AN ABSTRACT OF THE THESIS OF

Kenneth J. Rodnick for the degree of Master of Science in

Department of Fisheries presented on March 11, 1983

Title: Seasonal distribution and habitat selection by the redside

shiner, balteatus, in a small Oregon stream Redacted for Privacy Abstract approved: Hiram W. Li

Seasonal habitat availability, utilization, and selection byyoung

of the year (<25 mm) and adult (>25 mm) , Richardsonius balteatus, were studied for 1 year in sections of Greasy Creek, Benton

County, Oregon. Intensive stream mapping procedures and snorkling observations provided most of the quantitative measures for habitat availability and utilization respectively.

A multivariate discriminant analysis and classification suggested spatial segregation of young of the year and adult redside shiners along gradients of water velocity and depth of the water column.

Throughout the year, young redside shiners occupied shallower water than adults and utilized areas with lower mean water velocities.

Associated with increased winter stream flows and lowered water temperatures (< 100 C), redside shiners were inactive and found in habitats offering the most cover and refuge from current.

Overwintering areas populated by redside shiners included undercut banks, root wads, bank failures, fallen trees, and backwaters. During the transitional period between winter andsummer, adult redside

shiners shifted from overwintering habitats to the fasterwater of the

main channel. Activities related to spawning and aggressive defense

of space accompanied this shift. Young redside shiners continued to

utilize protected margins.

A multivariate discriminant analysis and classification comparing

available and utilized stream habitats provided indices ofhabitat

selection. Both young of the year and adult redside shinerswere

relatively selective in the stream habitats they utilized. The

importance of four physical components (depth, current velocity, substrate composition, and cover forms) varied seasonally and with the life stage considered.

Similar patterns of habitat utilization for redside shinerswere observed in four larger streams and rivers. The availability of large, deep pools was important, new habitat for bothyoung and adult redside shiners during periods of reduced stream flow in larger streams and rivers. SEASONAL DISTRIBUTION AND HABITAT SELECTION BY THE

REDSIDE SHINER, RICHARDSONIUS BALTEATUS, IN A SMALL OREGON STREAM

by

Kenneth J. Rodnick

A THESIS

submitted to

Oregon State University

in partial fulfillment of the requirements for the degree of

Master of Science

Completed March 11, 1983

Commencement June 1983 APPROVED:

Redacted for Privacy Associate Professor of Fisheries, in charge of major Redacted for Privacy

Head of Departmeft of Fisheries and Wildlife

Redacted for Privacy Dean of Gradua School

Date thesis is presented March 11, 1983

Typed by LaVon Mauer for Kenneth J. Rodnick ACKNOWLEDGEMENTS

I would like to dedicate this manuscript to my parents and family

who have always supported my academic interests and activities.

Dr. Paul Reimers sparked my interests in behavioral research and

the stream ecology of the redside shiners. My undergraduate studies and experiences with Dr. Peter Moyle and Dr. Joseph Cech further developed my background and appreciation for fisheries research in the field and labora*ory.

I would like to extend a special thanks to Dr. Norbert Hartmann,Dr.

James Hall, and Dr. Fred Everest for their helpful ideas and criticisms throughout the study. Concurrent with my research, Gordie

Reeves developed his own research interests concerning the interaction between redside shiners and juvenile salmonids in streams.Gordie assisted with the field work and was a valuable source of observations, comments, and discussion.

I owe much of my personal growth and accomplishments during my graduate program to my major professor, Dr. Hiram Li, and his wife

Judy. They extended themselves well beyond any of my initial expectations. Dr. Li's office door was always open and he was an unlimited source of energy, ideas, encouragement, and criticisms.

This research was funded by Oregon Water Research and Technology through the Water Resources Research Institute Project W93-B-077 ORE and the Cooperative Fisheries Research Unit at Oregon State

University. TABLE OF CONTENTS

Page

I. INTRODUCTION 1

II. STUDY AREA 5

III. MATERIALS AND METHODS 9

Sampling Sites 9

Sampling Methods 9

Selection of Habitat Variables 11

Statistical Methods and Analysis 15

IV. RESULTS 18

Summer Habitat Utilization 18

Habitat Discrimination by Life Stages 23

Habitat Selection 23

Winter Habitat Utilization 25

Habitat Discrimination by Life Stages 34

Habitat Selection 34

Transitional Habitat Utilization 35

Habitat Discrimination by Life Stages 41

Habitat Selection 41

General Behavior Patterns 42

V. DISCUSSION 43

VI. LITERATURE CITED 53 LIST OF FIGURES

Figures Page

1. Location of Greasy Creek. 6

2. Location of sampling points in measurements ofstream

habitat availability (mapping). Sampling begins at

the downstream end of the study site andproceeds

upstream. Sampling points occur at 2 m intervals,

both across the stream and moving upstream.

Alternate banks are used as references for each

transect. 12

3. Frequency histograms for utilized and available

depths of the water column during thesummer period. 20

4. Frequency histograms for utilized and available

current during the summer period. 21

5. Mean substrate composition for utilized and available

habitats during the summer period. 22

6. Frequency histograms for utilized and available

depths of the water column during the winter period. 31

7. Frequency histograms for utilized and available

current during the winter period. 32 Figures Page

8. Mean substrate composition for utilized and available

habitats during the winter period. 33

9. Frequency histograms for utilized and available

depths of the water column during the transitional

period. 38

10. Frequency histograms for utilized and available

current during the transitional period. 39

11. Mean substrate composition for utilized and available

habitats during the transitional period. 40 LIST OF TABLES

Table Page

1. Categories used to characterize Greasy Creek

substrate composition. 14

2. Habitat variables measured at summer locations of

redside shiner and corresponding available stream

habitats. 19

3. Variable loadings and unbiased classification results

for habitat discrimination by life stages. 24

4. Variable loadings and unbiased classification results

for habitat selection by young redside shiners. 26

5. Variable loadings and unbiased classification results

for habitat selection by adult redside shiners. 27

6. Stream habitat types selected by redside shiners

during winter periods. 29

7. Habitat variables measured at winter locations of

redside shiner and corresponding available stream

habitats. 30

8. Habitat variables measured during periods of changing

discharge between seasons (transitional habitats). 37 SEASONAL DISTRIBUTION AND HABITAT SELECTION BY THE

REDSIDE SHINER, RICHARDSONIUS BALTEATUS, IN A SMALL OREGON STREAM

INTRODUCTION

The main objective of this study was to examine the spatial and

temporal relationship of the redside shiner, Richardsonius balteatus,

to its stream habitat surroundings. Specific objectives included: 1)

to document and quantify seasonal patterns of habitat utilization by

the redside shiner in streams; 2) to quantify the corresponding habitat availability during different seasons; 3) to develop a multivariate approach to measure habitat selection by the redside shiner in streams.

The redside shiner is a small cyprinid, length to 180mm, occurring in coastal streams of Oregon and Washington, the Columbia

River below Snake River Falls, and the Skeena and Fraser systems of

British Columbia (Scott and Crossman 1973, Wydoski and Whitney 1979).

Because it occupies large lakes, small ponds, moderately fast streams, and irrigation ditches the redside shiner is considered one of the most abundant and widespread freshwater within its range

(Weisel and Newman 1951, Scott and Crossman 1973). Early studies focused on the high varability of anal fin ray counts over its geographic range (Eigenmann 1895). This variation led to numerous subspecies designations. Today just two forms are recognized: R. balteatus (10-24 anal rays) and R. egregius, the (8 or 9 anal rays) (McPhail and Lindsey 1970). The great variation in 2

anal fin rays has not been correlated with habitat differences and

still remains unresolved.

The redside shiner has been most intensively studied in lakes or

lake systems (Crossman 1959, a,b, Lindsey and Northcote 1961, Scott

and Crossman 1973, Wydoski and Whitney 1979). Relatively little is

known about the biology and behavior of the redside shiner in streams.

Redside shiners have been observed to partition lake resources with

the kamloops trout, Salmo gairdneri, and are suspected of competing with and serving as prey for the kamloops trout (Johannes and Larkin

1961). Unfortunately, non-selective chemical poisoning has been a common management measure to reduce redside shiner numbers in streams without any knowledge of general behavior and distribution in streams.

The study of patterns of distribution and abundance of organisms is fundamental to ecology (Andrewartha and Birch 1954). Liebig

(1840) found that these patterns are limited by the resource in shortest supply. Shelford (1913) developed the concept of zones of tolerance, whereby the distribution patterns are circumscribed by physiological limits. These patterns are of interest to students of niche analysis, community structure, and to those interested in habitat dynamics. Unfortunately, some of the terminology has been ambiguous in the past because of the interrelatedness of concepts

(Whitaker et al. 1973). The terminology of Whitaker et al. (1973) will be followed. The ecotope comprises niche dimensions (n) and habitat demensions (m). Population density is a response to each set of dimensions. The niche hypervolume is a response by the species to 3 the n variables by which all species in a specific association or community are related. This is identical to the realized niche of

Hutchinson (1958). The habitat hypervolume is formed from the m variables described the physical and chemical environment and is related to a diversities or between habitat comparisons.

Reasons for changes of abundance between habitats (Patches) have been proposed by Fretwell and Lucas (1970) and Fretwell (1972) in a formal framework. This framework suggests that can assess patch suitabilities and select which patch to occupy from the array that is available. Thus, habitat distributions results from a behavioral phenomenon involving stimuli and responses that is quantified by the number of individuals present in each defined habitat (Frewell 1972, Frazer and Sise 1980). The resulting environmental patchiness and dynamic resource availability have been shown to affect both terrestrial (Dyeser and Shugart 1978) and aquatic

(Frazer and Sise 1980) habitat utilization. Habitat selection by an organism should weight time and energetic expenditures with the environmental factors present (Southwood 1977).

It has been suggested that fishes tend to specialize with respect to specific habitat types and that stream environments are heterogeneous with patches arranged longitudinally (Mendelson 1975,

Gorman and Karr 1978). Unfortunately few studies of stream or lake populations of fishes have documented patterns of habitat utilization with the corresponding availability. The selection process, comparing patterns of utilization and availabilities, such as that examined in 4

predator-prey relationship has not been formally analyzed. There have

been field studies that have investigated temporal variability, including daily and seasonal changes in stream conditions and

behavior. Limited studies examining unfavorable winter periods have demonstrated drastic changes in stream environments and habitat utilization by fishes (Chapman and Bjornn 1969, Bustard and Narver

1975). Another consideration is that intraspecific size andage differences can reflect differences in habitat utilization (Gee and

Northcote 1963, Pianka 1976, Matthews and Hill 1979). 5

STUDY AREA

Greasy Creek, a small fourth order stream located 12kilometers

west of Corvallis, Benton County, Oregon, was selected for study

(Figure 1). Greasy Creek is a major tributary to the Marys River

system and originates on the southern slopes of Marys Peak. Starting

at an elevation of 150 meters, Greasy Creek flows eastward13

kilometers through a narrow agricultural valleyto its confluence with

the Marys River near Philomath, elevation 80meters. Total drainage area of the stream is approximately 100 square kilometers (U.S.G.S. topographic map, 7.5 minute).

Greasy Creek is located in the Oregon Coast Rangerain shadow and receives moderate annual precipitation (175-200 centimeters). Most of the precipitation occurs as rainfall between October and May.

Impervious sedimentary formations and shallow soils in theupper watershed provide little volume for water storage and littlecapacity for buffering stream discharge. Streamflow therefore closely follows the rainfall pattern. Mean daily discharge varies from less than 5 cfs in late summer to over 100 cfs during winter freshets (Wiltset al. 1960). Storm events result in mass substrate movement, tree fall, streambank deterioration, formation of debris jams, and high turbidities. In summary, wide fluctuations in streamflow are characteristic during winter months and severe water shortage characterize summer periods. Main channel water temperatures

7

value of 3°C during December and January (personal observations).

Dissolved oxygen is typically at or near saturation values.

Most of lower Greasy Creek is heavily used for irrigation and

various agricultural purposes. Water is withdrawn at several points

and streamside vegetation has been removed in many areas. Livestock

grazing occurs right up to the stream banks, animals are drivenacross

the stream channel, and many feedlots drain directly into thestream.

Stream banks are commonly steep (1-3 meters) and unstablewith constant

erosion creating a dynamic stream course. No fish hatcheries or

impoundments are present on Greasy Creek.

Twelve species of fishes were present in Greasy Creek of which

only five were abundant. The common Greasy Creek fishes included: 1)

the redside shiner, Richardsonius balteatus, 2) the speckled dace,

Rhinichthys osculus, 3) the reticulate sculpin, Cottus perplexus, 4)

the torrent sculpin, Cottus rhotheus, and 5) the cutthroat trout,

Salmo clarki.

Streamside vegetation primarily consisted of red alder, Alnus

rubra, willow, Salix spp., and maple, Acer macrophyllum, with an

understory dominated by salmonberry, Rubus spectabillis, and

blackberry, R. lacinlatum. Aquatic vegetation was limited to small

amounts of filamentous algae and diatoms.

Qualitative observations of redside shiner behavior was conducted

in 4 additional Oregon streams and rivers for comparative purposes.

These systems all had greater discharge values and greater watershed areas than Greasy Creek. They included 2 Willamette Valley streams 8

[the Luckiamute River (Polk County) and Mill Creek (Polk County)] and

2 coastal streams [the Smith River (Douglas County) and the Millicoma

River (Coos County)]. 9

MATERIALS AND METHODS

Sampling Sites

Ten permanent study sites were selected followingan extensive

survey to determine the longitudinal distribution limits of the

redside shiner in Greasy Creek. Each site was chosen to represent

available stream reaches at various distances upstream andconsisted

of a linear and meandering section. Study sites measured

approximately 20 meters in length and were marked by permanent wooden

stakes.

Sampling Methods

Intensive stream surveys were conducted during three different

discharge regimes: 1) summer low flows (August-September 1980), 2)

winter high flows (January-March 1981), and 3) decreasing transitional

flows (May-July 1981).

A variety of techniques was used to locate shiner and quantify

habitat utilization. Summer and transitional habitat utilization was measured by snorkling upstream through study sites. This is a rapid, effective stream survey method that has minimal disruptive effects on

fish behavior (Northcote and Wilkie 1963, Goldstein 1978). A comparison of snorkling and seining techniques demonstrated that reliable estimates of individual fish size and population size could be obtained with snorkling techniques and the different techniques gave similar estimates when used appropriately.Each redside shiner or group of shiners was identified, counted, and placed into groups of 10

<25 mm and >25 mm. A diving glove marked off in 1 cm intervals provided an underwater reference. Underwater visibility was a major factor influencing snorkling and 1 m was considered the minimum value for reliable observation. Snorkling observations were normally conducted between 1000 and 1500 hours to utilize the period of greatest underwater visibility. In addition, diel observations were conducted in order to note changes in habitat utilization and day/night activities. An underwater light and wooden probe were used to search for fish at night and in darkened areas of dense cover.

During the winter period, snorkling observations were limited by poor water clarity, extremely high current velocities, low water temperatures, and the inaccessible nature of refuge areas occupied by fish. Stunning fish by electroshocking and allowing the stream flow to carry them out of refuge areas was considered the only effective sampling technique.

Each redside shiner sighting was considered a data point and shiners were classified as young (<25 mm total length) or adults (>25 mm total length). During snorkling, fish were observed for 1 to 3 minutes to estimate a focal point of occurrence, the location where a fish spends the most time (Wickham 1967, Bovee and Cochnauer 1978).

Focal points were marked with a spark plug attached to a coded wooden buoy, and fish were then displaced downstream. Measurement of particular physicochemical stream components were recorded for each focal site the same day fish were observed. When shiners were not located within the study site boundaries, efforts were made to survey both upstream and downstream from the site until shiners were located. 11

After quantifying habitat utilization for the shiners, systematic

mapping of the total wetted area at each study site was conducted to

determine habitat availability. Variables recorded at each locus

during stream mapping were identical to those recorded during focal

sampling.

Mapping was conducted upstream in a systematic fashion and point

samples were taken at grid intervals of 2 meters (Figure 2). After

each transect, alternate banks were usedas a reference to reduce bank

bias. Mapping of available habitat was conducted less than 24 hours

after focal sampling to ensure that the changes of stream habitat would

be minimal. A minimum of 20 loci were recorded for each site to

adequately represent stream habitat availability. These sampling

techniques required Lhe effort of one or two individuals to collect

the data. Data from focal samples (utilization) and mapping

(availability) collected for each season were separately pooled and

analyzed.

Selection of Habitat Variables

The number of environmental variables that may affect species

distribution is potentially infinite. Three criteria used in the

selection of habitat variables for measurement included: 1) each variable should be related to environmental structure (availability) and be known to influence the animal's distribution (utilization); 2) each variable should be quickly and precisely measurable with non-destructive sampling techniques; and 3) each variable should accurately describe habitats and be highly specific. SAMPLING DIRECTION So.

e-rn 'Ia

4013

I I 49

10 fr .411-- FLOW DIRECTioN

0 2

meters

Figure 2. Location of sampling points in measurements of stream habitat availability (mapping).

Sampling begins at the downstream end of the study site and proceedsupstream. Sampling

points occur at 2 m intervals, both across the stream and movingupstream. Alternate

banks are used as references for each transect. 13

Evidence suggests that substrate composition, depth, and current velocity are three physical components important to the microhabitat specialization of stream fishes (Gorman and Karr 1978). In the present study, substrate composition was visually estimated with an

Aquascope viewing box, and percentages were assigned to categories

(Table 1). Substrate categories A through G correspond to alluvial material of increasing size with category H including organic debris

(leaves, twigs, branches, etc.). The depth of the water column was measured in centimeters with a graduated wooden dowel at each sampling point. Mean velocity was measured four-tenths (0.4) the distance off the bottom, with a Marsh McBirney electronic current meter model 201.

The distribution of stream fishes has also been positively correlated with different forms of cover (Boussu 1954, Butler and

Hawthorne 1968, Lewis 1969, Bustard and Narver 1975). A "presence" notation was recorded when various forms of defined cover were available, and defined as follows: overhead cover was an object

(tree, branch, etc.) above the water surface providing shade between

1000 and 1500 hours; undercut banks were cover under the banks; lastly, surface turbulence was an area with a broken water surface due to irregular instream structures and fast currents.

For each sampling period, air temperature, water temperature, and dissolved oxygen were recorded with a Yellow Springs instrument, temperature/oxygen meter model 54A. All three factors were measured at the beginning of each sampling period. Pilot tests found that they did not vary during the sampling time course. 14

Table 1. Categories used to characterize Greasy Creek substrate

composition.

Categories

A. Sand, silt, or clay

B. Small gravel < 2.5 cm

C. Gravel 2.5 - 7.5 cm

D. Cobble 7.5 - 15.0 cm

E. Rubble 15.0 - 30.0 cm

F. Boulders > 30. 0 cm

G. Bedrock

H. Woody debris leaves, twigs, branches,

etc. 15

Crucial to the measurement of habitat were the assumptions that stream habitats were heterogeneous and one or more of the measured environmental variables would be correlated with and help explain distribution patterns of the shiners.

Statistical Methods and Analysis

To characterize the Greasy Creek habitats utilized by the redside shiner and available habitats, summary statistics including means and

95% confidence intervals were calculated (SPSS 'Frequencies' subprogram). Preliminary examination of the data consisted of plotting univariate frequency histograms for the variables depth,mean current velocity, and substrate composition.

Stream habitat data by their very nature are always multivariate and should be analyzed in that fashion. Multivariate techniques are currently accepted by ecologists (Green 1980). However, these same techniques have been used by the ecologist studying stream fishes only recently. Historically, variables are treated singly as if only each variable were independent. When considering more than one variable for ecological studies, multivariate analysis often represents the most appropriate and powerful approach to describe structure (Green

1974, 1980; Colgan 1978).

Because a large number of variables were recorded during sampling, one objective of the analysis was to reduce the number of interdependent variables, thereby increasing comprehension and interpretation of results. Multivariate analysis of variance, specifically discriminant analysis techniques, were used to determine 16

which variables contributed most effectively to life-stage

differentiation. Discriminant analysis techniques were also used to

compare utilized and available habitat (habitat selection). The

discriminant analysis (Xerox Version, SPSS 602, Nie et al. 1975)

employed was stepwise, incorporating or eliminating variables based on

Wilks lambda, which maximized overall group differences (Klecka 1975).

In this fashion each variable is tested for statistical significance and assigned its relative importance by order of entry. Variables entered early in the analysis account for a considerable amount of between-group differentiation. Ancillary variables tested independently do not discriminate between groups and yet they collectively may provide additional discrimination in thepresence of other variables.

The particular discriminant procedure used was considered

"unbiased" because the computer randomly selected 75% of the original cases from each group for the analysis and ensuing discriminant functions. The remaining cases (25%) were used for classification purposes. Pimentel and Frey (1978) have reviewed the general assumptions and limitations of discriminant analysis and its application to empirical studies. They suggested that discriminant methods are robust from departures from assumptions.

Discriminant classification is a powerful tool for evaluating the effectiveness of the derived discriminant functions (Klecka 1975).

Scores for each data point were calculated with each case being assigned to a group based on these scores. Since the actual group was previously known, the percentage of correct classifications evaluated 17

the resolving power of the discriminant function.A classification

value of 75% was considered sufficient to describe group differences.

Several discriminant functions were generated for each intergroup

analysis and the final determinations were made when the addition of an extra variable did not improve the classification. In summary, the analysis of habitat selection is multivariate and incorporates measurements of both utilized and available habitats. Different sizes of fish and the different stream flow regimes, corresondingto different seasons were considered to obtain a comprehensive view of changing patterns of habitat selection. 18

RESULTS

During the 1 yr study period approximately 60 hrs of snorkling

observations were conducted, accounting for 615 young shiners and 316

adult shiners at focal points in Greasy Creek. During the winter

interval 56 young shiners and 161 adult shiners were located by

electroshocking technique. The overall mapping procedure physically

characterized 3650 square meters of stream habitat.Additional

snorkling observations in the 4 larger streams totaled 18 hrs.

Summer Habitat Utilization

Summer stream habitats were characterized by low stable flows,

clear water, and warm water temperatures in the main channel ranging

from 12.5 to 22.0° C. The majority of the sampling occurred between

15 and 18°C. Corresponding dissolved oxygen values were at ornear

saturation.

The numbers of shiners observed during this period were 327 young

and 125 adult fish. Shiners occurred in all 10 sampling sites

examined. Young shiners were quite uniform in size, ranging from

16-22 mm total length whereas adult fish ranged from 42-110 mm.

The data collected suggest habitat utilization differences

between young and adult shiners (Table 2, Figures 3, 4, 5).Recently emerged shiners and somewhat larger young-of-the-year shiners occupied shallow water areas with minimal water velocity in large aggregations

(mean group size±SD = 18.2±9.2). Young shiners were predominately found associated with very small particle substrates.Adult shiners 19

Table 2. Habitat variables measured at summer locations of redside

shiner and corresponding available stream habitats.

Young shiners Adult shiners Available Variable (n=327) (n=125) (area=1575

Depth 31.4cm ± 6.7 55.7cm ± 8.8 34.3cm ± 2.3 (x ± 95% CI)

Mean Velocity 5.4cm/sec ± 1.7 20.0cm/sec ± 5.5 16.5cm/sec ± 1.7 (x ± 95% CI)

Substrate Composition (% occurrence)

Sand/silt/clay 46.4 23.6 25.1

Small Gravel 17.6 33.3 38.9

Gravel 8.5 21.5 16.2

Cobble 3.6 4.7 4.2

Rubble 1.9 0.0 0.9

Boulders 5.9 4.6 1.8

Bedrock 6.0 2.4 6.0

Woody Debris 10.1 9.9 6.9

Cover Forms (% occurrence)

Instream 100 88 95

Overhead 39 58 54

Undercut Banks 11 25 11

Surface Turbulence 11 46 32 20

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during the summer period. 22

Young Shiner <25mm

Adult Shiner> 25mm

Availability

Figure 5. Mean substrate composition for utilized and available

habitats during the summer period. 23

were located in areas of faster water velocity and deeper water than

were young shiner (Table 2, Figures 3, 4). Areas utilized by adults

also contained a greater portion of gravel, cobble, undercut banks,

and surface turbulence (Table 2). The number of adult fish observed

aggregating in a group was typically less than young fish (mean group

size±SD = 8.7±5.8). Observations suggest that both young and

adult shiners aggregate and feed during most of the day with peak

activity occurring at dawn and dusk. Adults were located throughout

the water column and on the substrate, whereas young shinerswere

found at or near the water surface. Interestingly, most shiner

occupied similar stream positions throughout the 24-hr period.

Habitat Discrimination by Life Stages

The disciminant function incorporated mean water velocity and water column depth at the site of occurrence (Table 3). Adult shiners had higher postiive loadings on both variables, reflecting utilization of faster, deeper water microhabitats. During the classification phase of the discriminant analysis, 93.3% of the data cases not selected for analysis were properly assigned to the respective groups. Overall, the summer microhabitat analysis demonstrated intraspecific spatial separation based on measured environmental variables.

Habitat Selection

Differentiation between habitats utilized by young shiners and available habitats was related to the mean water velocity, the percent gravel and bedrock present, and the amount of instream cover 24

Table 3. Variable loadings and unbiased classification results for

habitat discrimination by life stages.

LOADINGS

Classification Variables Young / Adults Wilk's Lambda (%)

SUMMER

Depth 0.115 0.215 0.411 93.3 Mean Velocity 0.120 0.404

WINTER

Depth 0.100 0.148 0.763 86.1

TRANSITIONAL

Depth 0.503 1.912

Mean Velocity 0.195 0.771 0.323 95.2 Sand/silt/clay 0.863 0.312

Small Gravel 0.354 1.230 25

(Table 4). Loading values suggest young shiners selected slower water

areas with less gravel and bedrock, and more instream cover than was

generally available. A classification value of 73.5% suggests that

the resolution for this discriminant function is adequate but not

outstanding.

Stream habitats utilized by adult shiners and available habitats

were differentiated according to water depth, percent cobble present,

and surface turbulence (Table 5). Adult shiner loading values were

greater for all the variables compared to available habitats,

suggesting selection of deeper stream microhabiatts containing more

cobble and surface turbulence. A classification value of 80.8%

indicates group differentiation and seletion of specific habitats by

adult shiners.

Winter Habitat Utilization

Marked seasonal changes in stream habitats occurred during the

9-week period January 17-April 19, 1981. Intermittent floods and high

stream flows modified previously available habitats and created new habitats by channel expansion and deepening. Winter habitat availability could not be predicted from summer low flow surveys.

Main channel water temperatures were quite stable, ranging from 4.5°C

to 8.0°C, and dissolved oxygen values were always recorded at or near saturation.

Snorkling observations were limited to 1 hr intervals due to the temperature, velocity, and turbidity. Electroshocking proved helpful for locating fish and quantifying the numbers and life stage 26

Table 4. Variable loadings and unbiased classification results for

habitat selection by young redside shiners.

LOADINGS Classification Variables Young / Available Wilk's Lambda (%)

SUMMER

Mean Velocity -0.009 0.052

Small Gravel 0.031 0.066 0.722 73.5 Boulders 0.058 0.078

Instream Cover 44.099 41.682

WINTER

Turbulence -0.098 3.989

Small Gravel -0.001 0.067 0.385 90.2

Mean Velocity 0.005 0.047

TRANSITIONAL

Depth 0.032 0.118

Small Gravel 0.017 0.098 0.430 89.1

Woody Debris 0.087 -0.009 27

Table 5. Variable loadings and unbiased classification results for

habitat selection by adult redside shiners.

LOADINGS Classification Variables Adults / Available Wilk's Lambda (%)

SUMMER

Depth 0.175 0.093

Gravel 0.107 0.065 0.638 80.2

Turbulence 2.937 1.957

WINTER

Depth 0.137 0.088

Mean Velocity 0.021 0.060 0.466 88.0

Small Gravel -0.043 0.000

TRANSITIONAL

Depth 0.198 0.101 0.618 82.8 28

present at a particular site. Focal samples were recorded whenever

specific utilization patterns were evident, but sampling difficulties

associated with some of the winter habitats prohibited accurate

measurements. Adult shiners typically occupied areas of dense and

extensive cover, resulting in fewer focal samples than for young

shiners (119 versus 222). All observations of shiners were recorded

as classes of discrete winter habitat (Table 6). Five study sites

were sampled and fish were located in just three of them. When

shiners were not located in a chosen sampling section, theywere

usually observed a short distance up or downstream in associationwith

cover.

Both young and adult shiners utilized discrete, non-randomly distributed stream microhabitats, corresponding to increasedstream flows and lowered water temperatures. Young shiners occurred primarily in backwater areas including sidepools and quiet waterareas

(Table 6). Adult fish were found associated with a greater variety of habitat types, especially areas where bank failures and backwater areas were present. Both young and adult fish were located in areas with minimal water velocity, containing substrates dominated byvery small particles (sand, silt, or clay) and woody debris (Table 7,

Figures 6, 7, 8). All shiner microhabitats were usually associated with both instream and overhead cover forms.

Intraspecific differences in habitat utilization were evident as adults utilized deeper areas containing undercut banks and surface turbulence to a greater extent than did young fish (Table 7). Adults were distributed according to the location of root masses and debris 29

Table 6. Stream habitat types selected by redside shiners during

winter periods.

Numbers (% of total)

Young Adults Habitat Types (n=278) (n=280)

Undercut banks 0 (0) 21 (7.5) (with tree roots or woody debris)

Root wads 0 (0) 36 (12.9) (provided by a fallen tree)

Fallen trees 65 (23.4) 16 (5.7) (without root wads present)

Bank failure 37 (13.3) 106 (38.0) (with debris accumulation)

Backwater areas 176 (63.3) 101 (35.9) (including quiet sidepools) 30

Table 7. Habitat variables measured at winter locations of redside

shiner and corresponding available stream habitats.

Young shiners Adult shiners Available Variable (n=222) (n=119) (area=1060 m?)

Depth 54.8cm ± 2.8 83.0cm ± 4.6 51.3cm ± 3.3 (x ± 95% CI)

Mean Velocity 2.2cm/sec ± 0.2 4.1cm/sec ± 0.5 47.8cm/sec ± 4.6 (x ± 95% CI)

Substrate Composition (% occurrence)

Sand/silt/clay 57.5 63.5 26.8

Small Gravel 0.0 3.5 39.0

Gravel 0.0 2.2 17.3

Cobble 0.0 0.2 4.2

Rubble 0.0 0.0 0.3

Boulders 0.0 0.0 0.0

Bedrock 18.0 5.4 5.1

Woody Debris 24.5 25.2 7.3

Cover Forms (% occurrence)

Instream 100 100 99

Overhead 86 92 44

Undercut Banks 14 27 11

Surface Turbulence 0 8 66 31

1O0

2

09

40

99

a

0 10 za29 Mg SO 1111 70 OS 90I 00 110 12A 1701 Of

SO

2g 122ADULT SHMIER C >25/Vi

LS

16 .

10

1 I 1 I t 1 I a 111 ZS SO 441 CO SO 70 90IOC 110 IS ISO 1414

I

AvArlaz_rrr

1 Ell SO 441 OD On 79 SO M 1 011I II 120 170I 41

907111 C CM 2 Figure 6. Frequency histograms for utilized and available depths of

the water column during the winter period. 32

12B

10F

22T DUNS WINER C t2SMP1)

2 10 20 30 M WM7008901,0 111012; 170141

ss.

es.

I

or 111 29 SS t0 SO 1110 7 SSIS1 SO 110 128 IX, 140

S

4YA-T4.44121_Try

4

2

111

I0 20 311 41 SO OS 7 SS 1111 10 11 129 13 I110 PF.MI CURRENT M21.01ZM C OVUM

Figure 7. Frequency histograms for utilized and available current

during the winter period. 33

Young Shiner< 25riri

AdultShiner> 25m

MDR= 5.46X =POLE 6.2.40 GRAVEL 2.2-2% SMALL ORAVEL 3.5w3A

=VT DEBRIS Z5,12511

Availability

GRAVEL 17.3.17% 4.24X

O.]=0 PEINECCIL7

WOOP7 VESKZI 7.37X

MALL GRAVEL 311310

SAND,SILT.OR 28.821X

Figure 8. Mean substrate composition for utilized and available

habitats during the winter period. 34

in the water colum. Young shiners always occurred near the water

surface.

For any particular winter microhabitat similar sized shiners were

found together, the largest shiners found deepest within cover. Mean

group size for young fish was quite large when compared to adult fish

(37.0±22.6 versus 7.9±7.5). All adult shiners were inactive,

extremely dark in coloration, and appeared thin or emaciated. Shiners

remained closely associated with winter microhabitats until

streamflows decreased and main channel temperatures rose above 9-10°C.

Habitat Discrimination by Life Stages

Winter habitats utilized by young and adult redside shiners were

distinguished by water column depth (Table 3). Adult shiners had a

higher positive loading on the single variable, which reflected

utiz(sition of deeper water than young fish. Size specific

preferences were inferred from the statistic that 86.1% of the cases were properly classified.

Habitat Selection

Habitats utilized by young shiners and available habitats were distinguished by the variables surface turbulence, percent small gravel, and mean water velocity (Table 4). Negative loading values suggest that young shiners select areas without turbulence and small gravel. A reduced loading value for mean water velocity indicates a preference for slower water areas than typically available. The 35

classification value of 90.2% denotes group differentiation and strong

selection of specific winter habitats by young shiners.

Winter habitats utilized by adult shiners and available habitats were differentiated according to water column depth, mean water velocity, and percent small gravel present (Table 5). The

corresponding loading values suggest a selection by adult shiners of

deeper, slower water areas, containing less small gravel than the mean

available stream habiatat. An 88.0% classification value indicates strong selection of specific habitats by adult shiners.

Transitional Habitat Utilization

The transitional sampling period, occurring from May 10 to July

15, 1981, was characterized by decreasing stream flows and increasing water temperatures following the winter period. April 14 was the first recorded day when temperatures exceeded 10°C in the main channel. The water temperatures ranged from 10.0-17.5°C during this period. Dissolved oxygen values were always recorded at saturation and water clarity was very good (1-2 meter visibility). Sixty-six young shiners and 72 adult shiners were observed and fish occurred in all five sampling sites examined. Size of young shiners ranged from

24-28 mm and most adults exceeded 60 mm in total length. Focal sampling and stream mapping were completed on July 1 and newly emerged young shiners were first seen in shallow margins on July 15.

Corresponding to decreased stream flows and elevated water temperatures, shiners were extremely active thoughout the 24 hr period. Differences in habitat utilization and behavior patterns were 36

evident between young and adult shiners. Young shiners inhabited

shallow stream margins with very small particle, woody debris

dominated substrates, and slow water currents (Table 8, Figures 9, 10,

11). Mean group size was 22.0±17.1 fish. Brightly colored adult

shiners occurred in small groups (x = 3.4±2.4 fish) of similar sized

fish in deep water columns providing relatively fast water and gravel

substrates (Table 8, Figures 9, 10, 11). The presence of overhead

cover and cover provided by surface turbulence was also correlated

with the adult transitional habitat. During most of June and early

July, adults were actively feeding and aggressively interacting in

what was interpreted to be spawning behavior.A dominant male shiner

would hold a station just downstream froma riffle and physically

displace conspecifics downstream using the lateral aspect of hisbody.

Parallel swimming, erection of fins, and nipping behaviorwas

observed. It could not be discerned whether or not this "displacement

behavior" was confined to the male sex. Occasionally a small group of

male and female shiners would rapidly swim upstream into shallow, fast

moving water Sequential body undulations were performed just above

the substrate interstices for a brief period and then fish returned just downstream. No reproductive products were collected during observations. Although "displacement" behavior and apparent spawning was observed during daylight hours, most shiners were located in

similar stream positions throughout a 24 hr period. 37

Table 8. Habitat variables measured during periods of changing

discharge between seasons (transitional habitats).

Young shiners Adult shiners Available Variable (n=66) (n=72) (area=1016 m2)

Depth 20.8cm ± 4.5 76.5cm ± 2.8 39.3cm ± 2.7 (x ± 95% CI)

Mean Velocity 3.2cm/sec ± 1.1 41.0cm/sec ± 6.2 43.9cm/sec ± 3.8 (x ± 95% CI)

Substrate Composition (% occurrence)

Sand/silt/clay 63.6 21.9 16.9

Small Gravel 1.4 51.2 51.0

Gravel 6.8 15.3 15.5

Cobble 0.0 2.0 4.0

Rubble 0.0 0.0 1.0

Boulders 0.0 2.5 3.3

Bedrock 0.0 1.3 2.9

Woody Debris 28.2 5.8 5.4

Cover Forms (% occurrence)

Instream 100 100 99

Overhead 9 47 34

Undercut Banks 0 14 9

Surface Turbulence 0 71 65 38

¢22 punWINER ((am,

IV ZS 311 1111 r 6 7 El IS 11 13111

® ADULT vi:rim c>tstam)

16.

113

I 1 I ZIP NI 46 69 9 70 is im

18

AV AZ-ABILITY

4

t. MORN 1. 1101110so ....numem. ...111141110. 411WWWMWW

T i T l I 7 I I 1 II VA le 46 68 Si7 SO IStin 11 DETTP1 CCM )

Figure 9. Frequency histograms for utilized and available depths of

the water column during the transitional period. 39

0 10 28 318 48 28 8 7 111 NI188 110 its 118 t40

12

1 .

I 1 -1 s 1 to 38 40 211 0 ns 88 00 1 110 In 13B 140

4

I II 20 MI 4 20al Ts I I IIVI t 140 Waif cjpeprer Yeal=77 Cf24/8223 Figure 10. Frequency histograms for utilized and available current

during the transitional period. 40

Young Shiner <25m.T,

SMALL GRAVEL 1.4-1% RAW,s:M. T.OP GRAVEL 6-94% 13.4-71

WOODY OrRIS 28.2..21X

Adult Shiner> 25mm

SMALL GRA E1,2CIX

GRAVEL 16.3-mx rzeraz 2-zx sial_out 2.1.1X SAMD,SILT,OR BEDROCK 21.0..2= 1.7IX MOODY DEBRIS S.110%

Availability

SMALL ERA

GRAVEL 16.6101 COMAE

RUSJOILE iSX BOULDER

BEDROCK 2.0-3% RAM,S/11,00 WM DEBRIS 6.4EX

Figure 11. Mean substratecomposition forutilized and available

habitats during the transitional period. 41

Habitat Discrimination by Life Stages

Statistical separation of young and adult shiners was based on the variables water depth, percent sand, silt, or clay, percent small gravel, and mean water velocity (Table 3). Loading values for variables reflect young shiner habitats containing shallower, slower water areas, more sand, and less small gravel than adult habitats. The classification value of 92.5% suggests strong intraspecific differences in habitat utilization during the transitional period.

Habitat Selection

The discriminant analysis for selection indicated that habitats utilized by young shiners were best discriminated from available habitats by the variables depth, percent small gravel, and percent woody debris (Table 4). The corresponding loading values suggest that young shiners prefer shallower areas with more woody debris and less small gravel than the typically available habitat. The classification value of 89.1% denotes strong selection of specific habitats by young shiners.

Transitional habitats utilized by adult shiners were differentiated from available transitional habitats by depth of the water column (Table 5). Adult shiner loading values indicate selection of deeper habitats. This single variable discriminant function classified 82.8% of the cases. Selection of specific transitional stream habitats by adult shiners was therefore suggested. 42

General Behavior Patterns

Both young and adult redside shiners in Greasy Creek exhibited

site tenacity throughout the year. Redside shiners displaced from a

focal site by a diver would usually return.

Within the four larger streams examined, adult redside shiners did

not remain at particular sites during the summer and transitional

periods. They would move between different stream microhabitats.

Redside shiners in the larger streams utilized similar habitats

described for redside shiners in Greasy Creek and habitats not

available in Greasy Creek. Large pools with little current present

were not available in Greasy Creek and supported large numbers of

aggregating young and adult redside shiners in the larger streams.

Smaller numbers of adult redside shiners were found in shallow water

with substantial currents present. Adult shiners in faster water

were usually larger, deeper bodied, and more brillantly colored than

adults in large pools. Similar types of winter behavior and habitat

utilization was observed for the redside shiner in all of the streams

examined.

Stream locations occupied by redside shiners often contained

similar sized speckled dace and juvenile salmonids. Redside shiners

freely mingled with groups of dace and intersepcific distances were small. On the other hand, juvenile salmonids often acted aggressively with adult redside shiners and displaced them from stream territories or feeding stations. 43

DISCUSSION

Redside shiners were distributed over a variety of Greasy Creek

habitats and exhibited different behaviors depending on the size of

the fish, the array of habitats available, and seasonal shifts in

habitat availability. Both young of the year and adult redside

shiners were selective in the stream habitats they utilized throughout

the year of study. This was concluded from the unbiased

classification values following the discriminant analysis.Variables with the greatest statistical significance in distinguishing utilized from available habitat varied with the season and life stage considered.

Throughout the year depth of the water column was the most important variable in describing habitat selection by adult redside shiners. A wider variety of variables including depth, water velocity, substrate composition, and cover types described habitat selection by young redside shiners, depending on the sampling season considered. The habitat selection analysis for young redside shiners during the summer period resulted in the lowest classification value.

This suggests that habitat usage was the most similar to habitat availability. However, the value of 73.5% may be indicative of some habitat specialization. These results are especially interesting because young of the year redside shiner utilized similar stream habitats throughout the year regardless of the array of habitat types available. The changing availability of stream microhabitats through seasons resulted in the variety of selection variables chosen for analysis. 44

The discriminant analysis and classification indicated that depth

of the water column and mean velocity were the most critical variables

distinguishing young and adult redside shiner habitats.Although

additional size divisions could have been made, it appears that the

25-mm division reflected major intraspecific differences for redside

shiner habitat utilization and behavior. This pattern is similar to

the ontological shifts in habitats utilized by juvenile salmonids,one

from slow, shallow water to faster deeper water (Everest and Chapman

1972, Stein, et al. 1972). Because fish size is a major determinant

of propulsive efficiency and defines swimming capabilities, total body

length places an absolute limit on the current velocity thatcan be

occupied (Webb 1975). A larger fish with greater swimming

capabilities can successfully occupy a wider range of available

current velocities than smaller fish. Based on an estimated maximum

swimming speed of 10 body lengths per second for cyprinids (Blaxter

1969), a juvenile redside shiner (20 mm in length) could occupy current velocities up to 20 cm per second whereas an adult (75 mm in length) might occur in water flowing up to 75 cm per second.

Observations of redside shiner behavior and habitat utilization in larger streams suggests that life stage differences may not be as evident as in Greasy Creek. The pools of larger streams contained all sizes of redside shiners aggregating together. These observations justify the importance of measuring the habitat availability that corresponds to distribution. Habitat distribution may vary between streams due to differences in habitat availability. Therefore, the 45

results from Greasy Creek may not be applicable because selection

patterns may differ as availability changes.

Winter stream conditions and the corresponding changes in behavior of redside shiners demonstrated that environmental variability isan important factor influencing distribution. Physicochemical changes including reduced water temperatures and increased current velocities coincided with redside shiners shifting habitat locationsto suitable refuge areas and greatly reducing activity. Temperature has a profound effect on fish performance and behavior (Fry 1964). Low temperatures result in decreased standard and active metabolic rates as measured by oxygen consumption and swimming performance (Brett

1964). Personal observations in the field and in laboratory streams suggest that 9-10° C marked the upper threshold for drastic reductions in redside shiner activity. Similar cold-induced overwintering behavior by stream salmonids has been demonstrated in the field (Allen

1941, Chapman and Bjornn 1969, Bustard and Narver 1975), and in the laboratory (Hartman 1965, Mason 1966, Everest and Chapman 1972).

kedside shiners used similar types of winter habitat in Greasy

Creek, Oregon, occupied by juvenile coho salmon, Oncorhynchus kisutch, and steelhead trout, Salmo gairdneri, in Carnation Creek, British

Columbia (Bustard and Narver 1975). These were areas characterized by the presence of upturned root wads, logs, debris piles, and slack water. Only rubble substrates were not available during winter for redside shiners in Greasy Creek because of the large amounts of imbedded sediments present. Most of the winter habitats used by the redside shiners were not available during the summer low flow period. 46

Few backwater areas were included in the permanent study sitesbecause

selection of the study sites occurred during the summer low flow

period. It was noted, however, that the backwater areas were

extremely important overwintering habitat for redside shiners,

juvenile salmonids, and many other stream fishes. Backwater areas

were quite different both physically and chemically than the main

stream channel. Minimal water currents, a shallow water column,a

wider daily temperature flux, and a small substrates characterized

most of the backwater areas sampled. How these factors relate to the

selection of backwater areas during the winter period needs further

investigation. Presumably, overwintering in habitats associated with

cover enhances survival by reducing displacement, physical trauma, and

losses to predation.

During the transitional period between winter and summer, adults

move from habitats of slack water and dense cover to the faster water

of the main channel. This shift is accompanied by activities related

to spawning and aggressive defense of personal space during feeding.

Adults displayed a diverse repertoire of agonistic behavior similar

to those observed by Kalleberg (1958) for juvenile Atlantic salmon, S.

salar: nipping, chasing, fin erection, and physical displacement.

Juvenile redside shiners meanwhile continued to utilize protected

areas near stream margins.

Observations during different periods of the diel cycle revealed

that the redside shiner occupied very similar habitats during the 24 hr period. This was not the case for several other species in Greasy

Creek. During summer and transitional sampling periods, cutthroat 47

trout, S. clarki, was found in slow, backwater areas near densecover

at night and in fast water during the day. Sandrollers, Percopsis

transmontana, and largescale suckers, Catostomus macrocheilus, foraged

in the open channel at night but sought refuge in undercut banks and

in areas of dense cover during the day. The importance of nocturnal

refuges for salmonids and sandrollers has been documented by previous

studies (Chapman and Bjornn 1969, Gray and Dauble 1979) In summation,

changes in habitat availability and habitat utilization should be

examined temporally as well as spatially. Unfortunately most stream

habitat studies do not consider the temporal aspect and therefore

provide partial descriptions.

Habitat usage is considered selective if componentsare used

disproportionately to their availability (Ivlev 1961, Sale 1974,

Johnson 1980). Conversely, if components are used in similar

proportions to availability, usage is considered non selective and

describes a generalist's behavior. The process of habitat selection depends on the entire milieu of physicochemical factors present. If differential selection exists then choice must be based on available resources (Rosenzweig 1981).

Past studies relating distribution of stream fishes with habitat variables have not measured the availability of habitats (Binns and

Eiserman 1979, Orth and Maugham 1982). The relative abundance of fishes provides an index of suitability and distribution is considered a fixed pattern when related to habitat variables. As demonstrated in the present study there are more inclusive assumptions pertaining to habitat selection: 1) habitats differ in availability, 2) habitats 48

differ in basic suitability, and 3) individuals utilize the most

suitable habitats available to them (Fretwell and Lucas 1970).Fishes

may therefore occur in high densities in areas that are suboptimal,

but the best of that which is available. If stream habitats are

subject to dynamic flux, factors influencing habitat selection will

change as witnessed by seasonal changes in habitat selection.

Von Uexkull (1921) suggests that each animal has its own

"Merkwelt" (perceptual world), which is different from its environment

as the investigator perceives it. The design of the field work and

the type of data analysis are considered the most important steps to

ecological research (Colwell and Futuyma 1971). Conceptual

difficulties will typically occur because of the potentially infinite

number of environmental variables. Numerous physical, chemical, and

biological variables have been identified as major determinants of the

distribution and abundance of stream fishes (Chapman and Bjornn 1969,

Krebs 1978). Discussion of habitat is generally restricted to a small number of variables in order to increase the comprehension of objectives and interpretation of results.

Univariate statistics brings some quantitative analysis to ethology but results in single variables representing behavioral responses and assumes uncorrelated variables (Colgan 1978). Previous studies have suggested that physicochemical variables do not act independently and together they influence the behavior pattern of fishes (Gorman and Karr 1978, Matthews and Hill 1979). Measured habitat variables are typically correlated both conceptually and statistically (Dueser and Shugart 1978). An obvious example is the 49

positive correlation between current velocity and substrateparticle

size (Moon 1939). Univariate analysis is therefore an incomplete

method because it cannot account for correlations betweenstream

variables.

A multivariate discriminant function analysis providesan

objective basis for weighting the relative importance of each variable

to group differentiation (Klecka 1975). Unbiased classification based

on the derived discriminant function provides a measure ofgroup

dissimilarity. Multivariate model assumptions (1. unequalmean vectors, 2. homogeneous variance-covariance matrices, and 3. multivariate normal distribution) are identitical to univariate assumptions except the ways in which multivariate assumptionscan be violated increases greatly with the number of included variables

(Morrison 1976, Green 1980). Assumption 1 and assumption 2 were violated in every analysis except adult redside shiner selection during the transitional period. According to Green (1971), this violation usually occurs with ecological data.Assumption 3 could not be tested. Both the assumption of homoscedasticity and multivariate normality are quite restrictive for application of ecological data

(Green 1971). Consequences of not satisfying multivariate assumptions are difficult to interpret. For that reason, the descriptive results and conclusions for the present study identified relevant discriminant variables alone and did not involve predictions based on discriminant functions and coefficients. The goal of this type of analysis should not be to predict fish occurrence on habitat quality from the derived discriminant functions. 50

The type of multivariate analysis conducted during the present

study can detect and quantify differences between groups of

multivariate data. The groups of data that were compared included

distributional data for young and adult redside shiner (habitat

utilization for life stages) and the data for available habitats

(habitat selection). These analysis should provide insights to the

critical variables that should be measured to quantify and understand

habitat utilization and habitat selection in future studies of redside

shiners. The discriminant analysis could also be used to compare

distributional data for different species of fishes or stream habitats

differing in a spatial or temporal fashion.

The analytical results of this study suggest that four components

of stream habitat (depth, current velocity, substrate composition, and

various forms of cover) acting alone or together provided enough

information to describe the seasonal habitats of the redside shiner,

to differentiate habitats occupied by different life stages, and to document the degree of habitat selection occurring. This was adequate to describe the habitats of Greasy Creek, but should not be considered an exhaustive list. The numbers of redside shiners in Greasy Creek were less than those observed in larger streams and reported for lake systems in British Columbia (Grossman 1959a, Lindsey and Northcote

1963). The availability of large deep pools and lake-like habitats may be limiting in Greasy Creek and other small streams. Within the larger streams examined, adult shiners exhibited both aggregating behavior associated with pools and territorial behavior associated with faster, shallower water. Young shiners in larger streams 51 occupied both stream margins and large pools with adults. The large streams may be considererd an intermediate environment between the small stream and the lake where redside shiners may exhibit behaviors and utilize microhabitats specific to small stream and lake environments.

Several questions remain to be resolved. The redside shiner has been observed to utilize habitats differentially froma comparison of distribution patterns and patterns of habitat availability. Some hypotheses have been proposed concerning this selectiveuse, but it is not evident whether the reasons are physiologically based or involve ecological processes. Limitations in swimming capacity as mediated by size are suspected to be important in limiting young of the year shiners to streamside margins but, habitat suppression by adults, predator avoidance by protective substrate countershading (Seghers

1973), and distribution of food are all possible explanations for selective use of habitat. Observations of aggressive behavior by adult redside shiners provides ecological evidence that choice was involved concerning habitat occupation during summer and transitional periods. During winter, the relationship between ecological and physiological factors governing adult distribution is unclear. A series of experiments similar to those performed by Matthews and Hill

(1978) on the red shiner, Notropis lutrensis, are needed to examine these factors. In summary, this study is autecological and is incomplete because species distributions cannot be explained completely by physicochemical factors. Biological factors including interactions among species, competition, and predation may exclude 52

fishes from habitats which are physiologically tolerable. The

multivariate approach described in the present study can incorporate

biological variables such as the presence of other species,

interspecific densities, or interspecific distance. The biological

variables would be weighted along with physicochemical variables

asosociated with stream habitats. Interspecific interactions between

the redside shiner and other stream fisheswere observed and could

have influenced habitat selection. The aggressive behavior of

juvenile salmonids towards adult redside shiners might excludethe

redside shiners from a favorable stream location. By aggregating with

groups of speckled dace, both young and adult redside shiner might

reduce the probability of being preyed upon and increase the chances

of locating food sources.. Additional stream observations and

laboratory "removal" experiments should help evaluate the importance

of biological interactions to redside shiner habitat selection. These

biological interactions can be incorporated to define the ecotope which describes the full range of adapatations to external factors

concerning both niche and habitat (Whitaker et al. 1973). Expansion

of the present model to incorporate niche parameters is the nextstep

for greater comprehension of habitat selection by the redside shiner. 53

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