JUN 3 0 2003 KEN SALAZAR · Estimation of Trout Population Abundance The Seber-LeCren two pass removal model (Seber and LeCren 1967) ... the high growth rates of trout in chalk streams

JUN 3 0 2003

KEN SALAZARAttorney General

DONALD S. QUICKChief Deputy Attorney General

ALAN J. GILBERTSolicitor General

STATE OF COLORADODEPARTMENT OF LAW

OFFICE OF THE ATTORNEY GENERAL

June 27, 2003

STATE SERVICES BUILDING1525 Sherman Street - 5th FloorDenver. Colorado 80203Phone (303) 866-4500FAX (303)866-5691

SDMS Document ID

2036964Mr. Ron Eddy633 17th St. #3000Denver, Colorado 80202

RE: CDOW Response to "Comments of Resurrection Mining Company Regarding CDOWRetort" (sic)

Dear Ron:

By letter dated September 5, 2002, you transmitted Resurrection/Chadwick EcologicalConsultants (CEC) comments on the report entitled "Evaluation of 16 Years of Trout PopulationBiometrics in the Arkansas River, January 15, 2002. Enclosed is a response to those commentsalong with an updated analysis. Although CDOW continues to have more faith in its use ofscaling data than does CEC, it has incorporated resolutions to many of the other comments inthe response and attached updated evaluation which supercedes the previous Report.

We appreciate Resurrection's input.

Sincerely,

FOR THE ATTORNEY GENERAL

VICKY L: PETERSAssistant Attorney GeneralNatural Resources and Environment303-866-5110303-866-3558 (FAX)

Enclosures

Page 2

cc: Jerry EllingtonRichard SiskAngus CampbellRon CattanyLee PivonkaRuss AllenLaura CoppockPat DaviesGreg PolickyRobert Litle

AG File: nehring response cover ltr.doc

A Synopsis of Seventeen YearsTrout Population Biometricsin the Upper Arkansas River

R. Barry NehringAquatic Wildlife Researcher

andGreg Policky

Area Fisheries Biologist

Colorado Division of Wildlife

June 2003

INTRODUCTION

During the last half of the 19th century, the search for gold and silver in Coloradolead to the establishment of boomtowns like Leadville, Silverton, and Creede. Miningactivity expanded in the first half of the 20th century as the demand for lead, zinc, copper,molybdenum and other heavy metals grew, fueled by an industrial economy. In themountainous areas of Colorado, waste products from a century of mining activity wereoften piled alongside streams. Heavy metals from the tailings piles leached by water frommelting snows and mountain rainstorms found their way into mountain streams.

In the latter half of the 20th century, concerns over the potential negative impacts ofheavy metal pollution on aquatic biota of the upper Arkansas River lead to intensiveinvestigations (LaBounty et al. 1975; Roline and Boehmke 1981; Nesler 1982; Nehring1986; Roline 1988, Davies, Mclntyre, and Stednick 1997; and Davies, Brinkman, Mclntyre,and Clements 2000). Over the past 20 years, efforts to ameliorate the environmentalimpacts of heavy metal pollution have intensified.

In the 1980s, the Colorado Division of Wildlife (CDOW) began conductingextensive electrofishing investigations at numerous sites in the upper Arkansas River basinto assess the impact of heavy metal pollution on the fish populations in the river. This datacollection effort intensified in the late 1990s. It has continued through the late summer of2002. The primary purpose of these studies was to determine whether or not the troutpopulations were responding in a positive manner to the efforts of abatement of the heavymetal pollution. This report presents a synopsis of those electrofishing efforts together witha broad interpretation of the results of those studies.

METHODS

Indicator Species

In the field of aquatic biology indicator species are often used as a means ofassessing the effects of environmental perturbations. The geographical distribution, relativeabundance, and sensitivity of the indicator species in the area of impact are critical elementsthat must be properly addressed in order to effectively assess impact.

Historically, two sub-species of cutthroat trout were the only salmonids native to theupper Arkansas River basin (Behnke 1992; Behnke 2002). The greenback cutthroat trout(Oncorhynchus clarki stomias) was native to the mainstem river and numerous tributarieswhile the yellowfin cutthroat trout Oncorhynchus clarki macdonaldi was apparently alacustrine species that existed primarily in Twin Lakes (Behnke 2002). However, both sub-species were largely extirpated in the basin by the dawn of the 20th century. Behnke (2002)documents that the yellowfin cutthroat trout was probably extinct by 1910. Introducednormative rainbow trout (Oncorhynchus mykiss) hybridized with the cutthroat trout andoften out-competed them in their native habitat in the upper river basin and its tributaries.

Throughout the Arkansas River basin and across Colorado, introductions of othernormative salmonids such as the brook trout (Salvelinus fontinalis) and brown trout (Salmotruttd) aggravated the competitive disadvantage of the cutthroat trout. Taken together,hybridization with rainbow trout, competition with brown and brook trout, and impacts ofoverfishing have largely extirpated the greenback cutthroat trout from most aquatic habitatsin Colorado. A few small relict populations still exist or have been re-introduced in remoteheadwater streams, but they do not exist in the mainstem Arkansas River downstream ofLeadville, Colorado.

Over the past 20 years, electrofishing studies have consistently shown that browntrout are the dominant salmonid in most segments of the upper Arkansas River aroundLeadville, Colorado. Brook trout are relatively abundant in some areas, particularly in theLake Fork of the Arkansas River, Tennessee Creek, and portions of the East Fork of theArkansas River. Rainbow trout are occasionally encountered in some areas in some years.Occasionally large Snake River cutthroat trout (Oncorhynchus clarki bouvieri) areencountered as well. However, the presence of rainbow trout and Snake River cutthroattrout is likely the result of stocking.

All of the foregoing dictates that the brown trout is the only possible choice for anindicator fish species. It is present in sufficient numbers and reproductively active at mostsampling sites on the mainstem of the Arkansas River. In Colorado, the average life span ofstream-dwelling brown trout in healthy aquatic habitats is usually 6 to 8 years (Espegren etal. 1990). However, tagging studies have shown the maximum life expectancy can exceed10 years in some instances (Nehring 1980; Burkhard 1977).

Estimation of Trout Population Abundance

The Seber-LeCren two pass removal model (Seber and LeCren 1967) was used toestimate trout population abundance in the upper Arkansas River at virtually all study sitesin all years. The only exception-to this was at the two most downstream study sites in 1987and 1988. At these stations the Petersen mark-recapture model was used (Robson andRegier 1964). At these locations flow conditions and the width of the stream severelyreduced the electrofishing efficiency requirements for the two-pass removal estimationmodel. In those instances when electrofishing efficiency is less than 50 % to 60%, themark-recapture estimation procedure should be used. However, since the mid-1990s thetwo pass removal estimator has been used at virtually all sampling sites.

Trout population estimates with 95% confidence limits and estimates of brown troutabundance for fish > 15 cm/ha, > 30 cm/ha and > 35 cm/ha are presented in Table 1 in theRESULTS section of the report.

Estimation of Trout Population Biomass

Every fish was weighed (grams) and measured (millimeters total length) during thefield collections throughout the study. Using these length/weight data sets, a logarithmicregression (relating weight to length of the fish) was generated for each study site for each

year of sampling. These regression equations were then interfaced with the trout populationabundance estimates to generate an estimate of brown trout biomass (kilograms/ha) for eachstudy site each year of sampling. These data are presented in Table 1 in the RESULTSsection of the report.

Trout Population Age Structure Analysis

Age structure analysis over time can provide important insights into the overallhealth of a trout population. However, acquisition of age and growth information is a timeand labor intensive process. Large numbers offish scale samples, fin ray cross sections, orotoliths are needed to reduce trout population abundance information into life tables orsurvivorship tables over a period of years. For these reasons, utilization of age/growthinformation is a diagnostic tool that is often ignored by aquatic biologists.

Over the past 26 years CDOW management biologists and aquatic researchers havecollected thousands of trout scales for age and growth analysis of brown, brook, andrainbow trout populations in streams all across Colorado. For details see Nehring 1980,1986; Nehring and Anderson 1981, 1984, 1985; Nehring, Anderson and Winters 1983; andNehring and Miller 1987. At many sites, these data indicate that the average length of troutfor a given age and sampling site does not vary greatly from one year to the next. Theprimary reason for this phenomenon is that fish are poikilothermic animals and theirmetabolic rate is largely controlled by water temperature and the total cumulative thermaldegree-days each fish experiences in a calendar year (Elliott 1975a, 1975b, 1976).

Indeed, studies by Edwards, Densem, and Russell (1979) demonstrated thatdifferences in observed mean growth rates among brown trout collected from 9 differentEnglish streams were... "explained largely in terms of ambient temperature. Inparticular, the high growth rates of trout in chalk streams may be related almost entirelyto the thermal properties of such waters and not to direct effects of calcium or to indirecteffects operating through the productivity or diversity of food webs." Moreover, intensivemonitoring of water temperature in Colorado trout streams over a number of years indicatesthat in many streams there is little variation in the thermal profile and total cumulativedegree-days for a particular stream and monitoring site between years (Nehring andThompson 2001). Taken together, these findings suggest that age and growth informationcollected in one year at a given site may be interfaced with trout population data at that siteacross several years to derive a reasonably accurate approximation of the age structure ofthe trout population at that location.

Scale samples have been collected from brown trout at numerous samples sites inthe upper Arkansas River drainage over the past 18 years. Age and growth data for browntrout was developed from brown trout scales collected at study sites on the East Fork of theArkansas River, Tennessee Creek and the Arkansas River near study sites AR1 and A2 inMay 1986 (Nehring and Miller 1987). CDOW management biologists collected more than1,600 scale samples from brown, brook, and rainbow trout in the upper Arkansas Riverdrainage in September 1994. Approximately 1,250 of these samples were from browntrout. Age and growth data from these samples were interfaced with brown trout population

data collected at numerous sites in the river to generate life table data sets to evaluatelongevity and survival of trout among and between sites throughout the river from 1985through 2001. A new set of brown trout scale samples was collected at each sampling sitein August 2002. There were 830 readable scales in the entire sample.

The age and growth data for the September 1994 and August 2002 scale collectionsare summarized in Appendix Table I. Data summarized for each sampling site for the twocollections include numbers offish in each age group, mean length at the time of collectionfor each age class, mean back-calculated length for each prior age, and standard error ateach age.

Estimates of the age structure of all brown trout in each centimeter groupdetermined from the scale aging process were used to partition the estimated number oftrout present in the population in that centimeter grouping into the appropriate age class.All trout in each age class for all centimeters groups were then summed to derive anestimate of abundance for each age class of brown trout at a particular site in any givenyear. These data are presented in Table 2 in the RESULTS section of the report. Fish ageinformation from the September 1994 scale collections were used to generate the life tabledata for all years from 1985 through 2001. With the availability of new 2002 data, life tabledata were generated using the fish age information derived from the brown trout scalescollected at each sampling site in August of that year (Table 2).

The actual age and growth analysis on the fish scale samples was conducted usingthe DISBCAL computer software program developed by the Missouri Department ofConservation. This program allowed us to determine the age of each fish that had readablescales. The program also back-calculates approximate total body lengths at each prior age(annulus) since trout have a fixed number of scales on the body that grow in directproportion to the size of the fish as it increases in length and age.

RESULTS

Brown Trout Density and Biomass

Brown trout population estimates with 95% confidence limits, density (N/ha),biomass (Kg/ha) and density (N/ha) offish > 15 cm (6 inches), >30 cm (12 inches), and>35 cm (14 inches) for various sampling stations in the upper Arkansas River drainage from1985 through 2002 are given in Table 1. Age specific estimates of brown trout abundanceby sampling period and sampling location(s) over a period of years are presented in Table 2.

Results of the electrofishing in August 2002 largely reinforced trends that were veryapparent from the data from 1999 through August 2001 (Table 1). In general, density(n/ha) of brown trout > 15 cm (6 inches) and biomass (kg/ha) are at or near all-time highlevels at most sampling sites in August 2002. At many sites estimates of density andbiomass have been increasing every year since 1999. These trends are largely true for thestudy sites on the East Fork of the Arkansas River (EF1 and EF2), Tennessee Creek, at sitesAR1, AR3, AR4, and AR6 on the mainstem of the Arkansas River, and in the Lake Fork of

the Arkansas River (LF1) downstream of Turquoise Lake. In August 2002, density andbiomass of brown trout decreased at study sites AR5 (above Empire Gulch) and AR6A(near the PanArk Lodge).

Historically, density (n/ha) of brown trout > 15 cm (6 inches) and biomass (kg/ha)have been the lowest at sample sites downstream of California Gulch. However, in recentyears (1999 - 2002) brown trout density and biomass has increased dramatically in thisreach. At sampling sites AR3, AR4 and AR5 in August 2001, both density and biomass ofbrown trout were the highest for the period of record at that time. However, density andbiomass at sites AR3 and AR4 increased dramatically in 2002 compared to 2001. Thistrend could certainly be considered strong empirical evidence suggesting that efforts toameliorate impacts from heavy metal pollution appear to be having a positive effect on thetrout population.

In general, relative abundance of brown trout > 35 cm (14 inches) increases at themost downstream sampling sites (AR4, AR5, AR6, AR6A and AR7). This is primarily theresult of warmer water temperatures that exert the most control on trout growth rates(Edwards, Densem, and Russell 1979). For a specific sampling site, comparison of the dataon trout > 35 cm (14 inches) in Table 1 with the numbers of trout > 5 years of age (Table 2)indicates mat fish at the downstream sampling sites are larger than those upstream but notnecessarily older.

Estimates of Brown Trout Age and Growth

The year class abundance data in Table 2 tends to corroborate the same trendsobserved with brown trout density and biomass. Over the period of study, the greatestabundance of brown trout at 5, 6 and 7 years of age occur in the tributary streams (EastFork and Lake Fork of the Arkansas River, and Tennessee Creek) and at the moredownstream study sites on the mainstem of the Arkansas River (AR4, AR6A, and AR7).They are least abundant or completely missing at those sampling stations immediatelyupstream and downstream of the California Gulch confluence (AR1, AR2 and AR3).

For those years (1997 - 2002) when comparative data are available, there are starkdifferences in numbers of brown trout at each age at sampling sites AR1 and AR3 (Table2). Site AR1 is the mainstem reference site upstream of the confluence with CaliforniaGulch. Site AR3 is just downstream of the confluence with California Gulch. It isnoteworthy that paired-t test analysis (for a within years comparison) indicates that therelative abundance of age 1 brown trout at site AR1 is significantly lower compared toAR3. This indicates that survival of young-of-the-year (YOY) brown trout and recruitmentto age 1 is greater at the downstream site, and therefore not affected by high flows, whichimpact fish most profoundly in the first two months of life. In contrast, paired-t testanalyses indicate the relative abundance of brown trout for all year classes > age 2 issignificantly greater at AR1 compared to AR3. These data indicate that the relative survivalfor all year classes of brown trout > age 2 at study site AR3 is significantly poorer than thesame age fish at site AR1. These results strongly suggest that the effluent from CaliforniaGulch still impacts the fishery in the Arkansas River in the immediate vicinity downstream.

At study site AR3 on the Arkansas River (below the California Gulch confluence)there has been a modest increase in the abundance of 4 and 5 year-old brown trout in 2001and 2002. This increased survival among these age classes could be the result ofamelioration in ambient levels of heavy metal pollution.

Finally, over the past two years there has been an increase in the abundance of age 6and 7 brown trout at many study sites in tributary streams upstream of California Gulch andamong sampling sites farther downstream from the confluence with California Gulch.However, we are still not seeing increased abundance of older fish at AR3. Thedownstream data may suggest that efforts to reduce ambient levels of heavy metalpollutants are beginning to have a positive impact on the trout population. Below averagestream flows and warmer water temperatures may also be enhancing survival of older agetrout downstream and in the tributaries.

Table 1. Summary of brown trout population estimates with 95% confidence limits, based on two passmethod, density (N/ha), biomass (Kg/ha) and density (N/ha) offish > 15 cm (6 inches), >30 cm (12 inches),and >35 cm (14 inches) for various sampling stations in the upper Arkansas River drainage (1985 through2002).Sample Date Population

Estimate95%C.L. . N/Ha

> 15 cmKg/Ha> 15cm

N/Ha>30cm

N/Ha>35 cm

East Fork Arkansas River - Above CO Highway 9 1 Bridge (EF- 1 )10/25/1985a09/1 9/1 986a08/12/199109/14/199408/18/199708/30/199908/20/200108/14/2002

2311731086965110129166

±11±13±2±2±3±12±9±8

2,3692,120730462438742883

1,135

246.9197.355.633.841.361.876.278.9

...

13700070

00000070

East Fork Arkansas River -Below CO Highway 24 Bridge (EF-2)1 0/25/1 985a09/19/1986a08/15/199109/14/199408/18/199708/30/199908/20/200108/13/2002

185761118712197139144

±10±14±11±3

±15±10±9±7

1,312641933737

1,019820

1,3191,366

101.955.560.3

' 59.793.186.5123.8143.3

• ...090091020

000000010

Tennessee Creek below St. Kevin's Gulch confluence10/25/1985a09/19/198609/13/1994

120170121

±10±6±5

1,286932

1,726

158.4129.2164.9

570

1460

Tennessee Creek Above Powerline Crossing08/18/199708/30/199908/20/200108/13/2002

29637266

±1±13±2±2

4981,0641,1021,003

68.2103.999.595.7

5280470

0000

Tennessee Creek - Above confluence with Arkansas River08/12/1991 162 ±13 1,935 175.1 13 0

Arkansas River - AR1 below USGS gage @ confluence of East Fork/Tennessee Creek09/19/1986a08/13/199108/20/199704/20/199808/31/199904/19/200008/21/200108/13/2002

8111014211711961156187

±1±9±49±11±8±5±8±2

414614789650663337864

1,033

49.954.095.271.270.238.282.7100.6

151280618611

00000000

Arkansas River- AR2 immediately upstream of California Gulch confluence09/19/1986a10/13/1989

09/20/1994509/20/1 994c

10118710122

±3±4±5±3

1,4541,0951,282279

166.288.6102.835.1

591800

0000

a: Station location approximate but not the same as in subsequent sampling years from 1991 forward, b:East braid of split channel, c: West braid of split channel, d: very short station this year only, data biased.

Table l(cont). Summary of brown trout population estimates with 95 % confidence limits, based on two passmethod, density (N/ha), biomass (Kg/ha) and density (N/ha) offish > 15 cm (6 inches), >30 cm (12 inches),and >35 cm (14 inches) for various sampling stations in the upper Arkansas River drainage (1985 - 2002).Sample Date Population

Estimate95% C.L. N/Ha

> 15cmKg/Ha> 15cm

N/Ha> 30 cm

N/Ha>35 cm

Arkansas River - Below California Gulch confluence - AR310/13/198909/20/199408/20/199704/20/199808/31/199904/17/200008/21/200108/14/2002

50212112543296

202

±1±1±2±0±7

±16±11±2

314132129 •75337201554

1,168

23.322.518.34.832.718.564.7104.9

025 .1307171352

013600066

Arkansas River - Doc Smith's Ranch - AR410/25/198508/14/199109/22/199408/19/199704/20/199804/13/199909/01/199904/17/200008/22/200108/15/2002

43221886550478053191351

±9±2

±17±31±11±3±9±3

±17±6

1521662d958229175160279185662

1,230

27.8311. Id110.064.066.459.073.443.5167.8230.9

41396d10710412512112476250367

8237d

395783'688533135178

Arkansas River - above Empire Gulch confluence (AR5)08/14/199109/15/199408/19/199704/21/199810/07/199804/12/199909/01/199904/18/200008/22/200108/15/2002

508174428162815113482

±1±8

±11±2±5±2

±19±3±28±5

164264242138265202264168504310

33.246.156.641.960.749.755.039.677.240.5

496745775196333711363

2928115017508102412

Arkansas River - near the Pan-Ark Lodge (AR6A)10/06/199804/12/199909/02/199904/18/200008/23/200108/15/2002

1568710067167122

Ar04/21/199804/13/199909/01/199904/18/200008/23/200108/16/2002

2354254459124

±11±9±7±6±10±8

459255296197469342

102.455.862.551.583.867.8

209391204842128

821038133

51<ansas River - downstream of Kobe Bridge (AR6)

±1±3.0±1±17±7±6

147350164286271573

25.055.324.636.540.672.7

7100466950119

000172024

Table 1 (continued). Summary of brown trout population estimates with 95% confidence limits, based on twopass method, density (N/ha), biomass (Kg/ha) and density (N/ha) of fish > 15 cm (6 inches), >30 cm (12inches), and >35 cm (14 inches) for various sampling stations in the upper Arkansas River drainage (1985through 2002).Sample Date Population

Estimate95% C.L. N/Ha

> 15cmKg/Ha> 15cm

N/Ha>30cm

N/Ha> 3 5 c m

Arkansas River - upstream of Lake Creek confluence10/25/1985a

09/29/8807/29/9209/22/94

6210461182

±3±45±6±5

159458270798

31.675.463.9142.8

...94118224

37

3331

Arkansas River near Granite - downstream of Lake Creek confluence (AR7)09/17/198709/29/198804/21/199810/06/199804/12/199910/20/199904/17/200008/22/200108/16/2002

480904101895556101147118

±139±135±37±10±2±18±12±83±10

1,4582,749306272167170306474382

241.0345.569.8

' 56.237.329.456.785.357.9

393319134114803611516084

311030302820273425

Lake Fork of the Arkansas River near Halfmoon Creek confluence (LF1)08/13/199109/21/199408/20/199708/31/199908/21/200108/14/2002

8116260197155229

±11±3±6

±17±8

±12

343686253833796

1,174

57.496.565.4141.5103.1101.0

489078164114109

133423803833

a: Station location approximate but not necessarily the same as in subsequent sampling years, particularlyfrom 1991 forward.

10

Table 2. Year class abundance estimates for wild brown trout at various sampling sites for various years in theUpper Arkansas River drainage from 1987 through 2002.

SampleDate

Age in Years1 2 3 4 5 6 7

East Fork Arkansas River- Above CO Highway 91 Bridge (EF-1)08/12/9109/14/9408/12/9708/30/9908/20/0108/14/02

60365510435219404

8479

239201516134

29618393

275195138

217134103132309460

187140245301198118

14270

7.50

East Fork Arkansas River -Below CO Highway 24 Bridge (EF-2)08/15/9109/14/9408/18/9708/30/9908/20/0108/13/02

146130128488221

1,149

36214729180

259313

35517123266

204871

229322324353386173

847

262298448

0

383962

Tennessee Creek below St. Kevin's Gulch confluence09/19/8609/13/94

232881

25425

493578

134704

4935 43

Tennessee Creek Above Powerline Crossing08/18/9708/30/9908/20/0108/13/02

166444838

1,014

255693379356

96626263124

153290250248

206142174295

235293 46

Tennessee Creek - Above confluence with Arkansas River08/12/91 223 518 544 669 64 123

Arkansas River - AR1 below USGS gage @ confluence of East Fork/Tennessee Creek09/19/8608/13/9108/20/9704/20/9808/31/9904/19/0008/21/0108/13/02

107935614823397

229765

67344188185279

. 132407333

18017834322917089

303415

53291981511353884112

027403050443839

00800000

Arkansas River- AR2 immediately upstream of California Gulch confluence09/19/8610/13/89

09/20/94a09/20/94b

43537532780

15627421546

61849342870

312266622140

100601313

14249

Arkansas River - Below California Gulch confluence - AR310/13/8909/20/9408/20/9704/20/9808/31/9904/17/0008/21/0108/14/02

47694

264221319219232976

14438642414534

237225

334736105749126192

069017103240

06000006

03300030

a: East braid of split channelb: West braid of split channelc: The trout numbers by age for site AR1 are substantially different from that shown in the 2001 report.

11

Table 2 (continued). Year class abundance estimates for wild brown trout at various sampling sites forvarious years in the Upper Arkansas River drainage from 1987 through 2002.

SampleDate


Arkansas River - Smith's Ranch - AR410/25/8508/14/9109/22/9408/19/9704/20/9804/13/9909/01/9904/17/0008/22/0108/15/02

1 iJJ

1506791945157

21283

231834

5573530857169

7541148225

493231605120143836126164

22229764344534542140190

121853435563662248659

0406

212327177387

000000007

29Arkansas River - above Empire Gulch confluence (AR5)

08/14/9109/15/9408/19/9704/21/9810/07/9804/12/9909/01/9904/18/0008/22/0108/15/02

71456941917749101144154

8696123387059814519192

296574307235933910133

362332233235135277036

318352730371325276

^j3161873700

0000000300

Arkansas River - near the Pan- Ark Lodge (AR6A)10/06/9804/12/9909/02/9904/18/0008/23/0108/15/02

106865512514473

855367239495

132741123610046

11267727810760

602230243861

25157

221040

00000

22Arkansas River - downstream of Kobe Bridge (AR6)

04/21/9804/13/9909/01/9904/18/0008/23/0108/16/02

4610154

20170

310

4683486760145

31110622966125

447339316435

490980

300080

000000

Arkansas River - upstream of Lake Creek confluence09/29/8807/29/9209/22/94

21257

406

11483197

17292

247

6452104

04161

0711

0015

Arkansas River near Granite - downstream of Lake Creek confluence (AR7)09/17/8709/29/8804/21/9810/06/9804/12/9910/20/9904/17/0008/22/0108/16/02

594106663506518

15769172

562133132103535612016795

364851855127705610064

368376835646197010841

13520758492712575914

00

27251514 .9

2314

000000000

12.

Table 2 (continued). Year class abundance estimates for wild brown trout at various sampling sites for variousyears in the Upper Arkansas River drainage from 1987 through 202.

SampleDate


Lake Fork of the Arkansas River near Halfmoon Creek confluence downstream of C.R. 1 1 (LF1)08/13/9109/21/9408/20/9708/31/9908/21/0108/14/02

5371218449365474

2,121

245561186864 .271123

21210234

496229150

5276791197024

1785

L_ 64255184

40041411

0000

229

Age and Growth of Brown Trout

For all electrofishing data sets collected from 1985 through 2001, scale age andgrowth information collected during sampling in 1994 was used to stratify trout populationestimates into year classes and develop a life table for brown trout at each study site. Thelife table information is presented in Table 2. Age and growth data generated for each studysite from the 1994 scale sample collections are summarized in Table I in the Appendix.

Another set of scale samples was collected during electrofishing studies at eachstudy site in August 2002. Age and growth data generated for each study site from the 2002set of scale samples are summarized in Table II in the Appendix. These age and growthdata sets were used to generate estimates of brown trout age class abundance for each studysite for August 2002. Those data are presented in Table 2.

For this updated report, we developed two new life tables for study site AR1. Forone life table we used the age and growth data set for study site AR2 collected in September1994. For the second life table we used the age and growth data set collected at AR1 inAugust 2002. These data sets were used to develop life table information for comparisonwith that presented in Table 2 for study site AR1 in Nehring and Policky (2002). Thosecomparisons are shown in Table 3. Using either the scale data set collected at study siteAR2 in September 1994 or that collected at study site AR1 in August 2002, we end up withsubstantial numbers of age 5 trout for all years of study as seen in Table 3. That was not thecase using the 1994 data set from farther downstream that resulted in no trout estimated tobe older than age 4. However, it is also noteworthy that no matter which of the three ageand growth data sets are used, brown trout greater than age 5 have rarely been present atthis station. In contrast, brown trout estimated to be age 6 and even age 7 have regularlybeen detected throughout the study period at sampling stations EF1, EF2, AR4, AR5, AR6,AR6A, AR7, Tennessee Creek and on the Lake Fork of the Arkansas River. Only at studysites AR1, AR2, and AR3 are brown trout estimated to be > age 6 noticeably absent orpresent only in very low numbers in most years.

13

Table 3. Comparisons of year class abundance estimates for wild brown trout at sample siteAR1 using 3 different fish scale age and growth data sets for various years 1991 through2002.

SampleDate


Age Structure for Study Site AR1 using age-growth data from Site AR4 collected in August 199408/13/9108/20/9704/20/9808/31/9904/19/0008/21/01

286374573731369309

330436356356191556

9142818116058181

14337182821

Age Structure for Study Site AR1 using age-growth data from Site AR2 collected in August 199408/13/9108/20/9704/20/9808/31/9904/19/0008/21/0108/13/02

844897

20676

203637

7442888340109164

24425420020984

300304

270457341338159419537

24321829533528

0000000

Age Structure for Study Site AR1 using age-growth data from Site AR1 collected in August 200208/13/9108/20/9704/20/9808/31/9904/19/0008/21/0108/13/02

935614823397

229765

344188185279132407333

17834322917089

303415

[ 291981511353884112

27403050443839

0800000

After examining the age versus length frequency distributions for the two age andgrowth data sets for 1994 and 2002 for multiple sites, we believe it would be prudent tocollect a new set of scale samples at all sampling sites for at least the 2003 and 2004collections. If the study continues beyond 2004, an assessment based on the age andgrowth analyses for 2002, 2003, and 2004 can be made to determine whether or not it isnecessary to continue to collect scale samples at all study sites each year.

There are numerous reasons why it would be biologically sound to collect twoaddition scale data sets at each study site in 2003 and 2004. First, the data on age andgrowth in Appendix Tables I and II indicate that annual growth increments of trout areinversely related to elevation. Second, the study sites are not widely separated in distanceand there is a high probability that some movement of trout could be occurring betweenstudy sites within and between years. These sorts of movement, among both juvenile (age 1and 2) and adult (> age 3) trout have the potential for intermixing of trout of the same sizebut different ages at a given site in a given year. Such mixing has the potential todramatically change the size and age structure at a site between years. Thus, it seemsprudent to collect scale samples at all sites each year. This is the best way to maximize thevalidity of any effort to validate the age structure of the trout population within and betweenstudy sites across the years and minimize uncertainty.

14

There are many studies that have focused on the issue of movement among stream-dwelling salmonids (Bachman 1984; Clapp et al. 1990, Fausch and Young 1995; Gerking1959; Gowan and Fausch 1996; Gowan et al. 1994; Knouft and Spotila 2002; Meyers et al.1992; Miller 1957; Riley et al. 1992; Young 1994). Some indicate very little movement (<100 m) among stream-dwelling trout throughout their lifetime (Miller 1957; Gerking 1959;Bachman 1984). Other investigators found most trout movement was over distances < 800meters (Knouft and Spotila 2002). Still others documented movement over distances of 1to 2 Ion (Gowan and Fausch 1996). Two other studies documented seasonal movements ofadult brown trout up to 20 km (Meyers et al. 1992) and 33 km (Clapp et al. 1990).

Movement of trout between stations and years could be a complicating factor in theupper Arkansas River, particularly in drought years as the state has experienced in 2001 and2002. Indeed, in a similar study being conducted on the Eagle River biologists saw. largenumbers of unmarked brown trout from outside the study area(s) showing up in the studystations in 2002. This had not occurred in previous years (John Woodling, personalcommunication). Collecting age and growth information together with the color-codedtagging studies should help document whether or not substantial movement of brown troutbetween study sites is occurring in the upper Arkansas River basin.

DISCUSSION

Numerous extensive studies have examined the impacts of chronic heavy metalpollution on the aquatic biota of the upper Arkansas River over the past 27 years. Some ofthe more notable publications include LaBounty et al. 1975, Roline and Boehmke 1981,Nesler 1982, Nehring 1986, Roline 1988, Davies, Mclntyre and Stednick 1997, Davies,Brinkman, Mclntyre, and Clements 2000, Nehring and Policky 2002.

In October 1985, the Yak Tunnel drain surged, resulting in a large discharge of minedrain wastewater laden with iron oxide that turned the water of the upper Arkansas Riverbright orange. Despite dilution by flow augmentation from tributary streams, this pulse ofpolluted water was still orange when it flowed into Pueblo Reservoir, approximately 250km downstream a few days later. The CDOW was called upon to conduct an extensiveelectrofishing operation to determine whether or not the spill caused a substantial fish kill.There was no evidence of any fish kill. However, liver and kidney tissues from more than300 brown and rainbow trout were collected from numerous sites throughout the ArkansasRiver drainage from the East Fork of the Arkansas River downstream to Salida. A scalesample was collected from each fish that was sacrificed to facilitate cross correlation ofheavy metal content in liver and kidney tissues with increasing age within and betweensampling sites. These tissues were examined for bioaccumulation of lead, zinc, copper, andcadmium with increasing age. The study revealed that there was substantialbioaccumulation of copper in brown trout liver tissue with increasing age. Similarly,cadmium bioaccumulated in both liver and kidney tissues of brown trout with increasingage (Nehring 1986). Empirical evidence in the study also suggested that the level ofcadmium bioaccumulation in liver and kidney tissues was high enough that it might belinked to reduced longevity of brown trout in the river.

15

Between the mid-1970s and the mid-1990s, several studies repeatedly documentedthat discharges from the Yak Mine Drainage Tunnel and California Gulch were major pointsources of heavy metal contamination in the upper Arkansas River basin (LaBounty et al.1975; Roline and Boehmke 1981; Roline 1988, Davies, Mclntyre.and Stednick 1997; andDavies, Brinkman, Mclntyre, and Clements 2000).

Thus, it is not surprising that brown trout density, biomass and numbers of trout > 5years of age are depressed at the study sites in the Arkansas River drainage downgradient ofthe confluence with California Gulch. To a lesser extent this applies to the area of the riverthat received inflow from the Leadville Mine Drainage Tunnel. However, the existence ofempirical evidence showing correlation does not necessarily prove causation. That isalmost always the case with field investigations.

Nonetheless, given all of the foregoing results and studies referred to above, it ismost probable that chronic heavy metal pollution is the most significant factor responsiblefor the reduced density and biomass of brown trout as well as reduced survivorship amongolder fish in the Upper Arkansas River downgradient of California Gulch.

CONCLUSIONS

Results of trout population monitoring efforts at numerous sites throughout theupper Arkansas River basin over the past 17 years are strongly congruent with the findingsof other investigators (LaBounty et al. 1975; Roline and Boehmke 1981; Nehring 1986;Roline 1988; Davies, Mclntyre, and Stednick 1997; and Davies, Brinkman, Mclntyre, andClements 2000). All of these studies strongly suggest that chronic heavy metals pollutionin the reach of the Arkansas River in the immediate vicinity of the confluence withCalifornia Gulch have had negative impacts on the aquatic biota in the river, particularly inthe 1980s into the 1990s. It remains to be seen whether or not the recent increases indensity, biomass, and the larger numbers of older age brown trout at many study sitesobserved in 2001 and 2002 will continue over the next 2 or 3 years. If it does, that wouldbe strong empirical evidence suggesting that efforts to ameliorate heavy metal pollution inthe upper basin are having a positive impact on the brown trout population. Conversely, adecline in density, biomass, and numbers of older age trout decline over the next 2 to 3years at study sites AR3, AR4, and AR5 would suggest that the recent increases in thesebiostatistics observed in 2001 and 2002 had more to due with the below average flowconditions than with amelioration of the heavy metal pollution in the basin.

RECOMMENDATIONS

Guidelines for the collection of trout population data that would help reducevariability and sampling method(s)-induced "noise" in the data within study sites betweenyears were set forth in 2002 (Nehring and Policky 2002). Those guidelines included thefollowing:

1. Spring sampling should be eliminated. There is a high probability ofobtaining biased results when electrofishing sampling is conducted too early

16

in the spring or too late in the fall. Once the water temperatures drop below7-8 ° C juvenile salmonids go into a cryptic behavior mode during daylighthours, often burrowing deep into the interstitial spaces in the substrate(Campbell and Neuner 1985; Griffith and Smith 1993; Heggenes et al. 1993;Griffith and Smith 1995; Meyer and Griffith 1997). The water temperaturein the upper Arkansas River basin, at an elevation of 3,000 m in April wouldmost certainly would be < 7° C.

2. Avoid electrofishing in the fall (after mid-September through late October).Adult brown trout are often migratory during the fall spawning period. Movementof spawners into or out of study reaches could substantially bias the data. This maybe particularly important among older age classes of trout (> age 5).

3. Electroshocking should be done at almost the same time year after year.Mid-to-late August is the best time. Water flows are generally low at thistime of year. Low flows increase electrofishing efficiency. Watertemperatures are still high enough that juvenile trout have not yet changed tothe cryptic daylight behavior pattern that would result in substantial bias.

4. The same reach length at each study site should be sampled each year.Small changes in reach location or length between years can result insubstantial sampling method(s) induced "noise" in the data, decreasing theprobability of detecting meaningful changes in trout population biostatistics.A glaring example of this occurred at Doc Smith's Ranch (AR4) for August14,1991. See the data for this site in Table 1 for details. Adopted?

5. Data collected over the past 17 years clearly indicate that the two-pass removalestimator (Seber and LeCren 1967) is the appropriate model for use in populationestimation at most of the upstream study sites. It can be used at the mostdownstream study site near Granite, Colorado (downstream of the Lake Creekconfluence) if the electrofishing efficiency is known to be substantially greater than60% on the first electrofishing pass through the station.

These recommendations have been adopted by CDOW. In addition, we suggest thata complete set of scale samples be collected at each sampling site for at least the 2003 and2004 field seasons, and continued tagging. This will provide the most accurate and preciseinformation for estimating the relative abundance and survival rates for brown trout amongand between study sites and years. While it would be nice to corroborate the age ofindividual fish using both scale aging and otolith or fin ray analyses, the otolith method ofaging requires lethal sampling, and fin ray sampling adversely affect the fish. Lethalsampling and significant adverse effects would be counter-productive when the primaryreason for conducting the studies is to evaluate longevity and survival of brown trout in theupper Arkansas River basin.

17

ACKNOWLEDGEMENTS

Virtually all of the fish population data used in this study were collected by CDOWArkansas River basin management biologists Greg Policky and Rick Anderson, and thefield crews under their supervision. Copies of all field data were provided by Greg Policky.Age and growth analyses were completed using the computer software program DISBCALby the senior author and temporary employees under his supervision. For all troutpopulation data sets from 1985 through 2001, Kelly Thompson converted data from thefield notes into a format for input into the GOLDMEDL program. Barbara Poole did thesame for the August 2002 data sets. The GOLDMEDL software program was used togenerate estimates of trout population numbers, density, biomass, and age class abundance.The data sets generated from these analyses are contained in Tables 1, 2 and in this report.Summaries of the age and growth data derived from the 1994 and 2002 scale collections aresummarized in Appendix Tables I and II.

LITERATURE CITED

Bachman, R. A. 1984. Foraging behavior of free-ranging wild and hatchery brown trout ina stream. Transactions of the American Fisheries Society 113:1-32.

Behnke, R. J. 2002. Trout and salmon of North America. The Free Press. New York,New York. 359 pages.

Behnke, R. J. 1992. Native trout of western North America. American Fisheries SocietyMonograph 6. American Fisheries Society. Bethesda, Maryland.

Burkhard, W. T. 1977. Taylor River flow investigations. Colorado Division of WildlifeInterim Job Report, Federal Aid Project F-51-R. Fort Collins.

Campbell, R. F., and J. H. Neuner. 1985. Seasonal and diurnal shifts in habitat utilized byresident rainbow trout in western Washington Cascade Mountain streams. Pages39-48 in F. W. Olson, R. G. White, and F. H. Hamre, editors. Symposium on smallhydropower and fisheries. American Fisheries Society, Western Division andBioengineering Section, Bethesda, Maryland.

Clapp, D. F., R. D. Clark, Jr., and J. S. Diana. 1990. Range, activity, and habitat of large,free-ranging brown trout in a Michigan stream. Transactions of the AmericanFisheries Society 119:1022-1034.

Davies, P. H., M. W. Mclntyre, and J. D. Stednick. 1997. Arkansas River research study:1995 annual progress report. Colorado Division of Wildlife. Fort Collins.

Davies, P. H., S. F. Brinkman, M. W. Mclntyre, and W. H. Clements. 2000. ArkansasRiver research study: 1999 annual progress report. Colorado Division of Wildlife.Fort Collins.

18

Edwards, R. W., J. W. Densem, and P. A. Russell. 1979. An assessment of the importanceof temperature as a factor controlling the growth rate of brown trout in streams.Journal of Animal Ecology 48:501-507.

Elliott, J. M. 1975a. The growth rate of brown trout (Salmo trutta L.) fed on maximumrations. Journal of Animal Ecology 44(3):805-821.

Elliott, J. M. 1975b. The growth rate of brown trout (Salmo trutta L) fed on reducedrations. Journal of Animal Ecology 44(3): 823-842.

Elliott. J. M. 1976. The energetics of feeding, metabolism, and growth of brown trout(Salmo trutta L.) in relation to body weight, water temperature, and ration size.Journal of Animal Ecology 45(3):923-948.

Espegren, G. D., D. D. Miller, and R. B. Nehring. 1990. Modeling the effects of variousangling regulations on trout populations in Colorado streams. Special ReportNumber 67 (DO W-R-S-67-90). Colorado Division of Wildlife. Fort Collins.

Fausch, K. D., and M. K. Young. 1995. Evolutionary significance units and movement ofresident stream fishes: a cautionary tale. American Fisheries Society Symposium17:360-370.

Gerking, S. D. 1959. The restricted movement of fish populations. Biological Review34:221-242.

Gowan, C., and K. D. Fausch. 1996. Long-term demographic responses of troutpopulations to habitat manipulation in six Colorado streams. EcologicalApplications 6:931-946.

Gowan, C., M. K. Young, K. D. Fausch, and S. C. Riley. 1994. Restricted movement inresident stream salmonids: A paradigm lost? Canadian Journal of Fisheries andAquatic Sciences 51:2626-2637.

Griffith, J. S., and R. W. Smith. 1993. Use of winter concealment cover by juvenilecutthroat trout and brown trout in the South Fork of the Snake River, Idaho. NorthAmerican Journal of Fisheries Management 13:823-830.

Griffith, J. S., and R. W. Smith. 1995. Failure of submersed macrophytes to provide coverfor rainbow trout throughout their first winter in the Henrys Fork of the SnakeRiver, Idaho. North American Journal of Fisheries Management 15:42—48.

Heggenes, J., 0. M. W. Krog, O. R. Lindas, J. G. Dokk, and T. Bremmes. 1993.Homeostatic behavioural responses in a changing environment: brown trout (Salmotrutta) become nocturnal during winter. Journal of Animal Ecology 62:295-308.

19

Knouft, J. H., and J. R. Spotila. 2002. Assessment of movements of resident stream browntrout, Salmo trutta L., among contiguous sections of stream. Ecology of FreshwaterFish 11:85-92.

LaBounty, J. F., J. J. Sartoris, L. D. Klein, E. F. Monk, and H.A. Salman. 1975.Assessment of heavy metals pollution in the upper Arkansas River of Colorado.Bureau of Reclamation Report Number REC-ERC-75-5. United States Departmentof the Interior. Washington, D.C.

Meyer, K. A., and J. S. Griffith. 1997. Effects of cobble-boulder substrate configuration onwinter residency of juvenile rainbow trout. North American Journal of FisheriesManagement 17:77-84.

Meyers, L. S., T. F. Thuemler, and G. W. Kornely. 1992. Seasonal movements of browntrout in northeast Wisconsin. North American Journal of Fisheries Management12:433-441.

Miller, R. B. 1957. Permanence and size of home territory in stream-dwelling cutthroattrout. Journal of Fisheries Research Board of Canada 14:687-691.

Nehring, R. B. 1980. Stream fisheries investigations. Colorado Division of Wildlife JobProgress Report. Federal Aid Project F-51-R5. Fort Collins.

Nehring, R. B. 1986. An evaluation of the possible impacts of heavy metal pollution onthe brown trout population of the upper Arkansas River. Colorado Division ofWildlife Report. Denver.

Nehring, R. B. 1986. Stream fisheries investigations. Colorado Division of Wildlife JobProgress Report. Federal Aid Project F-51 -Rl 1. Fort Collins.

Nehring, R. B., and R. M. Anderson. 1981. Stream fisheries investigations. ColoradoDivision of Wildlife Job Progress Report. Federal Aid Project F-51-R6. FortCollins.

Nehring, R. B., and R. M. Anderson. 1984. Stream fisheries investigations. ColoradoDivision of Wildlife Job Progress Report. Federal Aid Project F-51-R9. FortCollins.

Nehring, R. B., and R. M. Anderson. 1985. Stream fisheries investigations. ColoradoDivision of Wildlife Job Progress Report. Federal Aid Project F-51-RIO. FortCollins.

Nehring, R. B., R. M. Anderson, and D. Winters. 1983. Stream fisheries investigations.Colorado Division of Wildlife Job Progress Report. Federal Aid Project F-51-R8.Fort Collins.

20

Nehring, R. B., and D.D. Miller. 1987. Stream fisheries investigations. Colorado Divisionof Wildlife Job Progress Report. Federal Aid Project F-51-R12. Fort Collins.

Nehring, R. B., and K. G. Thompson. 2001. Impact assessment of some physical andbiological factors in the whirling disease epizootic among wild trout in Colorado.Colorado Division of Wildlife Special Report Number DOW-R-S-76-01. FortCollins.

Nehring, R. B., K. G. Thompson, D. Chacon, J. Padia, and A. Nikirk. 2001. Whirlingdisease investigations. Colorado Division of Wildlife Job Progress Report. FederalAid Project F-237-R8. Fort Collins.

Nehring, R. B. and J. P. Goertl, Jr. 1974. Acute toxicity of a zinc-polluted stream to fourspecies of salmonids. Bulletin of Environmental Contamination and Toxicology12(4):464-469.

Nesler, T.P. 1982. Fish populations and fishery of the upper Arkansas River, 1977 - 1980.Fryingpan-Arkansas fish research investigations. Colorado Division of WildlifeFinal Report. Fort Collins.

Riley, S. C., K. D. Fausch, and C. Gowan. 1992. Movement of brook trout (Salvdinusfontinalis) in four small subalpine streams in northern Colorado. Ecology ofFreshwater Fish 1:112-122.

Robson, D. S., and H. A. Regier. 1964. Sample size in Petersen mark-recaptureexperiments. Transactions of the American Fisheries Society 93:215-226.

Roline, R. A. 1988. The effects of heavy metals pollution of the upper Arkansas River onthe distribution of aquatic macrinvertebrates. Hydrobiologia 160:3-8.

Roline, R.A., and J. R. Boehrhke. 1981. Heavy metals pollution of the upper ArkansasRiver, Colorado, and its effects on the distribution of the aquatic macro fauna.Bureau of Reclamation Report Number REC-ERC-81-15. United StatesDepartment of the Interior. Washington, D.C.

Seber, G. A. F., and E. D. LeCren. 1967. Estimating population parameters from catcheslarge relative to the population. Journal of Animal Ecology 36:631 -643.

Young, M. K. 1994. Mobility of brown trout in south-central Wyoming streams. CanadianJournal of Zoology 72:2078-2083.

APPENDICES

21

Table I. Arkansas River back-calculated lengths (cm) of brown trout collected duringCDOW electrofishing operations, August 2002

Year N Age Lc S.E. LI S.E. L2 S.E L3 S.E L4

S.E. L5 S.E. L6 S.E L7 S.E L8 S.E L9 S.EClass (yr)

Arkansas River East Braid Brown Trout 1994Filename AR05ALC.ANU Body scale constant = 40.55

1993 16 1+ 12.8 0.26 8.1 0.19199219911990

19891 x O .7

1988—

916140.40o\J

123.4

2+3+4+

<;+— ' l

6+

—

15.818.121.2

25.625.1

0.530.590.33

8.78.39.0

7.4

0.280.250.25

Arkansas River West Braid SiteFilename AR05BLC

1993199219911990

1989

—

31350.39126.3

1 +2+3+4+

5+

—

12.518.224.525.4

27.7

0.97

—0.790.51

—

7.99.510.89.8

10.8

.ANU

0.42

—1.130.49

—

12.912.613.8

14.9

5 Brown

0.0.0.

.37,5249

TroutBody scale

14.517.515.0

15.9

~1.0.

—

15.917.3

17.6

0.600.53 19.6

20.6 --

September 1994constant =

~6470

—

22.220.0

18.9

40.72

0.670.45 23.7

23.9 --

Arkansas River Site 6 Sewer Lagoon Brown Trout September 1994Filename AR06LC.ANU Body scale constant = 25.00

1993199219911990

8961

1+2+3+4+

14.818.426.631.7

0.251.640.40

—

8.47.57.98.5

0.300.330.44

—

12.913.514.2

0.881.05

—

19.420.3

0.7324.2

1989 2 5+ 33.7 3.30 10.6 0.94 20.3 3.42 25.3 3.67 29.52.25 32.6 3.29

1988 1 6+ 34.7 — 8.3 — 17.7 — 25.3 -— 30.131.6 —- 33.5

22

Table I (continued). Arkansas River back-calculated lengths (cm) of brown troutcollected during CDOW electrofishing operations, August 2002

Year N Age Lc S.E. L, S.E. L2 S.E L3 S.E L4


Arkansas River Site 6 Sewer Lagoon Brown Trout September 1994Filename AR06LC.ANU Body scale constant = 36.49

1993199219911990

1989

1988—

8961

22.27131.7

1+2+3+4+

5+32.66+

—

14.818.426.631.7

33.73.2934.733.5

0.251.640.40

—

3.30

——

Arkansas River Site

9.08.38.89.4

11.5

9.2

0.270.330.42

—

0.94

—

7 Above RD

13.314.214.9

20.8

18.3

0.891.01

—

3.36

—

19.820.7

25.6

25.7

0.71—

3.63

—

44 Brown Trout SeptemberFilename AR07LC.ANU Body scale constant =

1993199219911990

1989

1988—

423225130.7161.55131.2

1 +2+3+4+

5+34.66+

—

14.621.125.431.2

36.91.2634.833.0

0.360.680.620.62

1.35

——

Arkansas River Site

7.98.08.48.2

9.2

7.1

0.220.230.220.25

0.28

—

7 Above RD

14.815.417.3

17.6

17.0

0.480.430.61

0.90

—

44 Brown TroutFilename AR07LC.ANU Body scale

1993199219911990

1989

1988—

423225130.6961.51131.4

1+2+3+4+

5+33.16+

—

14.621.125.431.2

36.91.2534.833.1

0.360.680.620.62

1.35

——

9.09.49.99.8

10.8

8.8

0.210.220.210.23

0.27

—

15.516.218.2

18.7

18.1

20.924.4

25.6

23.0

25.00

0.580.75

1.54

—

Septemberconstant =

0.480.410.58

0.87

—

21.324.9

26.2

23.7

44.67

0.560.73

1.49

—

24.5

29.7

30.2

1994

28.6

31.1

28.1

1994

28.8

31.4

28.5

23




Arkansas River Site 8 Upper Empire Gulch Brown Trout September 1994Filename AR08LC.ANU Body scale constant = 22.30

1993199219911990

1989

23241871.0241.60

1+2+3+4+

5+34.3

Arkansas

1993199219911990

1989

23241871.0241.59

1 +2+3+4+

5+34.3

14.621.928.034.6

36.31.86

0.33 8.50.54 8.10.531.02

1.76

8.910.4

8.5

0.220.200.320.36

0.93

15.117.019.2

18.7

0.440.680.44

2.25

24.126.9

25.1

River Site 8 Upper Empire Gulch Brown TroutFilename AR08LC.ANU Body scale constant =

14.621.928.034.6

36.31.86

0.330.540.531.02

1.76

8.68.39.110.6

8.7

0.220.200.320.35

0.93

15.217.119.3

18.8

0.440.680.43

2.23

24.227.0

25.2

0.961.14

1.35

32.5

29.4

September 199425.00

0.951.13

1.35

Arkansas River Site 9 Above Ball Town Brown Trout SeptemberFilename AR09LC.ANU Body scale constant = 25.00

1993199219911990

1989

1988--1987

—

282630131.0070.80128.0134.0

1 +2+3+4+

5+31.36+

—7+

—

15.220.927.131.0

32.70.6832.632.038.135.8

0.370.780.550.88

0.66

————

8.08.59.69.6

10.1

8.1

12.037.4

0.280.290.240.33

0.38

—

——

15.917.918.1

17.2

11.5

20.9

0.660.420.55

0.67

—

—

24.025.0

22.0

19.8

25.9

0.550.91

0.61

—

—

32.5

29.4

1994

29.5

27.9

24.5

31.9

24



Class

1993199219911990

1989

1988—1987~

S.E. L5 S.E. L6 S.E L7 S.E L8 S.E L9 S.E(yr)

Arkansas River Site 9 Above Ball Town Brown Trout September 1994Filename AR09LC.ANU Body scale constant = 47.02

28 1+ 15.2 0.37 9.3 0.2526 2+ 20.9 0.78 10.0 0.28 16.5 0.6530130.9970.75128.3134.3

3+4+

5+31.46+

—7+

—

27.131.0

32.70.6732.632.138.136.0

0.550.88

0.66

————

Arkansas River Site

11.211.3

11.7

9.9

13.737.5

0.220.31

0.34

—

——

18.7 0.4019.1 0,

18.3 0,

13.1 --

21.9 -

10 Granite Gage Brown

.53

.61

~

~

24.325.5

22.8

20.7

26.7

0.540.88

0.54

—

—

Trout SeptemberFilename AR10LC.ANU Body scale constant =

1993199219911990

1989

1988—

63821101.0241.24131.6

1 +2+3+4+

5+29.66+

—

14.218.525.129.1

31.53.2736.034.8

0.400.480.591.03

0.96

——

Arkansas River Site

7.08.78.99.3

9.0

8.9

0.390.190.280.36

0.77

—

15.0 0.16.7 0.16.2 1.

13.9 1,

16.0 -

10 Granite Gage Brown

,31,5204

.13

—

22.221.3

21.5

22.5

25.00

0.631.14

1.37

—

Trout SeptemberFilename AR10LC.ANU Body scale constant =

1993199219911990

1989

1988

—

63821101.0241.22131.7

1+2+3+4+

5+29.66+

—

14.218.525.129.1

31.50.7836.034.8

0.400.480.591.03

0.96

——

7.69.39.610.0

9.7

9.7

0.360.190.280.35

0.75

—

15.2 0,17.1 0,16.7 1,

14.5 1.

16.5 --

.31

.51

.01

,10

—

22.421.6

21.8

22.9

34.67

0.621.13

1.34

—

29.6

28.2

25.1

32.3

1994

26.1

26.3

28.6

1994

26.2

26.5

28.8

25




Arkansas River Site 11 Railroad Bridge Brown Trout September 1994Filename AR11LC.ANU Body scale constant = 25.00

19941993199219911990

1989

1988

1987—

711811190.7221.2922.21135.6

01+2+3+4+

5+24.26+30.67+

—

11.717.221.523.025.8

26.02.0432.02.8939.036.8

Arkansas River

0.420.331.090.890.69

2.00

3.0031.6

——

Site 11

9.410.19.18.9

8.6

8.72.8612.638.1

0.400.760.310.37

1.46

0.74

——

16.916.015.2

12.7

19.1

22.7

1.050.700.82

1.36

2.94

—

20.320.6

16.8

24.6

28.5

0.850.80

1.31

2.58

—

Railroad Bridge Brown Trout SeptemberFilename AR11LC.ANU Body scale constant =

19941993199219911990

1989

1988

1987—

711811190.7121.3222.24135.8

01+2+3+4+

5+24.36+30.77+

—

11.717.821.523.025.8 .

26.02.0232.02.8939.037.0

0.420.331.090.890.69

2.00

3.0031.6

——

10.511.310.610.4

10.1

10.42.8714.138.1

0.350.700.300.34

1.37

0.73

——

17.416.716.1

13.9

20.0

23.6

1.000.680.78

1.31

2.84

—

20.621.1

17.7

25.1

29.1

46.27

0.840.78

1.30

2.55

—

23.9

20.6

28.5

31.0

1994

24.0

21.1

28.8

31.5

26




Arkansas River Site 12 Fisherman's Bridge Brown Trout September 1994Filename AR12LC.ANU Body scale constant = 8.49

1993199219911990

1989

203831250.7316

1+2+3+4+

5+

12.18.26.31.

33.

2737

8

0.450.550.830.74

1.07

7.48.08.89.7

9.0

0.170.260.360.35

0.59

14.817.217.5

15.9

0.410.810.63

1.01

23.723.7

22.4

0.910.82

1.10

29.3

27.61.21 31.2 1.15

1988 8 6+ 37.5 1.38 9.7 0.86 16.5 1.19 22.7 1.07 28.41.00 32.5 1.00 35.6 1.25

Arkansas River Site 12 Fisherman's Bridge Brown Trout September 1994Filename AR09LC.ANU Body scale constant = 25.00

1993 20 1+ 12.2 0.45 8.0 0.171992 38 2+ 18.7 0.55 9.0 0.25 15.2 0.411991 31 3+ 26.3 0.82 10.0 0.35 17.8 0.79 23.8 0.901990 25 4+ 31.7 0.74 10.9 0.34 18.2 0.62 24.2 0.80 29.4

0.721989 16 5+ 33.8 1.07 10.3 0.57 16.8 0.97 23.0 1.07 28.0

1.19 31.3 1.131988 8 6+ 37.5 1.38 10.9 0.83 17.4 1.13 23.4 1.02 28.8

0.96 32.7 0.99 35.7 1.25

Arkansas River Site 14 Lake Greek Brown Trout September 1994Filename AR14LC.ANU Body scale constant = 9.29

19941993199219911990

2916840.90

01 +2+3+4+

10.016.818.627.129.7

—0.780.621.071.84

8.97.99.37.6

0000

.54

.37

.59

.88

15.216.615.3

0.581.402.01

23.422.3

1.380.66 .27.1

1989 3 5+ 32.2 2.78 9.1 0.35 17.4 2.23 22.1 3.46 26.43.08 30.6 3.17

27




Arkansas River Site 14 Lake Creek Brown Trout September 1994Filename AR14LC.ANU Body scale constant = 25.00

19941993199219911990

1989

2916840.9333.03

01 +2+3+4+

5+30

10.016.818.627.129.7

32.2.7 3.14

Tennessee

—0.780.621.071.84

2.78

Creek

9.68.910.48.8

10.2

Upper

0.460.350.570.82

0.35

Site 3Filename TNUP03LC.ANU

1993JL J7-7-/

199219911990

o\J2213170.60

1 +1 '

2+3+4+

13.518.223.5

0.410.430.59

6.66.36.8

0.160.180.17

15.517.216.1

18.1

Brown

0.561.341.86

2.18

Trout

23.622.7

22.6

1.350.59 27

3.36 26

.2

.7

September 1994Body scale constant =

11.411.014.0

0.270.380.57

15.119.0

18.68

0.620:60 22,.0

1989 14 5+ 27.0 0.64 7.1 0.33 14.3 0.68 19.7 0.66 23.60.54 25.7 0.53

1988 3 6+ 33.3 3.76 7.3 0.10 12.3 0.28 19.1 0.44 24.70.41 28.7 0.59 31.7 2.94

Tennessee Creek Upper Site 3 Brown Trout September 1994Filename TNUP03LC.ANU Body scale constant = 25.00

I 77 J

199219911990

1989

\>2213170.5914

i i2+3+4+

5+

131823

27

.5

.2

.5

.0

0.410.430.59

0.64

7.06.87.2

7.6

0.160.170.17

0.33

11.511.314.3

14.6

0.270.370.57

0.66

15.219.1

19.9

0.610.60

0.65

22.1

23.70.54 25.7 0.53

1988 3 6+ 33.3 3.76 7.9 0.35 12.7 0.89 19.3 1.11 24.91.39 28.8 1.96 31.8 2.96

28




Tennessee Creek Lower Site 4 Brown Trout September 1994Filename TNLW04LC.ANU Body scale constant = 25.00

1993199219911990

1989

1988

—

191915200.3021.06122.6

1+2+3+4+

5+24.26+

—

12.416.920.923.8

26.00.6528.026.2

0.260.350.270.38

1.00

——

7.18.46.97.6

8.5

7.2

0.220.380.180.26

1.96

—

13.012.813.3

13.7

10.5

0.380.270.38

3.22

—

17.818.2

17.7

14.0

0.290.38

2.77

—

21.9

21.5

19.2

Tennessee Creek Lower Site 4 Brown Trout September 1994Filename TNLW04LC.ANU Body scale constant = 50.83

1993 19 1+ 12.4 0.26 8.5 0.191992 19 2+ 16.9 0.35 10.0 0.33 13.7 0.3519911990

1989

1988

—

15200.3021.03123.2

3+4+

5+24.46+

—

20.923.8

26.00.6828.026.4

0.270.38

1.00

——

8.89.6

10.4

9.3

0.160.24

1.77

—

13.914.5

15.0

12.3

0.250.35

2.92

—

18.2.18.9

18.6

15.4

0.280.35

2.53

22.1

20.1

Half Moon Creek of Arkansas Site 9 Brown Trout September 1994Filename HC09LC.ANU Body scale constant = 25.00

19941993199219911990

1989

145131.742

01+2+3+4+

5+

5.611.616.322.224.4

24.2

0.751.90

—1.43

1.40

6.16.86.47.1

7.0

0.220.77

—0.75

0.57

11.912.912.9

13.7

1.81

—1.83

0.58

17.517.8

17.0

2.39 22.1

0.70 20.21.07 22.4 0.96

29




Half Moon Creek of Arkansas Site 9 Brown Trout September 1994Filename HC09LC.ANU Body scale constant = 26.26

19941993199219911990

1989

145131.7320.60

01+2+3+4+

5+22.

5.611.616.322.224.4

24.24 0.96

0.751.90

—1.43

1.40

6.16.96.57.2

7.1

East Fork Arkansas

0.210.77

—0.75

0.57

11.913.013.0

13.7

1.80

—1.82

0.58

17.617.8

17.0

Site 1 Brown Trout SeptemberFilename AREF01LC.ANU

1993199219911990

1989

14821140.3110

1+2+3+4+

5+

10.713.517.020.0

22.1

0.160.270.240.24

0.28

5.96.16.36.3

6.7

0.180.300.290.22

0.30

—2.39

0.70

1994

22.1

21.3

Body scale constant = 25.00

10.310.910.2

10.6

0.470.340.30

0.49

14.615.1

14.7

0.260.42

0.53

18.2

18.10.42 20.8 0.37

East Fork Arkansas Site 1 Brown Trout September 1994Filename AREF01LC.ANU Body scale constant = 40.68

1993199219911990

14821140.30

1+2+3+4+

10.713.517.020.0

0.160.270.240.24

6.87.17.57.5

0.160.260.260.20

10.711.611.1

0.430.310.28

14.815.5

0.250.38 18.3

1989 10 5+ 22.1 0.28 7.9 0.28 11.5 0.45 15.3 0.50 18.40.41 20.9 0.36

30




East Fork Arkansas Site 2 Brown Trout September 1994Filename AREF02LC.ANU Body scale constant = 25.00

1993199219911990

1989

1988

91511170.64140.4621.15

1+2+3+4+

5+21.6+20,

11.615.217.821.7

23.5,9 0.40

23.9.6 0.01

0.580.270.380.57

0.52

0.6522.6

6.77.17.37.6

7.1

6.70.69

0.400.200.250.38

0.23

0.49

12.111.711.9

27.3

11.8

0.150.350.50

0.36

0.41

15.316.6

15.5

15.6

East Fork Arkansas Site 2 Brown Trout SeptemberFilename AREF02LC.ANU

1993199219911990

1989

1988

91511170.62140.4421.02

1+2+3+4+

5+22.6+21.

1.615.217.821.7

23.50 0.40

23.9.9 0.05

0.580.270.380.57

0.52

0.6522.7

7.68.28.48.8

8.4

8.40.68

Lake Fork Arkansas

0.370.170.220.36

0.22

0.44

0.360.62

0.35

0.80

1994

19.8

19.2

18.2

Body scale constant = 41.90

12.512.412.7

12.8

12.6

0.130.320.48

0.33

0.35

15.617.1

16.2

16.4

Site 8 Brown Trout SeptemberFilename LF08LC.ANU Body scale

1993199219911990

1989

1988—1987

—

104924100.7680.72131.7128.1

1+2+3+4+

5+32.6+

—7+

—

13.317.024.929.7

34.25 0.59

36.0• 34.5

34.2- 31.1

0.800.500.500.40

0.65

————

7.47.27.48.4

8.0

8.7

7.133.6

0.310.140.180.34

0.41

—

——

12.413.616.6

14.5

14.4 •

12.6

0.350.59

0.33

0.71

1994

20.0

19.5

19.7

constant = 25.00

0.300.630.86

0.68

—

—

18.922.1

22.7

20.6

17.9

0.791.01

1.23

—

—

26.4

28.8

26.4

24.9

31




Lake Fork Arkansas Site 8 Brown Trout September 1994Filename LF08LC.ANU Body scale constant = 37.09

1993199219911990

1989

1988—1987--

104924100.7480.70131.9128.3

1+2+3+4+

5+32.66+

—7+

—

13.317.024.929.7

34.20.5936.034.634.231.2

0.800.500.500.40

0.65

————

8.08.08.39.4

9.0

9.7

8.133.6

0.300.130.170.32

0.40

—

——

12.8 0.2914.2 0.6117.1 0.83

15.2 0.66

15.2 -

13.4 --

--

—

Arkansas River Brown Trout AprilFilename ARKSBRBC.96

19931992

1991

1990

1989

11

260.30271.1380.83

3+4+

5+29.96+30.27+31.1

32.031.0

30.2.0.2830.71.1332.00.76

—

0.28

1.1330.60.7131.6

14.515.4

13.0

12.81.1313.40.71

East Fork Arkansas

—

0.34

0.56

0.9231.9

Body scale

28.6 -27.1 -

24.4 0.

22.8 1.

23.6 1.0.70

19.222.4

23.1

21.2

18.5

1996constant =

~

47

09

18

31.630.1

27.4

28.1

28.8

0.76. 0.97

1.20

—

—

26.5

——

0.38

1.14

0.91

26.6

29.0

26.7

25.2

30.9

29.0

29.5

30.2

Site 1 Brook Trout September 1994Filename AREF01BK.ANU

199319921991

1331

1+2+3+

11.815.419.2

0.280.37

—

7.47.27.2

East Fork Arkansas

0.171.04

—

Body scale

12.2 1.11.6 -

constant =

0717.0

11.25

—

Site 2 Brook Trout September 1994Filename AREF02BK.ANU

19931992

04

1+2+

__—

15.6 1.48 7.0 0.82

Body scale

11.0 1.

constant =

22

11.25

32




Tennessee Creek Upper Site 3 Brook Trout September 1994Filename TNUP03BK.ANU Body scale constant = 11.25

199319921991

19941993199219911990

1994199319921991

1993199219911990

199319921991

251

205421.02

20123

2221

214

1+2+3+

Lake

01+2+3+4+

01+2+3+

1+2+3+4+

1+2+3+

13.5 0.50 8.9 0.2919.8 1.66 10.3 0.36 16.2 1.06 '21.0 — - 9.7 — 14.8 — - 18.4

Fork Arkansas Colo. Gulch Site 6 Brook Trout September 1994Filename LF06BK.ANU Body scale constant = 11.25

6.1 0.15

13.0 0.26 7.0 0.17 10.9 0.2919.6 0.49 6.5 0.39 12.8 0.41 17.2 0.5021.6 1.55 7.9 1.31 14.3 1.19 17.0 0.76 20.0

Lake Fork Arkansas Site 7 Brook Trout September 1994Filename LF07BK.ANU Body scale constant = 11.25

7.3 0.1713.5 — 6.818.0 1.85 7.2 0.05 12.1 1.2221.9 0.17 7.9 0.59 13.0 1.11 18.3 0.75


18.9 0.70 12.3 2.7219.9 0.25 8.3 0.73 12.8 0.3324.9 0.30 8.6 0.26 17.0 0.17 22.0 0.3126.6 — 9.3 — 14.2 — 22.9 -— 25.3

Lake Fork Arkansas Site 1 Brook Trout September 1994Filename LF01BK.ANU Body scale constant =11.25

14.9 0.65 8.6 0.5122,2 — - 14.2 — - 20.524.9 0.23 10.2 0.89 18.5 1.08 22.4 0.41

33





199319921991

199419931992

199419931992

19941993199219911990

19941993199219911990

214

211

211

41618201

102593832.35

1+2+3+

01+2+

01 +2+

01 +2+3+4+

01+2+3+4+

14.9 0.65 9.6 0.4922.2 — 15.0 — 20.7 —24.9 0.23 11.3 0.81 18.7 0.98 22.6 0.38


6.9 0.4516.4 — 7.920.5 — 7.8 — 18.3 —


6.9 0.4516.4 — - 8.420.5 — 8.3 —- 18.4 —


6.5 0.2410.7 0.45 7.3 0.3015.4 0.32 8.2 0.32 13.0 0.2319.6 0.40 8.1 0.32 14.0 0.43 17.8 0.4221,9 — 6.7 — 13.3 — - 18.3


6.1 0.1110.8 0.17 7.2 0.1714.4 0.63 6.8 0.55 11.5 0.6919.5 0.33 7.5 0.19 12.9 0.25 17.2 0.2520.9 1.79 7.0 0.31 11.8 1.72 15.8 2.46

20.8

18.9

34




Lake Fork Arkansas Colo. Gulch Site 6 Brook Trout September 1994Filename LF06BK.ANU Body scale constant = 21.83

19941993199219911990

1994199319921991

205421.04

20123

01+2+3+4+

01+2+'3+

6.1 0.15— —13.0 0.26 7.5 0.16 11 .1 0.2819.6 0.49 7.2 0.37 13.2 0.39 17.3 0.4921.6 1.55 8.6 1.22 14.6 1.07 17.2 0.66 20.1


7.3 0.1713.5 — 6.318.0 1.85 6.6 0.02 1 1 . 8 1.227.3 0.17 7.3 0.62 13.3 1.16 18.1 0.78

Arkansas River Site 6 Sewer Lagoon Brook Trout September 1994

19921991

199219911990

199319921991

41

1121.91

012

2+3+

2+3+4+

1+2+3+

Filename AR06BK.ANU Body scale constant = 11.25

24.5 2.18 9.3 0.70 18.8 1.3826.3 — 7.5 — 17.2 — 22.3 —

Arkansas River West Braid Brook Trout September 1994Filename AR05BK.ANU Body scale constant =11.25

13.5 — 7.2 . — 10.3 —16.8 — 7.2 — 10.7 — 14.924.7 2.00 8.6 2.47 15.6 4.46 20.8 2.22 23.4

Tennessee Creek Lower site Brook Trout September 1994Filename TNLW04BK.ANU Body scale constant = 11.25

... - .....

19.0 — 9.1 — 14.9 —19.5 0.50 8.0 0.25 12.5 0.44 16.2 0.16

35




Halfmoon Creek of the Arkansas Site 9 Brook Trout September 1994Filename HC09BK.ANU Body scale constant = 19.29

1994199319921991

45

01+

13 2+2 3+

6.912.116.620.4

0.190.600.320.75

Arkansas River Site

8.49.09.1

0.710.310.22

13.915.0

0.340.20 18.4 0.56

14 Lake Creek Rainbow Trout SeptemberFilename AR14RB

199319921991

. 122

1+2+3+

Arkansas

18.219.121.6

River

0.550.55

Site 12

13.511.610.1

.ANU Body scale

___-

0.660.11

Fisherman'sFilename AR12RB

1993199219911990

18551.

1 +2+3+4+

96

Arkansas

23.024.029.634.0

River

....

1.342.641.58

Site 12

13.812.414.213.0

15.614.2

constant =

1.250.51

Bridge Rainbow.AND Body scale

....

0.530.440.57

Fisherman'sFilename AR12RB

1993199219911990

18551.

1+2+3+4+

92

23.024.029.634.0

1.342.641.58

15.114.015.814.9

19.920.520.7

17.6

50.00

1.20

1994

Trout October 1994constant =

1.171.871.28

Bridge Rainbow.ANU Body scale

....

0.500.470.55

20.421.421.9

27.027.6

50.00

2.301.88 31.6

Trout October 1994constant =

1.131.841.23

27.228.2

76.19

2.301.81 31.8

36




Arkansas River West Braid Rainbow Trout September 1994Filename AR05BRB.ANU Body scale constant = 50.00

1991 1 3+ 23.6 — 11.5 —- 17.7 — 21.51990 2 4+ 27.5 0.20 9.8 0.64 13.0 0.42 18.9 0.09 24.7

0.091989 2 5+ 25.4 0.2.0 10.0 0.36 12.8 0.42 15.6 1.08 18.5

1.02 23.0 0.23

Arkansas River Rainbow Trout April 1996Filename ARKSRBBC.96 Body scale constant = 50.00

199419931992

1991

1990

1989

1988

—

1912101.1620.8431.7922.49133.7

2+3+4+

5+35.46+36.87+34.28+

—

25.830.734.7

35.51.5537.32.8234.52.4934.033.8

0.840.470.99

1.50

2.9637.12.5034.3

——

15.214.715.2

12.7

16.52.9015.72.5514.733:9

0.530.650.72

1.21

0.80

L5334.5

——

24.425.825.4

27.4

28.0

27.12.5025.334.0

0.721.041.07

0.82

1.34

0.81

——

29.932.1

32.3

33.1

31.8

28.6

0.701.24

0.15

1.12

1.80

—

34.3

34.5

35.6

34.0

31.3

37

Table II. Arkansas River back-calculated lengths (cm) of brown trout collectedduring CDOW electrofishing operations, August 2002



Arkansas River Brown Trout at Sampling Site ARl(below confluence of EastFork of the Arkansas and Tennessee Creek and upstream of California Gulch) -

Collected August 14, 2002

2001200019991998

29211741.02

1+2+3+4+

13192326

.6

.4

.2

.2

0.270.330.310.42

8.28.48.57.9

0.200.270.250.36

14.314.513.4

0.250.521.36

19.618.3

0.531.48 22.7

1997 4 5+ 28.5 0.56 8.3 0.65 12.1 1.09 17.6 1.17 22.60.69 26.0 0.97

Arkansas River Brown Trout at Sampling Site AR3A (downstream ofCalifornia Gulch) - Collected August 14, 2002

2001200019991998

1997—

35241941.00134.1

1+2+3+4+

5+

—

Arkansas

15.121.727.432.2

35.4

0.350.410.360.67

—

River Brown

10.111.610.912.2

12.0

0.150.300.241.16

—

16.718.217.3

18.8

Trout at Sampling SiteCollected

2001200019991998

1997

1996—1995

1994—

423223150.5431.35133.841.09123.9

1+2+3+4+

5+34.56+

—7+30.58+

16.024.030.134.1

38.51.3340.338.741.80.7241.232.6

0.390.390.350.41

0.68

——0.9736.1

——

10.311.611.412.0

11.5

9.5

10.71.1711.336.7

August

0.190.250.170.23

0.60

—

0.3939.4

——

15, 2002

17.518.318.1

17.4

12.1

13.81.1513.339.0

0.420.360.62

—

AR4

0.410.480.61

1.54

—

0.47

——

24.224.3

23.7

(Doc

25.524.8

24.5

15.5

19.2

17.4

0.500.81

—

Smith's

0.420.74.

1.02

.__.

0.68

—

29.5

28.9

Ranch)

30.3

30.3

21.8

24.3

18.7

38

Table II (continued). Arkansas River back-calculated lengths (cm) of brown troutcollected during CDOW electrofishing operations, August 2002



Arkansas River Brown Trout at Sampling Site AR5 (above Empire Gulch) -Collected August 15, 2002

2001200019991998

1997

2728980.7421.45

1+2+3+4+

5+34.1

Arkansas

1-6.724.130.333.6

35.90.76

River

0.380.460.470.74

0.11

Brown

11.413.012.212.6

12.7

TroutCollected

2001200019991998

1997

1996

1995

1994—1993~

172216200.76151.2691.3340.28128.8123.0

1+2+3+4+

5+27.16+29.97+23.78+

—9+

—

14.217.726.128.0

30.21.0935.40.8137.70.5841.132.540.125.8

0.350.591.040.66

0.96

0.5533.10.2029.6

————

8.38.38.38.7

8.0

8.60.667.51.289.235.78.331.4

Arkansas River Brown Trout at

0.250.420.360.49

0.55

19.419.319.3

18.1

0.500.560.77

0.67

at Sampling Site 6A

26.525.9

25.0

0.360.65

0.44

(near PanArk

30.9

29.5

Lodge) -August 15, 2002

0.260.250.250.30

0.55

0.40

0.4734.0

————

12.214.213.4

12.2

13.5

10.80.5212.538.811.035.8

Sampling Site 6- Collected August

2001200019991998

28261551.30

1+2+3+4+

15.925.030.434.8

0.350.360.421.52

9.510.311.612.4

0.230.27.0.731.19

0.600.720.52

0.96

1.10

0.30

————

20.718.4

17.9

18.6

14.7

17:7

13.239.2

(downstream

0.960.60

1.25

0.98

0.55

—

——

23.9

22.9

24.4

18.2

23.2 --

16.6 --

of Kobe Bridge)16, 2002

18.619.118.9

0.370.831.24

26.225.8

0.631.59 32.0

39




Arkansas River Brown Trout at Sampling Site 7 (near Granite) - CollectedAugust 16,2002

2001200019991998

1997—1996

20012000

31 .181761.10129.631.92

East

247

1 +2+3+4+

5+

—6+27.2

16.524.529.231.6

32.9•35.60.79

0.380.240.450.73

—

0.2130.8

9.9.8.9.

9.

6.0.

Fork of Arkansas RiverCO

1+2+

Highway 91

12.215.3

0.290.27

1093

3

857

0.0.0.0.

~

0.

27,23,4180

—

61

16.916.915.0

.13.1

11.5

Brown Trout atBridge) -

8.8.

55

0.0.

Collected

2537 11.7

0.280.630.85

—

0.43

Sampling

24.1 0.5222.2 1.25 27.5

18.8 — - 22.6 --

15.7 1.48 21.0

Site EF1 (upstream ofAugust 14, 2002

0.491999 5 3+ 16.2 0.16 7.7 0.28 10.7 0.28 13.7 0.321998 16 4+ 18.5 0.22 8.1 0.17 11.0 0.31 14.2 0.42 16.9

0.341997 3 5+ 20.8 0.23 7.8 0.27 10.1 0.44 13.6 0.81 17.0

0.64 19.6 0.271996 7 6+ 22.1 0.23 7.4 0.16 9.2 0.36 12.3 0.65 15.1

0.80 17.9 0.47 20.7 0.271995 3 7+ 25.7 1.47 7.5 0.20 9.1 0.14 12.7 0.68 15.3

0.59 18.5 1.25 21.1 1.95 24.0 1.91

East Fork of Arkansas River Brown Trout at Sampling Site EF3 (near COHighway 24 Bridge) - Collected August 13,2002

2001200019991998

22163081.00

1+2+3+4+

12,.417.422,26,

,6.9

0.320.250.451.24

8.48.99.69.7

0.210.170.220.43

13.814.814.1

0.270.260.63

19.219.2

0.330.80 23.4

40




Tennessee Creek Brown Trout at Sampling Site 7 (below the powerline) -Collected August 13,2002

2001200019991998

1997

1996

1995

19139140.34160.5880.572

1+2+3+4+

5+21.76+20.47+

12.716.418.020.7

24.00.4925.80.5328.9

0.330.390.520:32

0.42

0.5323.71.00

9.29.19.19.4

9.8

9.20.519.3

0.210.150.180.18

0.16

0.29

0.16

12.911.411.6

12.4

11.2

11.0

0.220.320.33

0.29

0.39

0.18

14.214.5

15.6

13.7

13.4

0.460.38

0.41

0.46

0.83

17.6

18.6

16.7

16.11.88 20.8 . 3.94 23.4 3.21 26.4 1.53

41

COLORADO DIVISION OF WILDLIFE (DOW)RESPONSE TO COMMENTS OF RESURRECTION MINING COMPANY

PREPARED BY CHAD WICK ECOLOGICAL CONSULTANTS (CEC)REGARDING

"EVALUATION OF 16 YEARS OF TROUT POPULATION BIOMETRICSIN THE UPPER ARKANSAS RIVER,

JANUARY 15, 2002"

1. Improper Age Estimation-CEC raises two issues:

A.) CEC argues that distributions for fish > 25 mm at AR1, EF2 and TCI are "nearlyidentical." Since DOW found numerous five and six year old fish at EF2 and TC1,DOW's assertion that there are no fish over five years old at AR1 is not supported bythe data.

The analysis reflected in the 2002 report relied upon length-age relationships derivedfrom 1994 sampling data for another sampling station, AR4. Additional analyses wasrecently completed using 2002 length and scale data for each sampling site, and datafrom AR2 that was taken in 1994. These two sets of data indicate similar life tableresults, with substantial numbers of trout estimated to be five years of age. However,the newer analysis confirms that virtually no fish at AR1 are six years or older. Theseanalyses are included in DOW's updated report that summarizes the data from 1985through August 2002. DOW maintains that AR1 does appear to be adverselyaffected.

The 1994 age and growth data set that was used to generate the life table data for siteAR1 in Table 2 of Nehring and Policy (2002) was described (at the time of collection)as "Arkansas River Site 7 Above Road 44". This age and growth data set correspondsto study site AR4 - Doc Smith's Ranch. The data set was used to generate the lifetable information in the 2002 report because 1) it was the one of the largest data sets(N=l 15), and 2) it contained fish aged 5 and 6. In preparing the 2002 report, wechose not to use the September 1994 scale sets for study site AR2 because 1) the datasets were much smaller, and 2) sampling at the station was discontinued after 1994because it was a braided channel with degraded habitat. In retrospect, the 1994 scaleset for study site AR2 was the better choice to partition the brown trout population atAR1 because of its proximity to the site and the temperature regime would be similar,as suggested by the consultants for Resurrection Mining Company.

B) CEC concludes that "[t]he claim that Sites AR1 and AR2 are impacted byCalifornia Gulch is not justified on the basis of age." DOW stated that fish werelikely adversely affected by heavy metal contamination in the vicinity of California

Gulch. This statement was not meant to imply that AR1 and 2, just because they arein the vicinity of California Gulch, are impacted by California Gulch which, as notedlater by CEC, is downstream of these sampling stations.

2. Incomplete and Obsolete Data - CEC notes apparent inconsistencies in thereporting of the data. First, CEC states that 1994 scale data were not accuratelyreflected in Table 2 for AR2. These data have been re-analyzed in the updatedReport; therefore, this comment has been superceded. Second, CEC contends thatFall of 1994 Tennessee Creek data were not presented in Tables 1 or 2. The 1994Tennessee Creek data available to DOW is from downstream of St. Kevin's Gulch,and are represented in Tables 1 and 2. Data for Tennessee Creek above the PowerlineCrossing and above the confluence with the Arkansas River for 1994 are not knownto exist.

In addition, CEC asserts that length-age relationships may have improved as waterquality has improved downstream of the remedial actions. In DOW's updatedanalysis, life table data for study site AR2 for the years 1989 and 1994 wererecalculated using age and growth data from scales collected at AR2 in September of1994 and August 2002. Both scale sets indicate a substantial number of brown troutestimated to be five years old, and a small number to be six years old. In addition, inthe updated report, scales collected at each study site in August of 2002 were used togenerate site-specific age and growth relationships at each study site. This approachis recommended for collections in the future.

3. Scale Technique- CEC questions the reliability of scale studies for aging -especially fish older than three years ~ and recommends instead otoliths, fin rays,tagging, or some other method. DOW generally disagrees. Scale studies remain thepredominant methodology for estimating age populations. See, e.g., "Age andGrowth of Fish," Summerfelt, R.C., and Hall, G.E. (Iowa State University Press,1987). Although otoliths and fin rays may be somewhat more accurate, one results indeath, and the other in the crippling offish, thus skewing the very population data themethod is designed to measure.

DOW has considerable experience with scaling studies; therefore, inaccuraciesassociated with the method are minimized. As for the concern about underestimatingnumbers of older fish, DOW did estimate that over 11% of the fish sampled were fiveyears or older. However, there were far fewer at the sites apparently impacted bycontamination. Thus, the method does allow DOW to determine the age of fish overthree years old, and was accurate enough to demonstrate disparities in the age-structures at different sites. Given the low percentage of fish over five years old, theuse of otoliths or fin rays to more definitively age older fish is particularlyunwarranted. DOW has, however, initiated tagging in an effort to more clearlyelucidate issues of age of fish and/or movement between study sites.

4. Impacts at Site AR1- See response IB above.

5. Control Site- DOW has not suggested that a site other than AR1 be selected as thecontrol site; unfortunately, a more appropriate control site is not available. However,as recognized by the Consulting Team for the MOU Parties, this doe:s not mean thatAR1 is not impacted by heavy metals. Bioaccumulation of cadmium in liver andkidney tissues of brown trout downstream of the Leadville Drain trnnel on the EastFork of the Arkansas River and at all sites in the'Pj?' ~ ̂ 7"";i tne u iper ArkansasRiver was well documented in 1985 (Nehring 1986), and significant differences inwater quality and aquatic life remain. (See, Site Characterization Report, 2002.)

\

LITERATURE CITED -

Nehring, R.B., and G. Policky, 2002. Evaluation of 16 years of tn/ut populationbiometrics in the Upper Arkansas River. Colorado Division of Wi dlife Report.

Nehring, R.B. 1986. An Evaluation of the Possible Impacts of F avy MetalPollution on the Brown Trout Population of the Upper Arkansas ;ver. ColoradoDivision of Wildlife Report.

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