Appendix H

ESTIMATING FISH DENSITIES
ENVIRONMENTAL IMPACT STATEMENT 253

APPENDIX H: ESTIMATING FISH DENSITIES 

ESTIMATING REPRODUCING DENSITIES OF FISH 

Fish density was determined by using available data from existing reports and research that was 

conducted to measure fish densities in lakes. The Liss et al. 1999 Phase II report contains a table 

(table 4.3) of mark-and-recapture densities for 10 lakes with reproducing (self-sustaining) fish 

populations. In that table, the average reported density for each of the 10 lakes was applied to each year 

between 1989 and 2003. For these 10 lakes, the data collected by Oregon State University and the U.S. 

Geological Survey are listed in table H-1. 

For some of the lakes, fish densities were estimated from mark-and-recapture data for sampled 

reproducing populations (Liss et al. 1998), stocking records, and calculated annual mortality rates of 

stocked fish. Others were estimated from a variety of other information reported in Liss et al. 1998, 

including apparent impacts to long-toed salamanders and the condition of fish in a particular lake. A 

density of 222 fish/acre was considered to be the average density for reproducing fish populations in lakes 

with high densities of fish. Unless a lake was reported to have a lower density of reproducing fish or a 

population of brook trout, a density of 222 fish/acre was used for each year for lakes with reproducing 

fish. 

Reproducing brook trout populations are seldom maintained at low densities and have been reported to 

reach densities as high as 700 fish/acre. For lakes in the North Cascades Complex with reproducing brook 

trout populations, the following numbers were used: an average of 222 fish/acre for lakes with high 

densities and a maximum of 700 fish/acre (average of 461 fish/acre). 

There were few lakes with low densities of reproducing fish; the densities in these lakes ranged from 11 

to 53 fish/acre, for an average of 33 fish/acre. Other lakes contained low densities of reproducing fish, 

where reproduction was inadequate to sustain fish populations. If these low-density reproducing 

populations are not supplemented with hatchery fish, they would likely be eliminated over a period of a 

few decades due to variations in reproductive success. The average value of 33 fish/acre was applied to 

these lakes for each year between 1989 to 2003. 

ESTIMATING DENSITIES FOR LAKES WITH 

NONREPRODUCING FISH AND MIXED-MANAGEMENT LAKES 

Maximum literature values for yearly survival rates of fish stocked in mountain lakes (including both 

natural and angling mortalities) are about 90% survival for the first two years (before fish are large 

enough to be caught by anglers) and 60% each year after they enter the sport fishery. For the first two 

years after stocking, the stocking density was multiplied by a 90% survival rate. After the first two years, 

a 60% survival rate was used. Year-by-year after stocking, fish numbers for a stocked year class generally 

declined in an exponential fashion until about the 10th year after stocking, when approximately 

1 fish/acre would be left. 
A PPENDIXES

254 DRAFT MOUNTAIN LAKES FISHERY MANAGEMENT PLAN

Some lakes have a combination of nonreproducing and reproducing fish. In these mixed-management 

lakes, both approaches were used for estimating density. For each lake, the total density per year was 

calculated. This number represents the total number of stocked fish from each stocked year class and fish 

from natural reproduction that were present in a lake for each calendar year. The total yearly densities for 

each year from 1989 to 2003 are presented in table H-1 for each of the 91 lakes in the North Cascades 

Complex that has a history of fish stocking. 

Using this information, table 6 in the “Alternatives” chapter was generated to show the average density 

for each lake. 
ENVIRONMENTAL IMPACT STATEMENT 255 TABLE H-1: FISH SURVIVAL CALCULATIONS Lake Name NPS Lake Code 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 

Azure MP-09-01 0 0 0 0 0 0 0 0 0 0 0 0 Battalion MLY-02-01 237 289 280 272 252 237 230 267 261 256 242 232 Bear MC-12-01 222 222 222 222 222 222 222 222 222 222 222 222 Berdeen M-08-01 222 222 222 222 222 222 222 222 222 222 222 222 Berdeen, Lower M-07-01 222 222 222 222 222 222 222 222 222 222 222 222 Berdeen, Upper M-09-01 222 222 222 222 222 222 222 222 222 222 222 222 Blum (Largest / Middle No. 3) M-11-01 222 222 222 222 382 420 400 344 287 255 238 230 Blum (Lower / West, No. 4) LS-07-01 461 461 461 461 461 461 461 461 461 461 461 461 Blum (Small / North, No. 2) MC-01-01 0 0 0 0 0 0 0 0 0 0 0 0 Blum (Vista / Northwest, No. 1) MC-02-01 0 0 0 0 0 0 0 0 0 0 0 0 Bouck, Lower DD-04-01 222 222 222 222 222 222 222 222 222 222 222 222 Bouck, Upper DD-05-01 27 69 56 48 28 14 62 53 46 28 69 56 Bowan MR-12-01 77 65 57 34 17 8 111 98 88 53 26 13 Coon MM-10-01 159 213 154 210 152 111 64 32 16 8 4 104 Copper MC-06-01 105 90 78 47 77 60 50 29 15 76 66 58 Dagger MR-04-01 259 259 259 259 259 259 259 259 259 259 259 259 Dee Dee, Upper MR-15-01 53 52 52 51 51 51 51 51 51 51 92 88 Dee Dee (Tamarack, Lower) MR-15-02 43 43 43 43 43 43 43 43 43 43 43 43 Despair, Lower M-14-01 0 0 0 0 0 0 0 0 0 0 0 0 Despair, Upper M-13-01 0 0 0 0 0 0 0 0 0 0 0 0 Diobsud No. 1 LS-01-01 11 61 56 52 35 23 17 14 13 12 11 0 Diobsud No. 2, Lower LS-02-01 74 274 254 236 171 123 98 86 80 77 76 75 Diobsud No. 3, Upper LS-03-01 35 30 27 16 98 85 75 45 99 80 68 40 
TABLE H-1: FISH 

SURVIVAL 

CALCULATIONS (CONTINUED) 

256 DRAFT MOUNTAIN LAKES FISHERY MANAGEMENT PLAN Lake Name NPS Lake Code 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 

Doubtful CP-01-01 222 222 222 222 222 222 222 222 222 222 222 222 Doug's Tarn M-21-01 222 222 222 222 222 222 222 222 222 222 222 222 East, Lower MC-14-02 0 0 0 0 0 0 0 0 0 0 0 0 East, Upper MC-14-01 0 0 0 0 0 0 0 0 0 0 0 0 Firn MP-02-01 82 73 44 22 11 5 3 1 1 0 0 26 Green M-04-01 222 222 222 222 222 222 222 222 222 222 222 222 Green Bench LS-04-01 0 0 0 0 0 0 0 0 0 0 0 0 Hanging MC-08-01 222 222 222 222 222 222 222 222 222 222 222 222 Hidden SB-01-01 127 115 82 58 93 82 75 58 93 82 75 58 Hidden Lake Tarn EP-14-01 10 5 53 47 42 25 13 6 54 47 42 25 Hi-Yu M-01-01 20 10 5 3 1 112 100 90 138 103 82 48 Hozomeen HM-02-01 461 461 461 461 461 461 461 461 461 461 461 461 Ipsoot LS-06-01 100 100 100 100 100 100 100 100 100 100 100 100 Jeanita DD-01-01 78 56 44 39 36 34 34 33 33 33 33 33 Kettling MR-05-01 103 103 103 103 103 103 103 103 103 103 103 103 Kwahnesum MC-07-01 199 173 128 72 188 155 132 78 39 182 156 136 McAlester MR-10-01 204 204 204 204 204 204 204 204 204 204 204 204 Middle, Lower MC-16-02 0 0 0 0 0 0 0 0 0 0 0 0 Middle, Upper MC-16-01 0 0 0 0 0 0 0 0 0 0 0 0 Monogram M-23-01 264 243 232 227 225 223 275 269 264 247 235 228 Monogram Tarn M-23-11 50 50 50 50 50 50 50 50 50 50 50 50 Nert M-05-01 0 0 0 0 0 0 0 0 0 0 0 0 Noisy Creek, Upper LS-14-01 0 0 0 0 0 0 0 0 0 0 0 No Name PM-01-01 83 69 58 35 84 69 59 35 17 9 4 2 Panther Potholes, Lower RD-05-02 77 141 106 80 46 98 79 67 39 20 10 5 Panther Potholes, Upper RD-05-01 288 234 137 69 34 17 9 4 2 1 0 0 Pegasus EP-10-01 0 0 0 0 0 0 0 0 0 0 0 
TABLE H-1: FISH SURVIVAL CALCULATIONS (CONTINUED)

ENVIRONMENTAL IMPACT STATEMENT 257 Lake Name NPS Lake Code 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 

Pond SE of Kettling Lakes MR-09-01 29 26 16 8 44 38 33 20 10 45 38 34 Quill, Lower M-24-02 58 56 53 45 39 36 35 34 33 33 33 33 Quill, Upper M-24-01 54 52 50 43 38 36 34 34 33 33 33 33 Rainbow MR-14-01 233 233 233 233 233 233 233 233 233 233 233 233 Rainbow, Upper (North) MR-13-01 646 578 346 173 87 43 22 11 5 3 1 1 Rainbow, Upper (South) MR-13-02 114 150 105 71 39 20 10 34 29 25 15 7 Rainbow, Upper (West) MM-11-01 112 100 60 30 15 8 4 2 1 40 36 33 Redoubt MC-11-01 0 0 0 0 0 0 0 0 0 0 0 0 Reveille, Lower MC-21-02 0 0 0 0 0 0 0 0 0 0 0 0 Reveille, Upper MC-21-01 0 0 0 0 0 0 0 0 0 0 0 0 Ridley HM-03-01 108 87 51 57 42 32 65 51 42 71 54 89 Sky EP-13-01 0 0 0 0 0 0 0 0 0 0 0 Skymo PM-03-01 222 222 222 222 222 222 222 222 222 222 222 222 Sourdough PM-12-01 461 461 461 461 612 748 719 657 571 652 611 585 Sourpuss ML-01-01 0 0 0 0 0 0 0 0 0 0 0 0 Stiletto MR-01-01 47 40 36 21 11 5 41 36 31 19 9 5 Stout EP-09-02 222 222 222 222 222 222 222 222 222 222 222 222 Stout, Lower EP-09-01 222 222 222 222 222 222 222 222 222 222 222 222 Sweet Pea ML-02-01 36 30 25 15 36 30 25 15 8 4 41 36 Talus Tarn M-06-01 0 0 0 0 0 0 0 0 0 0 0 0 Tapto, Lower MC-17-03 0 0 0 0 0 0 0 0 0 0 0 0 Tapto, Middle MC-17-02 0 0 0 0 0 0 0 0 0 0 0 0 Tapto, Upper MC-17-01 0 0 0 0 0 0 0 0 0 0 0 0 Tapto, West MC-17-04 0 0 0 0 0 0 0 0 0 0 0 0 Thornton, Lower M-20-01 95 85 51 26 13 6 3 2 1 112 101 91 Thornton, Middle M-19-01 98 72 57 33 162 139 122 73 165 134 114 67 Thunder RD-02-01 628 413 269 190 124 90 64 48 40 37 35 34 
TABLE H-1: FISH 

SURVIVAL 

CALCULATIONS (CONTINUED) 

258 DRAFT MOUNTAIN LAKES FISHERY MANAGEMENT PLAN Lake Name NPS Lake Code 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 

Tiny MC-15-01 0 0 0 0 0 0 0 0 0 0 0 0 Torment ML-03-01 7 40 35 31 18 9 47 40 35 21 10 5 Trapper GM-01-01 222 222 222 222 222 222 222 222 222 222 222 222 Triplet, Lower SM-02-01 193 193 193 193 193 193 193 193 193 193 193 193 Triplet, Upper SM-02-02 186 186 186 186 186 186 186 186 186 186 186 186 Triumph M-17-01 75 61 51 30 108 91 79 47 94 75 63 37 Unnamed FP-01-01 0 0 0 0 0 0 0 0 0 0 0 Unnamed MR-11-01 29 81 65 52 71 51 92 70 54 71 52 40 Unnamed MR-16-01 37 37 37 37 37 37 37 37 37 37 37 37 Vulcan ML-04-01 0 0 0 0 0 0 0 0 0 0 0 0 Wilcox/Lillie, Upper EP-06-01 257 240 301 289 281 257 240 231 226 224 223 223 Wilcox/Sandie, Lower EP-05-01 256 239 230 226 298 290 282 258 240 231 227 224 Wild MC-27-01 0 0 0 0 0 0 0 0 0 0 0 0 Willow HM-04-01 210 166 97 80 80 74 106 86 71 96 90 129