Before the treaties were signed, the tribes enjoyed the bounty of a land blessed with abundant resources upon which their culture depended. Some of the most important were the rich assemblage of anadromous fish populations in the rivers of the basin. Salmon populations were numerous and represented five species: chinook (Oncorhynchus tshawytscha), coho (O. kisutch), steelhead and rainbow (O. mykiss), sockeye and kokanee (O. nerka), and chum (O. keta). The Columbia Basin supported the Pacific's largest run of chinook, or king salmon, known to weigh as much as 125 pounds and measure more than five feet in length (Brown 1982). Other important native anadromous species included the lamprey (Lampetra tridentata) and white sturgeon (Acipenser transmontanus). Other fish species were also utilized.
This lifestyle, and the fisheries upon which it depended, were reserved by the tribes when they signed treaties with the United States. While yielding control of vast tracts of land, the tribes retained ownership of the salmon runs so vital to their culture. These treaties, though challenged often, have been reaffirmed repeatedly as legally binding documents in numerous court decisions.
Now the salmon are disappearing. The eels cannot be found in much of their former territory. Sturgeon are less abundant and populations have become fragmented. What could not be done legally in the past, is now being done in practice by the widespread mismanagement of natural resources. The treaties are being ignored and broken.
Current Status of Anadromous Fish in the Columbia River Basin
As long as the resources on which salmon, Pacific lamprey, and white sturgeon depended were maintained--i.e., the cool, clear waters, complex stream systems, and the interconnectedness of the parts--these anadromous species thrived and enabled the Indians of the Columbia River Basin to prosper. As described below, much of this has changed drastically in a relatively short time.
Salmon
During the last century in the Columbia River Basin, salmon runs, once the largest in the world, have declined over 90%. The 7.4-12.5 million average annual number of fish above Bonneville Dam has dropped to 600,000. Of these, approximately 350,000 are produced in hatcheries (ODFW and WDFW 1995).
Spawning salmon populations in the Columbia River produced
enough offspring historically to replace themselves fivefold. However,
the magnitude of cumulative mortality impacts is now so large that these
species are biologically unable to compensate, and populations cannot replace
themselves on a consistent basis. Many salmon stocks have been extirpated
from major portions of their historical range (Table
3.1 ). Furthermore, the majority of Columbia River
Basin natural salmon populations are on a downward trend, and many are
approaching extirpation (CRITFC 1992a). Snake River chinook and sockeye
have been listed under the federal Endangered Species Act. What is considered
to be a local population today may simply be a fragment of what was historically
a large, continuous population. Declines in natural production are indicated
generally by declining numbers of redds in tributary streams.
Pacific Lamprey
Since the completion of the hydropower system in the Columbia Basin, numbers of Pacific lamprey have declined dramatically compared with historical levels of abundance and distribution. For example, the name of the ancestral Nez Perce village Hasotino (located on present day Asotin Creek), means "the great eel fishery" (Spiden 1908). Counts at Bonneville Dam have exceeded 300,000 lamprey in the past (Starke and Dalen 1995). These counts include only those fish that passed the counting station during the 18 hours of counting, i.e., they do not include lamprey that passed through navigation locks or at night. Counts of Pacific lamprey returning over lower Snake River dams were in the thousands in 1969, but declined to hundreds by 1978 (Hammond 1979) and numbered only 40 individuals total in 1993 (L. Basham, Fish Passage Center, Portland, personal communication 1994). Although tribal proposals for lamprey recovery have been submitted since 1991, lamprey were not considered high priority when compared to salmon stocks. Recently, the CTUIR have received funding to research lamprey declines in the tribe's ceded land, as well as address passage concerns at the Columbia Basin mainstem dams.
White Sturgeon
Colonization of the Columbia Basin by white settlers profoundly affected the sturgeon populations and habitat. Like other North American sturgeon populations, Columbia Basin white sturgeon were commercially exploited for their flesh and eggs (Bajkov 1949; Smith 1990). Prior to purposeful commercial harvest, vast numbers were simply killed because they damaged gear of commercial salmon fishers. Once a market was established, white sturgeon were commercially extirpated from the lower Columbia River by 1899 (Craig and Hacker 1940; Galbreath 1985).
White sturgeon populations today are considerably reduced, even though they are still found throughout much of their historical habitat (PSMFC 1992). Hydroelectric development on the Columbia and Snake rivers has created a series of reservoirs, which trapped and separated the single historical white sturgeon population into a number of separate land-locked (reservoir) populations (North et al. 1993). Populations above Bonneville Dam are characterized by the following river reaches: (1) Lower Columbia River above Bonneville Dam, (2) Mid-Columbia River, and (3) Lower Snake River.
Past attempts to maintain or restore declining salmon numbers all assumed that technology alone could "fix" the damage caused by disregard for the underlying, interconnected processes of nature which gave rise to and sustained the great salmon runs of the Columbia Basin. Simple solutions could not replace the complexity of nature; naturally these attempts failed.
As the Columbia Basin was progressively developed to reap the full benefits of hydropower, agriculture, forestry, mining, and urbanization, periodic attempts were made to ameliorate the resultant declines in salmon production. Dams were equipped with fish ladders for returning adult salmon and bypass facilities for outmigrating smolts. Large scale hatchery programs were funded to replace production lost from areas flooded or blocked by dams. Screens were required on irrigation diversions. Laws were promulgated, but not enforced, to restore and maintain water quality and quantity and to protect ecosystems on which imperiled species depended for survival. Additional water was spilled to assist smolts over dams. Smolts were collected and barged around dams. Billions of dollars have been spent over the years to maintain salmon production in the Columbia River Basin.
Nevertheless all these efforts have proven inadequate to maintain anadromous fish numbers and productivity. The lesson is inescapable: technical solutions alone cannot maintain salmon populations in the face of massive disregard for, and destruction of, the ecosystems within which salmon evolved. If the remaining salmon are to be preserved and restored to tribal goal levels, the natural structure and functions of the salmon's ecosystems, combined with wise use of technical expertise, must be foremost. Accomplishing this requires a common understanding of habitat requirements of salmon relative to the present conditions they face in the Columbia River Basin.
The various salmon species pass through vast expanses of geography during the course of their life cycles (Figures 3.1 and 3.2). A typical salmon starts life as an egg in the gravel of a stream, often hundreds of miles from the Pacific Ocean where they graze and gain the majority of their adult size. Between stream bed and ocean, salmon need a wide variety of quality habitats in order to grow and develop from a small freshwater fish into a large marine feeder. Because salmon depend on the health of several different ecosystems for their survival, and because so many different cultures in the Pacific Northwest hold them in such high esteem, the salmon are both a bellweather and a lightening rod in the struggle which now rages to retain the ecological and cultural integrity of this vast region. The biological context for the tribal recovery plan consists of the habitat within which the salmon live, the rich collection of biological strategies which the salmon have evolved to flourish in these habitats, and the connections of land, water, plants, and animals which scientists call the ecosystem.
Habitat of Anadromous Fish in the Columbia River Basin
The Columbia River Basin
The Columbia River Basin encompasses nearly 260,000 square miles. The river drains most of Washington and Idaho, half of Oregon, Montana west of the Continental Divide, small portions of Wyoming, Utah, and Nevada, and 40,000 square miles of British Columbia. The 1,214-mile-long river begins at Columbia Lake, high in the Rocky Mountains of British Columbia, Canada. It initially flows northwest for 218 miles, then turns south for the next 280 miles. After crossing the United States-Canada border into northeastern Washington, the Columbia River flows south, west, and south again across central Washington in a broad curve commonly known as "Big Bend." Just below the mouth of the Snake River, the Columbia turns west for its remaining 210 miles. It cuts through the heart of the Cascade Mountains, thus forming the Columbia River Gorge; flows into the Columbia River Estuary; and finally empties into the Paci-fic Ocean at Astoria, Oregon.
The Columbia's largest tributary, the Snake River, begins in Wyoming, Utah, and Nevada and flows westward through the southern part of Idaho. It then turns north and forms the boundary of today's Oregon and Idaho. Near Lewiston, Idaho, the Snake River turns west-ward and flows through eastern Washington until it enters the Columbia River near Pasco, Washington.
The land mass over which much of the Columbia River now flows did not exist until the Tertiary period (30-60 million years ago). Although the Columbia River Basin is relatively young in terms of geologic time, it comprises portions of eight physiographic provinces: Northern Rocky Mountains, Columbia Mountains/Okanogan Highlands, Cascade Mountains, Columbia Plateau/Columbia Basalt Plain, Snake River Plain, Blue Mountains, Willamette Lowland, and Coast Range. This rich variety of landforms has been determined by geology, past and present climate, and such processes as erosion and sedimentation.
Regional differences in climate and elevation have created a unique range of environmental conditions. For example, annual precipitation averages 10-20 inches in central Washington, eastern Oregon, and southern Idaho, and 40-140 inches between the Columbia River Gorge and the mouth of the Columbia River.
Periodic massive disturbances are an integral part of the natural environment that forms the basis for the ecology and evolution of anadromous fish in the Columbia River Basin. Natural events of large magnitude, such as the Mount St. Helens eruption which impacted steelhead runs on the Toutle River in Washington, have often occurred in localized regions.
Climatic cycles such as El Niño, which results in below-average snowpack and rainfall, are a part of the North Pacific region to which the salmon have adapted. The distribution pattern of warm and cold ocean currents and associated nutrient upwellings, which affect salmon production, are also cyclical in nature. Salmon populations (coho and tule fall chinook) which rear primarily south of Vancouver Island appear to have lower natural survival during El Niño events; whereas populations (bright fall chinook, upper Columbia summer chinook, and sockeye) that rear in the Gulf of Alaska seem to have better than average survival (PFMC 1985).
Columbia River Subbasins
Numerous subbasins compose the Columbia River Basin east of the Cascade Range. Watersheds in these subbasins share many hydrologic features such as precipitation predominantly in the form of snow, relatively stable peak flows during spring as snow melts, and low flows during dry summers, punctuated by thunderstorms. The seasonal spring peak flows and summer low flows in this geographic region are a product of regional climate. Hydrologic features of streams in these watersheds result from the interaction of the seasonal precipitation with the soils, geology, vegetation, terrain, and other climatic features of the region. Streamflow characteristics are increasingly influenced by a combination of land and water uses, such as road building, vegetation conversions, and irrigation. Salmon have evolved races and life history characteristics to linked to dominant features of their habitats, such as streamflow and water temperature patterns. For example, chinook have adapted to high summer water temperatures, low summer flows, decreasing fall water temperatures, and increasing flows in producing spring, summer, and fall races with various life history features by adjusting upstream and downstream migration timing, rearing time spent in freshwater, size of streams used for spawning and rearing, and other features.
Salmonids and Pacific lamprey, similar to other anadromous species, have evolved with high spring flows as a mechanism to facilitate passage to the ocean for the adult phase of the life cycle. Although the frequency and magnitude of rainfall-dominated stream peak flows in any part of the Columbia River Basin is a function of the long-term climatic regime of that locale, their effects in stream channels (e.g., sediment loads, and frequency and intensity of channel scouring) vary according to topographic and geologic structure of the watersheds and channel morphology. Soils and topography also determine the inherent ability of a given watershed to provide stable, cool summer flows during the low-flow period.
The primary subbasins of interest to the Columbia River treaty tribes are those located upstream from Bonneville Dam. The tribes share management responsibilities in these basins with state and federal governments. These subbasins (Figure 3.3; descriptions provided in Appendix A) are numbered from 1 to 20, beginning at the point furthest downstream, in the order in which their major tributaries enter the Columbia, and then the Snake river mainstems. The number of stream miles historically utilized by salmon species in each subbasin compared to the amount of habitat currently suitable for salmon species is provided in Table 3.2 .
The Columbia River Estuary
The Columbia River Estuary is a variable mixture of fresh and salt water and sediments at the coastal end of the Columbia River Basin. The estuary, which now has a surface area of approximately 41,200 hectares (101,750 acres), has been formed over geologic time by the forces of volcanism, glaciation, hydrology, and the erosion and deposition of sediments. Circulation of sediments and cycling of nutrients within the estuary are driven by river hydrology and coastal oceanography. Sea levels have risen since the late Pleistocene, with the result that coarse and fine sands have been deposited in submerged river channels.
The Pacific Ocean
Three major current systems in the North Pacific Ocean affect Columbia River Basin salmon: the Alaska Gyre, Subarctic Current, and California Current (Ware and Thomson 1991). Upwelling events off the Oregon and Washington coasts are correlated with coho survival rates (Nickelson 1986). In addition, periodic El Niño events bring in warmer water with fewer nutrients, and negatively affect salmon production (Pearcy 1992).
Environmental variation in the ocean has always been a feature of the salmon life cycle. Salmon have been able to survive through these variations by natural compensatory survival mechanisms that act as a buffer (Foerster 1968). Increased stress in other aspects of the life cycle has reduced buffering capacity and the salmon's ability to cope with environmental variation. Fluctuations in the ocean environment must be evaluated in order to understand the entire life cycle. Indices of ocean surface temperature, coastal upwelling, and weather patterns provide insight to changes in ocean productivity. Ocean growth patterns as recorded in salmon scales will provide biological measurements of the changes in ocean productivity. However, the best way to restore the buffering mechanisms and thus increase the probability of long-term survival of naturally reproducing populations is to reduce the stresses in the other stages of the life cycle.
Adaptation of Anadromous Species
Anadromous fish have developed a complex set of behaviors that are useful in adapting to change in the Columbia River Basin, as well as to the individual watershed conditions under which they have evolved. The salmon's life history can be described as a series of biological functions (e.g., spawning, feeding, and migration) that are carried out in a series of temporally and geographically connected environments (Thompson 1959; Rothschild 1986). Within each of these physical environments, individual fish from a single population may exhibit different patterns of use of available habitat to express different biological functions, such as feeding, resting, and avoiding predators. A population may produce some fish which smolt in their first year and others which smolt in their second or even third year of life. Salmon parr may use both upper and lower portions of watersheds to rear prior to smolting. These kinds of life stage-habitat interactions are more fully discussed by RASP (1992b).
The anadromous life cycle and the strong tendency for homing to streams and rivers of origin have contributed to the evolution of numerous stocks of salmon (Groot and Margolis 1991).
The evolution of different life history types has occurred in response to differences in individual streams to which the animals have homed. Furthermore, salmon have the capacity to stray and thus colonize (or recolonize) new areas after disturbance. Thus, salmon have inherent resilience as a result of their anadromy, life span, and life history characteristics that help compensate for environmental fluctuations in freshwater habitats.
Such characteristics take advantage of spatial and seasonal variations in resource availability, lessen the risk that all populations would be extirpated by a single disturbance, or would react identically to the same set of environmental conditions (Reiman and McIntyre 1993). This has helped to buffer salmon populations against catastrophes (Steward 1993; Stearns 1976; Wootton 1990; Healey 1991). For example, large numbers of Toutle River fish strayed to other streams and fish migrations were delayed after the 1980 Mount St. Helens eruption (Martin et al. 1984). Subsequently, recovering vegetation helped to create the physical, chemical, and trophic base necessary for the recolonization of salmon stocks impacted by Mount St. Helens eruptions (Martin et al. 1986; Bisson et al. 1988). The behaviors which are important in colonization and recolonization are influenced substantially by habitat quality and quantity. For example, chinook introduced to New Zealand in 1905 from a single population in California have successfully colonized different river basins, and now exhibit differences in life history traits which could be the result of localized environmental factors.
Information about homing and straying behaviors is not available for Pacific lamprey (Beamish 1980). Because lamprey are a primitive species with fossil records dating back nearly 300 million years (Bardack and Zangerl 1968) and wide distribution throughout the northern hemisphere, they have no doubt been resilient to changing environmental conditions.
Anadromous Fish of the Columbia River Basin
The anadromous species of particular interest to the Columbia River treaty tribes are salmon and steelhead, Pacific lamprey, and white sturgeon. These species share a common anadromous life cycle, yet differ in specific life history details and requirements.
The evidence available suggests that salmonids appeared between 20 and 100 million years ago, and have evolved in the Pacific Northwest over the last 10 cycles of glaciation (Stearly 1992). There are five species of salmon prevalent in the Columbia River Basin. These include chinook (Oncorhynchus tshawytscha), coho (O. kisutch), sockeye and kokanee (O. nerka), chum (O. keta), and steelhead and rainbow (O. mykiss). Chinook, coho, sockeye, chum, and steelhead are anadromous species (Figure 3.2); kokanee and rainbow do not migrate to sea prior to sexual maturity. Adults of all Columbia River salmon species die after spawning, except for steelhead which may spawn more than once. Predominant life history characteristics, such as areas required for spawning and rearing, timing of adult migration back to spawning grounds, and number of eggs produced for each of these species are provided in Table 3.3.
All of the salmon species, including steelhead, may be divided into three basic life history types for the purposes of description. The life history types of salmon are stream, lake, and ocean, referring to where the young reside at the end of the first year of life. Chum salmon and the fall race of chinook salmon are ocean type, in which the young enter salt water some time during the year following their deposition as eggs. A typical ocean type, taking the fall chinook salmon for example, starts life as an egg in the gravel of the Columbia River above Richland, Washington in October, emerges from its gravel nursery in February or March, moves down river, and enters the Columbia River estuary, in the vacinity of Astoria, Oregon from June through September. The typically ocean type fall chinook spends its second, third, and sometimes fourth, winters of life in the ocean and returns to spawn on its fourth or fifth birthday.
The stream and lake types of salmon have the same basic life cycle, except that the second winter of life is spent in stream or lake, respectively. Coho salmon, the spring race of chinook salmon, and steelhead are all stream types, while sockeye salmon are lake types. As is the case with any teaching model, this simplified life history explanation cannot capture the rich diversity of ages and types which are present in most healthy salmon populations. For example, some chinook populations may have both stream and ocean types within the same race. But the basic concept is that most biological species (e.g chinook, coho, sockeye, chum, steelhead) exhibit a diversity of strategies which allow them to adapt to different biological and physical circumstances, and these strategies are shared across species.
Life history strategies of salmon are also identified by the season of the year in which the adults return to freshwater on their way to the spawning grounds. Prior to the entry of western culture in the early 19th century, adult salmon were likely to have entered the Columbia during all seasons of the year. It is probable that human development, in conjunction with harvest, acted to reduce the number of life history types of salmon in the Columbia River Basin; hence, there are now times of the year when practically no adult salmon can be found in the mainstem Columbia River.
Salmon once occupied nearly 13,000 miles of Columbia River
Basin streams and rivers. According to conservative estimates, the Columbia
River Basin, both above and below Bonneville Dam, once produced between
10 and 16 million salmon annually (NPPC 1986). Historically, salmon runs
in the Columbia River Basin consisted of 16% fall chinook, 12% spring chinook,
30% summer chinook, 11% coho, 23% sockeye, 8% steelhead, and less than
1% chum. These runs extended from March through October generally (Figure
3.4), though steelhead runs extended through the winter.
Habitat Requirements of Salmon
Tributary
Tributary habitat for salmon must be available for adult migration from the ocean, as well as holding, spawning, egg incubation, juvenile rearing and overwintering, and smolt migration to the ocean. Salmon, in general, spawn in gravel beds in rivers, streams, or lake shores in late summer and early winter. Watersheds tributary to the mainstem Columbia and Snake rivers are the primary nursery and rearing areas. Juvenile fish production is a function of the quantity and quality of available habitat. Factors that contribute to high-quality salmon habitat include: well-oxygenated cold water; spawning and rearing areas with low levels of surface fine sediments in the stream bed; abundant amounts of large woody debris in the channel; frequent large pools greater than 1 meter in depth; off-channel aquatic habitats fed by groundwater; stable stream beds; banks that overhang stream margins; and natural levels and types of riparian vegetation occupying the floodplain area.
Deep pools in streams supplied by cool groundwater shelter returning adults until they are ready to spawn. Clean, stable gravel beds with continuous subsurface flow protect developing
eggs through the winter months. As juveniles hatch, emerge from the gravel, and grow, they use a succession of habitat types, but prefer areas with both protective cover and access to a reliable food supply. Intact adjacent wetlands and subsurface aquifers cool and maintain flows during hot summer periods of reduced rainfall. Undisturbed floodplains with numerous side channels expand the amount of available rearing area and provide shelter during cold winter months.
Mainstem
Mainstem Columbia and Snake rivers provide critical adult holding, spawning, incubation, juvenile rearing habitat, and are migration corridors for adults and juveniles. Over time, the Columbia basin streamflow has largely defined freshwater salmon productivity and has a major influence on ocean survival, which is largely dictated by the quantity and quality of smolts that enter and mature to adults in the ocean. Successful completion of each salmon life stage within the mainstem is dependent on critical physical and chemical habitat factors, including hydrological regimes driven by routine meteorological sequences, maintenance of hydraulic geometry factors, and continual organic and inorganic nutrient cycling (Hynes 1970; Heede and Rinne 1990).
Specific requirements include temperature ranges from 7.2-15.6°C (EPA et al. 1971), dissolved oxygen normally saturated at levels greater than 7 mg/l (Reiser and Bjornn 1979), turbidity ranges from 10-25 nephelometric units (Lloyd 1987) and nitrate-nitrogen ranges from 0.02-0.03 mg/l. Also critical for different life stages are diversity in river velocities, which range from 15-100 cm/s, and diversity in substrate size and river depth (Groot and Margolis 1991).
Large, small, and particulate organic matter provide structure and diversity to channel morphology (Maser et al. 1988). Large debris traps organic and inorganic sediment, which provide habitat diversity for salmon and niches for primary and secondary producers (Lisle 1986). In order for salmon populations to proliferate, diversity in secondary production is important. Rearing salmon depend upon different populations of macroinvertebrates at different times (Waters 1969) and drift insects provide high levels of nutrient levels necessary for successful growth and migration.
Estuary
Estuary residence is crucial for rearing juvenile salmonids and for adults preparing to migrate upstream (Healey 1982; McDonald et al. 1987; Wissmar and Simenstad 1988). Juvenile salmon spend days or weeks in the estuary acclimating to increasing concentrations of salt and adjusting to new food supplies. During this period they use aquatic vegetation and channel structures as cover from predators. Adults use estuary areas to readjust their body chemistry to a freshwater environment.
Ocean
An area of marine waters off the mouth of the estuary has been identified as an important transition habitat used by juveniles before they migrate further into the ocean (Figure 3.2). All free-ranging anadromous fish use the ocean as a feeding ground, where they grow to maturity. The ocean habitat provides feeding opportunities and conditions necessary for salmon to attain adulthood. Salmon are generally distributed over the northern Pacific Ocean and Bering Sea (some populations or subpopulations remain in coastal waters or freshwater), where they stay for 1-7 years until they mature. Growth and mortality rates for populations caught in ocean fisheries (e.g., fall chinook and coho) are reasonably well known (Groot and Margolis 1991). Less is known, however, about spring chinook, sockeye, and steelhead.
Pacific lamprey or "eel" are restricted in North America to the Pacific Coast and coastal islands from the Aleutians to Baja, California. Pacific lamprey were once widely distributed throughout the Columbia Basin in Oregon, Washington, and Idaho (Kan 1975; Wydoski and Whitney 1979). Distribution was likely a function of access to suitable spawning and rearing areas (Kan 1975).
Size estimates of predevelopment populations of Pacific lamprey are not available, but some counts at Bonneville Dam have exceeded 300,000 lamprey annually (Starke and Dalen 1995). These counts include only those fish that passed the counting station during the 18 hours of counting, i.e., they do not include lamprey that passed through navigation locks or at night. Night time passage can be equal to or greater than the numbers migrating during daylight hours. Data from the commercial harvest of Pacific lamprey at Willamette Falls indicate that 116.6 tons on average were harvested from 1943 to 1949 (Mattson 1949). An indication of predevelopment abundance of Pacific lamprey in the Snake River Basin is reflected in the name of the ancestral Nez Perce village, Hasotino, (near present day Asotin Creek) which means "the great eel fishery" (Spiden 1908).
Habitat Requirements of Pacific Lamprey
Tributary
The life cycle of Pacific lamprey is similar to that of salmonids (Figure 3.2). Although they reach the spawning grounds in mid-summer (Kan 1975; Beamish 1980), Pacific lamprey generally spawn the following spring. Thus, adult lamprey spend approximately 1 year in freshwater. Spawning generally occurs in small tributary streams, where both sexes construct a crude redd (Scott and Crossman 1973), generally located in the center of the stream near the tailout of a pool, and immediately upstream of shoreline depositional areas (Beamish 1980). Mating is repeated several times in the redd, with each mating followed by actions that move substrate over newly laid eggs. Water temperatures of 10-15oC have been measured in Clear Creek, a tributary of the John Day River, during spawning (Kan 1975). Adults die soon afterward and provide valuable nutrients to small tributaries where salmon fry rear (Kan 1975).
Eggs typically hatch into ammocoetes in less than 2 weeks; these newly hatched larvae, which are filter feeders, then drift downstream and bury themselves in silt, mud, or fine gravel along the margins and backwaters of streams and rivers (Scott and Crossman 1973; Hammond 1979). Ammocoetes generally spend 5-6 years in freshwater (Scott and Crossman 1973). In the fall of their last year, they metamorphose into macrophthalmia, which resemble the adult form. This transformation process is generally completed by early winter.
Mainstem
Downstream migration of macrophthalmia appears to be stimulated by and dependent on late winter and early spring floods (Hammond 1979). Because they are not strong swimmers, lamprey appear to be dependent on spring flows to carry them to the ocean (Kan 1975; Beamish 1980). The upstream, spawning migration of adults generally begins in early spring. Adult lamprey use the mainstem in returning to their spawning grounds, but do not feed during this period. They were once an important food source for juvenile and adult sturgeon in the mainstem (Kan 1975).
Estuary
Pacific lamprey appear to travel directly into the open ocean, rather than feed in the estuary of nearby coastal waters (Kan 1975; Beamish 1980), as do some other lamprey species.
Ocean
Pacific lamprey rear in the ocean habitat for up to 3.5 years (Beamish 1980), and range in excess of 100 km offshore, often in areas of considerable depth (up to 800 m) (Kan 1975; Beamish 1980; Figure 3.2). Adult lamprey in the ocean are parasitic on many fish species, including salmon. They attach themselves to fish and other animals and feed on blood and body fluids through a hole rasped in the flesh of the host.
White sturgeon (Acipenser transmontanus) are a large, long-lived species, commonly reaching 70 years of age and weighing in excess of 1,000 pounds (Bajkov 1949; Scott and Crossman 1973; Beamesderfer et al. 1995). Today the only population in the Columbia Basin that migrates to the ocean is downstream from Bonneville Dam. Dams have effectively trapped and separated the historical single population of white sturgeon into a number of separate reservoir populations, and thus created a number of functionally isolated nonanadromous populations upstream from Bonneville Dam (North et al. 1993). Remaining populations are thus considered to be landlocked or resident in the reservoirs upstream from Bonneville. They do not migrate to the ocean. Rather, they complete their life cycle in the mainstem Columbia and Snake rivers (Figure 3.2).
Historically abundant populations of white sturgeon occupied the Columbia Basin, and millions of pounds were harvested commercially during the turn of the century (Craig and Hacker 1940; Galbreath 1985). Prior to hydroelectric development white sturgeon were semi-anadromous throughout much of the Columbia and Snake river basins, with the exception of the geographically isolated Kootenai River population (Northcote 1973).
Habitat requirements of White Sturgeon
Mainstem
White sturgeon spawn in areas of high water velocities (greater than 0.8 m/s) over areas of bedrock, rubble, and large boulders (Parsley et al. 1993). Historical spawning areas were probably located at the downstream end of falls, cascades, and rapids. Today these conditions are met in the tailrace areas immediately downstream from hydroelectric dams. Sturgeon begin spawning when water temperatures are 10-18oC, with optimal temperatures between 13 and 15oC. White sturgeon are broadcast spawners, and probably spawn in small groups consisting of a single female and several males. Newly laid eggs are extremely adhesive, and drift to the river bottom where they adhere to bottom substrates. Hatching generally occurs within 7-12 days (Miller and Beckman 1993). Eggs can be killed if temperatures rise above 18oC. Newly hatched white sturgeon have an internal yolk sac. These yolk sac larvae disperse by swimming vertically into the current and drifting downstream. The larvae metamorphose within a 25- to 30-day period, after which they grow rapidly. Females require an average of 23 years before they spawn, with males maturing earlier. These fish continue to grow throughout their life cycles.
Estuary
Although reservoir populations do not have access to the Columbia River Estuary, the estuary is an important rearing area for juvenile and adult white sturgeon downstream from Bonneville Dam (DeVore et al. 1995). The estuary provides access to the ocean, other drainages, and a variety of seasonally abundant prey. In addition, the estuary facilitated restoration of white sturgeon after commercial fisheries decimated populations at the turn of the century (McCabe and Tracy 1993; DeVore et al. 1995). Salinities greater than 16 parts per thousand are known to be lethal to larvae and fry (Brannon et al. 1985).
Ocean
White sturgeon use the ocean for rearing and as a migration route to other drainages along the Pacific Coast (Scott and Crossman 1973; DeVore and Grimes 1993). White sturgeon residing in the ocean have been found to be in superior condition relative to those in the estuary or freshwater (DeVore and Grimes 1993).