Fish-Movement Ecology in High-Gradient Headwater 

Streams: Its Relevance to Fish Passage Restoration 

Through Stream Culvert Barriers 

Hoffman, R., and Dunham, J. 

Open-File Report 2007–1140 

U.S. Department of the Interior 

U.S. Geological Survey 
ii

U.S. Department of the Interior 

DIRK KEMPTHORNE, Secretary 

U.S. Geological Survey 

Mark D. Myers, Director 

U.S. Geological Survey, Reston, Virginia 2007 

Revised and reprinted: 2007 

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Suggested citation: 

Hoffman, R., and Dunham, J., 2007, Fish Movement Ecology in High Gradient Headwater Streams: Its 

Relevance to Fish Passage Restoration Through Stream Culvert Barriers: U.S. Geological Survey, OFR 2007-

1140, p. 40. 

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iii

Contents 

Contents ..............................................................................................................................................................................iii

Executive Summary............................................................................................................................................................1

Introduction .........................................................................................................................................................................4

General Characteristics of Fish Movement ...................................................................................................................5

Station Keeping Movements and Activities...............................................................................................................5

Ranging Movements and Activities.............................................................................................................................7

Migration..........................................................................................................................................................................7

Accidental Displacement..............................................................................................................................................7

Other Definitions of Migration and Dispersal............................................................................................................8

Characteristics of Salmonid Movement in Headwater Streams ...............................................................................8

Distribution of Salmonids in Headwater Streams ......................................................................................................10

Impacts of Human-Placed Barriers on Fish Populations ..........................................................................................11

Culverts and Fish Passage..............................................................................................................................................13

Information needs for fish passage restoration through culverts...........................................................................13

Identifying Key Biological Responses of Native Populations to Barriers ..........................................................15

Threats of Invasion by Nonnative Fishes .................................................................................................................15

Relevance for Fish Passage Restoration..................................................................................................................15

Relevance of Barriers in Intermittent Streams .......................................................................................................17

Conclusions .......................................................................................................................................................................17

Acknowledgements .........................................................................................................................................................18

References.........................................................................................................................................................................19

Appendix I: .........................................................................................................................................................................29

Appendix II:........................................................................................................................................................................33

Tables 

Table 1: Characteristics of movement categories and activities (after Kennedy 1985, Lidicker and Stenseth 

1992, and Dingle 1996)..........................................................................................................................................6 

Table 2: General factors affecting the upstream movement of fish through culverts .........................................14
1

Fish-Movement Ecology in High-Gradient 

Headwater Streams: Its Relevance to Fish 

Passage Restoration Through Stream Culvert 

Barriers 

Hoffman, R., and Dunham, J. 

Executive Summary 

Restoration of fish passage through culvert barriers has emerged as a major issue 

in the Pacific Northwest and nationwide. The problem has many dimensions, including 

the huge number of potential barriers, uncertainty about which structures are actually 

barriers, the benefits and risks involved with restoration, and the financial costs and 

timelines. This report attempts to address what we call “thinking outside of the pipe” in 

terms of fish passage information needs. This means understanding the value of each 

potential passage restoration project in the context of other possible projects, and to view 

individual restoration projects within a larger landscape of habitats and population 

processes. 

In this report we provide a brief review of some essential characteristics of animal 

movement and examples from a focal group of fishes in Washington State: salmon, trout, 

and char. While several other fishes and many other species use streams where culvert 

passage barriers may occur, it is the salmonids that are by far the most widespread and in 

most cases extending furthest into the headwaters of stream networks in Washington. We 

begin this report by outlining some basic characteristics of animal movement and then 

apply that foundation to the case of salmonid fishes. Next we consider the consequences 

of disrupting fish movement with human-constructed barriers, such as culverts. Finally, 

this body of evidence is summarized and we propose a short list of what we view as high 

priority information needs to support more effective restoration of fish passage through 

culverts. 

Movement is an essential mechanism by which mobile animals acquire the 

resources necessary for the successful completion of their life-cycles. It also plays a 

crucial role in how animals are distributed across the landscape and the persistence of 

populations and species. Regardless of how little or how far an animal moves, the 

purpose (e.g., foraging, reproduction, growth, refuge) and intensity (e.g., short, long, 

energetic, attenuated) of that animal’s movement is intricately related to how its life 

history requirements change daily and/or seasonally. Animal movement can be 

differentiated into four general categories: station keeping, ranging, migration, and 

accidental displacement. Each category and its associated activities can be defined 

relative to purpose, frequency and pattern, temporal-frame, and spatial-scale. 
2

These movements and activities are expressions of the way animals go about 

acquiring from the habitats within which they reside the resources they need for survival 

and the completion of their life-cycles. Station keeping movements and activities (i.e., 

foraging, commuting, and territorial behavior) typically occur within an animal’s home 

range. Foraging is a regular, reiterative set of movements and activities (e.g., searching, 

hunting, gathering, collecting, etc.) that facilitate the acquisition of resources. 

Commuting also is a regular, reiterative movement or activity that not only facilitates 

resource acquisition but also the avoidance of predators. Territorial behavior includes 

any number of agonistic movements or behaviors used by an animal to establish or 

defend territory within its home range. Ranging can be differentiated into movements 

and activities that facilitate the exploration of or dispersal to new habitat. An exploring 

individual is one that leaves its home range and travels to a contiguous or disjunct 

location, and in a short period of time returns to the original home range. Animals that 

disperse do so by making one-way excursions from their present home range to a new 

location where they establish a new home range. Migration is generally a regular and 

predictable long-distance movement undertaken by animals to seasonally move between 

contiguous and/or disjunct locations. The general expression of migratory movement is 

for an animal to move relatively quickly through multiple contiguous and/or disjunct 

habitats from a location that provides resources for growth and maturation to a location 

that provides resources for reproduction, birth, and the nurturance of offspring. The 

accidental displacement of animals from their home ranges occurs due to unpredictable 

environmental stochastic events such as forest and rangeland fires, debris flows, flooding, 

hurricanes, alteration and fragmentation of habitat by humans, and the introduction of 

invasive species. 

Resident salmonids in headwater streams of the western United States express 

many of the general types of movements described above. They can be quite mobile and 

their patterns of movement vary relative to species. Indeed, movement in many salmonid 

species can extend over long temporal and large spatial scales, is fundamental to the 

persistence of populations across generations, and is an expression of their diverse life 

history patterns and their capacity to respond to dynamic environmental conditions and 

events. 

Salmonids are the fish species most often found at the upper limits of headwater 

streams in the western United States. They are well adapted to life in these streams and 

have evolved behaviors useful for exploiting the many types of headwater stream 

habitats. However, to be able to utilize these habitats, individuals must be able to access 

them. That is why biological corridors and habitat connectivity are so important to the 

persistence of species, populations, and population-sustaining processes. The presence of 

salmonid species in headwater streams is further influenced by factors such as stream 

physical constraints (e.g., channel slope, elevation, stream size, presence of barriers to 

upstream migration), cycles of naturally occurring environmental and habitat disturbance, 

and limitation of food resources. 

Salmonids have coexisted with the presence of naturally occurring barriers to 

upstream movement in headwater streams for a very long time. However, when humanplaced movement barriers restrict or eliminate the upstream movement of fish and isolate 

upstream populations, consequences are likely. Impacts include: (1) reduction or 

elimination of the ability of fish to disperse to or reach upstream habitats; (2) eventual 

extirpation of mobile life history types from upstream populations; (3) fragmentation and 

isolation of upstream populations; (4) increased vulnerability to the negative impacts of 
3

stochastic environmental and habitat disturbances; (5) restriction of upstream populations 

to potentially marginal and degraded habitats; (6) prevention of recolonization of 

disturbed upstream habitats; and (7) population-level genetic impacts such as the 

disruption of gene flow from downstream populations , increased genetic drift in 

upstream populations, development of genetic bottlenecks, loss of genetic diversity, and 

reduced effective population size. 

Culverts placed in streams have long been seen as potential impediments to the 

upstream movement of fish. Four basic levels of culvert-caused restriction to fish 

passage have been identified: complete; partial; low-flow related; and variable passage 

due to culvert modification. Numerous studies have identified various factors affecting 

the ability of fish to pass through culverts including: (1) the behavioral and physiological 

capacity of different fish species; (2) physical conditions within culverts; and (3) stream 

channel physical conditions just below the downstream openings of culverts. A few 

studies have investigated how fish passage may be enhanced by roughening the sides of 

culverts or retrofitting them with baffles. Ultimately, predicting the impact of any single 

culvert on fish upstream movement can be problematic without knowledgeable guidance. 

Several assessment manuals have been developed that can help determine the restrictive 

capacity and intensity of impact of a culvert on fish passage. 

Given what we know of the importance of movement to fishes in headwater 

streams and the undesirable consequences of disrupting connectivity, the question of fish 

passage restoration seems to have an obvious answer. That is, fish passage restoration 

presents a major opportunity to restore connectivity to countless miles of blocked stream 

habitats in Washington State and throughout the region. However, restoration can be 

very expensive, resources are almost always limited, and can potentially facilitate 

invasions by nonnative aquatic species. These considerations lead to questions about 

tradeoffs and the relative values of individual fish passage restoration projects, within the 

context of other possible activities, including passage restoration in other locations, or 

perhaps the value of other management activities to benefit fishes. 

The question of priorities for restoration projects may be just as valuable as 

restoration itself in terms of the balance of planning versus “on the ground” actions that 

benefit fishes. Managers are well-aware of the need for prioritization. Prioritization 

schemes are based on assumptions about how biological systems function (e.g., 

relationships among different factors) and estimates of key parameters (e.g., habitat 

quality and probability of population persistence). However, information may or may not 

be available to quantitatively define these relationships, processes, or estimates of basic 

parameters. Much more could be learned about virtually every aspect of fish movement, 

habitat requirements, population persistence, characteristics of fish barriers, and so on; 

and any information addressing these issues would provide relevant contributions. It is 

clear that a considerable amount of work has been focused on fish movement, local 

habitat requirements, and characterization of fish barriers. Considerably less work has 

been done on addressing the actual consequences of fish barriers in terms of their effects 

on populations, including the following key biological responses of native species: (1) 

expression of migratory life histories (e.g., species with obligate migration or partial 

migration); (2) population persistence; and (3) genetic impacts. 

Learning about restoration begins with an understanding of existing passage 

impairment. By understanding the impacts of current barriers on fish populations, we 

will have a useful template or baseline of information against which the success of 

restoration can be measured. Two general hypotheses and predictions about restoration 
4

are presented on pages 15-16, and a summary of major information needs is presented on 

page 17. The movement characteristics of selected western US salmonid species and 

subspecies are summarized in Appendix I, pages 29-32. Answers to WDFW questions 

concerning headwater stream fish species and populations are presented in Appendix II, 

pages 33-37. 

Introduction 

Restoration of fish passage through culvert barriers has emerged as a major issue 

in the Pacific Northwest and nationwide. The problem has many dimensions, including 

the huge number of potential barriers, uncertainty about which structures are actually 

barriers, the benefits and risks involved with restoration, and the financial costs and 

timelines. This report attempts to address what we call “thinking outside of the pipe” in 

terms of fish passage information needs. This means understanding the value of each 

potential passage restoration project in the context of other possible projects, and to view 

individual restoration projects within a larger landscape of habitats and population 

processes, which will be described below. Fortunately, thinking “inside of the pipe” is 

very well-developed (e.g., FishXing: http://www.stream.fs.fed.us/fishxing/). In other 

words, methods for identification of culverts that are fish passage barriers are wellestablished, as are design criteria for restoration for individual barriers (Clarkin et al. 

2005; see also references posted at http://www.stream.fs.fed.us/fishxing/). 

At the heart of fish passage restoration is the fundamental goal of restoring viable 

and productive fisheries and recovery of threatened and endangered species. Fish are not 

the only organisms affected by passage restoration, and current design criteria attempt to 

address most aquatic organisms (Clarkin et al. 2005). In practice, priority to passage 

restoration is often strongly weighted toward fishes. Identification of fish passage 

barriers may be considered as one of a series of steps in a decision process for an 

effective restoration program. Understanding which potential passage restoration 

projects carry the most value to fish or reduce risks most effectively is a critical piece of 

the decision process which is not well developed. As the investment in fish passage 

restoration and oversight of those expenditures increases (GAO 2001), the need to 

resolve issues that extend “outside of the pipe” grows. 

In this report we provide a brief review of some essential characteristics of animal 

movement and examples from a focal group of fishes in Washington State: salmon, trout, 

and char (for additional detail, see Fausch et al. 2006). While several other fishes and 

many other species use streams where culvert passage barriers may occur, it is the 

salmonids that are by far the most widespread and in most cases extending furthest into 

the headwaters of stream networks in Washington (Fransen et al. 2006). We begin this 

report by outlining some basic characteristics of animal movement and then apply that 

foundation to the case of salmonid fishes. Next we consider the consequences of 

disrupting fish movement with human-constructed barriers, such as culverts. Finally, this 

body of evidence is summarized and we propose a short list of what we view as high 

priority information needs to support more effective restoration of fish passage through 

culverts. 
5

General Characteristics of Fish Movement 

Movement is an essential mechanism by which mobile animals acquire the 

resources necessary for the successful completion of their life-cycles (Greenwood and 

Swingland 1983; Dingle 1996). It also plays a crucial role in how animals are distributed 

across the landscape and the persistence of populations and species (Ricklefs 1990; 

Fausch et al. 2006). An animal’s capacity for movement is determined by natural 

selection and is a function of such things as organism size, habitat, life history traits, and 

geographic range (Dingle 1996). Movement also has spatial and temporal components. 

Some movements occur over comparatively short distances within an animal’s home 

range. Home range, as it is used here, is defined as the area traveled by an animal, 

exclusive of large-scale migrations or uncharacteristic erratic wanderings, for the 

acquisition of resources needed for survival (Mace et al. 1983; Dingle 1996). These 

movements are associated with acquiring food, maintenance of territory, refuge seeking, 

and reproduction (Mace et al. 1983; Pyke 1983; Dingle 1996). Long distance movements 

undertaken by many animals also are associated with the acquisition of the resources 

necessary for survival and completion of an individual’s life-cycle. However, long 

distance movements may also occur involuntarily (at least in part) as a response to a 

naturally occurring displacement event (e.g., forest and rangeland fires, debris flows, 

flooding, etc.) or as individuals track availability of new and unoccupied suitable habitat 

(Stenseth 1983; Dingle 1996). 

Yet, regardless of how little or how far an animal moves, the purpose (e.g., 

foraging, reproduction, growth, refuge) and intensity (e.g., short, long, energetic, 

attenuated) of that animal’s movement is intricately related to how its life history 

requirements change daily and/or seasonally (Rankin 1985, esp., Chapter One: Plankton 

Migrations and Chapter Two: Movements of Benthic Macroinvertebrates; Dingle 1996). 

Many aquatic organisms make diel vertical, as well as horizontal excursions to acquire 

the resources necessary for survival and/or to avoid predation (Kerfoot 1985; Klemer 

1985). Many animals, including fishes seasonally travel long distances to habitats 

suitable for reproduction, resource acquisition and refuge (Sinclair 1983; Dingle 1996). 

In contrast, there are those species that never travel beyond their home range (e.g., 

resident salmonids in headwater tributaries), yet travel between and occupy different 

home range habitats during different seasons (Hilderbrand and Kershner 2000a; Baxter 

2002; Hendicks 2003; Colyer et al. 2005). 

Animal movement can be differentiated into four general categories: station 

keeping, ranging, migration, and accidental displacement (Dingle 1996). Each category 

and its associated activities can be defined relative to purpose, frequency and pattern, 

temporal-frame, and spatial-scale (Table 1). These movements and activities are 

expressions of the way animals go about acquiring from the habitats within which they 

reside the resources they need for survival and the completion of their life-cycles 

(Southwood 1977). 

Station Keeping Movements and Activities 

Station keeping movements and activities (i.e., foraging, commuting, and 

territorial behavior) typically occur within an animal’s home range (Hassel and 

Southwood 1978; Kennedy 1985). Foraging is a regular, reiterative set of movements 

and activities (e.g., searching, hunting, gathering, collecting, etc.) that facilitate the
6

Table 1: Characteristics of movement categories and activities (after Kennedy 1985, Lidicker and Stenseth 1992, and Dingle 1996). 
7

acquisition of resources (Stephens and Krebs 1986; Dingle 1996). Once the resource 

being sought is located and the animal acquires enough of the resource to meet its 

physiological requirements, foraging will temporarily cease. Commuting also is a 

regular, reiterative movement or activity that not only facilitates resource acquisition but 

also the avoidance of predators (Ogden and Quinn 1984; Kennedy 1985; Dingle 1996). 

Commuting is most often associated with the diel vertical “migrations” of organisms in 

lakes and marine habitats. However, any animal that moves daily from one home range 

location to another home range location to acquire resources or avoid predation, and 

returns to the original location, can be considered to be commuting. Territorial behavior 

includes any number of agonistic movements or behaviors used by an animal to establish 

or defend territory within its home range (Dingle 1996). Territorial behavior is usually of 

short duration and tends to occur irregularly. 

Ranging Movements and Activities 

Ranging can be differentiated into movements and activities that facilitate the 

exploration of or dispersal to new habitat (Lidicker and Stenseth 1992; Dingle 1996). An 

exploring individual is one that leaves its home range and travels to a contiguous or 

disjunct location, and in a short period of time returns to the original home range. This 

type of movement tends to be irregular and relatively erratic, yet can provide an 

exploring animal with information about the availability of resources in new suitable 

habitat (Lidicker and Stenseth 1992). Animals that disperse do so by making one-way 

excursions from their present home range to a new location where they establish a new 

home range. The new home range can be contiguous or disjunct with the original home 

range. Dispersal is often associated with habitat factors such as resource availability and 

carrying capacity, the movement of young animals seeking new home ranges, or adults 

seeking new breeding locations (Dingle 1996). 

Migration 

Migration is generally a regular and predictable long-distance movement 

undertaken by animals to seasonally move between contiguous and/or disjunct locations 

(Dingle 1996; Northcote 1998; Meka et al. 2003). The general expression of migratory 

movement is for an animal to move relatively quickly through multiple contiguous and/or 

disjunct habitats from a location that provides resources for growth and maturation to a 

location that provides resources for reproduction, birth, and the nurturance of offspring. 

Location, as it is used here, can be particular habitats within an animal’s home range or 

disjunct home ranges that are separated by relatively long distance. However, the 

migratory movement of anadromous salmonids from their natal stream to the ocean and 

back appears to occur along a continuum rather than between particular separate 

locations, especially the continuous movement of adults during the marine-phase of their 

life-cycle. Nonetheless, migration is usually a seasonally-associated round-trip 

movement, and the distance traveled and number of times an individual completes this 

journey varies by individual condition and species. 

Accidental Displacement 

There are times when animals are unpredictably and involuntarily forced to move 

from their home range by environmental stochastic events (Caughley 1994, Dingle 1996). 
8

These accidental displacements are typically rare relative to any given animal population 

yet occur often, worldwide (Pechmann et al. 1991; Alford and Richards 1999). Examples 

of displacement events include forest and rangeland fires, debris flows, flooding, 

hurricanes, alteration and fragmentation of habitat by humans, and the introduction of 

invasive species. 

Other Definitions of Migration and Dispersal 

As with many terms in ecology and evolutionary biology, the definitions of 

migration and dispersal are not standardized (Dingle 1996), and different usages can be 

quite confusing. Some useful examples are described by Neville et al. (2006a): “...it is 

necessary to clarify how we define two key terms related to connectivity: migration and 

dispersal. In population genetics, migration is often used to describe gene flow – the 

transfer of genetic material among populations. In the salmonid literature, and with most 

other ecological fields, migration is defined as the movement of individuals from natal 

habitats across landscapes or regions to utilize complementary habitats (Dunning et al. 

1992) in completing their life cycle. We use this definition of migration whenever 

possible. The term “dispersal” is also used confusingly across disciplines. In most of the 

ecological literature, the movement of individuals into non-natal habitats for breeding is 

often referred to as dispersal. In the salmonid literature this is referred to as “straying”, 

but to avoid confusion we use the term dispersal (Rieman and Dunham 2000). Generally, 

some dispersing individuals will breed successfully, whereas others may not.” In this 

report we follow the conventions outlined in Neville et al. (2006a). 

Characteristics of Salmonid Movement in Headwater Streams 

Almost 50 years ago Gerking (1959) proposed the “restricted movement 

paradigm” hypothesizing that resident stream fish moved very little. At the same time, 

long-distance movements by salmonids in streams have been documented for decades 

(e.g., Bjornn and Mallet 1964). More recently, this “restricted movement paradigm” has 

been challenged and concepts regarding fish movements have been greatly expanded 

(Grant and Noakes 1987; Gowan et al. 1994; Schlosser 1995; Fausch and Young 1995; 

Rodriguez 2002) indicating that resident salmonids in headwater streams can be quite 

mobile, and that their patterns of movement are diverse and vary relative to species (see 

Appendix I). Indeed, movement is fundamental to the persistence of salmonid 

populations across generations. It is an expression of their diverse life history patterns 

and their capacity to respond to dynamic environmental conditions and events (Fausch et 

al. 2006). Some resident salmonids in headwater tributaries can be relatively static and 

sedentary, moving at the channel unit level (e.g., pool, riffle, cascade, step, etc.) up to 

<1.5 km (e.g., Heggenes et al. 1991; Hilderbrand and Kershner 2000a; Hendricks 2003; 

Schrank and Rahel 2004); whereas other individuals move often and over long distances 

of from 2-194 km (Bjornn and Mallet 1964; Gowan and Fausch 1996; Baxter 2002; 

Schrank and Rahel 2004; Zurstadt and Stephan 2004). The movement patterns of 

resident salmonids also vary daily (Thurow 1997; Young et al. 1997; Baxter 2002) as 

well as seasonally (Gowan and Fausch 1996; Hilderbrand and Kershner 2000a; Baxter 

2002; Hendricks 2003; Schrank and Rahel 2004; Zurstadt and Stephan 2004; Colyer et al. 

2005; Mellina et al. 2005; Muhlfeld and Marotz 2005). This spatial and temporal 

variability in movement is, in part, related to local environmental conditions (Brenkman 

et al. 2001) such as high spring flow and runoff (Gowan and Fausch 1996; Mellina et al. 
9

2005; Muhlfeld and Marotz 2005), discharge (Brenkman et al. 2001; Hendricks 2003; 

Hostettler 2005), stream channel size and slope (Adams et al. 2000), and water 

temperature (Swanberg 1997; Brenkman et al. 2001; Muhlfeld and Marotz 2005). Other 

factors affecting salmonid movement include the size of individuals (Adams et al. 2000), 

characteristics of and requirements for spawning (Gowan and Fausch 1996; Hilderbrand 

and Kershner 2000a; Schrank and Rahel 2004), the acquisition of resources (e.g., food 

and suitable habitat; Fausch and Young 1995), and the presence of artificial barriers (e.g., 

dams and culverts; Zurstadt and Stephan 2004). 

The complex life-cycles of resident salmonids in headwater streams of the 

western United States can extend over long temporal and large spatial scales, and require 

multiple habitats for completion (Schlosser 1995; Swanberg 1997; Hilderbrand and 

Kershner 2000a; Harig and Fausch 2002). The quality and landscape geometry of these 

habitats also are critical to the long-term persistence of populations (Schlosser 1995; 

Hanski 1999; Rieman and Dunham 2000; Neville et al. 2006b). In this landscape-level 

context, movement imparts to resident fish the ability to access essential habitats that 

meet their physiological needs and their requirements for spawning, rearing, and refuge 

provided that the connectivity of these multiple habitat types remains intact (Schlosser 

1995; Hanski 1999; Rosenfeld et al. 2002; Neville et al. 2006a). Many anadromous 

salmonids also utilize headwater streams for spawning and rearing, and stream network 

continuity and connectivity are important landscape-level attributes associated with the 

successful completion of their life-cycles (Isaak et al. In Press). For example, recent 

studies have documented that intermittent headwater streams contribute to survival of 

anadromous salmonids (e.g., Wigington et al., In Press; Ebersole et al., In Review); and 

without access to these specialized habitats survival of individuals could be 

compromised, with possible population consequences. 

Salmonids in headwater streams of the western United States express many of the 

general types of animal movement (Table 1). Station keeping movements and activities 

are well represented by coastal cutthroat trout (Oncorhynchus clarkii clarkii) because the 

movement patterns of this species in headwater streams are relatively restricted 

(Heggenes et al. 1991; Hendricks 2003). Hendricks (2003) found that a high proportion 

of radio-tagged individuals did not change channel units on a daily basis, but did move 

from these units to other channel units as they foraged for food. He also found that some 

individuals, while foraging, actually commuted from an initial channel unit to new areas 

of the stream for feeding and refuge and then returned to the original channel unit. 

Several studies have identified territorial behavior associated with feeding locations in 

various salmonid species (e.g., brown trout, Salmo trutta; brook trout, Salvelinus 

fontinalis; coho salmon, Oncorhynchus kisutch; cutthroat trout), although not all 

individuals within a population equally express this behavior (Grant and Noakes 1987; 

Martel 1996; Sabo and Pauley 1997). The ability of salmonids to disperse is crucial to 

the continued persistence of populations in headwater streams. Larson et al. (2002) 

labeled as dispersers, rainbow trout (Oncorhynchus mykiss) that emigrated from a larger 

stream in which they had been present for decades, into a smaller tributary stream, 

eventually establishing a resident population in the smaller stream. Lamberti et al. (1991) 

also documented the dispersal of cutthroat trout that had been displaced downstream by a 

catastrophic debris flow back to the impacted upstream reaches one year after the event. 

Migratory movements by salmonids in headwater streams can be expressed in several 

ways. Some species such as resident bull trout (Salvelinus confluentus) and westslope 

cutthroat trout (Oncorhynchus clarkii lewisi) make within-basin migrations of variable 
10

distance (e.g., 2-194 km) for spawning (Swanberg 1997; Zurstadt and Stephan 2004); 

whereas anadromous salmonids such as coho (Oncorhynchus kitsuch) and chinook 

salmon (Oncorhynchus tshawytscha) are well known for their long distance migrations 

from natal streams to the Pacific Ocean, eventually returning to their natal streams to 

spawn and complete their life-cycle. There are also salmonid species such as mountain 

whitefish (Prosopium williamsoni; Coregoninae) and westslope cutthroat trout that make 

within-basin migrations of variable distance to winter refuge habitats (Baxter 2002; 

Zurstadt and Stephan 2004). 

Distribution of Salmonids in Headwater Streams 

Salmonids are the fish species most often found at the upper limits of headwater 

streams in the western United States (Wydoski and Whitney 1979; Kruse et al. 1997; 

Latterell et al. 2003; Cole et al. 2006; Fransen et al. 2006). They are well adapted to life 

in these streams and have evolved behaviors useful for exploiting the many types of 

headwater stream habitats (Northcote 1992; Fausch et al. 2002; Neville et al. 2006b). 

However, to be able to utilize these habitats, individuals must be able to access them. 

That is why biological corridors and habitat connectivity are so important to the 

persistence of species, populations, and population-sustaining processes (Fausch and 

Young 1995; Rosenberg et al. 1997; Dunham and Rieman 1999; Bryant et al. 2004; 

Muhlfeld and Marotz 2005; Neville et al. 2006a). Stream network connectivity supports 

and maintains the mobile and migratory life history patterns of stream fish that reside in 

or utilize headwater streams for the completion of their life cycles (Schlosser 1995; 

Neville et al. 2006a). The connectivity of stream habitats also facilitates upstream and 

downstream dispersal, allowing individuals to access suitable habitats for reproduction, 

rearing, growth, and refuge (Kruse et al. 2001; Jackson 2003; Schrank and Rahel 2004; 

Neville et al. 2006a), as well as the ability to recolonize habitats after disturbance 

(Dunham et al. 1997; Rieman et al. 1997; Roghair et al. 2002; Dunham et al. 2003). The 

ability of fish to move relatively unrestricted within and among habitats also contributes 

to the maintenance of total and effective population size (Hilderbrand and Kershner 

2000b; Kruse et al. 2001; Neville et al. 2006a, b, c), gene flow and genetic heterozygosity 

(Morita and Yokota 2002; Yamamoto et al. 2004; Neville et al. 2006a), and the diversity 

of species and fish assemblages (Peter 1998; Schlosser and Kallemeyn 2000). 

The presence of salmonid species in headwater streams is further influenced by 

factors such as stream physical constraints (Kruse et al. 1997; Dunham et al. 1999), 

cycles of environmental disturbance (Reeves et al. 1995; Dunham et al. 2003), and 

limitation of food resources (Hughes 1998). Kruse et al. (1997) found that the upstream 

distribution of Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri) in 

northwestern Wyoming streams was constrained by channel slope (i.e. ≥10%), elevation 

(i.e., >3182 m), stream size (i.e., wetted width), and the presence of barriers to upstream 

movement. Three studies of the distribution of fish in western and eastern Washington 

streams also determined that the upstream occurrence of trout (Oncorhynchus spp.) was 

constrained by the physical characteristics of stream channels (esp., diminishing channel 

size and increasing gradient), the diminishing availability of water, and the presence of 

natural and human-constructed barriers (Latterell et al. 2003; Cole et al.; 2006; Fransen et 

al. 2006). Unpredictable environmental disturbances to headwater streams can severely 

reduce local fish population size as well as lead to extirpation of populations from 

upstream habitats (Kruse et al. 2001; Dunham et al. 2003). According to Reeves et al. 
11

(1995), local fish populations come and go in these dynamic headwater stream 

environments and it is the ability to escape disturbed habitats and then eventually 

recolonize them that contributes to the persistence of fish populations in these habitats 

(Breitburg 1992; Breitburg and Loher 1994; Dunham et al. 1997; Rieman et al. 1997). 

The impact of food limitation on fish distribution appears to be indirect and related to 

density- and size-dependent effects (Chapman 1966; Grant and Kramer 1990; Dunham 

and Vinyard 1997; Hughes 1998). For instance, as the size of individuals within a 

population increases the carrying capacity of a food- or space-limited habitat decreases. 

This could lead to small, isolated and fragmented populations in upstream locations that 

can be quite vulnerable to the negative impacts of environmental stochastic disturbances 

(Lamberti et al. 1991; Ensign et al. 1997; Morita and Yokota 2002; Roghair et al. 2002). 

Impacts of Human-Placed Barriers on Fish Populations 

Salmonids have coexisted with the presence of naturally occurring barriers to 

upstream movement in headwater streams for a very long time. However, when humanplaced movement barriers restrict or eliminate the upstream movement of fish and isolate 

upstream populations, consequences are likely. The most obvious effect of humanplaced barriers is that they reduce or eliminate the ability of fish to disperse to or reach 

upstream habitats. Thus, the ability of downstream populations to support declining 

upstream populations is reduced or potentially eliminated (Jackson 2003); the ability of 

anadromous salmonids to reach important headwater spawning and rearing sites is also 

decreased or eliminated (Wigington In Press; Ebersole In Review); and upstream species 

richness is attenuated (Winston et al. 1991). These barriers, by reducing or eliminating 

the upstream migratory phase of a species’ life cycle can eventually extirpate mobile life 

history types from upstream populations (Nelson et al. 2002; Jackson 2003; Colyer et al. 

2005; Fausch et al. 2006; Neville et al. 2006a). As barriers decrease or eliminate 

upstream movement, remnant populations above the barriers become fragmented and 

isolated (Kruse et al. 2001; Jackson 2003), and potentially more vulnerable to the 

negative impacts of unpredictable environmental events that impact headwater streams 

(Kruse et al. 2001; Dunham et al. 2003). Human-placed barriers to upstream movement 

also diminish the capacity for long-term persistence of upstream populations by 

restricting them to potentially marginal and degraded habitats (Peter 1998; Hilderbrand 

and Kershner 2000b; Pringle et al. 2000; Jackson 2003; Fausch et al. 2006) and 

preventing the recolonization of disturbed upstream habitats (Fausch et al. 2006). 

Population-level genetic impacts due to isolation include the disruption of gene flow from 

downstream populations (Jackson 2003), increased genetic drift in upstream populations 

(Griswold 1996; Castric et al. 2001; Guy 2005; Wofford et al. 2005), development of 

genetic bottlenecks and the loss of genetic diversity (Yamamoto et al. 2004; Guy 2005; 

Wofford et al. 2005; Neville et al. 2006a, b), and reduced effective population size 

(Neville et al. 2006a, b, c). 

Several case-studies help illustrate the potential impacts of human-placed barriers 

on headwater stream fish populations: 

1. Morita and Yamamoto (2002) examined the impact of the placement of erosion 

control dams across streams in southwestern Hokkaido, Japan, on the persistence of 

white-spotted char (Salvelinus leucomaenis) populations above the dams. They found 

that of 52 study sites above dams, white-spotted char were absent from 17 of the sites, 

whereas char occupied all undammed upstream reaches surveyed. Morita and 
12

Yamamoto (2002) attributed the absence of char at the 17 sites to time since isolation 

of the population, and decreasing watershed size and stream channel gradient. They 

speculated that 12 more above-dam populations would disappear in the next 50 years. 

2. Hilderbrand and Kershner (2000b), examining abundance data for isolated 

populations of three cutthroat trout subspecies (O. c. lewisi, O. c. pleuriticus, and O. 

c. utah) in headwater streams of Idaho, Montana, and Utah found that stream length 

could be related to the diminished persistence of upstream fish populations. They 

concluded that if barriers were placed in headwater streams for the purpose of 

isolating native trout from introduced nonnative trout, there would typically be 

insufficient space (i.e., stream length) above the barriers to maintain the necessary 

effective population size to support viable native cutthroat trout populations in the 

face of isolation. 

3. Kruse et al. (2001) also studied the potential for using barriers to isolate native trout 

from introduced nonnative species. They studied 23 northwestern Wyoming stream 

populations of Yellowstone cutthroat trout (O. c. bouvieri) and determined that 21 of 

the populations would be large enough to minimize demographic risks of extinction. 

However, only seven populations would be large enough to maintain genetic viability 

(i.e. minimize potential for inbreeding and maintain within-population variability). 

They also speculated that even these populations, because of their sizes, would 

potentially be susceptible to extinction due to some unpredicted and catastrophic 

environmental disturbance. 

4. Wofford et al. (2005) assessed the effects of barriers on genetic variation in coastal 

cutthroat trout (O. c. clarkii) in an isolated headwater stream in western Oregon. 

They found that the barriers strongly influenced genetic structure and that the above 

barrier population had reduced gene flow and diversity, as well as increased genetic 

differentiation and drift. They concluded that these genetic consequences of habitat 

fragmentation and isolation could potentially compromise the long-term persistence 

of the population. 

5. Morita and Yokota (2002), using a simple individual-based model that assimilated 

population regulation mechanisms for white-spotted char, assessed the viability of 

populations fragmented and isolated above erosion control dams (also see Morita and 

Yamamoto 2002, above). They determined that the persistence of populations 

decreased substantially beginning around 30+ years since isolation. This was 

especially relevant for populations with small carrying capacity and low adult 

survival. The general conclusion was that small fragmented and isolated populations 

were not viable. 

6. Neville et al. (2006c) studied 55 populations of rainbow trout in headwater streams in 

central Idaho to compare within-population patterns of genetic diversity in relation to 

isolation by culvert barriers, habitat size, and history of wildfire-related disturbance. 

Diversity was greater in larger habitats that were not isolated by culvert barriers, and 

wildfire-related disturbance had no detectable influence. This was in spite of the fact 

that some populations studied were known to be completely or nearly extirpated by 

wildfire-related debris flows ten years before. The strong influence of culverts 

underscored the importance of connectivity to rainbow trout populations. 

It is clear that barriers to upstream movement restrict and often eliminate access 

to potentially critical upstream habitats. Limiting or eliminating dispersal and effectively 
13

fragmenting and isolating populations are key factors that increase the extinction risk for 

populations (Soulé 1983). Duncan and Lockwood (2001), examining the extinction risk 

among the world’s freshwater fish families, found no indication that a unifying set of 

intrinsic biological or ecological traits could predict taxonomic patterns of extinction. 

Rather, they hypothesized that extrinsic factors such as the damming of rivers and other 

human caused alterations of freshwater aquatic environments, even in headwater streams, 

were important drivers of the worldwide decline in freshwater fish species. Although 

many factors contribute to the persistence or extinction of headwater stream fish 

populations, the potential capacity for the continued long-term persistence of small 

populations fragmented and isolated above human-placed barriers remains problematic 

(Fausch et al. 2006). 

Culverts and Fish Passage 

Culverts placed in streams have long been seen as potential impediments to the 

upstream movement of fish. Laird (1988) identified four basic levels of culvert-caused 

restriction to fish passage: complete; partial; low-flow related; and variable passage due 

to culvert modification. Numerous studies have identified various factors affecting the 

ability of fish to pass through culverts. Some studies have examined the behavioral and 

physiological capacity of different fish species to move upstream through culverts; other 

studies have identified several types of physical conditions within culverts that impact 

fish passage; and still others have examined the impact of stream channel physical 

conditions just below the downstream openings of culverts on fish movement upstream 

(Table 2). A few studies have investigated how retrofitting culverts may enhance fish 

passage. For example, Bates and Powers (1998) found that a culvert with moderately 

roughened walls enhanced juvenile coho salmon passage through the culvert because the 

roughness created a less turbulent boundary layer which the fish could use, especially 

when water velocity was high; and McEnroe (2005) determined that a culvert retrofitted 

with baffles allowed juvenile steelhead trout to maintain their position within the culvert, 

and to move upstream in higher numbers than through a non-retrofitted culvert. 

Ultimately, predicting the impact of any single culvert on fish upstream movement can be 

problematic without knowledgeable guidance. Several assessment manuals have been 

developed that can help determine the restrictive capacity and intensity of impact of a 

culvert on fish passage. A well-known and rich source of information on fish passage 

through culverts is FishXing (http://www.stream.fs.fed.us/fishxing/ ). Pess et al. (2005) 

provide a detailed evaluation of fish responses to the reconnection of isolated habitats 

through the removal of culverts and other barriers to migration. 

Information needs for fish passage restoration through culverts 

Given what we know of the importance of movement to fishes in headwater 

streams and the undesirable consequences of disrupting connectivity, the question of fish 

passage restoration seems to have an obvious answer. That is, fish passage restoration 

presents a major opportunity to restore connectivity to countless miles of blocked stream 

habitats (Roni et al. 2002; Pess et al. 2005) in Washington State and throughout the 

region. The problem is that restoration can be very expensive (e.g., >$100,000 USD per 
14

Table 2: General factors affecting the upstream movement of fish through culverts. 

project) and resources are almost always extremely limited (GAO 2001). Less obvious is 

the potential for passage restoration to facilitate invasions by nonnative aquatic species 

(e.g., Fausch et al. 2006). These considerations lead to questions about tradeoffs and the 

relative values of individual fish passage restoration projects, within the context of other 

possible activities, including passage restoration in other locations, or perhaps the value 

of other management activities to benefit fishes. In other words, the question of priorities 

for restoration projects may be just as valuable as restoration itself in terms of the balance 

of planning versus “on the ground” actions that benefit fishes. 

 Managers are well-aware of the need for prioritization. Various schemes for 

prioritization of fish passage restoration projects are available or in development, such as 

the national Fish Passage Decision Support System currently implemented by the U.S. 

Fish and Wildlife Service (http://fpdss.fws.gov/index.jsp), and within the Pacific 

Northwest, the U.S. Forest Service, Region 6 (David Heller, personal communication), 

Washington Department of Fish and Wildlife (David Price, personal communication), 

and Rocky Mountain Region (Fausch et al. 2006). 

Prioritization schemes are based on assumptions about how biological systems 

function (e.g., relationships among different factors) and estimates of key parameters 

(e.g., habitat quality and probability of population persistence) (Roni et al. 2002). 

Information may or may not be available to quantitatively define these relationships, 

processes, or estimates of basic parameters. This is true of most management 

applications, which represent an integration of quantitative inference and expert opinion. 

Here we summarize what we view to be high priority information needs, based on our 

review of the issues and evidence surrounding fish passage restoration through culverts in 

Washington State and throughout the Pacific Northwest. 

 FACTOR REFERENCE 

Behavioral limitation 

willingness of individual to move through or over barrier (even if barrier 

is submerged or only partially restrictive) 

seasonal timing of upstream movement relative to depth and velocity of 

water in culvert 

Binder and Stevens 2004 

Laird 1988 

Physiological swimming capacity of species Binder and Stevens 2004 

Barrier type and culvert length Belford and Gould 1989 

Warren and Pardew 1998 

Water velocity through culvert relative to culvert length Belford and Gould 1989 

Baker and Votapka 1990 

Fitch 1995 

Turbulence level of water inside culvert Fitch 1995 

Water depth inside culvert Baker and Votapka 1990 

Fitch 1995 

Stream channel characteristics below downstream opening 

of culvert 

Height of culvert lip above water surface 

Size of plunge pool 

Bateman, unpubl. Data 

Fitch 1995 

Binder and Stevens 2004 

Kondratieff and Myrick 2005 
15

Identifying Key Biological Responses of Native Populations to Barriers 

Much more could be learned about virtually every aspect of fish movement, 

habitat requirements, population persistence, characteristics of fish barriers, and so on. 

Any information addressing these issues would provide relevant contributions. However, 

we see areas where certain information needs are higher priority, relative to decisions 

about priorities for fish passage restoration. From our review, it is clear that a 

considerable amount of work has been focused on fish movement, local habitat 

requirements, and characterization of fish barriers (e.g., FishXing). Considerably less 

work has been done on addressing the actual consequences of fish barriers in terms of 

their effects on populations, including the following key biological responses of native 

species: 

• Expression of migratory life histories (e.g., species with obligate migration or partial 

migration) 

• Population persistence (e.g., Morita and Yamamoto 2002), and 

• Genetic impacts (e.g., Neville et al. 2006a, b, c). 

These three categories of biological responses represent important population 

characteristics related to the long-term persistence and viability of fish populations. 

Threats of Invasion by Nonnative Fishes 

The tradeoffs involved with fish passage restoration to benefit native fishes versus 

facilitating invasions by nonnative fishes have been thoroughly reviewed in a separate 

report (see Fausch et al. 2006). Our recommendation for information needs related to this 

issue is similar to those for native species. Models to understand the influence of existing 

barriers on the success of invasions (e.g., as indicated by probability of occurrence) and 

monitoring and evaluation of responses of invasive species to passage restoration would 

provide very useful information. In the following section we provide more detailed 

examples of how this might be accomplished. 

Relevance for Fish Passage Restoration 

We see the issues highlighted above as high priorities because they address 

validation of key assumptions in existing prioritization schemes and the need to monitor 

the effectiveness of passage restoration (GAO 2001). Management actions will proceed 

with or without new information, but as the level of investment in fish passage restoration 

grows, so will the questions about priorities and effectiveness. Both could be continually 

evaluated and modified based on what is learned from new information suggesting more 

effective management alternatives. 

Learning about restoration begins with an understanding of existing passage 

impairment. By understanding the impacts of current barriers on fish populations, we 

will have a useful template or baseline of information against which the success of 

restoration can be measured. For instance, a few specific hypotheses and predictions 

about restoration could include the following: 

• Hypothesis: Passage barriers (A) reduce the size and dispersal connectivity of fish 

populations upstream, thus (B) decreasing the number of breeders or genetically 
16

effective size of local populations, (C) decreasing connectivity to migratory habitats, 

and (D) increasing the chance that a population may be locally extirpated. 

• Some predictions about existing barriers: 

• Fish populations should be less likely to occur upstream of fish passage 

barriers relative to similar habitats without barriers. 

• Genetic variability of populations upstream of barriers should be reduced 

relative to populations sampled from similar habitats without barriers. 

• Species or individuals with migratory life histories should be less likely to be 

present upstream of barriers relative to similar habitats without barriers. 

• Some predictions about restoration: 

• Restoration of fish passage should result in colonization of suitable habitats 

upstream of former barriers. 

• Within-population genetic variability should increase in populations upstream 

of former barriers. 

• Species or individuals with migratory life histories should be more likely 

to occur in habitats upstream of former barriers. 

• Hypothesis: Fish passage restoration will increase the probability of invasion by 

nonnative species, which will have negative impacts on desirable native fishes. 

• Predictions 

• Nonnative species will be more likely to occur in streams without barriers or 

in those where passage has been restored 

• Native species will be less likely to occur in habitats where nonnative species 

are present 

The preceding examples are very simplistic hypotheses and predictions and do not 

constitute a full study design to address all of the necessary measurable influence or 

“covariates” that could affect the outcome of restoration. For example, the success of 

invasion by nonnative species is likely conditioned on several different factors, including 

habitat suitability, dispersal ability, and biotic resistance in the receiving community 

(Dunham et al. 2002; Fausch et al. 2006). Other responses may also be relevant in the 

case of nonnatives (e.g., hybridization of closely related natives and nonnatives). The 

tools of landscape ecology, geographic information systems, molecular genetic markers, 

sampling methods, etc., are all now in place and available to address the impacts of 

barriers and develop testable hypotheses about restoration for design of effectiveness 

monitoring programs. The cost of research, monitoring, and evaluation would be very 

small in proportion to the huge costs associated with actual restoration and the 

overwhelming size of the problem. For example, in Bureau of Land Management and 

Forest Service lands alone in Oregon and Washington, the cost of fish passage restoration 

is estimated at over $375 million dollars (GAO 2001). Given these costs and 

uncertainties about restoration, some investment in research, monitoring, and evaluation 

seems very cost effective. 
17

Relevance of Barriers in Intermittent Streams 

Another growing issue is the importance of intermittent streams to fishes. Use of 

such habitats by fish has long been known, but more recent work reviewed here has 

shown that intermittent streams can be very important to salmon and trout, as well as 

other fishes. Better broad-scale models to predict and map the locations of such habitats 

by focal fish species might prove very useful, especially for anadromous species and 

perhaps native char in headwater streams. In the case of anadromous species, most of the 

obvious passage barriers in perennial streams have been restored, or are on a list of top 

priorities for local managers. It may be the case that many additional opportunities 

remain for fish passage restoration in intermittent streams. Research of this nature would 

be most effective with a team-based approach that integrates domain experts in biology, 

hydrology, and related disciplines. Since the focus of this literature review and requested 

assistance concerns higher-gradient streams, it is not clear how important this issue is if 

lower-gradient streams are omitted. We suspect that lower-gradient intermittent streams 

are much more likely to be important to fish, but this assumption is not tested. In some 

areas, char in particular can use smaller and higher gradient streams (e.g., Dolly Varden 

char S. malma in southeast Alaska; M. Bryant, Pacific Northwest Research Station, 

personal communication, 2005; see also Koizumi and Maekawa 2004). 

Conclusions 

In summary, the major information needs identified here include: 

• Identifying key biological responses of native populations to barriers 

• life history 

• population persistence/occurrence 

• genetic indicators of population size; 

• Threats of invasion by nonnative fishes and other species with potential impacts 

to native fishes; and 

• Identification of intermittent streams with high value to native fish populations. 

Desired outcomes from this new work would include the following: 

• Improved procedures for prioritization of fish passage restoration projects at 

broad scales (from validation with new information) 

• Improved response designs for effectiveness monitoring of restoration success: 

e.g., what to measure? 

• Improved efficiency and learning about effective fish passage restoration and 

increased viability and productivity of important fisheries and threatened and 

endangered species. 

• More efficient allocation of limited resources to fish passage restoration that 

maximizes benefits to native species. 
18

Acknowledgements 

The authors thank M. Fitzpatrick and J. Erickson for assistance with peer review 

of this report. Christian Torgersen and one anonymous reviewer provided helpful 

comments on an initial draft of this report. David Price of the Washington Department of 

Fisheries and Wildlife provided many helpful discussions of the issues. Doug Bateman 

(Oregon State University) provided a wealth of natural history observations on coastal 

salmonids that helped us think about the issues.
19

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29

Appendix I: Movement Characteristics of Species and Subspecies 

1. Bonneville Cutthroat Trout (Oncorhynchus clarkii utah) 

• Movement Patterns 

1. Relatively mobile, although seasonal (post-spawning continuum of 0.5-86.0 km) 

2. Greatest movement activity and distance: Spring (spawning, post-spawning) 

3. Variable-sporadic movement and limited distance: Summer-Winter (≤0.5 km) 

4. Individuals above barriers moved more frequently and had larger home ranges than 

individuals below barriers 

5. Important to maintain drainage connectivity and seasonal migration corridors 

• Dominant Movement Types 

1. Station keeping (Summer-Winter) 

2. Migratory (spawning; Spring) 

• Study locations: southeast Idaho, western Wyoming, and northern Utah 

• References: Hilderbrand and Kershner 2000a; Schrank and Rahel 2004; Colyer et al. 2005 

2. Coastal Cutthroat Trout (Oncorhynchus clarkii clarkii) 

• Movement Patterns 

1. Relatively short within-basin distances, primarily at the channel unit-scale with smaller 

proportion of population making reach- and segment-scale movements 

2. Seasonal component: greatest movement in April associated with peak spawning; least 

movement in October associated with low discharge 

3. Unit-scale movements common throughout year 

4. Reach- and segment-scale movements typically occur in winter and spring 

5. Habitats occupied by individuals change relative to discharge, water temperature, as 

well as spawning, refuge requirements, and feeding 

• Dominant Movement Types 

1. Station keeping 

2. Categories 

• No movement (0 channel units) 

• Local movement (1-5 channel units) 

• Longer distance movements (>5 channel units) 

• Pulsed movement (variable 1-3 above) 

• Study locations: western British Columbia; southwest Oregon 

• References: Heggenes et al. 1991; Hendricks 2003 

3. Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi) 

• Movement Patterns 

1. Seasonal with long distances and widespread distribution 
30

• Fall: downstream migration up to 194 km 

• Winter: sedentary downstream 

• Spring: upstream migration up to 475 km (related to spawning, water temperature, and 

discharge) 

• Summer: sedentary upstream 

2. Many individuals demonstrate homing behavior, returning to the same upstream channel 

habitat previously occupied 

3. Important to maintain habitat heterogeneity and drainage connectivity and account for 

diverse migratory behavior 

• Dominant Movement Types 

1. Station keeping (Summer and Winter) 

2. Migratory (Fall downstream; Spring upstream) 

• Study locations: central Idaho; central Oregon 

• References: Zurstadt and Stephan 2004; Starcevich 2006 

4. Rainbow Trout (Oncorhynchus mykiss) 

• Movement Patterns (non-anadromous) 

1. Unique seasonal movements suggest potential for discrete within-basin population 

structure (see Meka et al. 2003) 

• Summer-Winter: sedentary 

• Spring: increased upstream movement (can be long range up to >372-607 km) 

related, in part, to discharge 

2. Age-0 fish movement habitat-related (see Mitro and Zale 2002): in sections with simple 

bank habitat in autumn; then move to and over-winter in sections with complex bank 

habitat, high gradient, and large substrate 

• Dominant Movement Types 

1. Station keeping: Summer-Winter 

2. Migratory: Spring 

• Study locations: north-central British Columbia; southwest Alaska; southeast Idaho 

• References: Mitro and Zale 2002; Meka et al. 2003; Mellina et al. 2005 

5. Bull Trout (Salvelinus confluentus) 

• Movement Patterns 

1. Seasonal upstream and downstream migrations vary by: 

• Population 

• Time of year (Spring, Fall) 

• Distance (reported mean distances of 33 and 63 km; range 9-129 km) 

2. Migrations usually occur at night and are relatively rapid 

3. Individuals typically return to or near sites from which they migrated 
31

4. Juvenile emigration from natal habitat can occur in two pulses (Spring and Fall) – 

juveniles can stay in natal tributaries for up to 3 years 

5. Some populations can be non-migratory residents in headwater tributaries 

6. Timing and extent of movement related to water temperature and discharge 

7. Important to maintain drainage connectivity and diversity of complex habitats over large 

spatial-scale 

• Dominant Movement Types: 

1. Station keeping 

2. Migratory: variable distances for spawning and return to non-spawning habitat 

• Study locations: northwest Washington; northwest Idaho; northwest Montana 

• References: Swanberg 1997; Brenkman et al. 2001; Baxter 2002; Muhlfeld and Marotz 

2005; Downs et al. 2006 

6. Brook Trout (Salvelinus fontinalis) 

• Movement Patterns 

1. Upstream dispersal typically occurs in Summer 

2. Highest movement rates occur relative to runoff and before spawning, although overall 

summer movement relatively high 

3. Movement of up to 3.4 km relatively common 

4. Upstream dispersal restricted, in part, by channel gradient (although capable off moving 

into upstream habitat with steep gradient), size of individual, and barriers such as nearly 

vertical falls 

• Dominant Movement Type 

1. Station keeping with upstream dispersal 

• Study locations: central Idaho; northern Colorado 

• References: Gowan and Fausch 1996; Adams et al. 2000 

7. Mountain Whitefish (Prosopium williamsoni) 

• Movement Patterns 

1. Variable types of seasonal movement 

• Single summer reach-no fall migration 

• Single summer reach-fall migration of varying length (3-95 km) to over-wintering 

habitat-return to summer habitat 

• Multiple summer reaches-fall migration to over-wintering habitat-return to summer 

habitat 

• Summer reach-fall migration to over-wintering habitat-no return to summer habitat 

• Dominant Movement Types 

1. Station keeping 

2. Migration (roundtrip to over-wintering habitat) 
32

• Study locations: northeast Oregon; southeast Washington 

• References: Baxter 2002 

8. Largescale Suckers (Catostomus macrocheilus) 

• Movement Patterns 

1. Seasonal movement from upstream habitats (Spring-early Summer) to downstream 

over-wintering habitats (beginning mid-summer through early Fall) 

2. Long distance movements: 17.2-300 km; mean = 111 km 

3. Minimal movement during winter 

4. Return to upstream habitats in Spring 

• Dominant Movement Types 

1. Station keeping 

2. Migration (roundtrip to over-wintering habitat) 

• Study locations: northeast Oregon; southeast Washington 

• References: Baxter 2002 

9. Anadromous salmonids (coho, Oncorhynchus kisutch; chinook, Oncorhynchus tshawytscha) 

• These species utilize headwater tributaries for reproduction and as rearing habitats for 

offspring 

• Recent research has documented the importance of permanent as well as intermittent 

headwater streams for the continued survival and persistence of anadromous salmonid 

populations 

• Important environmental factors include maintenance of drainage connectivity, habitat size 

and quality, and availability of residual pool habitats in intermittent streams 

• Study locations: central Idaho; southwest Oregon 

• References: Ebersole et al. In Review; Isaak et al. In Press; Wigington et al. In Press 
33

Appendix II: Questions from Washington DFW (answers in italic) 

1. At what life stages is it important that headwater fish move upstream through road crossings? 

According to current guidelines, the standard is to allow passage of all species and life 

stages (Clarkin et al. 2005). For salmonid fish in particular, movement of smaller fish and 

therefore earlier life stages will be the obvious limiting factor in considering fish passage 

barriers, because movement of individuals during these life stages is most likely to be impeded. 

Work on movement of very small fish (<60 mm) is lacking, although it is generally believed fish 

of such small size do not move substantial distances. However movement of larger fish (>60 

mm) is known to play an important role in allowing access to seasonally productive habitat and 

to refugia. 

2. Are there physical cues where upstream movement by headwater fishes might be expected with 

respect to flow, seasons, and channel characteristics (e.g., gradient, roughness, pools, etc), 

disturbance, others? 

In general, temperature and discharge are believed to be the dominant “proximate” cues 

that influence upstream migration of fishes in headwaters. In other words, changes in these 

physical factors influence movement of fish during seasons in which upstream migration is most 

common. Within a given season, these factors can vary dramatically across years, and lead to 

substantial within-season variability in the timing and duration of upstream migration. 

The seasonal window of migration (e.g., fall versus spring) is believed to be attuned to 

selection for spawn timing and location, and represents an “ultimate” influence (i.e., 

presumably shaped by natural selection to maximize individual fitness) on upstream migration. 

Channel characteristics are more likely an “ultimate” factor influencing migration by fish in 

headwater streams, representing natural selection for use of refugia or spawning areas suitable 

for maximizing pre-spawning survival of adults, egg incubation, and juvenile rearing. Use of 

such habitats may also be conditioned on population density and spatial geometry (size and 

isolation) of habitats, and the roles of spatial geometry versus local habitat quality are likely 

scale-dependent. At larger spatial extents, the importance of geometric factors is likely to be 

more obvious than local factors traditionally associated with habitat quality (e.g., cover, 

sediment, temperature). 

3. How would you characterize the movement behaviors of headwater fishes? 

Movement behaviors of fish vary according to the spatial and temporal scale of movement 

under consideration. Migration and dispersal over longer times and distances are the most 

relevant considerations for fish passage restoration. Migration in salmonid fishes is typically 

defined in terms of the origin and destination of the migratory circuit. For example, a “fluvial” 

life history refers to individuals that migrate from natal spawning areas to larger riverine 

habitats and back. Various terms relating to different destinations have been proposed. As the 

evidence mounts for salmonid fishes in terms of direct (e.g., telemetry, mark and resight) and 

indirect (e.g., molecular markers) study of movements, it is becoming increasingly clear such 

classifications can lead to an overly simplistic view of the complex life histories of salmonid 

fishes. To develop a more realistic view of migration in salmonid fishes, new classifications 

would benefit by considering the following: 

• The “journey” between endpoints of migration, and more specifically patterns of use in 

what are believed to be migratory corridors. 
34

• The possibility of multiple endpoints in migration, including a clear definition of what 

defines an “endpoint.” For example, it is common for salmonids to move through multiple 

habitats during migration, and “stopovers” or exploratory excursions into different 

habitats may occur as is the case with other migratory species (Dingle 1996). 

• Differences among life stages in migratory behavior. Most research has focused on 

migration of large adult fish, but smaller individuals and earlier life stages can have 

considerably different patterns of migration and habitat use. For example, so-called 

“subadult” bull trout (generally referring to migratory fish <300 mm) show much more 

extensive use of stream habitats than do larger “adult” bull trout, including frequent use of 

small tributaries and intermittent streams (J. Dunham, personal observations). 

• The motivation for migration. It is critical to identify why fish migrate (e.g., for refuge, 

feeding, reproduction) in any classification of migratory behavior (e.g., Table 1). 

We are not aware of significant attempts to include these considerations into a more 

rigorous definition of migratory behavior by salmonid fishes, and such an effort would indeed 

be challenging. However, it is likely that we are not able to detect important patterns of 

migratory habitat use and selection with current classifications and methods of study. This may 

be more important for understanding habitat use in the higher order portions of stream 

networks and less so for headwater streams. In some cases, however, more study of the use of 

headwater streams by fish may be warranted (e.g., “subadult” trout and char). 

Dispersal is less understood than migration. It is an important process in terms of 

maintaining gene flow and spatial processes that contribute to persistence of fishes – especially 

those in dynamic headwater habitats (Rieman and Dunham 2000). Of the methods available to 

understand patterns of dispersal, molecular markers have perhaps proven the most effective for 

understanding interactions between fish in headwater streams and higher order stream 

habitats, as well as patterns of interaction among headwater streams (Neville et al. 2006a). 

Most studies of dispersal using molecular markers have focused on single stream networks. 

Comparisons among different networks to contrast the influence of historical (e.g., post-glacial 

dispersal) and local landscape characteristics (e.g., spatial structure, habitat quality, 

disturbance, barriers) on dispersal would help considerably in terms of understanding the 

nature of dispersal by fishes in headwater streams (e.g., Costello et al. 2003). In other words, 

broader-scale comparative studies of dispersal in headwater fishes would help to disentangle 

the influences of long-term historical processes versus landscape influences at intermediate 

spatio-temporal scales, and small-scale influences, such as barriers and localized disturbance 

(Neville et al. 2006a). 

4. How far do headwater fish move? 

There is no characteristic distance that headwater fish move, but maximum distances can 

range into hundreds of kilometers for non-anadromous species. Anadromous fish migrate 

thousands of kilometers, primarily within marine environments, in addition to their well-known 

long distance upstream migrations into river networks. 

5. How would you characterize the demographic effects of populations by artificially limiting 

movement of those fish that might be expected to move? 

Experience with headwater fishes shows that catastrophic factors are most likely to cause 

local extinctions (Dunham et al. 2003), and that demographic factors, while important, may be 

less likely to cause extinction unless population sizes are extremely low. Because headwater 

stream systems are naturally dynamic, the fishes that live in them are invariably those species 

with life histories tuned to rapid reproduction and the ability to move extensively within stream 
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networks when necessary. Thus, they are demographically resilient and plastic in the face of 

highly variable environments susceptible to unpredictable catastrophic environmental events. 

See Bisson et al. (2005) for an excellent case study whose results demonstrate, in part, the 

resiliency and plasticity of headwater stream salmonids. 

6. Considering demographic and genetic characteristics of headwater fish populations, how would 

you define a population within the stream network? 

Defining “populations” is one of the most difficult issues in ecology and may best be viewed 

in terms of different criteria and purposes for which operational units are defined. For 

example, new methods of genetic analysis (Neville et al. 2006a) can be used to cluster 

individuals into “populations” (based on theoretical expectations of linkage and HardyWeinberg equilibrium) or groups of individuals more likely to interbreed with each other than 

with individuals in other groups. Discontinuities in habitats can also be used to define what 

may be considered as “populations” for analyses of species occurrence or persistence (e.g., 

Dunham et al. 2002). In practice, both views may be useful for identifying “populations” and 

for understanding processes influencing fish population dynamics. For example, in the case of 

Lahontan cutthroat trout (O. c. henshawi), Dunham et al. (2002) defined “patches” of 

potentially suitable habitats based on environmental gradients and modeled the probability 

occurrence of cutthroat trout “populations” in patches. A finer-scale look at genetic 

structuring within one of the larger patches revealed significant spatial variability, however 

(Neville et al. 2006b). Thus, we view definitions of “populations” as dependent upon the 

objective of the study or management application, and the criteria and spatial scales of interest. 

7. Considering demographic and genetic risks to headwater fish populations, at what scale(s) 

would you consider the consequences of not providing passage? 

The consequences of not providing passage include increased probability of extinction, loss 

of genetic variability that could lead to inbreeding or more likely loss of evolutionary potential, 

as reviewed on pages 14-19. It should be noted that the persistence of isolated and fragmented 

populations above impassable barriers is primarily affected by external forcing factors (e.g., 

catastrophic disturbance), whereas the long-term viability of these populations is influenced 

more by intrinsic factors affecting populations (e.g., genetic, demographic). See Fausch et al. 

(2006) for a discussion of “persistence” versus “viability” as management goals. 

8. If we were to not provide headwater fish passage in forested landscapes under some 

circumstances, how might we identify/quantify or otherwise address the cumulative effects to 

fish populations in individual and neighboring streams? 

The issue of cumulative effects relative to fish passage is best considered in a spatial 

context. Within a particular watershed or stream network, the total amount of potentially 

suitable and known or probable occupied habitat could be considered relative to different 

scenarios involving removal of fish passage barriers. This would provide a simple, networkscale view of habitat gain or loss for different scenarios. A more spatially explicit view of 

cumulative effects would involve analyses of connectivity and size of habitats, which have been 

repeatedly demonstrated to be key factors driving fish populations in headwater streams 

(Fausch et al. 2006). A variety of metrics describing connectivity are available for describing 

fragmentation of stream networks (e.g., Isaak et al., in press) and could be used to estimate 

potential spatial cumulative effects of retaining or removing individual barriers or types of 

barriers across a stream network. This would be a relatively straightforward and inexpensive 

process that could utilize a geographic information system with basic spatial data and 

information on barrier locations and extent of fish distributions (e.g., Fransen et al. 2006). 
36

Time may also factor into cumulative effects assessments since some risks are time-dependent 

(see next answer). 

9. How much habitat can be omitted from access without incurring genetic or demographic risks 

to headwater fish populations? 

This question can only be addressed by studying these influences relative to existing 

barriers or by monitoring the impacts of passage restoration in a carefully designed study. 

Predictive models of the genetic or demographic effects of barriers could be developed to 

provide basic guidelines for “how much is enough” or alternatively “how much is not enough” 

in terms of identifying opportunities for fish passage restoration. An effort like this is currently 

underway in central Idaho, where genetic variability in rainbow trout from 55 different streams 

is being studied in relation to influences of habitat size, culvert barriers, and wildfire-related 

disturbance (Neville et al. 2006c). The goal is to develop a predictive model of the effects of 

these different factors to gain an understanding of which factors are most influential and where 

restoration could provide the greatest benefit to fish populations. Sometimes these models can 

lead to unexpected implications. For example, conventional wisdom would dictate we restore 

fish passage for larger habitats first. However, populations in small habitats are more 

vulnerable to extinction over short time frames (e.g., Morita and Yamamoto 2002) and may 

merit greater priority in time, even if small populations are less valuable overall than large 

populations. Prescriptions will clearly vary on a case-specific basis. 

10. How many fish and over what intervals is needed to alleviate genetic consequences of isolation 

(genetic drift, inbreeding, etc)? 

This is a difficult question to answer in practice. Based on theory, the rule of “one migrant 

per generation” or OMPG is commonly prescribed to minimize the chances of inbreeding and 

loss of evolutionary potential via genetic drift while allowing local populations to maintain 

their genetic distinctness (see Wang 2004 for a recent analysis). In other words, this is a 

balance between the forces of drift and “migration.” Here “migration” as used in the OMPG 

rule corresponds to what we define as “dispersal.” OMPG is based on the effective rate of 

gene flow – in other words, dispersing individuals that actually breed with the new population 

they move into. OMPG does not hold if dispersing individuals do not have the same 

reproductive success as fish in the receiving population. The key to finding an appropriate rule 

of thumb is an understanding of the relative genetic contributions of dispersing individuals to 

the receiving population – they are likely not random. In the face of this uncertainty it is 

commonly recommended that 1-10 individuals per generation may be needed to provide 

sufficient gene flow among artificially isolated populations. 

In the broader context, there is the question of “what is natural” in terms of gene flow? 

Fish populations are often naturally isolated, even in the absence of obvious physical barriers 

to movement in headwaters. There has not been enough comparative work (see answer to #3 

above) of gene flow among basins for headwater fishes to provide some general prescriptions 

for expected patterns of gene flow or dispersal relative to the spatial structure of stream 

networks and other factors that influence fish movement (e.g., Neville et al. 2006a). We view 

the question of “what is natural” as more important than basic prescriptions derived from 

OMPG. 

11. Are there science-based reasons for developing headwater fish passage criteria that differ 

among major land uses (i.e., forested, agricultural, or urban)? 

There could be a variety of possibilities depending on the criteria in question. It is wellknown that lands with different uses and the streams draining them exhibit different physical 

dynamics and patterns of fish occurrence. In the context of a cumulative effects analysis, this 
37

could lead to very different views of restoration priorities as described above. However, there 

is nothing inherently unique about different land uses per-se other than their impacts on the key 

considerations for identifying the impacts of different alternatives for passage restoration. 

12. Are there other questions related to this topic that you recommend be addressed? 

These are described in the literature synthesis. Two very important issues not addressed in 

this list are the need for a rigorous monitoring and evaluation program for fish passage 

restoration and consideration of the value of intermittent streams for fish populations, 

especially anadromous species of high value. There are many other issues that could be 

addressed, but relative to the objectives that appear most urgent for fish passage restoration, 

these two issues would seem to merit higher priority. 

13. Given the above questions, how would you summarize the movement/connectivity needs of 

resident fish in headwater streams over the short-term (day-to-day) and long-term (years) 

considering the dynamic nature of stream channels, disturbance, and recolonization? 

To answer this question would be to repeat what we have provided in the literature 

synthesis, so we refer to that for the answer.