threatened with extinction.
The State of California has acknowledged a serious decline in fisheries since the early 1980s. The California Advisory Committee on Salmon Steelhead and Trout studied and reported on this serious problem in 1988 in Restoring the Balance. This report lead to the adoption of SB2261, which set a goal of doubling the runs of anadromous fisheries by the year 2000. Unfortunately no dedicated funding was provided to accomplish this goal. Small funding sources have been available to restorationists ranging from the early Boscoe-Keene grants, Proposition 99 and 70, and most recently the Thompson bill SB271. These modest attempts at funding a recovery have been administered by the Department of Fish and Game and overseen and granted through by the California Advisory Committee on Salmon Steelhead and Trout. Some small but important gains in stream habitat improvement, and barrier modification have accomplished in this initial work. One outgrowth has been a concerted effort critique and continues to improve the techniques of stream restoration and improve on fish passage. But these efforts can not and have not been able to alter in any significant way the continuing decline in overall habitat quality, serious losses in overall population, and extinctions of some stocks of coho salmon.
Several programs have been devised to develop a coordinated consensus approach to dealing with the declines in salmonids (California Salmon Initiative and Watershed Restoration and Protection Advisory Council). No program to date has produced either funding or a concerted effort to deal with the obvious problems facing all anadromous fisheries today, habitat loss. The majority of the coho salmon life stages occur in freshwater and can be protected by laws that regulate inland waters, the remainder of their life is governed at sea by state national and international fishing laws. These laws often conflict and are not effectively enforced, leading to poor protection and little positive affect. The combined effect environmental damage and the value of multi-jurisdictional regulations, is unknown at best, and likely ineffective as shown by the product of continued declining populations. If we truly expect to protect coho salmon we must move to a single regulatory body that can protect them throughout their entire life cycle and in all the environments they inhabit.
CONCLUSION
In California all stocks of coho salmon have shown a precipitous decline for over 80 years. All coho salmon stocks South of Punta Gorda are at a mere fraction of the past abundance. Small coastal streams have either small or intermittent runs of adults or populations are extinct. Most stocks of coho have been heavily supplemented with hatchery fish and “wild” coho salmon rare in this part of California. The National Marine Fisheries Biological Review Team (BRT) conclusion was dire regarding Central California coho salmon stocks, “There was unanimous agreement among the BRT members that natural populations of coho salmon in this ESU are presently in danger of extinction.” For the remainder of Northern California coho salmon stocks the BRT concluded, “There was unanimous agreement among the BRT that coho salmon in this ESU are not in danger of extinction but are likely to become endangered in the foreseeable future if presents trends continue.
The collapse of coho populations and extinctions of others is felt throughout the food chain of the aquatic environment. The present losses of just salmon carcass is causing an ecological catastrophe for many other species, as some are slowly being starved of the nutrients that are recycled by salmon carcasses and others directly starved by not having this seasonal food source.
The listing is requested by the Salmon Steelhead Recovery Coalition after considerable study. Careful review of the existing data indicates the listing is warranted, and the SSRC request that the Fish and Game Commission use the special protections afforded by the California Endangered Species Act help protect and restore our coho salmon populations.
INFORMATION SOURCES
Maps and Figures - National Marine Fisheries Service (not included in this version but filed with original).
Baracco, A. California Department of Fish and Game, Sacramento CA 95814
Bartley, D.M. 1991. Population Genetic Structure of Pacific Salmon. Pages 280-291, In: T.J. Hassler, edition, Proceedings of the 1990 Northwest Pacific Chinook and Coho Salmon Workshop, California Cooperative Fishery Unit, Humbolt State University, Arcata.
Bovee, K.B. 1982. A guide to Stream Habitat Analysis Using the Instream Flow Incremental Methodology. Instream Flow Information Paper 12. U.S. Fish and Wildlife Service, Office of Biological Services; 248 pages.
Brown, L.R. and P.B. Moyle. 1991. Status of Coho Salmon in California. Report submitted to the National Marine Service.
BRT 1997. Status Review Update for Coho Salmon from Oregon and Northern California Coasts. BRT- Biological Review Team for the West Coast coho salmon included Peggy Busby, Robert Emmett, Dr. Jeffery Hard, Dr. Robert Iwamoto, Dr. Orlay Johnson, Dr. Robert Kope, Dr. Conrad Mahnken, Gene Mathews, Dr. Michael Schiewe, David Teel, Dr. Thomas Wainwright, William Wakitz, Dr. Robin Waples, Laurie Weitkamp, Dr. John Williams, and Dr. Gary Winans, all from the Northwest Fisheries Science Center (NWFSC), Dr. Peter Adams from the Southwest Fisheries Science Center (SWFSC), and Gregory Bryant from the NMFS Southwest Region.
California State Lands Commission. 1993. California’s rivers: A public trust report. Second edition, California State Lands Commission, 334 p. (Available from California State Lands Commission, 1807 13th St., Sacramento CA 95814.).
Chapman, D. W. and T.C. Bjonn. 1969. Distribution of Salmonids in Streams, with Special References to Food and Feeding. Pages 153-176, In: T.G. Northcote, edition, Symposium on Salmon and Trout in Streams, H.R. MacMillan Lectures in Fisheries, University of British Colombia.
Chilcote, M.W. ; S.A. Leider and J..J. Lock. 1986. Differential Reproductive Success of Hatchery and Wild Summer Run Steelhead Under Natural Conditions. Trans. Am. Fish Soc.; 115:726-735.
Cox, Dr. William, California Department of Fish and Game Sacramento CA.
Emmett, R.L. ; S.L. Stone; S.A. Hinton and M.E. Monaco. 1991. Distribution and Abundances of Fishes and Invertebrates in West Coast Estuaries, Volume 2: Species Life Histories Summaries. ELMR Rep. No. 8. NOS/NOAA Strategic Environmental Assessment Division., Rockville; MD, 329 pages.
Forest System Management Assessment Team ( FEMAT). 1993 Forest Ecosystem Management: an ecological, economic, and social assessment. USDA and five other federal agencies.
Fisk, L., E. Gurstung, and J. Thomas. Stream damage surveys-1966. Calif. Dep. Fish and Game, Inland Fish. Div., Administrative Rep. 66-10., 15 p.
Frissell, C. A. 1993. Topography of extinction and decline of native fishes in the Pacific Northwest and California (U.S.A.). Conserv. Biol. 7:342-354.
Fry, D.H. 1973. Anadromous Fishes of California. California Fish and Game, Sacramento; 111 pages.
Gregory, S. V., and P.A. Bisson. 1997. Degradation and loss of anadromous salmonid habitat in the Pacific Northwest. In D. J. Stouder, P. A. Bisson, and R. J. Naiman (editors), Pacific salmon and their ecosystems: Status and future options, p, 277-314. Chapman and Hall, New York..
Hassler, T.J. 1987. Coho Salmon. U.S. Fish and Wildlife Service Biologist. Report 82 (11.70); 19 pages.
Higgins, P. 1992. Northern California Stocks of Salmon, Steelhead, and Cutthroat: At Risk of Extinction. Pages 11-16 in J. Waldvogel, edition Proceedings of the tenth annual California Salmon Steelhead and Trout Restoration Federation conference. University of California Sea Grant, Eureka, California.
Hope, D. G. Environmental Specialist III , North Coast Regional Water Quality Control Board. Santa Rosa California.
Hope, David G. Coho Salmon (South of San Francisco) California Endangered Species Petition, California Fish and Game Commission. 1993
Hollock, R.J. and D.H. Fry. 1967. Five Species of Salmon, Oncorhynchus, in the Sacramento River, California. California Department of Fish and Game; 53:5-22.
Houston, D. B. 1983. Anadromous fish in Olympic National Park: A status report. Natl. Park Serv. Pacific North west Region, 72p. (Available from Olympic National Park, 600 East Park Avenue, Port Angeles, WA 98362.
Kreissman, B. 1991. California, an environmental atlas and guide. Bear Klaw Press, Davis, CA.
Lawson, P.W. 1993. Cycles in ocean productivity, trends in habitat quality, and the restoration of salmon runs in Oregon. Fisheries 18(8): 6-10.
Lichatowich, J.A. 1989. Habitat alteration and changes in abundance of coho (Oncorhyncus kisutch) and chinook salmon (O. tshawytscha) in Oregon’s coastal streams. In C.D. Levings, L.B. Holtby, and M.A. Anderson (editors), Proceedings of the workshop on effects of habitat alteration on salmonid stocks, p. 92-99. Can. Spec. Publ. Fish. Aquat. Sci. 105.
Lichatowich, J. A., and J. W. Nicholas. In press. Oregon’s first century of hatchery intervention in salmon production: Evolution of the hatchery program, legacy of a utilitarian philosophy, and management recommendations. In proceedings of the international Symposium on Biological Interactions of Enhanced and Wild Salmonids, 17-20 June, 1991 Nanimo, B.C. (Available from ODFE, P.O. Box 59, Portland, OR 97207.
McMahan, T.E., and L.B. Holtby. 1992 Behavior, habitat use, and movements of coho salmon (Oncorhyncus kisutch) smolts during seaward migration. Can. J. Fish. Aquat. Sci. 49:1478-1485.
MacLean and Evans. 1981. The Stock Concept, Discreetness of Fish Stocks and Fisheries Management. Canadian Journal of Fisheries and Aquatic Sciences; 38: 1889-1898.
Miller, W. H. 1990. Analysis of salmon and steelhead supplementation. Report to Dworshak Fish. Assist. Off., U.S. Fish Wild;. Serv. Tech. Rep. 1990, Contract DEA179-88bp92663, Proj. 88-100, 202 p. plus appendices.
Mills, T.J. 1983. Utilization of the Eel River Tributary Streams by Anadromous Salmonids, Appendix H. In: F. L. Reynolds, edition, 1983 Status Report of California Wild and Scenic Rivers: Salmon and Steelhead Fisheries. California Department of Fish and Game; 57 pages.
Moyle, Peter B. Inland Fishes of California 1976 (p.117-119)
Murphy, M.L. 1995. Forestry impacts on freshwater habitat of anadromous salmonids in the Pacific Northwest and Alaska- requirements for protection and restoration. U.S. Dep. Comm., NOAA Coastal Ocean Office, Silver Springs, MD, 156 p.
National Marine Fisheries Service Biological Review Team- West Coast coho salmon included Peggy Busby, Robert Emmett, Dr. Jeffery Hard, Dr. Robert Iwamoto, D. Orlay Johnson, Dr. Robert Kope, Dr. Conrad Manken, Gene Mathews, Dr. Michael Schwiewe, David Teel, Dr. Thomas Wainwright, William Wakatz, Dr. Robin Waples, Laurie Weitcamp, Dr. John Williams, and Dr. Gary Winans, (NWFSC) and Dr. Peter Williams and Gregory Bryant (SWFSC) Status Review Update for Coho Salmon from Oregon and Northern California 1997.
Nehlsen, W.; J.E> Williams and J.A. Lichatowich. 1991. Pacific Salmon at the Crossroads: Stocks at Risk from California, Oregon, Idaho, and Washington. Jack E. Williams, Division of Wildlife and Fisheries, U.S. Bureau of Land Management, 1849 C Street, NW Washington, DC 20240.
Nehlsen, W. ; J.E. Williams and Lichatowich. 1991. Pacific Salmon at the Crossroads; West Coast Stocks of Salmon, Steelhead, and Sea-Run Cutthroat Trout at Risk. Fisheries (Bethesda) ; 16: 4-21.
Nickleson, T.E., J. W. Nicholas, A. M. McGie, R.B. Lindsay, D. L. Bottom, R. J. Kaiser, and S.E. Jacobs. 1992. Status of anadromous salmonids in Oregon coastal basins. OR Department of Fish Wildl., Res. Dev. Sect. And Ocean Salmon Manage., 83 p. (available from Oregon Department of Fish and Wildlife, P.O. Box 59 Portland OR 97207.)
Nickelson, T. E. , M. F. Solazzi, and S. L. Johnson. 1986. Use of hatchery presmolts to rebuild wild populations in Oregon coastal streams. Can. J. fish. Aquat. Sci. 43:2443-2449.
Pacific Fisheries Management Council (PFMC). Review of Ocean Salmon Fisheries. 1996, 1997.
Pacific States Marine Fisheries Commission (PSMFC). 1994. Regional Mark Information System (RMIS) Coded-wire tag on-line database. (Available from Pacific States Marine Fisheries Commission, 45 SE 82nd Dr., Suite 100, Gladstone, OR 97027-2522.
Pearcy, W. G. 1992. Ocean ecology of North Pacific salmonids. Univ. Washington Press, Seattle, 179p.
Pearcy, W. G., and J. P. Fisher. 1988. Migrations of coho salmon during their first summer in the ocean. Fish, Bull. U.S. 86(2):173-186.
Ratliff, D. E. 1983. Ceratomxya shasta: Longevity, distribution, timing ,and abundance of the infective stage in Oregon. Can. Journal of Fish. Aquat. Sci. 40:1622-1632.
Ricker, W.E. 1972. Heredity and Environmental Factors affecting Certain Salmonid Populations. Pages 19-160 in R.C. Simon, P.A. Larkins, editors. The stock Concept in Pacific Salmon. University of British Colombia, Vancouver.
Reeves, G. H., F. H. Everest, and T. E. Nickelson. 1989. Identification of physical habitats limiting the production of coho salmon in western Oregon and Washington. U. S. Dep. Agric. Forest Serv., Pac. Northwest. Res. Stn. Portland, OR, 18p.
Ratliff, D.E. 1983. Ceratmyxa shasta: Longevity, distribution, timing, and abundance of the infective stage in central Oregon. Can J. Fish. Aquat. Sci. 40:1622-1632.
Sandercock, F. K. 1991. Life History of Coho Salmon, “Oncorhynchus kisutch”. Pages 397-445 in C. Groot and Margolis, editions. Pacific salmon life histories. University of British Colombia Press, Vancouver, British Colombia.
Sedell, J. R., and J. L. Froggatt. 1984. Importance of streamside forests to large rivers: the isolation of the Willamette River, Oregon, USA., from its floodplain by snagging and streamside forest removal. Verh. Internat. Limnol. 22:1828-1834.
Sedell, J.R., and K. J. Luchessa. 1982. Using the historical record as an aid to salmonid habitat enhancement. In N. B. Armantrout (editor), Acquisition and utilization of the aquatic habitat inventory information., p. 210-222.
Shapavolov, L. and A. C. Taft. 1954. The Life histories of the Steelhead Rainbow Trout ( Salmo gairdneri gairdneri) and Silver Salmon (Oncorhyncus kisutch). California Department of Fish and Game Fish Bulletin 98; 275 pages
Smith, Jerry J. 1990. The Effects of Sand Bar Formation and Inflows on Aquatic Habitat and Fish Utilization in Pescadero, San Gregorio, Waddell, and Pomponio, Creek Estuary/Lagoon System, 1985-1989; 102 pages.
Status Review Update for Coho Salmon from the Oregon and Northern California Coasts. Prepared by the West Coast Salmon Biological Review Team. March 28, 1997
Steward, C. R. and T.C. Bjornn. 1990. Supplementation of salmon and steelhead stocks with hatchery fish: A synthesis of published literature. U.S. Dep. Energy, Bonneville Power Administration, Fish and Wildlife, P.O. Box 3621, Portland, OR 97208.)
U. S. Fish and Wildlife Service. 1979. Klamath River Fisheries Investigations: Progress, Problems and Prospects. Annual Report, Arcata, California, November 21, 1979; 49 pages.
Waples, Robin and D.F. Teel . 1990. Conservation Genetics of Pacific Salmon I. Temporal Changes of All elec Frequency. Biol. Conserv.; 4: 144-156.