JUN 3 0 2003
KEN SALAZAR STATE OF COLORADO STATE SERVICES BUILDING Attorney General 1525 Sherman Street - 5th Floor DEPARTMENT OF LAW Denver. Colorado 80203 DONALD S. QUICK Phone (303) 866-4500 Chief Deputy Attorney General OFFICE OF THE ATTORNEY GENERAL FAX (303)866-5691 ALAN J. GILBERT Solicitor General SDMS Document ID June 27, 2003 2036964 Mr. Ron Eddy 633 17th St. #3000 Denver, Colorado 80202
RE: CDOW Response to "Comments of Resurrection Mining Company Regarding CDOW Retort" (sic)
Dear Ron:
By letter dated September 5, 2002, you transmitted Resurrection/Chadwick Ecological Consultants (CEC) comments on the report entitled "Evaluation of 16 Years of Trout Population Biometrics in the Arkansas River, January 15, 2002. Enclosed is a response to those comments along with an updated analysis. Although CDOW continues to have more faith in its use of scaling data than does CEC, it has incorporated resolutions to many of the other comments in the response and attached updated evaluation which supercedes the previous Report.
We appreciate Resurrection's input.
Sincerely,
FOR THE ATTORNEY GENERAL
VICKY L: PETERS Assistant Attorney General Natural Resources and Environment 303-866-5110 303-866-3558 (FAX)
Enclosures Page 2 cc: Jerry Ellington Richard Sisk Angus Campbell Ron Cattany Lee Pivonka Russ Allen Laura Coppock Pat Davies Greg Policky Robert Litle
AG File: nehring response cover ltr.doc A Synopsis of Seventeen Years Trout Population Biometrics in the Upper Arkansas River
R. Barry Nehring Aquatic Wildlife Researcher and Greg 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 Colorado lead to the establishment of boomtowns like Leadville, Silverton, and Creede. Mining activity 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 the mountainous areas of Colorado, waste products from a century of mining activity were often piled alongside streams. Heavy metals from the tailings piles leached by water from melting snows and mountain rainstorms found their way into mountain streams.
In the latter half of the 20th century, concerns over the potential negative impacts of heavy metal pollution on aquatic biota of the upper Arkansas River lead to intensive investigations (LaBounty et al. 1975; Roline and Boehmke 1981; Nesler 1982; Nehring 1986; Roline 1988, Davies, Mclntyre, and Stednick 1997; and Davies, Brinkman, Mclntyre, and Clements 2000). Over the past 20 years, efforts to ameliorate the environmental impacts of heavy metal pollution have intensified.
In the 1980s, the Colorado Division of Wildlife (CDOW) began conducting extensive electrofishing investigations at numerous sites in the upper Arkansas River basin to assess the impact of heavy metal pollution on the fish populations in the river. This data collection effort intensified in the late 1990s. It has continued through the late summer of 2002. The primary purpose of these studies was to determine whether or not the trout populations were responding in a positive manner to the efforts of abatement of the heavy metal pollution. This report presents a synopsis of those electrofishing efforts together with a 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 of assessing the effects of environmental perturbations. The geographical distribution, relative abundance, and sensitivity of the indicator species in the area of impact are critical elements that must be properly addressed in order to effectively assess impact.
Historically, two sub-species of cutthroat trout were the only salmonids native to the upper Arkansas River basin (Behnke 1992; Behnke 2002). The greenback cutthroat trout (Oncorhynchus clarki stomias) was native to the mainstem river and numerous tributaries while the yellowfin cutthroat trout Oncorhynchus clarki macdonaldi was apparently a lacustrine 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. Introduced normative rainbow trout (Oncorhynchus mykiss) hybridized with the cutthroat trout and often 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 other normative salmonids such as the brook trout (Salvelinus fontinalis) and brown trout (Salmo truttd) aggravated the competitive disadvantage of the cutthroat trout. Taken together, hybridization with rainbow trout, competition with brown and brook trout, and impacts of overfishing have largely extirpated the greenback cutthroat trout from most aquatic habitats in Colorado. A few small relict populations still exist or have been re-introduced in remote headwater streams, but they do not exist in the mainstem Arkansas River downstream of Leadville, Colorado.
Over the past 20 years, electrofishing studies have consistently shown that brown trout are the dominant salmonid in most segments of the upper Arkansas River around Leadville, Colorado. Brook trout are relatively abundant in some areas, particularly in the Lake Fork of the Arkansas River, Tennessee Creek, and portions of the East Fork of the Arkansas River. Rainbow trout are occasionally encountered in some areas in some years. Occasionally large Snake River cutthroat trout (Oncorhynchus clarki bouvieri) are encountered as well. However, the presence of rainbow trout and Snake River cutthroat trout is likely the result of stocking.
All of the foregoing dictates that the brown trout is the only possible choice for an indicator fish species. It is present in sufficient numbers and reproductively active at most sampling sites on the mainstem of the Arkansas River. In Colorado, the average life span of stream-dwelling brown trout in healthy aquatic habitats is usually 6 to 8 years (Espegren et al. 1990). However, tagging studies have shown the maximum life expectancy can exceed 10 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 to estimate trout population abundance in the upper Arkansas River at virtually all study sites in all years. The only exception-to this was at the two most downstream study sites in 1987 and 1988. At these stations the Petersen mark-recapture model was used (Robson and Regier 1964). At these locations flow conditions and the width of the stream severely reduced the electrofishing efficiency requirements for the two-pass removal estimation model. In those instances when electrofishing efficiency is less than 50 % to 60%, the mark-recapture estimation procedure should be used. However, since the mid-1990s the two pass removal estimator has been used at virtually all sampling sites.
Trout population estimates with 95% confidence limits and estimates of brown trout abundance for fish > 15 cm/ha, > 30 cm/ha and > 35 cm/ha are presented in Table 1 in the RESULTS section of the report.
Estimation of Trout Population Biomass
Every fish was weighed (grams) and measured (millimeters total length) during the field collections throughout the study. Using these length/weight data sets, a logarithmic regression (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 population abundance estimates to generate an estimate of brown trout biomass (kilograms/ha) for each study site each year of sampling. These data are presented in Table 1 in the RESULTS section of the report.
Trout Population Age Structure Analysis
Age structure analysis over time can provide important insights into the overall health of a trout population. However, acquisition of age and growth information is a time and labor intensive process. Large numbers offish scale samples, fin ray cross sections, or otoliths are needed to reduce trout population abundance information into life tables or survivorship tables over a period of years. For these reasons, utilization of age/growth information is a diagnostic tool that is often ignored by aquatic biologists.
Over the past 26 years CDOW management biologists and aquatic researchers have collected thousands of trout scales for age and growth analysis of brown, brook, and rainbow trout populations in streams all across Colorado. For details see Nehring 1980, 1986; Nehring and Anderson 1981, 1984, 1985; Nehring, Anderson and Winters 1983; and Nehring and Miller 1987. At many sites, these data indicate that the average length of trout for a given age and sampling site does not vary greatly from one year to the next. The primary reason for this phenomenon is that fish are poikilothermic animals and their metabolic rate is largely controlled by water temperature and the total cumulative thermal degree-days each fish experiences in a calendar year (Elliott 1975a, 1975b, 1976).
Indeed, studies by Edwards, Densem, and Russell (1979) demonstrated that differences in observed mean growth rates among brown trout collected from 9 different English streams were... "explained largely in terms of ambient temperature. In particular, the high growth rates of trout in chalk streams may be related almost entirely to the thermal properties of such waters and not to direct effects of calcium or to indirect effects operating through the productivity or diversity of food webs." Moreover, intensive monitoring of water temperature in Colorado trout streams over a number of years indicates that in many streams there is little variation in the thermal profile and total cumulative degree-days for a particular stream and monitoring site between years (Nehring and Thompson 2001). Taken together, these findings suggest that age and growth information collected in one year at a given site may be interfaced with trout population data at that site across several years to derive a reasonably accurate approximation of the age structure of the trout population at that location.
Scale samples have been collected from brown trout at numerous samples sites in the upper Arkansas River drainage over the past 18 years. Age and growth data for brown trout was developed from brown trout scales collected at study sites on the East Fork of the Arkansas River, Tennessee Creek and the Arkansas River near study sites AR1 and A2 in May 1986 (Nehring and Miller 1987). CDOW management biologists collected more than 1,600 scale samples from brown, brook, and rainbow trout in the upper Arkansas River drainage in September 1994. Approximately 1,250 of these samples were from brown trout. 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 evaluate longevity and survival of trout among and between sites throughout the river from 1985 through 2001. A new set of brown trout scale samples was collected at each sampling site in August 2002. There were 830 readable scales in the entire sample.
The age and growth data for the September 1994 and August 2002 scale collections are summarized in Appendix Table I. Data summarized for each sampling site for the two collections include numbers offish in each age group, mean length at the time of collection for each age class, mean back-calculated length for each prior age, and standard error at each age.
Estimates of the age structure of all brown trout in each centimeter group determined from the scale aging process were used to partition the estimated number of trout 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 an estimate of abundance for each age class of brown trout at a particular site in any given year. These data are presented in Table 2 in the RESULTS section of the report. Fish age information from the September 1994 scale collections were used to generate the life table data for all years from 1985 through 2001. With the availability of new 2002 data, life table data were generated using the fish age information derived from the brown trout scales collected at each sampling site in August of that year (Table 2).
The actual age and growth analysis on the fish scale samples was conducted using the DISBCAL computer software program developed by the Missouri Department of Conservation. This program allowed us to determine the age of each fish that had readable scales. 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 direct proportion 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 from 1985 through 2002 are given in Table 1. Age specific estimates of brown trout abundance by 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 very apparent 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 high levels at most sampling sites in August 2002. At many sites estimates of density and biomass have been increasing every year since 1999. These trends are largely true for the study sites on the East Fork of the Arkansas River (EF1 and EF2), Tennessee Creek, at sites AR1, 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 and biomass 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 recent years (1999 - 2002) brown trout density and biomass has increased dramatically in this reach. At sampling sites AR3, AR4 and AR5 in August 2001, both density and biomass of brown trout were the highest for the period of record at that time. However, density and biomass at sites AR3 and AR4 increased dramatically in 2002 compared to 2001. This trend could certainly be considered strong empirical evidence suggesting that efforts to ameliorate impacts from heavy metal pollution appear to be having a positive effect on the trout population.
In general, relative abundance of brown trout > 35 cm (14 inches) increases at the most downstream sampling sites (AR4, AR5, AR6, AR6A and AR7). This is primarily the result 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 data on 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 not necessarily older.
Estimates of Brown Trout Age and Growth
The year class abundance data in Table 2 tends to corroborate the same trends observed with brown trout density and biomass. Over the period of study, the greatest abundance of brown trout at 5, 6 and 7 years of age occur in the tributary streams (East Fork and Lake Fork of the Arkansas River, and Tennessee Creek) and at the more downstream study sites on the mainstem of the Arkansas River (AR4, AR6A, and AR7). They are least abundant or completely missing at those sampling stations immediately upstream and downstream of the California Gulch confluence (AR1, AR2 and AR3).
For those years (1997 - 2002) when comparative data are available, there are stark differences in numbers of brown trout at each age at sampling sites AR1 and AR3 (Table 2). Site AR1 is the mainstem reference site upstream of the confluence with California Gulch. Site AR3 is just downstream of the confluence with California Gulch. It is noteworthy that paired-t test analysis (for a within years comparison) indicates that the relative abundance of age 1 brown trout at site AR1 is significantly lower compared to AR3. This indicates that survival of young-of-the-year (YOY) brown trout and recruitment to age 1 is greater at the downstream site, and therefore not affected by high flows, which impact fish most profoundly in the first two months of life. In contrast, paired-t test analyses indicate the relative abundance of brown trout for all year classes > age 2 is significantly greater at AR1 compared to AR3. These data indicate that the relative survival for all year classes of brown trout > age 2 at study site AR3 is significantly poorer than the same age fish at site AR1. These results strongly suggest that the effluent from California Gulch 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 2001 and 2002. This increased survival among these age classes could be the result of amelioration in ambient levels of heavy metal pollution.
Finally, over the past two years there has been an increase in the abundance of age 6 and 7 brown trout at many study sites in tributary streams upstream of California Gulch and among sampling sites farther downstream from the confluence with California Gulch. However, we are still not seeing increased abundance of older fish at AR3. The downstream data may suggest that efforts to reduce ambient levels of heavy metal pollutants are beginning to have a positive impact on the trout population. Below average stream flows and warmer water temperatures may also be enhancing survival of older age trout downstream and in the tributaries. Table 1. Summary of brown trout population estimates with 95% confidence limits, based on two pass method, 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 through 2002). Sample Date Population 95%C.L. . N/Ha Kg/Ha N/Ha N/Ha Estimate > 15 cm > 15cm >30cm >35 cm East Fork Arkansas River - Above CO Highway 9 1 Bridge (EF- 1 ) 10/25/1985a 231 ±11 2,369 246.9 ... 0 09/1 9/1 986a 173 ±13 2,120 197.3 13 0 08/12/1991 108 ±2 730 55.6 7 0 09/14/1994 69 ±2 462 33.8 0 0 08/18/1997 65 ±3 438 41.3 0 0 08/30/1999 110 ±12 742 61.8 0 0 08/20/2001 129 ±9 883 76.2 7 7 08/14/2002 166 ±8 1,135 78.9 0 0 East Fork Arkansas River -Below CO Highway 24 Bridge (EF-2) 1 0/25/1 985a 185 ±10 1,312 101.9 • ... 0 09/19/1986a 76 ±14 641 55.5 0 0 08/15/1991 111 ±11 933 60.3 9 0 09/14/1994 87 ±3 737 ' 59.7 0 0 08/18/1997 121 ±15 1,019 93.1 0 0 08/30/1999 97 ±10 820 86.5 9 0 08/20/2001 139 ±9 1,319 123.8 10 0 08/13/2002 144 ±7 1,366 143.3 20 10 Tennessee Creek below St. Kevin's Gulch confluence 10/25/1985a 120 ±10 1,286 158.4 14 09/19/1986 170 ±6 932 129.2 57 6 09/13/1994 121 ±5 1,726 164.9 0 0 Tennessee Creek Above Powerline Crossing 08/18/1997 29 ±1 498 68.2 52 0 08/30/1999 63 ±13 1,064 103.9 80 0 08/20/2001 72 ±2 1,102 99.5 47 0 08/13/2002 66 ±2 1,003 95.7 0 0 Tennessee Creek - Above confluence with Arkansas River 08/12/1991 162 ±13 1,935 175.1 13 0 Arkansas River - AR1 below USGS gage @ confluence of East Fork/Tennessee Creek 09/19/1986a 81 ±1 414 49.9 15 0 08/13/1991 110 ±9 614 54.0 12 0 08/20/1997 142 ±49 789 95.2 8 0 04/20/1998 117 ±11 650 71.2 0 0 08/31/1999 119 ±8 663 70.2 6 0 04/19/2000 61 ±5 337 38.2 18 0 08/21/2001 156 ±8 864 82.7 6 0 08/13/2002 187 ±2 1,033 100.6 11 0 Arkansas River- AR2 immediately upstream of California Gulch confluence 09/19/1986a 101 ±3 1,454 166.2 59 0 10/13/1989 187 ±4 1,095 88.6 18 0 09/20/19945 101 ±5 1,282 102.8 0 0 09/20/1 994c 22 ±3 279 35.1 0 0 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 pass method, 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 95% C.L. N/Ha Kg/Ha N/Ha N/Ha Estimate > 15cm > 15cm > 30 cm >35 cm Arkansas River - Below California Gulch confluence - AR3 10/13/1989 50 ±1 314 23.3 0 0 09/20/1994 21 ±1 132 22.5 25 . 13 08/20/1997 21 ±2 129 • 18.3 13 6 04/20/1998 12 ±0 75 4.8 0 0 08/31/1999 54 ±7 337 32.7 7 0 04/17/2000 32 ±16 201 18.5 17 0 08/21/2001 96 ±11 554 64.7 13 6 08/14/2002 202 ±2 1,168 104.9 52 6 Arkansas River - Doc Smith's Ranch - AR4 10/25/1985 43 ±9 152 27.8 41 8 08/14/1991 22 ±2 1662d 311. Id 396d 237d 09/22/1994 188 ±17 958 110.0 107 39 08/19/1997 65 ±31 229 64.0 104 57 04/20/1998 50 ±11 175 66.4 125 83' 04/13/1999 47 ±3 160 59.0 121 68 09/01/1999 80 ±9 279 73.4 124 85 04/17/2000 53 ±3 185 43.5 76 33 08/22/2001 191 ±17 662 167.8 250 135 08/15/2002 351 ±6 1,230 230.9 367 178 Arkansas River - above Empire Gulch confluence (AR5) 08/14/1991 50 ±1 164 33.2 49 29 09/15/1994 81 ±8 264 46.1 67 28 08/19/1997 74 ±11 242 56.6 45 11 04/21/1998 42 ±2 138 41.9 77 50 10/07/1998 81 ±5 265 60.7 51 17 04/12/1999 62 ±2 202 49.7 96 50 09/01/1999 81 ±19 264 55.0 33 8 04/18/2000 51 ±3 168 39.6 37 10 08/22/2001 134 ±28 504 77.2 113 24 08/15/2002 82 ±5 310 40.5 63 12 Arkansas River - near the Pan-Ark Lodge (AR6A) 10/06/1998 156 ±11 459 102.4 209 82 04/12/1999 87 ±9 255 55.8 39 10 09/02/1999 100 ±7 296 62.5 120 38 04/18/2000 67 ±6 197 51.5 48 13 08/23/2001 167 ±10 469 83.8 42 3 08/15/2002 122 ±8 342 67.8 128 51 Ar
10 Table 2. Year class abundance estimates for wild brown trout at various sampling sites for various years in the Upper Arkansas River drainage from 1987 through 2002. Sample Age in Years Date 1234567 East Fork Arkansas River- Above CO Highway 91 Bridge (EF-1) 08/12/91 60 84 296 217 187 09/14/94 365 79 183 134 140 08/12/97 510 239 93 103 245 08/30/99 435 201 275 132 301 08/20/01 219 516 195 309 198 14 7 08/14/02 404 134 138 460 118 270 .50 East Fork Arkansas River -Below CO Highway 24 Bridge (EF-2) 08/15/91 146 362 355 229 84 09/14/94 130 147 171 322 7 08/18/97 128 291 232 324 262 38 08/30/99 488 80 66 353 298 39 08/20/01 221 259 204 386 448 62 08/13/02 1,149 313 871 173 0 Tennessee Creek below St. Kevin's Gulch confluence 09/19/86 232 25 493 134 49 09/13/94 881 425 578 704 35 43 Tennessee Creek Above Powerline Crossing 08/18/97 166 255 96 153 206 08/30/99 444 693 626 290 142 23 08/20/01 838 379 263 250 174 52 08/13/02 1,014 356 124 248 295 93 46 Tennessee Creek - Above confluence with Arkansas River 08/12/91 223 518 544 669 64 123 Arkansas River - AR1 below USGS gage @ confluence of East Fork/Tennessee Creek 09/19/86 107 67 180 53 0 0 08/13/91 93 344 178 29 27 0 08/20/97 56 188 343 198 40 8 04/20/98 148 185 229 151 30 0 08/31/99 233 279 170 135 50 0 04/19/00 97 . 132 89 38 44 0 08/21/01 229 407 303 84 38 0 08/13/02 765 333 415 112 39 0 Arkansas River- AR2 immediately upstream of California Gulch confluence 09/19/86 435 156 618 312 100 14 10/13/89 375 274 493 266 60 2 09/20/94a 327 215 428 622 13 4 09/20/94b 80 46 70 140 13 9 Arkansas River - Below California Gulch confluence - AR3 10/13/89 476 144 33 0 0 0 09/20/94 94 38 47 6 6 3 08/20/97 264 64 36 9 0 3 04/20/98 221 24 10 0 0 0 08/31/99 319 145 57 17 0 0 04/17/00 219 34 49 10 0 0 08/21/01 232 237 126 32 0 3 08/14/02 976 225 192 40 6 0 a: East braid of split channel b: West braid of split channel c: 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 for various years in the Upper Arkansas River drainage from 1987 through 2002. Sample Age in Years Date 1 2 3 4 5 6 7 Arkansas River - Smith's Ranch - AR4 1 i 10/25/85 JJ 55 49 22 12 0 0 08/14/91 150 735 323 229 185 40 0 09/22/94 679 308 160 76 34 6 0 08/19/97 194 57 51 43 35 21 0 04/20/98 51 16 20 44 56 23 0 04/13/99 57 9 14 53 36 27 0 09/01/99 212 75 38 45 62 17 0 04/17/00 83 41 36 42 24 7 0 08/22/01 231 148 126 140 86 38 7 08/15/02 834 225 164 190 59 7 29 Arkansas River - above Empire Gulch confluence (AR5) 08/14/91 7 86 29 36 3 0 09/15/94 145 96 65 23 18 j^ 0 08/19/97 69 123 74 32 35 3 0 04/21/98 41 38 30 23 27 16 0 10/07/98 91 70 72 32 30 18 0 04/12/99 77 59 35 35 37 7 0 09/01/99 49 81 93 135 13 3 0 04/18/00 101 45 39 27 25 7 3 08/22/01 144 191 101 70 27 0 0 08/15/02 154 92 33 36 6 0 0 Arkansas River - near the Pan- Ark Lodge (AR6A) 10/06/98 106 85 132 112 60 25 0 04/12/99 86 53 74 67 22 15 0 09/02/99 55 67 112 72 30 7 0 04/18/00 125 23 36 78 24 22 0 08/23/01 144 94 100 107 38 10 0 08/15/02 73 95 46 60 61 40 22 Arkansas River - downstream of Kobe Bridge (AR6) 04/21/98 46 46 31 44 4 3 0 04/13/99 101 83 110 73 9 0 0 09/01/99 54 48 62 39 0 0 0 04/18/00 201 67 29 31 9 0 0 08/23/01 70 60 66 64 8 8 0 08/16/02 310 145 125 35 0 0 0 Arkansas River - upstream of Lake Creek confluence 09/29/88 212 114 172 64 0 0 0 07/29/92 57 83 92 52 41 7 0 09/22/94 406 197 247 104 61 11 15 Arkansas River near Granite - downstream of Lake Creek confluence (AR7) 09/17/87 594 562 364 368 135 0 0 09/29/88 1066 1331 851 376 207 0 0 04/21/98 63 32 85 83 58 27 0 10/06/98 50 103 51 56 49 25 0 04/12/99 65 53 27 46 27 15 0 10/20/99 18 56 70 19 12 14. 0 04/17/00 157 120 56 70 57 9 0 08/22/01 69 167 100 108 59 23 0 08/16/02 172 95 64 41 14 14 0
12. Table 2 (continued). Year class abundance estimates for wild brown trout at various sampling sites for various years in the Upper Arkansas River drainage from 1987 through 202. Sample Age in Years Date 1 2 3 4 5 6 7 Lake Fork of the Arkansas River near Halfmoon Creek confluence downstream of C.R. 1 1 (LF1) 08/13/91 537 245 212 52 17 4 0 09/21/94 1218 561 102 76 85 0 0 08/20/97 449 186 34 79 L_ 64 0 0 08/31/99 365 864 . 496 119 25 4 0 08/21/01 474 271 229 70 51 14 22 08/14/02 2,121 123 150 24 84 11 9
Age and Growth of Brown Trout
For all electrofishing data sets collected from 1985 through 2001, scale age and growth information collected during sampling in 1994 was used to stratify trout population estimates into year classes and develop a life table for brown trout at each study site. The life table information is presented in Table 2. Age and growth data generated for each study site 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 each study site in August 2002. Age and growth data generated for each study site from the 2002 set of scale samples are summarized in Table II in the Appendix. These age and growth data sets were used to generate estimates of brown trout age class abundance for each study site for August 2002. Those data are presented in Table 2.
For this updated report, we developed two new life tables for study site AR1. For one life table we used the age and growth data set for study site AR2 collected in September 1994. For the second life table we used the age and growth data set collected at AR1 in August 2002. These data sets were used to develop life table information for comparison with that presented in Table 2 for study site AR1 in Nehring and Policky (2002). Those comparisons are shown in Table 3. Using either the scale data set collected at study site AR2 in September 1994 or that collected at study site AR1 in August 2002, we end up with substantial numbers of age 5 trout for all years of study as seen in Table 3. That was not the case using the 1994 data set from farther downstream that resulted in no trout estimated to be older than age 4. However, it is also noteworthy that no matter which of the three age and growth data sets are used, brown trout greater than age 5 have rarely been present at this station. In contrast, brown trout estimated to be age 6 and even age 7 have regularly been 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 study sites AR1, AR2, and AR3 are brown trout estimated to be > age 6 noticeably absent or present only in very low numbers in most years.
13 Table 3. Comparisons of year class abundance estimates for wild brown trout at sample site AR1 using 3 different fish scale age and growth data sets for various years 1991 through 2002. Sample Age in Years Date 1 2 3 4 5 6 7 Age Structure for Study Site AR1 using age-growth data from Site AR4 collected in August 1994 08/13/91 286 330 91 14 08/20/97 374 436 428 33 04/20/98 573 356 181 7 08/31/99 731 356 160 18 04/19/00 369 191 58 28 08/21/01 309 556 181 21 Age Structure for Study Site AR1 using age-growth data from Site AR2 collected in August 1994 08/13/91 84 74 244 270 24 0 08/20/97 48 42 254 457 32 0 04/20/98 97 88 200 341 18 0 08/31/99 206 83 209 338 29 0 04/19/00 76 40 84 159 53 0 08/21/01 203 109 300 419 35 0 08/13/02 637 164 304 537 28 0 Age Structure for Study Site AR1 using age-growth data from Site AR1 collected in August 2002 08/13/91 93 344 178 [ 29 27 0 08/20/97 56 188 343 198 40 8 04/20/98 148 185 229 151 30 0 08/31/99 233 279 170 135 50 0 04/19/00 97 132 89 38 44 0 08/21/01 229 407 303 84 38 0 08/13/02 765 333 415 112 39 0
After examining the age versus length frequency distributions for the two age and growth data sets for 1994 and 2002 for multiple sites, we believe it would be prudent to collect a new set of scale samples at all sampling sites for at least the 2003 and 2004 collections. If the study continues beyond 2004, an assessment based on the age and growth analyses for 2002, 2003, and 2004 can be made to determine whether or not it is necessary to continue to collect scale samples at all study sites each year.
There are numerous reasons why it would be biologically sound to collect two addition scale data sets at each study site in 2003 and 2004. First, the data on age and growth in Appendix Tables I and II indicate that annual growth increments of trout are inversely related to elevation. Second, the study sites are not widely separated in distance and there is a high probability that some movement of trout could be occurring between study sites within and between years. These sorts of movement, among both juvenile (age 1 and 2) and adult (> age 3) trout have the potential for intermixing of trout of the same size but different ages at a given site in a given year. Such mixing has the potential to dramatically change the size and age structure at a site between years. Thus, it seems prudent to collect scale samples at all sites each year. This is the best way to maximize the validity of any effort to validate the age structure of the trout population within and between study 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; Gerking 1959; 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 < 800 meters (Knouft and Spotila 2002). Still others documented movement over distances of 1 to 2 Ion (Gowan and Fausch 1996). Two other studies documented seasonal movements of adult 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 the upper Arkansas River, particularly in drought years as the state has experienced in 2001 and 2002. Indeed, in a similar study being conducted on the Eagle River biologists saw. large numbers of unmarked brown trout from outside the study area(s) showing up in the study stations in 2002. This had not occurred in previous years (John Woodling, personal communication). Collecting age and growth information together with the color-coded tagging studies should help document whether or not substantial movement of brown trout between study sites is occurring in the upper Arkansas River basin.
DISCUSSION
Numerous extensive studies have examined the impacts of chronic heavy metal pollution on the aquatic biota of the upper Arkansas River over the past 27 years. Some of the 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 mine drain wastewater laden with iron oxide that turned the water of the upper Arkansas River bright orange. Despite dilution by flow augmentation from tributary streams, this pulse of polluted water was still orange when it flowed into Pueblo Reservoir, approximately 250 km downstream a few days later. The CDOW was called upon to conduct an extensive electrofishing 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 than 300 brown and rainbow trout were collected from numerous sites throughout the Arkansas River drainage from the East Fork of the Arkansas River downstream to Salida. A scale sample was collected from each fish that was sacrificed to facilitate cross correlation of heavy metal content in liver and kidney tissues with increasing age within and between sampling sites. These tissues were examined for bioaccumulation of lead, zinc, copper, and cadmium with increasing age. The study revealed that there was substantial bioaccumulation of copper in brown trout liver tissue with increasing age. Similarly, cadmium bioaccumulated in both liver and kidney tissues of brown trout with increasing age (Nehring 1986). Empirical evidence in the study also suggested that the level of cadmium bioaccumulation in liver and kidney tissues was high enough that it might be linked to reduced longevity of brown trout in the river.
15 Between the mid-1970s and the mid-1990s, several studies repeatedly documented that discharges from the Yak Mine Drainage Tunnel and California Gulch were major point sources 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; and Davies, Brinkman, Mclntyre, and Clements 2000).
Thus, it is not surprising that brown trout density, biomass and numbers of trout > 5 years of age are depressed at the study sites in the Arkansas River drainage downgradient of the confluence with California Gulch. To a lesser extent this applies to the area of the river that received inflow from the Leadville Mine Drainage Tunnel. However, the existence of empirical evidence showing correlation does not necessarily prove causation. That is almost always the case with field investigations.
Nonetheless, given all of the foregoing results and studies referred to above, it is most probable that chronic heavy metal pollution is the most significant factor responsible for the reduced density and biomass of brown trout as well as reduced survivorship among older fish in the Upper Arkansas River downgradient of California Gulch.
CONCLUSIONS
Results of trout population monitoring efforts at numerous sites throughout the upper Arkansas River basin over the past 17 years are strongly congruent with the findings of other investigators (LaBounty et al. 1975; Roline and Boehmke 1981; Nehring 1986; Roline 1988; Davies, Mclntyre, and Stednick 1997; and Davies, Brinkman, Mclntyre, and Clements 2000). All of these studies strongly suggest that chronic heavy metals pollution in the reach of the Arkansas River in the immediate vicinity of the confluence with California Gulch have had negative impacts on the aquatic biota in the river, particularly in the 1980s into the 1990s. It remains to be seen whether or not the recent increases in density, biomass, and the larger numbers of older age brown trout at many study sites observed in 2001 and 2002 will continue over the next 2 or 3 years. If it does, that would be strong empirical evidence suggesting that efforts to ameliorate heavy metal pollution in the upper basin are having a positive impact on the brown trout population. Conversely, a decline in density, biomass, and numbers of older age trout decline over the next 2 to 3 years at study sites AR3, AR4, and AR5 would suggest that the recent increases in these biostatistics observed in 2001 and 2002 had more to due with the below average flow conditions than with amelioration of the heavy metal pollution in the basin.
RECOMMENDATIONS
Guidelines for the collection of trout population data that would help reduce variability and sampling method(s)-induced "noise" in the data within study sites between years were set forth in 2002 (Nehring and Policky 2002). Those guidelines included the following:
1. Spring sampling should be eliminated. There is a high probability of obtaining biased results when electrofishing sampling is conducted too early
16 in the spring or too late in the fall. Once the water temperatures drop below 7-8 ° C juvenile salmonids go into a cryptic behavior mode during daylight hours, 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 temperature in the upper Arkansas River basin, at an elevation of 3,000 m in April would most 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. Movement of spawners into or out of study reaches could substantially bias the data. This may be 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 this time of year. Low flows increase electrofishing efficiency. Water temperatures are still high enough that juvenile trout have not yet changed to the 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 in substantial sampling method(s) induced "noise" in the data, decreasing the probability of detecting meaningful changes in trout population biostatistics. A glaring example of this occurred at Doc Smith's Ranch (AR4) for August 14,1991. 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 removal estimator (Seber and LeCren 1967) is the appropriate model for use in population estimation at most of the upstream study sites. It can be used at the most downstream study site near Granite, Colorado (downstream of the Lake Creek confluence) if the electrofishing efficiency is known to be substantially greater than 60% on the first electrofishing pass through the station.
These recommendations have been adopted by CDOW. In addition, we suggest that a complete set of scale samples be collected at each sampling site for at least the 2003 and 2004 field seasons, and continued tagging. This will provide the most accurate and precise information for estimating the relative abundance and survival rates for brown trout among and between study sites and years. While it would be nice to corroborate the age of individual fish using both scale aging and otolith or fin ray analyses, the otolith method of aging requires lethal sampling, and fin ray sampling adversely affect the fish. Lethal sampling and significant adverse effects would be counter-productive when the primary reason for conducting the studies is to evaluate longevity and survival of brown trout in the upper Arkansas River basin.
17 ACKNOWLEDGEMENTS
Virtually all of the fish population data used in this study were collected by CDOW Arkansas River basin management biologists Greg Policky and Rick Anderson, and the field 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 DISBCAL by the senior author and temporary employees under his supervision. For all trout population data sets from 1985 through 2001, Kelly Thompson converted data from the field notes into a format for input into the GOLDMEDL program. Barbara Poole did the same for the August 2002 data sets. The GOLDMEDL software program was used to generate 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 are summarized in Appendix Tables I and II.
LITERATURE CITED
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19 Knouft, J. H., and J. R. Spotila. 2002. Assessment of movements of resident stream brown trout, Salmo trutta L., among contiguous sections of stream. Ecology of Freshwater Fish 11:85-92.
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20 Nehring, R. B., and D.D. Miller. 1987. Stream fisheries investigations. Colorado Division of Wildlife Job Progress Report. Federal Aid Project F-51-R12. Fort Collins.
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APPENDICES
21 Table I. Arkansas River back-calculated lengths (cm) of brown trout collected during CDOW 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.E Class (yr)
Arkansas River East Braid Brown Trout 1994 Filename AR05ALC.ANU Body scale constant = 40.55
1993 16 1+ 12.8 0.26 8.1 0.19 1992 9 2+ 15.8 0.53 8.7 0.28 12.9 0..37 1991 16 3+ 18.1 0.59 8.3 0.25 12.6 0.,52 15.9 0.60 1990 14 4+ 21.2 0.33 9.0 0.25 13.8 0.49 17.3 0.53 19.6 0.40
1 x O .7 \Jo <;+ 1989 —' l
1988 1 6+ 25.6 7.4 14.9 17.6 20.6 -- — 23.4 — 25.1 Arkansas River West Braid Site 5 Brown Trout September 1994 Filename AR05BLC.ANU Body scale constant = 40.72
1993 3 1 + 12.5 0.97 7.9 0.42 1992 1 2+ 18.2 9.5 14.5 ~~ — — 1991 3 3+ 24.5 0.79 10.8 1.13 17.5 1.64 22.2 0.67 1990 5 4+ 25.4 0.51 9.8 0.49 15.0 0.70 20.0 0.45 23.7 0.39 1989 1 5+ 27.7 10.8 15.9 18.9 23.9 -- — — —— — 26.3 — Arkansas River Site 6 Sewer Lagoon Brown Trout September 1994 Filename AR06LC.ANU Body scale constant = 25.00
1993 8 1+ 14.8 0.25 8.4 0.30 1992 9 2+ 18.4 1.64 7.5 0.33 12.9 0.88 1991 6 3+ 26.6 0.40 7.9 0.44 13.5 1.05 19.4 0.73 1990 1 4+ 31.7 8.5 14.2 20.3 — — — 24.2 1989 2 5+ 33.7 3.30 10.6 0.94 20.3 3.42 25.3 3.67 29.5 2.25 32.6 3.29 1988 1 6+ 34.7 — 8.3 — 17.7 — 25.3 -— 30.1 31.6 —- 33.5
22 Table I (continued). Arkansas River back-calculated lengths (cm) of brown trout collected during CDOW electrofishing operations, August 2002 Year N Age Lc S.E. L, 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.E Class (yr)
Arkansas River Site 6 Sewer Lagoon Brown Trout September 1994 Filename AR06LC.ANU Body scale constant = 36.49
1993 8 1+ 14.8 0.25 9.0 0.27 1992 9 2+ 18.4 1.64 8.3 0.33 13.3 0.89 1991 6 3+ 26.6 0.40 8.8 0.42 14.2 1.01 19.8 0.71 — 1990 1 4+ 31.7 — 9.4 — 14.9 — 20.7 24.5 1989 2 5+ 33.7 3.30 11.5 0.94 20.8 3.36 25.6 3.63 29.7 2.27 32.6 3.29 1988 1 6+ 34.7 — 9.2 — 18.3 — 25.7 — 30.2 — 31.7 — 33.5 — Arkansas River Site 7 Above RD 44 Brown Trout September 1994 Filename AR07LC.ANU Body scale constant = 25.00
1993 42 1 + 14.6 0.36 7.9 0.22 1992 32 2+ 21.1 0.68 8.0 0.23 14.8 0.48 1991 25 3+ 25.4 0.62 8.4 0.22 15.4 0.43 20.9 0.58 1990 13 4+ 31.2 0.62 8.2 0.25 17.3 0.61 24.4 0.75 28.6 0.71 1989 6 5+ 36.9 1.35 9.2 0.28 17.6 0.90 25.6 1.54 31.1 1.55 34.6 1.26 1988 1 6+ 34.8 7.1 17.0 23.0 28.1 — — — — — 31.2 33.0 — — Arkansas River Site 7 Above RD 44 Brown Trout September 1994 Filename AR07LC.ANU Body scale constant = 44.67
1993 42 1+ 14.6 0.36 9.0 0.21 1992 32 2+ 21.1 0.68 9.4 0.22 15.5 0.48 1991 25 3+ 25.4 0.62 9.9 0.21 16.2 0.41 21.3 0.56 1990 13 4+ 31.2 0.62 9.8 0.23 18.2 0.58 24.9 0.73 28.8 0.69 1989 6 5+ 36.9 1.35 10.8 0.27 18.7 0.87 26.2 1.49 31.4 1.51 33.1 1.25 1988 1 6+ 34.8 8.8 — 18.1 — 23.7 — 28.5 — — 31.4 — 33.1 —
23 Table I (continued). Arkansas River back-calculated lengths (cm) of brown trout collected during CDOW 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.E Class (yr)
Arkansas River Site 8 Upper Empire Gulch Brown Trout September 1994 Filename AR08LC.ANU Body scale constant = 22.30
1993 23 1+ 14.6 0.33 8.5 0.22 1992 24 2+ 21.9 0.54 8.1 0.20 15.1 0.44 1991 18 3+ 28.0 0.53 8.9 0.32 17.0 0.68 24.1 0.96 1990 7 4+ 34.6 1.02 10.4 0.36 19.2 0.44 26.9 1.14 32.5 1.02 1989 4 5+ 36.3 1.76 8.5 0.93 18.7 2.25 25.1 1.35 29.4 1.60 34.3 1.86
Arkansas River Site 8 Upper Empire Gulch Brown Trout September 1994 Filename AR08LC.ANU Body scale constant = 25.00
1993 23 1 + 14.6 0.33 8.6 0.22 1992 24 2+ 21.9 0.54 8.3 0.20 15.2 0.44 1991 18 3+ 28.0 0.53 9.1 0.32 17.1 0.68 24.2 0.95 1990 7 4+ 34.6 1.02 10.6 0.35 19.3 0.43 27.0 1.13 32.5 1.02 1989 4 5+ 36.3 1.76 8.7 0.93 18.8 2.23 25.2 1.35 29.4 1.59 34.3 1.86
Arkansas River Site 9 Above Ball Town Brown Trout September 1994 Filename AR09LC.ANU Body scale constant = 25.00
1993 28 1 + 15.2 0.37 8.0 0.28 1992 26 2+ 20.9 0.78 8.5 0.29 15.9 0.66 1991 30 3+ 27.1 0.55 9.6 0.24 17.9 0.42 24.0 0.55 1990 13 4+ 31.0 0.88 9.6 0.33 18.1 0.55 25.0 0.91 29.5 1.00 1989 7 5+ 32.7 0.66 10.1 0.38 17.2 0.67 22.0 0.61 27.9 0.80 31.3 0.68 1988 1 6+ 32.6 8.1 11.5 19.8 24.5 — — — — -- 28.0 — 32.0 — 1987 1 7+ 38.1 12.0 25.9 31.9 — — 20.9 — — 34.0 35.8 37.4 — — — —
24 Table I (continued). Arkansas River back-calculated lengths (cm) of brown trout collected during CDOW electrofishing operations, August 2002 Year N Age Lc S.E. L, 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.E Class (yr) Arkansas River Site 9 Above Ball Town Brown Trout September 1994 Filename AR09LC.ANU Body scale constant = 47.02
1993 28 1+ 15.2 0.37 9.3 0.25 1992 26 2+ 20.9 0.78 10.0 0.28 16.5 0.65 1991 30 3+ 27.1 0.55 11.2 0.22 18.7 0.40 24.3 0.54 1990 13 4+ 31.0 0.88 11.3 0.31 19.1 0,.53 25.5 0.88 29.6 0.99 1989 7 5+ 32.7 0.66 11.7 0.34 18.3 0,.61 22.8 0.54 28.2 0.75 31.4 0.67 1988 1 6+ 32.6 — 9.9 13.1 --~ 20.7 — 25.1 — — 28.3 — 32.1 — 1987 1 7+ 38.1 — 13.7 — 21.9 -~ 26.7 — 32.3 ~ 34.3 36.0 37.5 — — — Arkansas River Site 10 Granite Gage Brown Trout September 1994 Filename AR10LC.ANU Body scale constant = 25.00
1993 6 1 + 14.2 0.40 7.0 0.39 1992 38 2+ 18.5 0.48 8.7 0.19 15.0 0.,31 1991 21 3+ 25.1 0.59 8.9 0.28 16.7 0.,52 22.2 0.63 1990 10 4+ 29.1 1.03 9.3 0.36 16.2 1.04 21.3 1.14 26.1 1.02 1989 4 5+ 31.5 0.96 9.0 0.77 13.9 1,.13 21.5 1.37 26.3 1.24 29.6 3.27 1 8.9 16.0 -— 22.5 28.6 1988 6+ 36.0 — — — — 31.6 — 34.8 — Arkansas River Site 10 Granite Gage Brown Trout September 1994 Filename AR10LC.ANU Body scale constant = 34.67
1993 6 1+ 14.2 0.40 7.6 0.36 1992 38 2+ 18.5 0.48 9.3 0.19 15.2 0,.31 1991 21 3+ 25.1 0.59 9.6 0.28 17.1 0,.51 22.4 0.62 1990 10 4+ 29.1 1.03 10.0 0.35 16.7 1,.01 21.6 1.13 26.2 1.02 1989 4 5+ 31.5 0.96 9.7 0.75 14.5 1.,10 21.8 1.34 26.5 1.22 29.6 0.78 — — 1988 1 6+ 36.0 9.7 — 16.5 -- 22.9 28.8 31.7 34.8 — — — —
25 Table I (continued). Arkansas River back-calculated lengths (cm) of brown trout collected during CDOW 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.E Class (yr)
Arkansas River Site 11 Railroad Bridge Brown Trout September 1994 Filename AR11LC.ANU Body scale constant = 25.00
1994 7 0 11.7 0.42 1993 11 1+ 17.2 0.33 9.4 0.40 1992 8 2+ 21.5 1.09 10.1 0.76 16.9 1.05 1991 11 3+ 23.0 0.89 9.1 0.31 16.0 0.70 20.3 0.85 1990 19 4+ 25.8 0.69 8.9 0.37 15.2 0.82 20.6 0.80 23.9 0.72 1989 2 5+ 26.0 2.00 8.6 1.46 12.7 1.36 16.8 1.31 20.6 1.29 24.2 2.04 1988 2 6+ 32.0 3.00 8.7 0.74 19.1 2.94 24.6 2.58 28.5 2.21 30.6 2.89 31.6 2.86 1987 1 7+ 39.0 12.6 22.7 28.5 — 31.0 — — — — 35.6 36.8 38.1 — — — Arkansas River Site 11 Railroad Bridge Brown Trout September 1994 Filename AR11LC.ANU Body scale constant = 46.27
1994 7 0 11.7 0.42 1993 11 1+ 17.8 0.33 10.5 0.35 1992 8 2+ 21.5 1.09 11.3 0.70 17.4 1.00 1991 11 3+ 23.0 0.89 10.6 0.30 16.7 0.68 20.6 0.84 1990 19 4+ 25.8 . 0.69 10.4 0.34 16.1 0.78 21.1 0.78 24.0 0.71 1989 2 5+ 26.0 2.00 10.1 1.37 13.9 1.31 17.7 1.30 21.1 1.32 24.3 2.02 1988 2 6+ 32.0 3.00 10.4 0.73 20.0 2.84 25.1 2.55 28.8 2.24 30.7 2.89 31.6 2.87 — 1987 1 7+ 39.0 — 14.1 — 23.6 — 29.1 31.5 — 35.8 37.0 38.1 — — —
26 Table I (continued). Arkansas River back-calculated lengths (cm) of brown trout collected during CDOW 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.E Class (yr)
Arkansas River Site 12 Fisherman's Bridge Brown Trout September 1994 Filename AR12LC.ANU Body scale constant = 8.49
1993 20 1+ 12.2 0.45 7.4 0.17 1992 38 2+ 18.7 0.55 8.0 0.26 14.8 0.41 1991 31 3+ 26.3 0.83 8.8 0.36 17.2 0.81 23.7 0.91 1990 25 4+ 31.7 0.74 9.7 0.35 17.5 0.63 23.7 0.82 29.3 0.73 1989 16 5+ 33.8 1.07 9.0 0.59 15.9 1.01 22.4 1.10 27.6 1.21 31.2 1.15 1988 8 6+ 37.5 1.38 9.7 0.86 16.5 1.19 22.7 1.07 28.4 1.00 32.5 1.00 35.6 1.25
Arkansas River Site 12 Fisherman's Bridge Brown Trout September 1994 Filename AR09LC.ANU Body scale constant = 25.00
1993 20 1+ 12.2 0.45 8.0 0.17 1992 38 2+ 18.7 0.55 9.0 0.25 15.2 0.41 1991 31 3+ 26.3 0.82 10.0 0.35 17.8 0.79 23.8 0.90 1990 25 4+ 31.7 0.74 10.9 0.34 18.2 0.62 24.2 0.80 29.4 0.72 1989 16 5+ 33.8 1.07 10.3 0.57 16.8 0.97 23.0 1.07 28.0 1.19 31.3 1.13 1988 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 1994 Filename AR14LC.ANU Body scale constant = 9.29
1994 2 0 10.0 — 1993 9 1 + 16.8 0.78 8.9 0.54 1992 16 2+ 18.6 0.62 7.9 0.37 15.2 0.58 1991 8 3+ 27.1 1.07 9.3 0.59 16.6 1.40 23.4 1.38 1990 4 4+ 29.7 1.84 7.6 0.88 15.3 2.01 22.3 0.66 .27.1 0.90 1989 3 5+ 32.2 2.78 9.1 0.35 17.4 2.23 22.1 3.46 26.4 3.08 30.6 3.17
27 Table I (continued). Arkansas River back-calculated lengths (cm) of brown trout collected during CDOW 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.E Class (yr)
Arkansas River Site 14 Lake Creek Brown Trout September 1994 Filename AR14LC.ANU Body scale constant = 25.00
1994 2 0 10.0 — 1993 9 1 + 16.8 0.78 9.6 0.46 1992 16 2+ 18.6 0.62 8.9 0.35 15.5 0.56 1991 8 3+ 27.1 1.07 10.4 0.57 17.2 1.34 23.6 1.35 1990 4 4+ 29.7 1.84 8.8 0.82 16.1 1.86 22.7 0.59 27.2 0.93 1989 3 5+ 32.2 2.78 10.2 0.35 18.1 2.18 22.6 3.36 26.7 3.03 30.7 3.14
Tennessee Creek Upper Site 3 Brown Trout September 1994 Filename TNUP03LC.ANU Body scale constant = 18.68
199JL J7-7-3/ \Jo 1 +' 1992 22 2+ 13.5 0.41 6.6 0.16 11.4 0.27 1991 13 3+ 18.2 0.43 6.3 0.18 11.0 0.38 15.1 0.62 1990 17 4+ 23.5 0.59 6.8 0.17 14.0 0.57 19.0 0:60 22,.0 0.60 1989 14 5+ 27.0 0.64 7.1 0.33 14.3 0.68 19.7 0.66 23.6 0.54 25.7 0.53 1988 3 6+ 33.3 3.76 7.3 0.10 12.3 0.28 19.1 0.44 24.7 0.41 28.7 0.59 31.7 2.94
Tennessee Creek Upper Site 3 Brown Trout September 1994 Filename TNUP03LC.ANU Body scale constant = 25.00
I 77 J \> i i 1992 22 2+ 13.5 0.41 7.0 0.16 11.5 0.27 1991 13 3+ 18.2 0.43 6.8 0.17 11.3 0.37 15.2 0.61 1990 17 4+ 23.5 0.59 7.2 0.17 14.3 0.57 19.1 0.60 22.1 0.59 1989 14 5+ 27.0 0.64 7.6 0.33 14.6 0.66 19.9 0.65 23.7 0.54 25.7 0.53 1988 3 6+ 33.3 3.76 7.9 0.35 12.7 0.89 19.3 1.11 24.9 1.39 28.8 1.96 31.8 2.96
28 Table I (continued). Arkansas River back-calculated lengths (cm) of brown trout collected during CDOW 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.E Class (yr)
Tennessee Creek Lower Site 4 Brown Trout September 1994 Filename TNLW04LC.ANU Body scale constant = 25.00
1993 19 1+ 12.4 0.26 7.1 0.22 1992 19 2+ 16.9 0.35 8.4 0.38 13.0 0.38 1991 15 3+ 20.9 0.27 6.9 0.18 12.8 0.27 17.8 0.29 1990 20 4+ 23.8 0.38 7.6 0.26 13.3 0.38 18.2 0.38 21.9 0.30 1989 2 5+ 26.0 1.00 8.5 1.96 13.7 3.22 17.7 2.77 21.5 1.06 24.2 0.65 1988 1 6+ 28.0 7.2 10.5 — 14.0 — 19.2 22.6 26.2 — — — — — Tennessee Creek Lower Site 4 Brown Trout September 1994 Filename TNLW04LC.ANU Body scale constant = 50.83
1993 19 1+ 12.4 0.26 8.5 0.19 1992 19 2+ 16.9 0.35 10.0 0.33 13.7 0.35 1991 15 3+ 20.9 0.27 8.8 0.16 13.9 0.25 18.2. 0.28 1990 20 4+ 23.8 0.38 9.6 0.24 14.5 0.35 18.9 0.35 22.1 0.30 1989 2 5+ 26.0 1.00 10.4 1.77 15.0 2.92 18.6 2.53 1.03 24.4 0.68 1988 1 6+ 28.0 9.3 — 12.3 — 15.4 20.1 23.2 26.4 — — — — Half Moon Creek of Arkansas Site 9 Brown Trout September 1994 Filename HC09LC.ANU Body scale constant = 25.00
1994 1 0 5.6 1993 4 1+ 11.6 0.75 6.1 0.22 1992 5 2+ 16.3 1.90 6.8 0.77 11.9 1.81 1991 1 3+ 22.2 — 6.4 — 12.9 — 17.5 1990 3 4+ 24.4 1.43 7.1 0.75 12.9 1.83 17.8 2.39 22.1 1.74 1989 2 5+ 24.2 1.40 7.0 0.57 13.7 0.58 17.0 0.70 20.2 1.07 22.4 0.96
29 Table I (continued). Arkansas River back-calculated lengths (cm) of brown trout collected during CDOW 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.E Class (yr)
Half Moon Creek of Arkansas Site 9 Brown Trout September 1994 Filename HC09LC.ANU Body scale constant = 26.26
1994 1 0 5.6 1993 4 1+ 11.6 0.75 6.1 0.21 1992 5 2+ 16.3 1.90 6.9 0.77 11.9 1.80 1991 1 3+ 22.2 6.5 13.0 17.6 — — — — 1990 3 4+ 24.4 1.43 7.2 0.75 13.0 1.82 17.8 2.39 22.1 1.73 1989 2 5+ 24.2 1.40 7.1 0.57 13.7 0.58 17.0 0.70 21.3 0.60 22.4 0.96
East Fork Arkansas Site 1 Brown Trout September 1994 Filename AREF01LC.ANU Body scale constant = 25.00
1993 14 1+ 10.7 0.16 5.9 0.18 1992 8 2+ 13.5 0.27 6.1 0.30 10.3 0.47 1991 21 3+ 17.0 0.24 6.3 0.29 10.9 0.34 14.6 0.26 1990 14 4+ 20.0 0.24 6.3 0.22 10.2 0.30 15.1 0.42 18.2 0.31 1989 10 5+ 22.1 0.28 6.7 0.30 10.6 0.49 14.7 0.53 18.1 0.42 20.8 0.37
East Fork Arkansas Site 1 Brown Trout September 1994 Filename AREF01LC.ANU Body scale constant = 40.68
1993 14 1+ 10.7 0.16 6.8 0.16 1992 8 2+ 13.5 0.27 7.1 0.26 10.7 0.43 1991 21 3+ 17.0 0.24 7.5 0.26 11.6 0.31 14.8 0.25 1990 14 4+ 20.0 0.24 7.5 0.20 11.1 0.28 15.5 0.38 18.3 0.30 1989 10 5+ 22.1 0.28 7.9 0.28 11.5 0.45 15.3 0.50 18.4 0.41 20.9 0.36
30 Table I (continued). Arkansas River back-calculated lengths (cm) of brown trout collected during CDOW electrofishing operations, August 2002 Year N Age Lc S.E. L, 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.E Class (yr)
East Fork Arkansas Site 2 Brown Trout September 1994 Filename AREF02LC.ANU Body scale constant = 25.00
1993 9 1+ 11.6 0.58 6.7 0.40 1992 15 2+ 15.2 0.27 7.1 0.20 12.1 0.15 1991 11 3+ 17.8 0.38 7.3 0.25 11.7 0.35 15.3 0.36 1990 17 4+ 21.7 0.57 7.6 0.38 11.9 0.50 16.6 0.62 19.8 0.64 1989 14 5+ 23.5 0.52 7.1 0.23 27.3 0.36 15.5 0.35 19.2 0.46 21.,9 0.40 1988 2 6+ 23.9 0.65 6.7 0.49 11.8 0.41 15.6 0.80 18.2 1.15 20,.6 0.01 22.6 0.69
East Fork Arkansas Site 2 Brown Trout September 1994 Filename AREF02LC.ANU Body scale constant = 41.90
1993 9 1+ 1.6 0.58 7.6 0.37 1992 15 2+ 15.2 0.27 8.2 0.17 12.5 0.13 1991 11 3+ 17.8 0.38 8.4 0.22 12.4 0.32 15.6 0.35 1990 17 4+ 21.7 0.57 8.8 0.36 12.7 0.48 17.1 0.59 20.0 0.62 1989 14 5+ 23.5 0.52 8.4 0.22 12.8 0.33 16.2 0.33 19.5 0.44 22.0 0.40 1988 2 6+ 23.9 0.65 8.4 0.44 12.6 0.35 16.4 0.71 19.7 1.02 21..9 0.05 22.7 0.68
Lake Fork Arkansas Site 8 Brown Trout September 1994 Filename LF08LC.ANU Body scale constant = 25.00
1993 10 1+ 13.3 0.80 7.4 0.31 1992 49 2+ 17.0 0.50 7.2 0.14 12.4 0.30 1991 24 3+ 24.9 0.50 7.4 0.18 13.6 0.63 18.9 0.79 1990 10 4+ 29.7 0.40 8.4 0.34 16.6 0.86 22.1 1.01 26.4 0.76 1989 8 5+ 34.2 0.65 8.0 0.41 14.5 0.68 22.7 1.23 28.8 0.72 32.5 0.59 1 26.4 1988 6+ 36.0 — 8.7 — 14.4 • — 20.6 — — 31.7 —• 34.5 — 1987 1 7+ 34.2 7.1 — 24.9 — 12.6 — 17.9 28.1 — — —- 31.1 — 33.6 —
31 Table I (continued). Arkansas River back-calculated lengths (cm) of brown trout collected during CDOW 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.E Class (yr)
Lake Fork Arkansas Site 8 Brown Trout September 1994 Filename LF08LC.ANU Body scale constant = 37.09
1993 10 1+ 13.3 0.80 8.0 0.30 1992 49 2+ 17.0 0.50 8.0 0.13 12.8 0.29 1991 24 3+ 24.9 0.50 8.3 0.17 14.2 0.61 19.2 0.76 1990 10 4+ 29.7 0.40 9.4 0.32 17.1 0.83 22.4 . 0.97 26.6 0.74 1989 8 5+ 34.2 0.65 9.0 0.40 15.2 0.66 23.1 1.20 29.0 0.70 32.6 0.59 1988 1 6+ 36.0 — 9.7 — 15.2 --- 21.2 — 26.7 — 31.9 — 34.6 — 1987 1 7+ 34.2 8.1 13.4 -- 18.5 25.2 — — — — -- 28.3 31.2 33.6 — — — Arkansas River Brown Trout April 1996 Filename ARKSBRBC.96 Body scale constant = 26.5
1993 1 3+ 32.0 14.5 28.6 - 31.6 — 1992 1 4+ 31.0 15.4 27.1 -~ 30.1 30.9 — — — 1991 26 5+ 30.2 0.28 13.0 0.34 24.4 0.47 27.4 0.38 29.0 0.30 29.9 .0.28 1990 27 6+ 30.7 1.13 12.8 0.56 22.8 1.09 28.1 1.14 29.5 1.13 30.2 1.13 30.6 1.13 1989 8 7+ 32.0 0.71 13.4 0.92 23.6 1. 18 28.8 0.91 30.2 0.83 31.1 0.76 31.6 0.71 31.9 0.70
East Fork Arkansas Site 1 Brook Trout September 1994 Filename AREF01BK.ANU Body scale constant = 11.25
1993 13 1+ 11.8 0.28 7.4 0.17 1992 3 2+ 15.4 0.37 7.2 1.04 12.2 1.07 1991 1 3+ 19.2 — 7.2 — 11.6 - 17.0 — East Fork Arkansas Site 2 Brook Trout September 1994 Filename AREF02BK.ANU Body scale constant = 11.25
1993 0 1+ __— 1992 4 2+ 15.6 1.48 7.0 0.82 11.0 1.22
32 Table I (continued). Arkansas River back-calculated lengths (cm) of brown trout collected during CDOW electrofishing operations, August 2002 Year N Age Lc S.E. L, 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.E Class (yr)
Tennessee Creek Upper Site 3 Brook Trout September 1994 Filename TNUP03BK.ANU Body scale constant = 11.25
1993 2 1+ 13.5 0.50 8.9 0.29 1992 5 2+ 19.8 1.66 10.3 0.36 16.2 1.06 ' 1991 1 3+ 21.0 — - 9.7 — 14.8 — - 18.4
Lake Fork Arkansas Colo. Gulch Site 6 Brook Trout September 1994 Filename LF06BK.ANU Body scale constant = 11.25
1994 2 0 6.1 0.15 1993 0 1+ 1992 5 2+ 13.0 0.26 7.0 0.17 10.9 0.29 1991 4 3+ 19.6 0.49 6.5 0.39 12.8 0.41 17.2 0.50 1990 2 4+ 21.6 1.55 7.9 1.31 14.3 1.19 17.0 0.76 20.0 1.02
Lake Fork Arkansas Site 7 Brook Trout September 1994 Filename LF07BK.ANU Body scale constant = 11.25
1994 20 0 7.3 0.17 1993 1 1+ 13.5 — 6.8 1992 2 2+ 18.0 1.85 7.2 0.05 12.1 1.22 1991 3 3+ 21.9 0.17 7.9 0.59 13.0 1.11 18.3 0.75
Lake Fork Arkansas Site 8 Brook Trout September 1994 Filename LF08BK.ANU Body scale constant = 11.25
1993 2 1+ 18.9 0.70 12.3 2.72 1992 2 2+ 19.9 0.25 8.3 0.73 12.8 0.33 1991 2 3+ 24.9 0.30 8.6 0.26 17.0 0.17 22.0 0.31 1990 1 4+ 26.6 — 9.3 — 14.2 — 22.9 -— 25.3
Lake Fork Arkansas Site 1 Brook Trout September 1994 Filename LF01BK.ANU Body scale constant =11.25
1993 2 1+ 14.9 0.65 8.6 0.51 1992 1 2+ 22,2 — - 14.2 — - 20.5 1991 4 3+ 24.9 0.23 10.2 0.89 18.5 1.08 22.4 0.41
33 Table I (continued). Arkansas River back-calculated lengths (cm) of brown trout collected during CDOW 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.E Class (yr)
Lake Fork Arkansas Site 1 Brook Trout September 1994 Filename LF01BK.ANU Body scale constant = 33.59
1993 2 1+ 14.9 0.65 9.6 0.49 1992 1 2+ 22.2 — 15.0 — 20.7 — 1991 4 3+ 24.9 0.23 11.3 0.81 18.7 0.98 22.6 0.38
Lake Fork Arkansas Site 3 Brook Trout September 1994 Filename LF03BK.ANU Body scale constant = 1.86
1994 2 0 6.9 0.45 1993 1 1+ 16.4 — 7.9 1992 1 2+ 20.5 — 7.8 — 18.3 —
Lake Fork Arkansas Site 3 Brook Trout September 1994 Filename LF03BK.ANU Body scale constant = 11.25
1994 2 0 6.9 0.45 1993 1 1 + 16.4 — - 8.4 1992 1 2+ 20.5 — 8.3 —- 18.4 —
Lake Fork Arkansas Site 4 Brook Trout September 1994 Filename LF04BK.ANU Body scale constant = 11.25
1994 4 0 6.5 0.24 1993 16 1 + 10.7 0.45 7.3 0.30 1992 18 2+ 15.4 0.32 8.2 0.32 13.0 0.23 1991 20 3+ 19.6 0.40 8.1 0.32 14.0 0.43 17.8 0.42 1990 1 4+ 21,9 — 6.7 — 13.3 — - 18.3 20.8
Lake Fork Arkansas Site 5 Brook Trout September 1994 Filename LF05BK.ANU Body scale constant = 12.72
1994 10 0 6.1 0.11 1993 25 1+ 10.8 0.17 7.2 0.17 1992 9 2+ 14.4 0.63 6.8 0.55 11.5 0.69 1991 38 3+ 19.5 0.33 7.5 0.19 12.9 0.25 17.2 0.25 1990 3 4+ 20.9 1.79 7.0 0.31 11.8 1.72 15.8 2.46 18.9 2.35
34 Table I (continued). Arkansas River back-calculated lengths (cm) of brown trout collected during CDOW 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.E Class (yr)
Lake Fork Arkansas Colo. Gulch Site 6 Brook Trout September 1994 Filename LF06BK.ANU Body scale constant = 21.83
1994 2 0 6.1 0.15 1993 0 1+ — — 1992 5 2+ 13.0 0.26 7.5 0.16 11.1 0.28 1991 4 3+ 19.6 0.49 7.2 0.37 13.2 0.39 17.3 0.49 1990 2 4+ 21.6 1.55 8.6 1.22 14.6 1.07 17.2 0.66 20.1 1.04
Lake Fork Arkansas Site 7 Brook Trout September 1994 Filename LF07BK.ANU Body scale constant = 2.40
1994 20 0 7.3 0.17 1993 1 1+ 13.5 — 6.3 1992 2 2+' 18.0 1.85 6.6 0.02 11.8 1.22 1991 3 3+ 7.3 0.17 7.3 0.62 13.3 1.16 18.1 0.78
Arkansas River Site 6 Sewer Lagoon Brook Trout September 1994 Filename AR06BK.ANU Body scale constant = 11.25
1992 4 2+ 24.5 2.18 9.3 0.70 18.8 1.38 1991 1 3+ 26.3 — 7.5 — 17.2 — 22.3 —
Arkansas River West Braid Brook Trout September 1994 Filename AR05BK.ANU Body scale constant =11.25
1992 1 2+ 13.5 — 7.2 . — 10.3 — 1991 1 3+ 16.8 — 7.2 — 10.7 — 14.9 1990 2 4+ 24.7 2.00 8.6 2.47 15.6 4.46 20.8 2.22 23.4 1.91
Tennessee Creek Lower site Brook Trout September 1994 Filename TNLW04BK.ANU Body scale constant = 11.25
1993 0 1+ ... - ..... 1992 1 2+ 19.0 — 9.1 — 14.9 — 1991 2 3+ 19.5 0.50 8.0 0.25 12.5 0.44 16.2 0.16
35 Table I (continued). Arkansas River back-calculated lengths (cm) of brown trout collected during CDOW 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.E Class (yr)
Halfmoon Creek of the Arkansas Site 9 Brook Trout September 1994 Filename HC09BK.ANU Body scale constant = 19.29
1994 4 0 6.9 0.19 1993 5 1+ 12.1 0.60 8.4 0.71 1992 13 2+ 16.6 0.32 9.0 0.31 13.9 0.34 1991 2 3+ 20.4 0.75 9.1 0.22 15.0 0.20 18.4 0.56
Arkansas River Site 14 Lake Creek Rainbow Trout September 1994 Filename AR14RB.ANU Body scale constant = 50.00
1993 . 1 1+ 18.2 13.5 ___- 1992 2 2+ 19.1 0.55 11.6 0.66 15.6 1.25 1991 2 3+ 21.6 0.55 10.1 0.11 14.2 0.51 17.6 1.20
Arkansas River Site 12 Fisherman's Bridge Rainbow Trout October 1994 Filename AR12RB.AND Body scale constant = 50.00
1993 1 1 + 23.0 .... 13.8 .... 1992 8 2+ 24.0 1.34 12.4 0.53 19.9 1.17 1991 5 3+ 29.6 2.64 14.2 0.44 20.5 1.87 27.0 2.30 1990 5 4+ 34.0 1.58 13.0 0.57 20.7 1.28 27.6 1.88 31.6 1.96
Arkansas River Site 12 Fisherman's Bridge Rainbow Trout October 1994 Filename AR12RB.ANU Body scale constant = 76.19
1993 1 1+ 23.0 15.1 .... 1992 8 2+ 24.0 1.34 14.0 0.50 20.4 1.13 1991 5 3+ 29.6 2.64 15.8 0.47 21.4 1.84 27.2 2.30 1990 5 4+ 34.0 1.58 14.9 0.55 21.9 1.23 28.2 1.81 31.8 1.92
36 Table I (continued). Arkansas River back-calculated lengths (cm) of brown trout collected during CDOW electrofishing operations, August 2002 Year N Age Lc S.E. L, 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.E Class (yr)
Arkansas River West Braid Rainbow Trout September 1994 Filename AR05BRB.ANU Body scale constant = 50.00
1991 1 3+ 23.6 — 11.5 —- 17.7 — 21.5 1990 2 4+ 27.5 0.20 9.8 0.64 13.0 0.42 18.9 0.09 24.7 0.09 1989 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 1996 Filename ARKSRBBC.96 Body scale constant = 50.00
1994 19 2+ 25.8 0.84 15.2 0.53 24.4 0.72 1993 12 3+ 30.7 0.47 14.7 0.65 25.8 1.04 29.9 0.70 1992 10 4+ 34.7 0.99 15.2 0.72 25.4 1.07 32.1 1.24 34.3 1.16 1991 2 5+ 35.5 1.50 12.7 1.21 27.4 0.82 32.3 0.15 34.5 0.84 35.4 1.55 1990 3 6+ 37.3 2.96 16.5 0.80 28.0 1.34 33.1 1.12 35.6 1.79 36.8 2.82 37.1 2.90 1989 2 7+ 34.5 2.50 15.7 L53 27.1 0.81 31.8 1.80 34.0 2.49 34.2 2.49 34.3 2.55 34.5 2.50 1988 1 8+ 34.0 14.7 25.3 28.6 31.3 — — — 33.7 33.8 — 33:9 34.0 — — — — —
37 Table II. Arkansas River back-calculated lengths (cm) of brown trout collected during CDOW 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.E Class (yr)
Arkansas River Brown Trout at Sampling Site ARl(below confluence of East Fork of the Arkansas and Tennessee Creek and upstream of California Gulch) - Collected August 14, 2002
2001 29 1+ 13.6 0.27 8.2 0.20 2000 21 2+ 19.4 0.33 8.4 0.27 14.3 0.25 1999 17 3+ 23.2 0.31 8.5 0.25 14.5 0.52 19.6 0.53 1998 4 4+ 26.2 0.42 7.9 0.36 13.4 1.36 18.3 1.48 22.7 1.02 1997 4 5+ 28.5 0.56 8.3 0.65 12.1 1.09 17.6 1.17 22.6 0.69 26.0 0.97
Arkansas River Brown Trout at Sampling Site AR3A (downstream of California Gulch) - Collected August 14, 2002
2001 35 1+ 15.1 0.35 10.1 0.15 2000 24 2+ 21.7 0.41 11.6 0.30 16.7 0.42 1999 19 3+ 27.4 0.36 10.9 0.24 18.2 0.36 24.2 0.50 1998 4 4+ 32.2 0.67 12.2 1.16 17.3 0.62 24.3 0.81 29.5 1.00 1997 1 5+ 35.4 23.7 — 28.9 — 12.0 — 18.8 — — 34.1 — Arkansas River Brown Trout at Sampling Site AR4 (Doc Smith's Ranch) Collected August 15, 2002
2001 42 1+ 16.0 0.39 10.3 0.19 2000 32 2+ 24.0 0.39 11.6 0.25 17.5 0.41 1999 23 3+ 30.1 0.35 11.4 0.17 18.3 0.48 25.5 0.42 1998 15 4+ 34.1 0.41 12.0 0.23 18.1 0.61 24.8 0.74. 30.3 0.54 1997 3 5+ 38.5 0.68 11.5 0.60 17.4 1.54 24.5 1.02 30.3 1.35 34.5 1.33 1996 1 6+ 40.3 9.5 12.1 15.5 .__. 21.8 — — — — 38.7 33.8 — — 1995 4 7+ 41.8 0.97 10.7 0.39 13.8 0.47 19.2 0.68 24.3 1.09 30.5 0.72 36.1 1.17 39.4 1.15 1994 1 8+ 41.2 — 11.3 — 13.3 — 17.4 — 18.7 — 23.9 32.6 — 36.7 — 39.0 —
38 Table II (continued). Arkansas River back-calculated lengths (cm) of brown trout collected during CDOW electrofishing operations, August 2002 Year N Age Lc S.E. L, 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.E Class (yr)
Arkansas River Brown Trout at Sampling Site AR5 (above Empire Gulch) - Collected August 15, 2002
2001 27 1+ 1-6.7 0.38 11.4 0.25 2000 28 2+ 24.1 0.46 13.0 0.42 19.4 0.50 1999 9 3+ 30.3 0.47 12.2 0.36 19.3 0.56 26.5 0.36 1998 8 4+ 33.6 0.74 12.6 0.49 19.3 0.77 25.9 0.65 30.9 0.74 1997 2 5+ 35.9 0.11 12.7 0.55 18.1 0.67 25.0 0.44 29.5 1.45 34.1 0.76
Arkansas River Brown Trout at Sampling Site 6A (near PanArk Lodge) - Collected August 15, 2002
2001 17 1+ 14.2 0.35 8.3 0.26 2000 22 2+ 17.7 0.59 8.3 0.25 12.2 0.60 1999 16 3+ 26.1 1.04 8.3 0.25 14.2 0.72 20.7 0.96 1998 20 4+ 28.0 0.66 8.7 0.30 13.4 0.52 18.4 0.60 23.9 0.76 1997 15 5+ 30.2 0.96 8.0 0.55 12.2 0.96 17.9 1.25 22.9 1.26 27.1 1.09 1996 9 6+ 35.4 0.55 8.6 0.40 13.5 1.10 18.6 0.98 24.4 1.33 29.9 0.81 33.1 0.66 1995 4 7+ 37.7 0.20 7.5 0.47 10.8 0.30 14.7 0.55 18.2 0.28 23.7 0.58 29.6 1.28 34.0 0.52 1994 1 8+ 9.2 12.5 17:7 23.2 -- 41.1 — — — — — 28.8 — 32.5 — 35.7 — 38.8 — 1993 1 8.3 13.2 16.6 -- 9+ 40.1 — — 11.0 — — ~ 23.0 — 25.8 — 31.4 — 35.8 — 39.2 — Arkansas River Brown Trout at Sampling Site 6 (downstream of Kobe Bridge) - Collected August 16, 2002
2001 28 1+ 15.9 0.35 9.5 0.23 2000 26 2+ 25.0 0.36 10.3 0.27. 18.6 0.37 1999 15 3+ 30.4 0.42 11.6 0.73 19.1 0.83 26.2 0.63 1998 5 4+ 34.8 1.52 12.4 1.19 18.9 1.24 25.8 1.59 32.0 1.30
39 Table II (continued). Arkansas River back-calculated lengths (cm) of brown trout collected during CDOW 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.E Class (yr)
Arkansas River Brown Trout at Sampling Site 7 (near Granite) - Collected August 16,2002
2001 31 . 1 + 16.5 0.38 9.1 0.27 2000 18 2+ 24.5 0.24 9.0 0.,23 16.9 0.28 1999 17 3+ 29.2 0.45 8.9 0.,41 16.9 0.63 24.1 0.52 1998 6 4+ 31.6 0.73 9.3 0.80 15.0 0.85 22.2 1.25 27.5 1.10 1997 1 5+ 32.9 9.3 ~ .13.1 18.8 — - 22.6 -- — — — — 29.6 — • 1996 3 6+ 35.6 0.21 6.8 0.61 11.5 0.43 15.7 1.48 21.0 1.92 27.2 0.79 30.8 0.57
East Fork of Arkansas River Brown Trout at Sampling Site EF1 (upstream of CO Highway 91 Bridge) - Collected August 14, 2002
2001 24 1+ 12.2 0.29 8.5 0.25 2000 7 2+ 15.3 0.27 8.5 0.37 11.7 0.49 1999 5 3+ 16.2 0.16 7.7 0.28 10.7 0.28 13.7 0.32 1998 16 4+ 18.5 0.22 8.1 0.17 11.0 0.31 14.2 0.42 16.9 0.34 1997 3 5+ 20.8 0.23 7.8 0.27 10.1 0.44 13.6 0.81 17.0 0.64 19.6 0.27 1996 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 0.27 1995 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 CO Highway 24 Bridge) - Collected August 13,2002
2001 22 1+ 12,.4 0.32 8.4 0.21 2000 16 2+ 17.4 0.25 8.9 0.17 13.8 0.27 1999 30 3+ 22,,6 0.45 9.6 0.22 14.8 0.26 19.2 0.33 1998 8 4+ 26,.9 1.24 9.7 0.43 14.1 0.63 19.2 0.80 23.4 1.00
40 Table II (continued). Arkansas River back-calculated lengths (cm) of brown trout collected during CDOW 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.E Class (yr)
Tennessee Creek Brown Trout at Sampling Site 7 (below the powerline) - Collected August 13,2002
2001 19 1+ 12.7 0.33 9.2 0.21 2000 13 2+ 16.4 0.39 9.1 0.15 12.9 0.22 1999 9 3+ 18.0 0.52 9.1 0.18 11.4 0.32 14.2 0.46 1998 14 4+ 20.7 0:32 9.4 0.18 11.6 0.33 14.5 0.38 17.6 0.34 1997 16 5+ 24.0 0.42 9.8 0.16 12.4 0.29 15.6 0.41 18.6 0.58 21.7 0.49 1996 8 6+ 25.8 0.53 9.2 0.29 11.2 0.39 13.7 0.46 16.7 0.57 20.4 0.53 23.7 0.51 1995 2 7+ 28.9 1.00 9.3 0.16 11.0 0.18 13.4 0.83 16.1 1.88 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 BIOMETRICS IN 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 "nearly identical." 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 by the data.
The analysis reflected in the 2002 report relied upon length-age relationships derived from 1994 sampling data for another sampling station, AR4. Additional analyses was recently completed using 2002 length and scale data for each sampling site, and data from AR2 that was taken in 1994. These two sets of data indicate similar life table results, 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. These analyses are included in DOW's updated report that summarizes the data from 1985 through August 2002. DOW maintains that AR1 does appear to be adversely affected.
The 1994 age and growth data set that was used to generate the life table data for site AR1 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 corresponds to study site AR4 - Doc Smith's Ranch. The data set was used to generate the life table 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, we chose not to use the September 1994 scale sets for study site AR2 because 1) the data sets were much smaller, and 2) sampling at the station was discontinued after 1994 because it was a braided channel with degraded habitat. In retrospect, the 1994 scale set for study site AR2 was the better choice to partition the brown trout population at AR1 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 by California Gulch is not justified on the basis of age." DOW stated that fish were likely 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 are in the vicinity of California Gulch, are impacted by California Gulch which, as noted later by CEC, is downstream of these sampling stations.
2. Incomplete and Obsolete Data - CEC notes apparent inconsistencies in the reporting of the data. First, CEC states that 1994 scale data were not accurately reflected in Table 2 for AR2. These data have been re-analyzed in the updated Report; therefore, this comment has been superceded. Second, CEC contends that Fall of 1994 Tennessee Creek data were not presented in Tables 1 or 2. The 1994 Tennessee 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 Powerline Crossing and above the confluence with the Arkansas River for 1994 are not known to exist.
In addition, CEC asserts that length-age relationships may have improved as water quality has improved downstream of the remedial actions. In DOW's updated analysis, life table data for study site AR2 for the years 1989 and 1994 were recalculated using age and growth data from scales collected at AR2 in September of 1994 and August 2002. Both scale sets indicate a substantial number of brown trout estimated to be five years old, and a small number to be six years old. In addition, in the updated report, scales collected at each study site in August of 2002 were used to generate site-specific age and growth relationships at each study site. This approach is 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 the predominant methodology for estimating age populations. See, e.g., "Age and Growth 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 in death, and the other in the crippling offish, thus skewing the very population data the method is designed to measure.
DOW has considerable experience with scaling studies; therefore, inaccuracies associated with the method are minimized. As for the concern about underestimating numbers of older fish, DOW did estimate that over 11% of the fish sampled were five years or older. However, there were far fewer at the sites apparently impacted by contamination. Thus, the method does allow DOW to determine the age of fish over three 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, the use of otoliths or fin rays to more definitively age older fish is particularly unwarranted. DOW has, however, initiated tagging in an effort to more clearly elucidate 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 the control 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 that AR1 is not impacted by heavy metals. Bioaccumulation of cadmium in liver and kidney tissues of brown trout downstream of the Leadville Drain trnnel on the East Fork of the Arkansas River and at all sites in the'Pj?' ~ ^7"";i tne u iper Arkansas River was well documented in 1985 (Nehring 1986), and significant differences in water 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 population biometrics in the Upper Arkansas River. Colorado Division of Wi dlife Report.
Nehring, R.B. 1986. An Evaluation of the Possible Impacts of F avy Metal Pollution on the Brown Trout Population of the Upper Arkansas ;ver. Colorado Division of Wildlife Report.