Demographics and 2008 Run Timing of Adult Lost River 

(Deltistes luxatus) and Shortnose (Chasmistes brevirostris) 

Suckers in Upper Klamath Lake, Oregon, 2008 

Open-File Report 2009-1183

Prepared in cooperation with the 

Bureau of Reclamation

U.S. Department of the Interior

U.S. Geological Survey

Demographics and 2008 Run Timing of Adult 

Lost River (Deltistes luxatus) and Shortnose 

(Chasmistes brevirostris) Suckers in Upper 

Klamath Lake, Oregon, 2008 

By Eric C. Janney, Brian S. Hayes, David A. Hewitt, Patrick M. Barry, Alta Scott, Justin Koller, Mark Johnson, and 

Greta Blackwood

Prepared in cooperation with the Bureau of Reclamation

Open-File Report 2009–1183

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2009

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Suggested citation:

Janney, E.C., Hayes, B.C., Hewitt, D.A., Barry, P.M., Scott, A.C., Koller, J.P., Johnson, M.A., and G. Blackwood, 

2009, Demographics and 2008 run timing of adult Lost River (Deltistes luxatus) and shortnose (Chasmistes 

brevirostris) suckers in Upper Klamath Lake, Oregon, 2008: U.S. Geological Survey Open-File Report 2009-1183,

32 p.

Any use of trade, product, or firm names is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual 

copyright owners to reproduce any copyrighted material contained within this report.
iii

Contents

Abstract ......................................................................................................................................................................... 1

Introduction.................................................................................................................................................................... 2

Study Methods............................................................................................................................................................... 3

Sampling and Fish Handling ...................................................................................................................................... 3

Remote Passive Integrated Tag Antenna Systems.................................................................................................... 4

Survival Analysis........................................................................................................................................................ 4

Recruitment Analysis ................................................................................................................................................. 5

Length Frequency Analysis........................................................................................................................................ 6

Demographics and Spawning Characteristics ............................................................................................................... 7

Lost River Suckers..................................................................................................................................................... 7

2008 Catch Summary and Run Timing................................................................................................................... 7

Survival and Recruitment Analysis ......................................................................................................................... 8

Upper Klamath Lake Shoreline Spawning Subpopulation................................................................................... 8

Sprague and Williamson River Spawning Subpopulation ................................................................................... 8

Length-Composition Analysis ................................................................................................................................. 9

Shortnose Suckers..................................................................................................................................................... 9

2008 Catch Summary and Run Timing................................................................................................................... 9

Survival and Seniority........................................................................................................................................... 10

Length-Composition Analysis ............................................................................................................................... 10

Discussion ................................................................................................................................................................... 10

Acknowledgments........................................................................................................................................................ 11

References Cited......................................................................................................................................................... 12

Figures

Figure 1. Upper Klamath Lake map, showing sampling locations for Lost River suckers and shortnose 

suckers. Inset illustrates the general location of Upper Klamath Lake in south-central Oregon............................... 14

Figure 2. Number of Lost River suckers captured at four Upper Klamath Lake lakeshore spawning areas 

and average daily water temperature (oC) in Upper Klamath Lake, Oregon, 2008 .................................................. 15

Figure 3. Number of individual Lost River suckers detected on underwater passive integrated 

transponder (PIT) tag antennas at four lakeshore spawning areas and water temperature (oC) in 

Upper Klamath Lake, Oregon, 2008 ........................................................................................................................ 16

Figure 4. Number of Lost River suckers captured in the upstream weir trap on the Williamson River 

during the 2008 field season.................................................................................................................................... 17

Figure 5. Number of Lost River suckers detectioned on passive integrated transponder (PIT) tag antenna 

located in the Williamson River weir upstream trap ................................................................................................. 18

Figure 6. Summary of Lost River suckers captured in the Chiloquin Dam fish ladder on the Sprague River, 

Oregon, 2008........................................................................................................................................................... 19

Figure 7. Summary of the first remote detection of individual Lost River suckers on the downstream 

antenna (that is, entrance) at the Chiloquin Dam fish ladder on the Sprague River, Oregon, 2008......................... 20

Figure 8. Apparent annual survival (φ) and seniority (γ) probabilities (95% confidence intervals) of 

Lost River suckers from the lakeshore-spawning subpopulation in Upper Klamath Lake, Oregon, 1999–2007 ...... 21
iv

Figures—Continued

Figure 9. Apparent annual survival (φ) probabilities (95% confidence intervals) of Lost River suckers tagged 

with 125 and 134 kHz PIT tags from the Williamson and Sprague Rivers spawning subpopulation, 2001–06........ 22

Figure 10. Length frequencies of male and female Lost River suckers captured in spring trammel net 

sampling at Upper Klamath Lake lakeshore spawning areas, 1999–2008............................................................... 23

Figure 11. Growth rates of male and female Lost River suckers captured in spring trammel net sampling 

at Upper Klamath Lake lakeshore spawning areas, 1999–2008, and in the Sprague and Lower Williamson

Rivers, 2001–08...................................................................................................................................................... 24

Figure 12. Length frequencies of male and female Lost River suckers captured in spring sampling in the 

Williamson and Sprague Rivers, 2001–08............................................................................................................... 25

Figure 13. Summary of the number of shortnose sucker (SNS) detected on the upstream trap antenna on the 

Williamson River weir. ............................................................................................................................................. 26

Figure 14. Apparent annual survival (φ) and seniority (γ) probabilities (95% confidence intervals) of adult shortnose 

suckers in Upper Klamath Lake, Oregon, 1999–2007 ............................................................................................. 27

Figure 15. Length frequencies of male and female shortnose suckers captured in the Williamson and 

Sprague Rivers, 2001–08 ........................................................................................................................................ 28

Figure 16. Growth rates of male and female shortnose suckers captured in the Sprague and Lower 

Williamson Rivers, 2001–08 .................................................................................................................................... 29

Tables

Table 1. The total number of Lost River and shortnose suckers captured in Upper Klamath Lake (UKL) and its 

tributary rivers in 2008 ............................................................................................................................................. 30

Table 2. The total number of unique Lost River suckers and shortnose suckers detected by remote stations in 

Upper Klamath Lake (UKL) and its tributary rivers in 2008...................................................................................... 30

Table 3. Model selection results for ten candidate models of survival and recapture probability for lakeshorespawning Lost River suckers in Upper Klamath Lake, Oregon,1999–2000 ............................................................. 31

Table 4. Model selection results for nine candidate models of survival and recapture probability for the adult 

shortnose suckers in Upper Klamath Lake, Oregon, 2000–2008............................................................................. 32
v

Conversion Factors and Acronyms

SI to Inch/Pound

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

millimeter (mm) 0.03937 inch (in.)

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32.

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C=(°F-32)/1.8.

Acronyms

FDX full-duplex

FL fork length

LRS Lost River sucker

PIT passive integrated transponder

SNS shortnose suckers

UKL Upper Klamath Lake

USGS U.S. Geological Survey
1

Demographics and 2008 Run Timing of Adult 

Lost River (Deltistes luxatus) and Shortnose 

(Chasmistes brevirostris) Suckers in Upper 

Klamath Lake, Oregon, 2008 

By Eric C. Janney, Brian S. Hayes, David A. Hewitt, Patrick M. Barry, Alta Scott, Justin Koller, Mark Johnson, and 

Greta Blackwood

Abstract

We used capture–recapture data to assess population dynamics of endangered Lost River suckers 

(Deltistes luxatus) and shortnose suckers (Chasmistes brevirostris) in Upper Klamath Lake, Oregon. 

The Cormack–Jolly–Seber method was used to estimate apparent survival probabilities, and a temporal 

symmetry model was used to estimate annual seniority probabilities. Information theoretic modeling 

was used to assess variation in parameter estimates due to time, gender, and species. In addition, length 

data were used to detect multiple year-class failures and events of high recruitment into adult spawning 

populations. Survival of adult Lost River and shortnose suckers varied substantially across years. 

Relatively high annual mortality was observed for the lakeshore-spawning Lost River sucker 

subpopulation in 2002 and for the river spawning subpopulation in 2001. Shortnose suckers experienced 

high mortality in 2001 and 2004. This indicates that high mortality events are not only species specific, 

but also are specific to subpopulations for Lost River suckers. Seniority probability estimates and length 

composition data indicate that recruitment of new individuals into adult sucker populations has been 

sparse. The overall fitness of Upper Klamath Lake sucker populations are of concern given the low 

observed survival in some years and the paucity of recent recruitment. During most years, estimates of 

survival probabilities were lower than seniority probabilities, indicating net losses in adult sucker 

population abundances. The evidence for decline was more marked for shortnose suckers than for Lost 

River suckers. Our data indicated that sucker survival for both species, but especially shortnose suckers, 

was sometimes low in years without any observed fish kills. This indicates that high mortality can occur 

over a protracted period, resulting in poor annual survival, but will not necessarily be observed in 

association with a fish kill. A better understanding of the factors influencing adult survival and 

recruitment into spawning populations is needed. Monitoring these vital parameters will provide a 

quantitative means to evaluate population status and assess the effectiveness of conservation and 

recovery efforts.
2

Introduction

Lost River suckers (Deltistes luxatus) and shortnose suckers (Chasmistes brevirostris) are longlived, late-maturing catostomids that are endemic to the Upper Klamath River basin in southern Oregon 

and northern California (Scoppettone and Vinyard, 1991). Historical accounts indicate that both species 

once were extremely abundant throughout the upper basin and were used in a subsistence fishery by 

Native Americans and later in a popular recreational snag fishery that was closed in 1987 (Markle and 

Cooperman, 2002). Declining population abundance trends and range reductions were noted for both 

species as early as the mid-1960s. The extent of these declines was not evident, however, until the mid1980s, when recreational catch rates exhibited dramatic decreases that were attributable in part to 

overfishing (Markle and Cooperman, 2002; National Research Council, 2004). Estimated annual fishery 

harvest of spawning suckers in the Sprague and Williamson rivers ranged from more than 10,000 fish in 

1968 to 687 fish in 1985 (Markle and Cooperman, 2002). In addition to declining catches, age data from 

suckers collected during a 1986 fish kill indicated that the Lost River sucker (LRS) population was 

composed of old individuals and that no substantial recruitment had occurred during the previous 

15 years (Scoppettone and Vinyard, 1991; U.S. Fish and Wildlife Service, 1993). These findings led to 

the federal listing of both species under the Endangered Species Act in 1988 (U.S. Fish and Wildlife 

Service, 1993). Upper Klamath Lake probably contains the largest remaining populations of both 

species (National Research Council, 2004). 

Life history and spawning characteristics of suckers in Upper Klamath Lake are understood 

reasonably well (Scoppettone and Vinyard, 1991; Moyle, 2002; Cooperman and Markle, 2003). Age 

estimates for Lost River suckers have exceeded 40 years, and most individuals reach maturity at 

7–9 years. For shortnose suckers (SNS), ages greater than 30 years have been estimated, and most 

individuals reach maturity at 5–7 years (National Research Council, 2004). In both species, males 

typically reach maturity earlier than females. Both species are obligate lake dwellers and typically only 

leave Upper Klamath Lake to make spawning runs up lake tributaries (that is, Sprague and lower 

Williamson Rivers) between March and May of each year. Shortnose suckers spawn primarily in the 

Williamson and Sprague Rivers, but two distinct subpopulations of Lost River suckers have been 

identified in Upper Klamath Lake (National Research Council, 2004). One subpopulation migrates up 

the Williamson and Sprague Rivers, and the other spawns at several springwater upwelling areas along 

the eastern shoreline of the lake. Tagging data indicate a high degree of spawning site (that is, river or 

lakeshore) fidelity and little reproductive mixing between the two subpopulations (U.S. Geological 

Survey, unpub. data). 

Although fishing mortality was eliminated with the closure of the recreational fishery, poor 

survival of adult suckers has been shown still to be a factor precluding recovery of Upper Klamath Lake

populations (Janney and others, 2008). Upper Klamath Lake has progressed to a hypereutrophic state 

due to increased nutrient loading from wetland drainage, grazing, and timber harvest (Eilers and others,

2004). These conditions lead to massive blooms of the cyanobacterium, Aphanizomenon flos-aquae, 

between June and October of each year (Kann and Smith, 1999). The algal blooms and their subsequent 

die-offs produce water-quality conditions that are deleterious to fish health (that is, low concentrations 

of dissolved oxygen, elevated concentrations of ammonia, and high pH). Poor water-quality conditions 

are thought to have contributed to a number of substantial fish kills in the lake, most recently during the 

summers of 1986, 1995, and 1997 (National Research Council, 2004) and to a much lesser extent in the 

summer of 2003 (U.S. Geological Survey, unpub. data).
3

In this report, we summarize 2008 adult sucker run timing data and analyze capture–recapture 

data to evaluate demographic trends in adult LRS and SNS populations. Annual adult survival and 

recruitment parameters were modeled and compared to assess differences attributable to species, 

spawning subpopulation, sex, and year. In addition to estimating recruitment parameters from capturerecapture data, we assessed relative changes in length composition to provide additional insight into the 

relative frequency and magnitude of recruitment into the adult sucker populations. A comprehensive 

analysis of data collected up to 2007 is given in Janney and others (2008). This report is a continuation 

of the data analysis and interpretation reported in Janney and others (2008) with additional data 

collected during spring 2008 added to the analysis.

Study Methods

Sampling and Fish Handling

The Lost River sucker subpopulation that spawns along the eastern shoreline of Upper Klamath 

Lake was sampled at four known spawning areas (fig. 1) using 30-m trammel nets (1.8 m high; two 30-

cm-mesh outer panels; one 3.8-cm-mesh inner panel; foam-core float line; lead-core bottom line) twice 

per week between February and May from 1999 to 2008. The only exception to this sampling schedule 

occurred in 2006, when each spawning area was sampled only once per week. Nets were set at each area 

starting at the shoreline and extended out in a semicircular fashion that encompassed the perimeter of 

identified spawning areas. 

Lost River and shortnose suckers also were sampled three times per week from 2000 to 2008 

during the same months stated above at the Chiloquin Dam fish ladder on the Sprague River. Before 

sampling at the fish ladder, a screen was placed over the bottom entrance (outflow) to prevent fish from 

exiting, and the upstream end (inflow) was blocked by a board to lower the water level in the fish 

ladder. A combination of dip nets and short trammel nets was then used to collect fish trapped in the 

ladder. 

Additional trammel-net sampling for adult suckers was conducted from 1995 to 2008 at various 

sites in Upper Klamath Lake as well as in the lower Williamson River from 1995 to 2006 (Janney and 

others, 2006). A resistance board weir with a live trap (described in detail by Tobin [1994]) also was 

deployed on the Williamson River at river kilometer 10 from 2005 to 2008 to improve capture rates of 

suckers during spawning migrations (fig. 1). The weir functioned by restricting sucker passage to two 

weir sections. An upstream live trap was used to capture adult fish as they migrated upriver through the 

weir, and a downstream trap was used to allow downriver migrating suckers to pass the weir. High 

flows in the Williamson River during most of the 2006 spawning season inundated the weir and allowed 

suckers to pass over and around the weir without swimming through the trap. 

Suckers captured at all sample locations were identified to species and gender and were scanned 

for the presence of a passive integrated transponder (PIT) tag. If a PIT tag was not detected, one was 

inserted into the abdominal musculature. From 1995 to 2004, suckers were tagged with 125-kHz, fullduplex (FDX) PIT tags; from 2005 to 2007, fish were tagged with 134.2 kHz, FDX tags. All fish were 

released immediately after being tagged.
4

Remote Passive Integrated Tag Antenna Systems

In addition to traditional capture techniques (that is, trammel nets and fish ladders), detections 

from remote underwater PIT tag antennas were incorporated into the capture–recapture study design 

beginning in 2005; this was done in an attempt to improve the probability of recapturing previously 

tagged suckers. Suckers detected by these systems were not physically handled; however, those fish 

were confirmed to be alive and thus were counted as live recaptures in survival analyses. Locations of 

fixed, underwater PIT tag detection systems included: one each in the upstream and downstream traps of 

the Williamson River fish weir (2005–08); a river-wide array immediately upstream of the weir (2007–

08); an array immediately downstream of the Chiloquin Dam (2008); the entrance, middle, and exit of 

the Chiloquin Dam fish ladder (2006–08); shoreline spawning areas (2005–08); and two river wide 

arrays installed in close proximity about 2.5 river kilometers upstream of Chiloquin Dam (2007–08; 

fig. 1).

Survival Analysis

We used a Cormack–Jolly–Seber live-recapture model (Schwarz and Seber, 1999) in program 

MARK (White and Burnham, 1999) to obtain maximum likelihood estimates of apparent survival (φi)

and recapture probability pi for adult LRS and SNS. Apparent survival is the complement of the sum of 

mortality and permanent emigration (Pollock and others, 2007). Although temporary emigration may 

have occurred due to skipped spawning, radio-telemetry data indicate that permanent emigration out of 

Upper Klamath Lake and its tributaries by either species is uncommon (U.S. Geological Survey, unpub.

data). Therefore, we believe our estimates of apparent survival were nearly equivalent to true survival. 

Lost River sucker data were analyzed separately on the basis of spawning subpopulations (that is, river 

versus lakeshore spawners). Lost River sucker capture events in Upper Klamath Lake nonspawning 

areas were excluded from analysis because the spawning stock membership of those fish could not be 

ascertained. Double-tagging data (U.S. Geological Survey, unpub. data) indicated that PIT tag loss in 

suckers was almost nonexistent and did not introduce substantial negative bias into estimates. 

We assessed whether our data conformed to the assumptions of the Cormack–Jolly–Seber model 

using goodness-of-fit testing in the program UCARE (Choquet and others, 2005). Goodness-of-fit tests 

pooled over time indicated significant departures from frequencies expected under the Cormack–Jolly–

Seber model for Lost River sucker subpopulations and for shortnose suckers. Lack of fit can be an 

indication of model assumption violations, sparse data, or lack of independence. Closer examination of 

our goodness-of-fit tests for individual time periods revealed no consistent or systematic bias that would 

suggest tagging effects. Lack of fit in our data probably was due to a combination of data sparsity at the 

beginning of the study, lack of independence, and spawning periodicity (that is, individuals not 

spawning in each year). The lack of independence (that is, overdispersion) probably results from 

schooling behavior and is relatively common in capture–recapture studies of schooling fish (Pollock and 

others, 2007). A quasi-likelihood correction factor (ĉ) was determined from the most general model for 

each species by use of the median ĉ estimation method (Cooch and White, 2006; Lost River sucker 

lakeshore subpopulation ĉ =1.44, Lost River sucker river subpopulation ĉ =3.40, shortnose sucker ĉ 

=2.26). These ĉ-values were applied to the set of considered models to compensate for overdispersion 

by inflating variance estimates. Applying a variance inflation factor is recommended when 

heterogeneity is detected, and supports a conservative approach to inference (Anderson and others,

1994). 
5

A number of models were fitted in program MARK to the Lost River sucker lakeshore and river 

spawning subpopulations and the shortnose sucker datasets. The most general model in each set of 

models allowed for year and sex effects, and the year × sex interaction effect on φ and p. The most 

general model also incorporated a possible effect of PIT tag type (that is, 125 versus 134.2 kHz) on p for 

the last 3 years of the study. We hypothesized that differences in recapture probabilities may have 

existed due to the greater detection distances of 134.2 kHz tags at remote underwater antennas. 

Using the most general model as a starting point, models with fewer parameters were 

constructed by constraining φ and p to remain constant across years, sexes, or both. Additive models 

also were used to reduce parameters (that is, achieve a more parsimonious model) and determine 

whether differences in φ and p between the sexes were consistent over time (Pollock and others, 2007). 

These less-parameterized models were used to select a more parsimonious model and to test the effects 

of time and sex on φ. We used Akaike’s information criterion corrected for small-sample bias (AICc) 

and adjusted for overdispersion (that is, quasilikelihood AICc [QAICc]; Burnham and Anderson, 2002) 

as a statistical criterion to evaluate the competing models. Akaike weights (wi) are reported to provide a 

measure of the relative weight or likelihood of each model being the best model in the set given the data 

(Burnham and Anderson, 2002). 

Rather than making inference from parameter estimates using only the best model (that is, that 

with the smallest AICc value) in the set, parameter estimates were weighted based on wi. Modelaveraged parameter estimates account for model selection uncertainty in the estimated precision of the 

parameter and thus produce unconditional estimates of variance and standard error (Buckland and 

others, 1997). To potentially improve survival estimate precision and to evaluate the difference in 

survival between the two sucker species, we conducted a preliminary analysis using recapture data from 

both species grouped into one model set. We hypothesized that if differences in survival between the 

two species were small or at least consistent, then a more-parsimonious model with either no species 

effect or an additive species effect would be selected and would result in better estimate precision. 

Model selection results from this preliminary analysis, however, suggested a strong species effect and 

indicated that the pooling of data from the two species did not produce a more-parsimonious model.

Recruitment Analysis

A primary concern in understanding and managing sucker populations is the estimation of 

changes in population size over time (Franklin, 2001). In addition to survival, recruitment can be 

estimated from open population capture-recapture data. Specifically, the reverse-time analogue of 

survival, termed 'seniority' and denoted γi can be estimated. This parameter is defined as the probability 

that an animal present in the sampled population at period i is an ‘old’ animal that also was present in 

period i–1. Population rate of change:

i 1

i

i

N

N

λ +  

 =    

then can be estimated without estimating either Ni or Ni+1 using the formula:

1

i

i

i

φ λ

γ +

= 

.
6

Pradel (1996) introduced a likelihood that models the entire capture history and is based on the temporal 

symmetry of capture-recapture data (Nichols and Hines, 2002). This approach combines probabilities 

describing forward time (that is, survival) and reverse-time (that is, seniority) processes, allowing the 

direct estimation and modeling of λ. The assumptions of the Pradel (1996) model are similar to those in 

the Cormack-Jolly-Seber model; however, the former also assumes that the study area is well defined 

and does not expand over time, and assumes no permanent trap response in capture probability.

The incorporation of underwater PIT tag antennas systems into our capture-recapture study 

design in 2005 created a situation in which previously marked fish have a much greater probability of 

being resighted than unmarked fish have of being captured, marked, and released. In essence, the 

underwater antenna systems create a dramatic “trap-happy” response regarding capture probability (Otis 

and others, 1978). This difference in capture probabilities does not create bias in survival estimates. 

Including remote detections in capture histories, however, would create substantial bias in seniority 

estimates and thus also bias estimates of population rate of change (Hines and Nichols, 2002). To avoid 

bias resulting from differences in capture probability, we modeled survival and seniority separately. 

Capture histories used to model survival included physical captures and remote detections, but seniority 

models included physical captures only. Early estimates of γ are not reported because of poor precision 

due to sparse data and because it has been shown that the initial two γ estimates are likely to be 

substantially more biased than subsequent estimates (Hines and Nichols, 2002).

Length Frequency Analysis

Fork length (FL) of spawning LRS collected from the Williamson and Sprague Rivers from 

2000 to 2008 and from lakeshore spawning LRS areas from 1999 to 2008 were used to visually assess 

changes in spawner size structure over time. Fork length data also were collected from SNS collected in 

Upper Klamath Lake and in the Williamson and Sprague Rivers from 2000 to 2008. Although this type 

of length analysis is qualitative, it was useful for documenting growth trends and corroborating evidence 

of recruitment, or the lack thereof, from seniority estimates. Length data were grouped annually by 

species, spawning subpopulation (for LRS), and sex to avoid size bias resulting from annual changes in 

species composition and sex ratio. We calculated recent annual growth rates for each sex of each species 

by tracking changes in the median of the dominant mode in the length frequencies. An average annual 

growth rate was calculated as the slope of a simple linear regression of the medians in successive years. 

The analysis was performed using the package mixdist (see Macdonald and Green, 1988) in the 

R software environment (R Development Core Team, 2007).
7

Demographics and Spawning Characteristics

Lost River Suckers

2008 Catch Summary and Run Timing

We captured 834 individual LRS in trammel nets at lakeshore spawning areas along the eastern 

shoreline of Upper Klamath Lake. Of these, 375 (45 percent) were tagged prior to 2008 (table 1). 

Systematic trammel net sampling at lakeshore spawning areas in 2008 indicated that LRS spawning 

activity began in mid March and continued through late May, and peak spawning activity occurred 

between mid and late April (fig. 2). The majority of lakeshore spawners were captured at Sucker 

Springs (35 percent), followed by Cinder Flat (26 percent), Silver Building Spring (23 percent), and 

Ouxy Spring (16 percent). 

In addition to LRS physically captured in trammel nets, 5,801 individually tagged LRS were 

detected swimming over underwater PIT tag antennas at the lakeshore spawning areas. More individuals 

were detected at Sucker Springs than at any other shoreline spawning area (table 2; fig. 3). Lost River 

suckers were detected at the lakeshore spawning areas from the first week of March until the remote 

systems were removed during the first week of June 2008 (fig. 3). Only 12 percent of the LRS detected 

on the lakeshore remote stations also were captured physically during lakeshore trammel net surveys; 86

percent of the LRS physically captured also were detected on the underwater PIT tag antennas.

We captured 469 individual LRS in Upper Klamath Lake trammel net surveys conducted at prespawn staging areas in the vicinity of Modoc Point and Goose Bay between April 1 and May 2, 2008 

(table 1). Of these, 62 (13 percent) were tagged prior to the 2008 sample season. Of the LRS captured at 

pre-spawn staging areas, 74 percent were subsequently captured or detected at the Williamson River 

weir and only 3 percent later were captured or detected at lakeshore spawning areas along the eastern 

side of Upper Klamath Lake.

A total of 1,319 LRS were captured in the upstream trap of the Williamson River fish weir. Of 

these, only 88 (6.5 percent) were tagged prior to 2008 (table 1). Most were captured between mid- to 

late April when water temperatures were between 10o

C and 12oC (fig. 4). The remote PIT tag antennas 

at the weir (that is, the upstream and downstream trap antennas, and river-wide array) detected 7,920 

individual LRS between February 20 and June 1, 2008. High streamflow during mid-April likely 

reduced the efficiency of the weir trap to capture suckers; however, the high flows coincided with a 

decrease in water temperature that may have delayed spawning runs (fig. 4). There also was a reduction 

in upstream trap antenna detections coinciding with the decrease in temperature and increased river 

flows (fig. 5).

We captured 507 individual LRS in the Chiloquin Dam fish ladder on the Sprague River in 2008 

(table 1). Of these, 52 percent were tagged prior to 2008. Lost River suckers were first captured in the 

fish ladder on March 26 but peak catches and remote detections did not occur until late April when 

water temperatures were between 10oC and 15oC (fig. 6). The remote PIT tag antennas installed at the 

downstream entrance, the middle ladder cell, and the upstream exit of the fish ladder detected 883 

individual LRS between March 11 and June 8. Most were detected on the antenna located at the 

downstream entrance of the fish ladder. The middle antenna detected 152 individual LRS, although the 
8

antenna at the upstream exit of the ladder detected only 11 individuals. Seventy-five percent of LRS 

detected at the entrance of the fish ladder in 2008 were tagged prior to 2008. In 2008, the additional 

river-wide antenna array installed about 75 m below Chiloquin Dam detected 2,700 individual LRS 

between March 15 and June 8, 2008. Of these, only 21 percent also were detected on the antenna at the 

entrance to the fish ladder.

Survival and Recruitment Analysis

Upper Klamath Lake Shoreline Spawning Subpopulation

Between February and May 1999–2008, we captured, tagged, and released 3,780 female and 

5,728 male Lost River suckers at lakeshore spawning areas. Of these, we subsequently recaptured or 

remotely detected 2,794 females and 4,006 males on at least one occasion. Ten candidate CormackJolly-Seber type models were fitted for the lakeshore Lost River sucker subpopulation (table 3). 

According to QAICc values, the best model had additive sex and year effects for φ and sex, year, and 

tag type effects for p. This model accounted for most of the wi (73 percent) assigned to the candidate 

models. Model-averaged estimates varied to some extent by year, and female survival was consistently, 

albeit only slightly, higher than male survival (fig. 8). Estimate precision improved substantially in later 

years when remote PIT tag antenna systems became incorporated into the study design. With the 

exception of 2002, survival probabilities for the shoreline spawning LRS subpopulation were within the 

range expected from a healthy population exhibiting a long-lived, late maturing life history strategy.

Because capture histories constructed for recruitment analysis consisted only of physical 

captures, seniority parameter sampling variances were substantially larger than those of survival

estimates. On the basis of QAICc values, the best model had a sex effect but no year effect for γ and 

additive sex and year effects for p. This model accounted for the majority of the wi (67 percent) assigned 

to the candidate models. Model-averaged estimates varied little by year and were consistently above 

0.95 for both sexes, suggesting only minor recruitment of new spawning adults into the lakeshore 

spawning subpopulation between 2001 and 2007 (fig. 8). Estimates were consistently, albeit slightly, 

higher for male than females (that is, fewer male recruits). Seniority probability estimates were mostly 

higher than survival estimates suggesting consistent but only slightly declining LRS numbers for the

lakeshore spawning subpopulation since 2001.

Sprague and Williamson River Spawning Subpopulation

Between 2000 and 2008, we tagged and released 8,901 female Lost River suckers and 6,157

males in the Williamson and Sprague Rivers. Of these, we subsequently recaptured or remotely detected 

5,530 females and 3,605 males on at least one occasion. The structure of the top ranked model for river 

spawning Lost River suckers was the same as the one described above for the lakeshore-spawning 

subpopulation, except the river spawning subpopulation also exhibited a strong tag-type effect (that is, 

125 kHz vs. 134.2 kHz PIT tags) on survival. The model-averaged φ estimates varied by year, and 

female φ consistently but only slightly exceeded male φ ( fig. 9). Comparisons of φ estimate effect size 

and 95 percent CIs between the two subpopulations suggest that φ of the river spawning segment was 

substantially lower than that of the lakeshore segment in 2001. Modeling results indicated that survival 

in 2005 and 2006 was substantially lower for fish marked with 125 kHz tags (2000–04) than for fish 

marked with 134.2 kHz PIT tags (2005–06) (fig. 9). The tag type effect on survival was not an A priori 

hypothesis, but rather an exploratory ad hoc model that was run to determine if the overall fit of our 

most general model could be improved. We do not expect that this effect is a result of technical issues 
9

associated with the type of tag (e.g., higher failure or loss of 125 kHz tags) because models including 

this effect were not supported in analyses for either the LRS lakeshore spawning segment or the SNS

population. Technical issues would be expected to show up in any population or spawning segment in 

which 125 kHz tags were used. We suspect that what shows up as an effect on survival due to the type 

of PIT tag is likely attributable to an interaction between changes in our sampling scheme and 

substructuring of the river-spawning LRS population. Groups of spawning LRS appear to be fidelic to 

certain sections of the river, with some fish migrating farther than others. Fish tagged recently with 134 

kHz tags, particularly those that spawn lower in the river, have not had as many opportunities to be 

captured or detected. We expect that as more years of data are collected, this effect will become less 

pronounced.

Length-Composition Analysis

Length frequencies of Lost River suckers captured in trammel net sampling at Upper Klamath 

Lake lakeshore spawning areas showed very little size diversity (fig. 10) and a steadily declining 

percentage of fish that could be considered recruitment size (Janney and others, 2008). These length 

frequencies corroborate with seniority probability estimates obtained from capture-recapture data that 

indicate very little recruitment of new adults into the lakeshore spawning LRS subpopulation. The 

dominant group or cohort of male lakeshore spawning LRS grew approximately 10 mm FL (fork length) 

per year between 1999 and 2008, and females grew approximately 12 mm/yr during the same period 

(fig. 11). Size frequencies of male and female LRS captured during spawning surveys in the Sprague 

and Williamson Rivers show a similar trend; however, the river subpopulation was on average slightly 

smaller and exhibited slightly slower growth rates (figs. 11 and 12). Both Upper Klamath Lake

spawning subpopulations exhibited substantially slower growth rates than LRS in Clear Lake Reservoir, 

CA (Barry and others, 2009). The disparity in growth rates between the two systems is likely a result of 

a younger (that is, lower on the growth curve) LRS population in Clear Lake.

Shortnose Suckers 

2008 Catch Summary and Run Timing

We captured 672 SNS in trammel nets at Upper Klamath Lake pre-spawn staging areas in the 

vicinity of Modoc Point and Goose Bay. Of these, 137 (20 percent) had been tagged in a previous year. 

Eighty-five percent of the SNS captured in Upper Klamath Lake trammel net samples were later 

detected on antenna arrays in the Williamson and Sprague Rivers. Only five SNS were captured during 

trammel net sampling at lakeshore spawning areas. Underwater PIT tag antennas detected 42 individual 

SNS at lakeshore spawning areas with most detections occurring in mid- to late May. Only six

individual SNS that were captured, tagged, and released at Upper Klamath Lake pre-spawn staging 

areas were subsequently detected at the lakeshore spawning areas during the 2008 field season. Four of 

the six were detected at the shoreline areas after being detected earlier in the sample season at the 

Williamson River fish weir.

We captured 288 SNS in the Williamson River weir trap, 68 (24 percent) of which were tagged 

prior to 2008. The three remote underwater PIT tag antenna systems at the weir detected a total of 4,061

individual SNS between February 20 and June 1, 2008 (table 2). The upstream trap antenna at the weir 

detected 772 SNS. A peak in detections on the upstream weir trap antenna occurred between early and 

mid-May when water temperatures reached 10o

C (fig. 13). An additional 92 individual SNS were 

detected on the weir array after the weir was removed at the end of May. These fish were most likely 
10

moving back downstream to Upper Klamath Lake after spawning. We captured 239 individual SNS in 

the Chiloquin Dam fish ladder more than 35 sample occasions. Of these, 139 (58 percent) were already 

tagged. The three remote antennas at the fish ladder detected 771 individual SNS between February 27 

and June 9, 2008 (table 2). The downstream ladder antenna detected 764, the middle antenna detected 

287, and the upstream antenna detected only 98 individual SNS. 

Survival and Seniority

Between 1995 and 2008, we captured, tagged, and released 8,743 female shortnose suckers and 

5,553 male shortnose suckers. Of these, we subsequently recaptured or remotely detected 4,054 females 

and 2,088 males on at least one occasion. A total of nine CJS type models were fitted for the adult 

shortnose sucker population (table 4). According to QAICc values, the best model had additive sex and 

year effects for φ and year and tag type effects and an additive sex effect for p. This model accounted 

for approximately 60 percent of the weight in the model set, while the remaining candidate models 

together accounted for 40 percent (table 4). The model averaged φ estimates varied considerably by 

year; female φ was slightly and consistently higher than male φ (fig. 14). Shortnose sucker survival was 

generally lower than that of Lost River suckers and was especially low in 2001 and 2004.

On the basis of QAICc values of seniority models, the best model had no sex effect and a year 

effect only for 2006 for γ and both sex and year effects for p. This model accounted for 50 percent of the

wi assigned to the candidate models. Model-averaged γ estimates did not vary by year except for 2006,

and were consistently above 0.95 for both sexes. This suggests that with exception of 2006, very little

recruitment of new adult SNS occurred between 2001 and 2007 (fig. 14). Overall, seniority probability

estimates were consistently higher than survival estimates, suggesting a substantial decline in adult SNS 

numbers since 2001.

Length-Composition Analysis

Length frequencies of SNS captured in Upper Klamath Lake and the Williamson and Sprague 

River areas indicate little diversity in the size structure of the population (fig. 15). Very few suckers that 

could be considered recruitment size were captured between 1999 and 2008 (Janney and others, 2008). 

Although SNS seniority estimates and model results indicated substantial recruitment into the adult 

population in 2006, very few recruit size individuals were captured during that year. The dominant 

group or cohort of SNS suckers grew approximately 5 mm FL per year between 2000 and 2008 (fig.

16). These growth rates are substantially slower than those suggested from length frequency data 

collected at Clear Lake Reservoir, CA (Barry and others, 2009).

Discussion

The overall fitness of sucker populations in Upper Klamath Lake should be of concern given the 

low observed survival in some years and the paucity of recent recruitment. During most years, estimates 

of survival probabilities were lower than seniority probabilities, indicating net losses in adult population 

abundances. The evidence for decline was more marked for shortnose suckers than for Lost River 

suckers.

Model selection results and the effect size of annual differences in survival suggest considerable 

interannual variation. Our data indicated that survival for both species, but especially SNS, was 

sometimes low in years without any observed fish kills. This suggests that high mortality can occur over 

a protracted period, resulting in poor annual survival, but will not necessarily be observed in association 
11

with a fish kill. In contrast, water-quality conditions during summer 2003 were thought to be especially 

poor (Wood and others, 2005) and 53 adult Lost River suckers and 29 shortnose suckers were found 

dead during that summer (U.S. Geological Survey, unpub. data). Survival estimates for both sucker 

species in 2003, however, indicated that annual mortality was relatively low. This suggests that although 

small, local fish kills can occur, such kills do not necessarily translate to high annual mortality at the 

population level. Available data indicate that poor water-quality conditions resulting from massive algal 

blooms are present every summer (Wood and others, 2005), but we do not know why these conditions 

lead to increased mortality in some years but not other years.

Comparison of effect size and 95 percent CI between Lost River sucker subpopulations indicated 

that survival was markedly lower for the river spawners than for lakeshore spawners in 2001. This 

suggests that although the subpopulations reside together in Upper Klamath Lake for most of the year,

their population dynamics and status are different. Possible reasons for differences in survival between 

the spawning subpopulations should be investigated in future analyses. If differential survival is 

observed in future years, it may have implications for overall species status determinations and recovery 

goals.

Populations of both species exhibited a transition from mostly old individuals, little size 

diversity, and consistently poor recruitment in the late 1980s and early 1990s to primarily small, recruitsized fish and few large individuals by the late 1990s (Janney and others, 2008). This marked shift in 

size structure to smaller individuals suggests that substantial recruitment into sucker spawning 

populations occurred sometime during the 1990s. In recent years, populations of both species have 

exhibited a slow increase in median FL (5–12 mm/yr) and have exhibited little size diversity. This 

homogeneous size structure suggests that the populations contain mostly similarly aged individuals and 

that recent recruitment is almost nonexistent.

A common difficulty in capture–recapture studies is that parameter estimate precision and 

effective modeling depend not only on the number of individuals marked and released but also on the 

number that survive and are subsequently captured again (Williams and others, 2002). Due to the 

sparsity of recapture data, a number of the survival estimates from the beginning of this study had wide 

95 percent CIs or were estimated on a boundary and therefore were of limited value. In addition to 

increases in sampling effort and consistency in 2000, remote underwater PIT tag detection systems were 

incorporated into the study design in 2005. The use of this relatively new technology improved 

recapture probabilities by an order of magnitude and dramatically improved the precision of survival 

estimates. These improvements will allow future analyses to begin investigating the roles that algal 

blooms, water quality, disease, and water management play in sucker population dynamics.

Acknowledgments

The authors of this report would like to thank Mathew Abel, Nolan Banish, Ryan Braham, 

Nathan Harris, and Jody Pope for their hard work, dedication, and attention to detail. They were crucial 

to the success of this project. David R. Anderson provided invaluable advice concerning data analysis. 

We would also like to thank Scott Vanderkooi and Rip Shively of the USGS Klamath Falls field station 

for their assistance. The Bureau of Reclamation is to thank for the financial support and willingness to

see this project through. 
12

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Lost River (Deltistes luxatus) and shortnose (Chasmistes brevirostris) suckers in Clear Lake 

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brevirostris) sucker recovery plan: Portland, Oregon, 108 p.
14

Figure 1. Upper Klamath Lake map, showing sampling locations for Lost River suckers and shortnose suckers. 

Inset illustrates the general location of Upper Klamath Lake in south-central Oregon.
15

Cinder Flats

Number of suckers captured 0

10

20

30

40

50

4

6

8

10

12

14

16

18

20

LRS Catch 

N = 218

Average Temperature

Ouxy Springs

0

10

20

30

40

50

2

4

6

8

10

12

14

16

18

20

N = 135

Silver Building Spring

3/01/08 3/08/08 3/15/08 3/22/08 3/29/08 4/05/08 4/12/08 4/19/08 4/26/08 5/03/08 5/10/08 5/17/08 5/24/08 5/31/08 

0

10

20

30

40

50

2

4

6

8

10

12

14

16

18

20

N = 192

Sucker Springs

Date

3/01/08 3/08/08 3/15/08 3/22/08 3/29/08 4/05/08 4/12/08 4/19/08 4/26/08 5/03/08 5/10/08 5/17/08 5/24/08 5/31/08 

0

10

20

30

40

50

Average Temperature ( oC )

2

4

6

8

10

12

14

16

18

20

N = 289

Figure 2. Number of Lost River suckers captured at four Upper Klamath Lake lakeshore spawning 

areas and average daily water temperature (oC) in Upper Klamath Lake, Oregon, 2008. Temperature 

loggers were placed away from spring influence near each sample location. Only the first capture of an 

individual at a spring is included.
16

Cinder Flats

0

20

40

60

80

100

120

140

160

4

6

8

10

12

14

16

18

20

Remote LRS

Average Temperature

N = 1371

Ouxy Springs

0

20

40

60

80

100

120

140

160

Temperature ( oC )

2

4

6

8

10

12

14

16

18

20

N = 784

Silver Building Spring 3/01/08 3/08/08 3/15/08 3/22/08 3/29/08 4/05/08 4/12/08 4/19/08 

4/26/08 5/03/08 5/10/08 5/17/08 5/24/08 5/31/08 

Number of remote detections

0

20

40

60

80

100

120

140

160

2

4

6

8

10

12

14

16

18

20

 N = 1119

Sucker Springs

Date

3/01/08 3/08/08 3/15/08 3/22/08 3/29/08 4/05/08 4/12/08 4/19/08 4/26/08 5/03/08 5/10/08 5/17/08 5/24/08 5/31/08 

0

20

40

60

80

100

120

140

160

2

4

6

8

10

12

14

16

18

20

N = 2527 

Figure 3. Number of individual Lost River suckers detected on underwater passive integrated

transponder (PIT) tag antennas at four lakeshore spawning areas and water temperature (oC) in Upper 

Klamath Lake, Oregon, 2008. Temperature loggers were placed away from spring influence near each 

sample location. Only the first detection of an individual at a spring is included.
17

2008 Weir 

Date

3/01/08 3/08/08 3/15/08 3/22/08 3/29/08 4/05/08 4/12/08 4/19/08 4/26/08 5/03/08 5/10/08 5/17/08 5/24/08 5/31/08 

Streamflow (ft3/s)

600

800

1000

1200

1400

1600

1800

2000

2200

2400

Number of suckers captured

0

20

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60

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100

120

140

160

180

Streamflow (ft3

/s)

LRS Lost River Sucker 

N = 1319

2008 Weir 

3/01/08 3/08/08 3/15/08 3/22/08 3/29/08 4/05/08 4/12/08 4/19/08 4/26/08 5/03/08 5/10/08 5/17/08 5/24/08 5/31/08 

Temperature ( oC)

2

4

6

8

10

12

14

16

18

20

Number of suckers captured

0

20

40

60

80

100

120

140

160

180

Average Temperature 

LRS Lost River Sucker

N = 1319

Figure 4. Number of Lost River suckers captured in the upstream weir trap on the Williamson River 

during the 2008 field season.
18

2008 Weir Trap Antenna detections

2/22/08 2/29/08 3/07/08 3/14/08 3/21/08 3/28/08 4/04/08 4/11/08 4/18/08 4/25/08 5/02/08 5/09/08 5/16/08 5/23/08 5/30/08 

Number of Detections

0

20

40

60

80

100

120

140

160

180

Temperature ( oC )

2

4

6

8

10

12

14

16

18

20

LRS

Average Temperature

N = 1884

2008 Weir Trap Antenna detections

Date

2/22/08 2/29/08 3/07/08 3/14/08 3/21/08 3/28/08 4/04/08 4/11/08 4/18/08 4/25/08 5/02/08 5/09/08 5/16/08 5/23/08 5/30/08 

Number of Detections

0

20

40

60

80

100

120

140

160

180

Streamflow (ft3/s)

600

800

1000

1200

1400

1600

1800

2000

2200

2400

LRS

Streamflow (ft3

/s)

N = 1884

Figure 5. Number of Lost River suckers detectioned on passive integrated transponder (PIT) tag 

antenna located in the Williamson River weir upstream trap. Only the first detection was included for

individuals detected multiple times on the antenna.
19

2008 Chiloquin Dam 3/01/08 3/08/08 3/15/08 3/22/08 3/29/08 

4/05/08 4/12/08 4/19/08 4/26/08 5/03/08 5/10/08 5/17/08 5/24/08 5/31/08 

Average temperature ( oC)

0

5

10

15

20

25

Number of suckers captured

0

20

40

60

80

100

120

140

Average Temperature 

Lost River Sucker 

N = 507

2008 Chiloquin Dam

Date

3/01/08 3/08/08 3/15/08 3/22/08 3/29/08 4/05/08 4/12/08 4/19/08 4/26/08 5/03/08 5/10/08 5/17/08 5/24/08 5/31/08 

Streamflow (ft3/s)

200

400

600

800

1000

1200

1400

1600

1800

2000

Number of suckers captured

0

20

40

60

80

100

120

140

Streamflow (ft3/s)

Lost River Sucker

N = 507 

Figure 6. Summary of Lost River suckers captured in the Chiloquin Dam fish ladder on the Sprague 

River, Oregon, 2008.
20

2008 Chiloquin Dam Downstream antenna

3/01/08 3/08/08 3/15/08 3/22/08 3/29/08 4/05/08 4/12/08 4/19/08 4/26/08 5/03/08 5/10/08 5/17/08 5/24/08 5/31/08 

Number of detections

0

20

40

60

80

100

120

Temperature ( oC )

0

5

10

15

20

25

LRS Lost River Sucker 

N = 871

Average Temperature

2008 Chiloquin Dam Downstream Antenna

Date

3/01/08 3/08/08 3/15/08 3/22/08 3/29/08 4/05/08 4/12/08 4/19/08 4/26/08 5/03/08 5/10/08 5/17/08 5/24/08 5/31/08 

Number of detections

0

20

40

60

80

100

120

Streamflow (ft3/s)

200

400

600

800

1000

1200

1400

1600

1800

2000

LRS Lost River Sucker 

N = 871

Streamflow (ft3/s)

Figure 7. Summary of the first remote detection of individual Lost River suckers on the downstream 

antenna (that is, entrance) at the Chiloquin Dam fish ladder on the Sprague River, Oregon, 2008. 

Average daily water temperatures (°C ) and stream flow (cfs) are also reported.
21

0.40

0.45

0.50

0.55

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

Apparent annual survival

Seniority

1999 2000 2001 2002 2003 2004 2005 2006 2007

0.40

0.45

0.50

0.55

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

Apparent annual survival

Seniority

Apparent survival and seniority probabilities

Female

Male

Figure 8. Apparent annual survival (φ) and seniority (γ) probabilities (95% confidence intervals) of Lost 

River suckers from the lakeshore-spawning subpopulation in Upper Klamath Lake, Oregon, 1999–2007. 

Population rate of change can be estimated from φ and γ estimates using the formula:

( )

( )

( 1)

i

i

i

φ λ

γ 

+

= .
22

2001 2002 2003 2004 2005 2006

Apparent annual survival probability

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Female 125 kHz

Male 125 kHz

Female 134 kHz

Male 134 kHz

Figure 9. Apparent annual survival (φ) probabilities (95% confidence intervals) of Lost River suckers tagged with 

125 and 134 kHz PIT tags from the Williamson and Sprague Rivers spawning subpopulation, 2001–06. The 2003 

estimates were on the boundary of 1.0, indicating estimability problems; thus, the estimates are not presented.
23

Figure 10. Length frequencies of male and female Lost River suckers captured in spring trammel net sampling at 

Upper Klamath Lake lakeshore spawning areas, 1999–2008. Dots along the x-axis represent median lengths.
24

Figure 11. Growth rates of male and female Lost River suckers captured in spring trammel net sampling at Upper 

Klamath Lake lakeshore spawning areas, 1999–2008, and in the Sprague and Lower Williamson Rivers, 2001–08.

Growth rates were estimated by tracking changes in the median of the dominant mode in the length frequencies. 

An average annual growth rate was calculated as the slope of a simple linear regression of the medians in 

successive years.
25

Figure 12. Length frequencies of male and female Lost River suckers captured in spring sampling in the 

Williamson and Sprague Rivers, 2001–08. Dots along the x-axis represent median lengths.
26

2008 Weir Trap Antenna detections 2/22/08 2/29/08 3/07/08 3/14/08 3/21/08 3/28/08 4/04/08 4/11/08 4/18/08 

4/25/08 5/02/08 5/09/08 5/16/08 5/23/08 5/30/08 

Number of Detections

0

20

40

60

80

100

Temperature ( oC )

2

4

6

8

10

12

14

16

18

20

SNS

N = 772

Average Temperature

2008 Weir Trap Antenna detections

Date

2/22/08 2/29/08 3/07/08 3/14/08 3/21/08 3/28/08 4/04/08 4/11/08 4/18/08 4/25/08 5/02/08 5/09/08 5/16/08 5/23/08 5/30/08 

Number of Detections

0

20

40

60

80

100

Streamflow (ft3/s)

600

800

1000

1200

1400

1600

1800

2000

2200

2400

SNS

N = 772

Streamflow (ft3

/s)

Figure 13. Summary of the number of shortnose sucker (SNS) detected on the upstream trap antenna on the 

Williamson River weir. 
27

Apparent survival and seniority probabilities

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Apparent annual survival

Seniority

2000 2001 2002 2003 2004 2005 2006 2007

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Apparent annual survival

Seniority

Female

Male

Figure 14. Apparent annual survival (φ) and seniority (γ) probabilities (95% confidence intervals) of adult 

shortnose suckers in Upper Klamath Lake, Oregon, 1999–2007. Population rate of change can be estimated from 

φ and γ estimates using the formula:

( )

( )

( 1)

i

i

i

φ λ

γ 

+

= .
28

Figure 15. Length frequencies of male and female shortnose suckers captured in the Williamson and Sprague 

Rivers, 2001–08. Dots along the x-axis represent median lengths.
29

Figure 16. Growth rates of male and female shortnose suckers captured in the Sprague and Lower Williamson 

Rivers, 2001–08. Growth rates were estimated by tracking changes in the median of the dominant mode in the 

length frequencies. An average annual growth rate was calculated as the slope of a simple linear regression of the 

medians in successive years.
30

Table 1. The total number of Lost River and shortnose suckers captured in Upper Klamath Lake (UKL) and its 

tributary rivers in 2008. 

[Totals only include the first capture at a location; however, individuals may have been captured at more than one location. 

Recaptures from previous years are the percentage of fish captured that already had a passive integrated transponder (PIT) 

tag] 

Capture location

Lost River 

suckers % Recaptures Shortnose suckers % Recaptures

UKL pre-spawn staging areas 469 13.0 % 672 19.8 %

Williamson River fish weir 1,319 6.5 % 288 22.6 %

Chiloquin Dam fish ladder 507 52.1 % 239 57.3 %

UKL lakeshore spawning areas 834 45.0 % 5 100 %

Table 2. The total number of unique Lost River suckers and shortnose suckers detected by remote stations in 

Upper Klamath Lake (UKL) and its tributary rivers in 2008. 

[Totals include the first detection at a particular location; however, Individuals may have been detected at more than one 

location during the spawning season]

Remote station location Lost River suckers Shortnose suckers Total

Williamson and Sprague Rivers

Williamson River fish weir 7,923 4,061 11,984

Chiloquin Dam fish ladder 883 771 1,654

Chiloquin Dam array 2,700 777 3,477

UKL lakeshore spawning areas

Sucker Spring 4,248 27 4,275

Silver Building Spring 3,492 17 3,509

Ouxy Spring 2,512 9 2,521

Cinder Flat 3,076 9 3,085
31

Table 3. Model selection results for ten candidate models of survival and recapture probability for lakeshore-spawning Lost River suckers in Upper 

Klamath Lake, Oregon,1999–2000.

[Akaike’s Information Criterion corrected for small sample size and overdispersion (quasilikelihood AICc [QAICc]; overdispersion factor cˆ = 1.44); values were 

used to select the best model from among ten candidate models of survival (φ) and recapture probability p for the lakeshore-spawning subpopulation of Lost 

River suckers in Upper Klamath Lake, Oregon, 1999 to 2008 (period symbol = parameter is constant over the given attribute; ×= full model effects; + = additive 

effects. The best model is presented first; ΔQAICc represents the difference between the QAICc value of a model and that of the best model. Akaike weights (wi) 

provide a measure of each model’s relative weight or likelihood of being the best model in the set given the data. Number of parameters is the total number that 

is theoretically estimable by the model]

Model QAICc ΔQAICc wi Number of 

parameters

φ (sex year p sex year + )   125 kHz( × × ) 134.2 kHz(.)  

 

22,778 0.0 0.730 30

φ (sex year p sex year + )   125 kHz( × × ) 134.2 kHz(sex year × )   22,781 2.7 0.190 33

φ (sex year p sex year × )   125 kHz( × × ) 134.2 kHz(sex year × )   22,783 4.5 0.077 40

φ (sex year p sex year × )   125 kHz( + × ) 134.2 kHz(sex year + )   22,792 13.8 0.001 33

φ (sex year p sex year × )   125 kHz( + + ) 134.2 kHz(sex year + )   22,798 19.7 0.000 30

φ ( year p sex year )   125 kHz( × × ) 134.2 kHz(.)  

 

22,844 66.1 0.000 29

φ (sex year p sex year × × ) ( ) 22,851 72.5 0.000 34

φ (. . ) p sex year   125 kHz( × × ) 134.2 kHz( )   22,875 97.3 0.000 21

φ ( year p year ) ( ) 23,122 344.3 0.000 17

φ ( year p sex tag type ) × ( ) 36,093 13,314.

5

0.000 11
32

Table 4. Model selection results for nine candidate models of survival and recapture probability for the adult 

shortnose suckers in Upper Klamath Lake, Oregon, 2000–2008.

[Akaike’s Information Criterion corrected for small sample size (AICc) and overdispersion (quasilikelihood AICc [QAICc]; 

overdispersion factor cˆ = 2.26); values were used to select the best model from among nine candidate models of survival 

(φ) and recapture probability p for adult shortnose suckers in Upper Klamath Lake, Oregon, 1995–2008 (period symbol = 

parameter is constant over the given attribute; ×= full model effects; + = additive effects. The best model is presented first; 

ΔQAICc represents the difference between the QAICc value of a model and that of the best model. Akaike weights (wi) 

provide a measure of each model’s relative weight or likelihood of being the best model in the set given the data. Number of 

parameters is the total number that is theoretically estimable by the model]

Model QAICc Model ΔQAICc wi Number of parameters

φ (sex year p sex year tag type + + × ) ( ) 15,665 0.0 0.602 31

φ (sex year p sex year tag type × + × ) ( ) 15,667 2.1 0.208 43

φ (sex year p year tag type × × ) ( ) 15,667 2.3 0.190 41

φ (sex year p sex year tag type + × × ) ( ) 15,682 17.2 0.000 45

φ (sex year p sex year tag type × × × ) ( ) 15,684 19.5 0.000 56

φ ( year p year tag type ) × ( ) 15,695 30.2 0.000 28

φ (sex year p year tag type + × ) ( ) 15,719 53.8 0.000 29

φ (sex p sex year tag type ) + × ( ) 15,825 160.1 0.000 20

φ (.) + × p sex year tag type ( ) 15,854 189.3 0.000 19
Publishing support provided by the U.S. Geological Survey

Publishing Network, Tacoma Publishing Service Center

For more information concerning the research in this report, contact the 

Director, Western Fisheries Research Center

U.S. Geological Survey

6505 NE 65th Street

Seattle, Washington 98115

http://wfrc.usgs.gov/
Janney and others— Demographics and 2008 Run Timing of Adult Lost River and Shortnose Suckers, Upper Klamath Lake, Oregon, 2008 —Open-File Report 2009-1183