G.G.Oliver and Associates Environmental Science

Transcription

1 G.G.Oliver and Associates Environmental Science Watershed Restoration Aquatic Science Fisheries Research Kootenay Region Small Lakes Stocking Assessment: 22 Prepared for Ministry of Water, Land and Air Protection 25 Industrial Rd. G Cranbrook, B.C. V1C 7G5 Prepared by G. G. Oliver, M.Sc., R.P.Bio. GG Oliver and Associates Environmental Science st Ave S. Cranbrook, B.C. V1C 6Y3 January 23

2 EXECUTIVE SUMMARY Twelve small lakes in the Kootenay Region were investigated in September through October 22 to assess the performance of selected rainbow trout stocks intended for use in monoculture systems or lakes having a coarsefish presence. Gillnet surveys were completed at Boundary and Summit lakes in the West Kootenay and Echo (N and S), Edwards, Grundy, Horseshoe, Jim Smith, Kaufman, Larchwood, Norbury and Rosen lakes in the East Kootenay. Length-weight relationships, lengthat-age and condition factor were determined and evaluated against current stocking rates and management regimes. Measurements of total dissolved solids (TDS) and ph were also collected to update current water chemistry conditions. Condition factor ranged from a low of 9.66 to high of Small lakes currently under monoculture management regimes utilizing Pennask all female sterile stocks displayed the best condition while coarsefish lakes utilizing Blackwater strains demonstrated a poorer condition. Only in the former case was small lake management objectives achieved. In some cases, survival of Blackwater strains in coarsefish lakes was extremely poor. The results of netting surveys for candidate lakes are summarized individually and recommendations to changes in current management strategies are provided. January 23 ii

3 ACKNOWLEDGEMENTS The following people are gratefully acknowledged for contributions of information and assistance during this study: Ministry of Water, Land and Air Protection W.T. Westover, Fisheries Biologist, Cranbrook, B.C. J. Bell, Fisheries Technician, Nelson, B.C. Kevin Franck and Associates Kevin Franck, Draftsman, Cranbrook, B.C. Bill Westover and John Bell assisted with netting surveys and provided sources of information necessary in the completion of the report. Kevin Franck provided all digitizing and drafting services during report preparation. January 23 iii

4 TABLE OF CONTENTS EXECUTIVE SUMMARY...II ACKNOWLEDGEMENTS...III TABLE OF CONTENTS...IV LIST OF TABLES...VI LIST OF FIGURES...VII 1. INTRODUCTION BACKGROUND METHODS WATER CHEMISTRY FISH SAMPLING ANALYTICAL PROCEDURES RESULTS PHYSICAL AND CHEMICAL CHARACTERISTICS BIOLOGICAL CHARACTERISTICS Boundary Lake Echo Lake North Echo Lake South Edwards Lake Grundy Lake Horseshoe Lake Jim Smith Lake Kaufman Lake Larchwood Lake Norbury Lake Rosen Lake Summit Lake CONDITION FACTOR, STOCKING DENSITY AND ANGLER USE...5 January 23 iv

5 4. DISCUSSION LITERATURE CITED...54 APPENDIX BATHYMETRIC MAPS FOR SELECTED LAKES...55 APPENDIX PHOTOGRAPHIC PLATES...65 January 23 v

6 LIST OF TABLES TABLE 1. PHYSICAL AND CHEMICAL CHARACTERISTICS OF SMALL LAKES IN THE STUDY AREA.7 TABLE 2. BACK-CALCULATED LENGTHS AT SUCCESSIVE ANNULI FOR RAINBOW TROUT IN ECHO LAKE S. 95% CONFIDENCE LIMITS ARE SHOWN IN BRACKETS TABLE 3. BACK-CALCULATED LENGTHS AT SUCCESSIVE ANNULI FOR RAINBOW TROUT IN EDWARDS LAKE. 95% CONFIDENCE LIMITS ARE SHOWN IN BRACKETS...19 TABLE 4. BACK-CALCULATED LENGTHS AT SUCCESSIVE ANNULI FOR RAINBOW TROUT IN GRUNDY LAKE. 95% CONFIDENCE LIMITS ARE SHOWN IN BRACKETS TABLE 5. BACK-CALCULATED LENGTHS AT SUCCESSIVE ANNULI FOR RAINBOW TROUT IN HORSESHOE LAKE. 95% CONFIDENCE LIMITS ARE SHOWN IN BRACKETS....3 TABLE 6. BACK-CALCULATED LENGTHS AT SUCCESSIVE ANNULI FOR RAINBOW TROUT IN LARCHWOOD LAKE. 95% CONFIDENCE LIMITS ARE SHOWN IN BRACKETS...38 TABLE 7. BACK-CALCULATED LENGTHS AT SUCCESSIVE ANNULI FOR RAINBOW TROUT IN SUMMIT LAKE. 95% CONFIDENCE LIMITS ARE SHOWN IN BRACKETS January 23 vi

7 LIST OF FIGURES FIGURE 1. LOCATION OF STUDY AREA....3 FIGURE 2. RAINBOW TROUT STOCK SELECTION AND STOCKING RATE AT BOUNDARY LAKE FROM 1997 TO FIGURE 3. LENGTH FREQUENCY DISTRIBUTION OF EASTERN BROOK TROUT SAMPLED IN BOUNDARY LAKE ON OCTOBER 18, FIGURE 4. LENGTH-WEIGHT RELATIONSHIP FOR EASTERN BROOK TROUT SAMPLED IN BOUNDARY LAKE ON OCTOBER 18, FIGURE 5. LENGTH-WEIGHT PLOT SHOWING EASTERN BROOK TROUT CONDITION FACTOR (B=11.8) FOR BOUNDARY LAKE....1 FIGURE 6. LENGTH FREQUENCY DISTRIBUTION OF RAINBOW TROUT SAMPLED IN ECHO LAKE N ON OCTOBER 8, FIGURE 7. LENGTH-WEIGHT RELATIONSHIP FOR RAINBOW TROUT SAMPLED IN ECHO LAKE N ON OCTOBER 8, FIGURE 8. LENGTH-WEIGHT PLOT SHOWING RAINBOW TROUT CONDITION FACTOR (B=13.51) FOR ECHO LAKE N...12 FIGURE 9. RAINBOW TROUT STOCK SELECTION AND STOCKING RATE AT ECHO LAKE N FROM 1996 TO FIGURE 1. LENGTH FREQUENCY DISTRIBUTION OF RAINBOW TROUT SAMPLED IN ECHO LAKE S ON OCTOBER 8, FIGURE 11. BODY:SCALE RELATIONSHIP FOR RAINBOW TROUT IN ECHO LAKE S FIGURE 12. RAINBOW TROUT STOCK SELECTION AND STOCKING RATE AT ECHO LAKE S FROM 1996 TO FIGURE 13. LENGTH-WEIGHT RELATIONSHIP FOR RAINBOW TROUT SAMPLED IN ECHO LAKE S ON OCTOBER 8, FIGURE 14. LENGTH-WEIGHT PLOT SHOWING RAINBOW TROUT CONDITION FACTOR (B=11.77) FOR ECHO LAKE S FIGURE 15. RAINBOW TROUT STOCK SELECTION AND STOCKING RATE AT EDWARDS LAKE FROM 1996 TO FIGURE 16. LENGTH FREQUENCY DISTRIBUTION OF RAINBOW TROUT SAMPLED IN EDWARDS LAKE ON OCTOBER 9, FIGURE 17. BODY:SCALE RELATIONSHIP FOR RAINBOW TROUT IN EDWARDS LAKE...19 January 23 vii

8 FIGURE 18. LENGTH-WEIGHT RELATIONSHIP FOR RAINBOW TROUT SAMPLED IN EDWARDS LAKE ON OCTOBER 9, FIGURE 19. LENGTH-WEIGHT PLOT SHOWING RAINBOW TROUT CONDITION FACTOR (B=12.13) FOR EDWARDS LAKE...2 FIGURE 2. LENGTH FREQUENCY DISTRIBUTION OF KOKANEE SAMPLED IN EDWARDS LAKE ON OCTOBER 9, FIGURE 21. LENGTH-WEIGHT PLOT SHOWING KOKANEE CONDITION FACTOR (B=11.97) FOR EDWARDS LAKE...22 FIGURE 22. LENGTH FREQUENCY DISTRIBUTION OF RAINBOW TROUT SAMPLED IN GRUNDY LAKE ON SEPTEMBER 23, FIGURE 23. RAINBOW TROUT STOCK SELECTION AND STOCKING RATE AT GRUNDY LAKE FROM 1996 TO FIGURE 24. BODY:SCALE RELATIONSHIP FOR RAINBOW TROUT IN GRUNDY LAKE...25 FIGURE 25. LENGTH-WEIGHT RELATIONSHIP FOR RAINBOW TROUT SAMPLED IN GRUNDY LAKE ON SEPTEMBER 23, FIGURE 26. LENGTH-WEIGHT PLOT SHOWING RAINBOW TROUT CONDITION FACTOR (B=11.42) FOR GRUNDY LAKE...27 FIGURE 27. RAINBOW TROUT STOCK SELECTION AND STOCKING RATE AT HORSESHOE LAKE FROM 1996 TO FIGURE 28. LENGTH FREQUENCY DISTRIBUTION OF RAINBOW TROUT SAMPLED IN HORSESHOE LAKE ON SEPTEMBER 25, FIGURE 29. BODY:SCALE RELATIONSHIP FOR RAINBOW TROUT IN HORSESHOE LAKE...3 FIGURE 3. LENGTH-WEIGHT RELATIONSHIP FOR RAINBOW TROUT SAMPLED IN HORSESHOE LAKE ON SEPTEMBER 25, FIGURE 31. LENGTH-WEIGHT PLOT SHOWING RAINBOW TROUT CONDITION FACTOR (B=1.12) FOR HORSESHOE LAKE...31 FIGURE 32. RAINBOW TROUT STOCK SELECTION AND STOCKING RATE AT JIM SMITH LAKE FROM 1996 TO FIGURE 33. LENGTH FREQUENCY DISTRIBUTION OF YELLOW PERCH SAMPLED IN JIM SMITH LAKE ON SEPTEMBER 3, FIGURE 34. LENGTH-WEIGHT RELATIONSHIP FOR YELLOW PERCH SAMPLED IN JIM SMITH LAKE ON SEPTEMBER 3, FIGURE 35. LENGTH-WEIGHT PLOT SHOWING YELLOW PERCH CONDITION FACTOR (B=1.32) FOR JIM SMITH LAKE...34 January 23 viii

9 FIGURE 36. RAINBOW TROUT STOCK SELECTION AND STOCKING RATE AT KAUFMAN LAKE FROM 1997 TO FIGURE 37. LENGTH FREQUENCY DISTRIBUTION OF EASTERN BROOK TROUT SAMPLED IN KAUFMAN LAKE ON SEPTEMBER 25, FIGURE 38. LENGTH-WEIGHT RELATIONSHIP FOR EASTERN BROOK TROUT SAMPLED IN KAUFMAN LAKE ON SEPTEMBER 25, FIGURE 39. LENGTH-WEIGHT PLOT SHOWING EASTERN BROOK TROUT CONDITION FACTOR (B=11.32) FOR KAUFMAN LAKE FIGURE 4. RAINBOW TROUT STOCK SELECTION AND STOCKING RATE AT LARCHWOOD LAKE FROM 1996 TO FIGURE 41. LENGTH FREQUENCY DISTRIBUTION OF RAINBOW TROUT SAMPLED IN LARCHWOOD LAKE ON SEPTEMBER 26, FIGURE 42. BODY:SCALE RELATIONSHIP FOR RAINBOW TROUT IN LARCHWOOD LAKE FIGURE 43. LENGTH-WEIGHT RELATIONSHIP FOR RAINBOW TROUT SAMPLED IN LARCHWOOD LAKE ON SEPTEMBER 26, FIGURE 44. LENGTH-WEIGHT PLOT SHOWING RAINBOW TROUT CONDITION FACTOR (B=1.91) FOR LARCHWOOD LAKE....4 FIGURE 45. RAINBOW TROUT STOCK SELECTION AND STOCKING RATE AT NORBURY LAKE FROM 1996 TO FIGURE 46. LENGTH FREQUENCY DISTRIBUTION OF EASTERN BROOK TROUT AND RAINBOW TROUT SAMPLED IN NORBURY LAKE ON SEPTEMBER 25, FIGURE 47. RAINBOW TROUT STOCK SELECTION AND STOCKING RATE AT ROSEN LAKE FROM 1996 TO FIGURE 48. LENGTH FREQUENCY DISTRIBUTION OF RAINBOW TROUT SAMPLED IN ROSEN LAKE ON OCTOBER 9, FIGURE 49. LENGTH-WEIGHT RELATIONSHIP FOR RAINBOW TROUT SAMPLED IN ROSEN LAKE ON OCTOBER 9, FIGURE 5. LENGTH-WEIGHT PLOT SHOWING RAINBOW TROUT CONDITION FACTOR (B=1.7) FOR ROSEN LAKE FIGURE 51. RAINBOW TROUT STOCK SELECTION AND STOCKING RATE AT SUMMIT LAKE FROM 1996 TO FIGURE 52. LENGTH FREQUENCY DISTRIBUTION OF RAINBOW TROUT SAMPLED IN SUMMIT LAKE ON OCTOBER 21, FIGURE 53. BODY:SCALE RELATIONSHIP FOR RAINBOW TROUT IN SUMMIT LAKE January 23 ix

10 FIGURE 54. LENGTH-WEIGHT RELATIONSHIP FOR RAINBOW TROUT SAMPLED IN SUMMIT LAKE ON OCTOBER 21, FIGURE 55. LENGTH-WEIGHT PLOT SHOWING RAINBOW TROUT CONDITION FACTOR (B=11.34) FOR SUMMIT LAKE FIGURE 56. A COMPARISON OF RAINBOW TROUT CONDITION FACTORS AMONG REPRESENTATIVE STUDY LAKES....5 FIGURE 57. A COMPARISON OF ANGLER USE AT SELECTED LAKES BASED ON AVAILABLE SLIM DATA. DATA SUMMARIZED AS THE MEAN OF 4 YEARS (1989, 9, 91 AND 96) January 23 x

11 1. Introduction Over the past twenty years, the small lakes management program in the Kootenay Region has included a variety of activities to improve the size and survival of hatchery-maintained rainbow trout fisheries and to expand the quality of local angling opportunities. Earlier management activities focused on special regulations, chemical rehabilitation and lake aeration at several small lakes in the East and West Kootenay. More recently, however, management activities have centered on special stock introductions into selected small lakes to off-set growth impairment due to early maturity issues or coarsefish interactions. To this end, the most appropriate stocks that best maximize rainbow trout production have been considered to improve angling quality at twelve small lakes in the Kootenay Region. The present report evaluates the status of fish populations after five years or less of special stock introduction. 1.1 Background Special stocks employed in the present evaluation include rainbow trout of either Pennask or Blackwater origin. The former stock has been substituted in Premier Lake to support regional hatchery operations since the mid-198 s owing to a chronic problem of early maturity in the original stock that plagued growth and survival of out-planted yearlings in stocking-dependent small lakes throughout the region. Selection for early maturity was artificially hastened by earlier hatchery operations that utilized two year old males as a donor source for fertilization needs during annual egg collections. Substitution of Pennask stock, known for its later maturity, into Premier Lake has corrected the problem and shifted the average age of first maturity to 3 and 4 years for male and female fish, respectively. Manipulation of eggs by heat shock treatment to create sterile females (i.e., all female triploids) has also been included in more recent hatchery operations. As a consequence of their sterile condition, growth efficiencies are directed at somatic development allowing individual females to achieve a larger overall size. Alternatively, Blackwater rainbow stock has been introduced due to their higher survival in coarsefish lakes and their ability to incorporate certain coarsefish species in their diet during later sub-adult and adult life stages. January 23 1

12 The present evaluation includes 2 lakes in the West Kootenay (Boundary and Summit lakes) and 1 lakes in the East Kootenay (Echo North and South, Edwards, Grundy, Horseshoe, Jim Smith, Kaufman, Larchwood, Norbury and Rosen lakes; Fig. 1). Boundary, Edwards, Jim Smith, Norbury and Rosen lakes contain coarsefish whereas Echo North and South, Grundy, Horseshoe, Larchwood and Summit lakes are managed as rainbow trout monoculture systems. Historically, Boundary, Kaufman, Norbury and Rosen lakes have been managed for both rainbow and eastern brook trout. Jim Smith Lake also supports self-sustaining populations of largemouth bass and yellow perch. Echo North and South (1986), Larchwood (1988) and Summit (1986) lakes were chemically rehabilitated to eradicate coarsefish species and establish monoculture fisheries. The purpose of the present study is to evaluate rainbow trout stocks across variable stocking densities and assess rainbow trout growth relative to physical, chemical and biological (single/multiple species) conditions. Stock evaluations examine age and growth and length-weight relationships and compare condition factors across lake environments and management regimes. Updates in chemical lake conditions are also assessed through measurements of ph and conductivity. Recommendations to changes in current management strategies are included where current stocks or stocking densities have not met expectations. 2. Methods 2.1 Water chemistry Total dissolved solids (TDS) and ph were measured at each selected lake during the period of assessment from mid-september through October 22. A 5 ml water sample was collected from the surface near the lake margin where depths exceeded.5 m and analyzed. TDS was measured with an Oakton TDS Testr 1 while ph was measured with an Oakton ph Testr 2; individual meters were calibrated with reference samples prior to use at each lake to assess precision and maintain accuracy. Further adjustments to the TDS meter beyond factory settings were not required over the duration of the study.. January 23 2

13 Figure 1. Location of study area. January 23 3

14 January 23 4

15 2.2 Fish sampling Fish collections were completed by gillnet surveys employing floating and sinking nets; use of a floating net was restricted to Grundy and Horseshoe lakes whereas all other study lakes were sampled by sinking net only. Ninety-two meter standard experimental gangs consisting of 6, 15 X 2.5 m variable mesh panels (ordered as 25, 76, 51, 89, 38 and 64 mm mesh sizes shoreward to lakeward) were deployed in littoral habitats and each set was placed perpendicular to the shoreline. Individual nets were anchored shoreward and lakeward; the lakeward end of the each net was supported with a buoy to mark the endpoint and assist with retrieval. Overnight sets were completed from 15: to 8: hours with an average soak time of ~17 hours. All sets were made from a 4 m aluminum boat. Individual fish samples were measured for length and weight. Fork lengths were obtained with a measuring board to the nearest millimeter and weights were measured to the nearest gram with an Ohaus Model CS 5 (-5 kg) electronic balance; each fish was supported in a plastic cradle that required taring prior to each measurement. A representative number of scales across the size range of the rainbow trout sample were removed within 3-5 rows of the lateral line immediately posterior to the dorsal fin and stored in individual scale envelopes. 2.3 Analytical procedures Rainbow trout scales were cleaned, mounted on a glass slide and read with a 3M TM 8 Microfiche reader at 6X magnification. Measurements of scale radius and distance from nucleus to each annulus were marked on a paper strip, body:scale relationship (mm) determined by regression analysis and lengths at successive annuli back-calculated using Lea s formula (Bagenal 1978). Ages were then assigned to length frequency distributions assembled for each rainbow trout sample. Length-weight data were log-transformed and a regression calculated to confirm isometric or allometric growth patterns among all sample populations. Fulton s condition factor (cf Bagenal 1978) was then used to compare the well being of fish sampled from each lake based on present stocking densities and corresponding lake productivity. Coefficients for each fish sample were again generated by regression analysis to derive the condition factor. For each regression calculated, a plot of residuals was inspected for equality of variance among individual samples. January 23 5

16 3. Results 3.1 Physical and chemical characteristics A summary of the physical and chemical characteristics of selected lakes in the study area are provided in Table 1. With the exception of Boundary Lake, all other lakes occur at a relatively low elevation and generally below 1 m. The majority of candidate systems are considered small kettle lakes in nature; water level fluctuation occurs primarily through direct surface run-off during snowmelt or natural upwelling springs. Boundary, Edwards, Jim Smith, Norbury, Rosen and Summit support inlet or outlet streams however, the amount of natural recruitment to each water body is unknown but considered marginal. The mean surface area of the study lakes is ~34 ha; exclusively, Summit Lake has the largest surface area at 15 ha. The majority of lakes are also considered shallow with maximum depths ranging from 6.5 to 17 m and mean depths ranging from m. Accordingly, the amount of shoal area is considered high with an average of 8% littoral area estimated across all lakes. ph ranges from 7.1 to 8.8 but all lakes lie within an acceptable limit for fish production. Total dissolved solids are highly variable ranging from 83 to 55 ppm. Across the range of candidate lakes, a comparison of MEI (Ryder et al. 1974), an index of lake productivity, suggests a production capability that ranges from low to moderate. A summary of lake bathymetry, for candidate lakes with completed physical surveys, is provided in Appendix Biological characteristics Boundary Lake Previous inventories have identified the species composition of Boundary Lake to include eastern brook trout, longnose sucker, rainbow trout and Westslope cutthroat trout (FISS database, Victoria, B.C.). With the exception of longnose sucker, all other species have been introduced through previous stocking programs. The catch January 23 6

17 Table 1. Physical and chemical characteristics of small lakes in the study area. Lake Watershed Latitude Longitude Elevation Surface Maximum Mean Shoal area ph TDS MEI 1 code (m) area (ha) depth (m) depth (m) (ha) (ppm) Boundary ::25 116:53: Echo N :52:35 115:48: Echo S :52:15 115:48: Edwards :5:3 115:7: Grundy :46: 115:39: Horseshoe :34:25 115:31: Jim Smith :29:4 115:5: Kaufman 5:7:5 115:37: Larchwood :57:1 115:47: Norbury :31:5 115:28: Rosen :23:5 115:15: Summit :9:2 117:38: Range MEI = morpho-edaphic index January 23 7

18 composition on October 18, 22 consisted of 12% eastern brook trout and 88% longnose sucker. The latter species ranged in size from 1-4 mm with corresponding weights from g. A review of the more recent stocking records (Fig. 2) in combination with the size distribution of eastern brook trout (Fig. 3), where lengths ranged from 132 to 48 mm, suggests that the population is currently sustained by natural production. Despite the lack of brook trout scale analysis to provide age-at-length information, length frequency distributions likely include age-groups 1+ through 4+. Although Boundary Lake has been planted with Blackwater stock since 1997, the absence of representative age classes from the single sinking gillnet set suggests extremely poor rainbow trout survival or downstream migration in the outlet stream. The length-weight relationship derived for eastern brook trout indicates that growth is isometric and that weight is slightly above expected proportions for the variety of dimensions observed (Fig. 4). Accordingly, the high degree of proportionality over the range of fish size sampled suggests that individuals are in good condition (Fig. 5; Plate 1 (Appendix 2)). 6 5 Numbers stocked Blackwater Genier Blackwater Genier Blackwater Genier Blackwater Genier Blackwater-Dragon AF3N Blackwater AF3N Figure 2. Rainbow trout stock selection and stocking rate at Boundary Lake from 1997 to 22. January 23 8

19 25 2 Percent occurrence Size category (mm) Figure 3. Length frequency distribution of eastern brook trout sampled in Boundary Lake on October 18, Log (W) = Log (FL); r 2 =.99; n=19 Weight (g) Fork length (mm) Figure 4. Length-weight relationship for eastern brook trout sampled in Boundary Lake on October 18, 22. January 23 9

20 Weight = 11.8 Length ; r 2 =.99; n=19 Weight (g) (Length/1)^3 Figure 5. Length-weight plot showing eastern brook trout condition factor (b=11.8) for Boundary Lake Echo Lake North Composition of the catch from a single sinking gillnet set on October 8, 22 consisted entirely of rainbow trout (n=38). The size distribution of trout ranged from mm and all fish were aged as age-group 1+ (Fig. 6). The absence of older fish in the sample brings into question the success of over-winter survival (i.e., owing to oxygen depletion associated with lake metabolism under ice cover); previous investigations in have observed age-groups in the catch with lengths exceeding 5 cm. Notwithstanding, growth is isometric (Fig. 7) and the general condition of fish is high (b=13.51; Plate 2), despite the large amount of scatter around the regression line (Fig. 8). A review of the stocking records indicates a consistent outplanting of 1 all female triploids per year over the last four years (Fig. 9). Observation of the body cavity confirmed the lack of any egg development among individuals and an examination of stomach contents revealed that the majority of fish had been feeding on freshwater shrimp. January 23 1

21 Percent occurrence Size category (mm) Figure 6. Length frequency distribution of rainbow trout sampled in Echo Lake N on October 8, Log (W) = Log (FL); r 2 =.96; n=38 Weight (g) Fork length (mm) Figure 7. Length-weight relationship for rainbow trout sampled in Echo Lake N on October 8, 22. January 23 11

22 6 5 Weight = Length -.5; r 2 =.95; n=38 4 Weight (g) (Length/1)^3 mm Figure 8. Length-weight plot showing rainbow trout condition factor (b=13.51) for Echo Lake N Numbers stocked Blackwater Genier (9.9 g) Blackwater-Dragon (21.7 g) Blackwater-Dragon (42.9 g) Pennask-Hath AF Pennask AF Pennask AF3N Pennask AF3N Pennask AF3N Blackwater AF3N Figure 9. Rainbow trout stock selection and stocking rate at Echo Lake N from 1996 to 22. January 23 12

23 3.2.3 Echo Lake South Rainbow trout (n=18) were the only species encountered in an overnight sinking gillnet set on October 8, 22. Size distribution varied from mm and ages were assigned from (Fig. 1). Size-at-age from scale interpretations are provided in Table 2; lengths estimated from the body:scale relationship incorporate the intercept of the length axis (a=19.71) shown in Figure 11. On average, the largest incremental growth was observed between the second and third year, although differences between year classes was evident (refer to ages 3 and 4; Table 2). Pennask all female triploids have been stocked at a rate of 1 fish per year for the last four years (Fig. 12); interestingly enough, 2 females were found to be egg bound. Similar to the results observed for the north lake, freshwater shrimp were a dominant component of the fall diet of fish sampled in the south lake. A review of the length-weight relationship indicates isometric growth albeit, slightly less than proportional (b=2.79; Fig. 13). Overall, the fish were in good condition (b=11.77; Plates 3 and 4) with considerable scatter observed for the older age-groups; outliers well above the trend line are representative of the two individuals that were egg bound (Fig. 14). Residual plots for each relationship were homoscedastic Percent occurrence Size category (mm) Figure 1. Length frequency distribution of rainbow trout sampled in Echo Lake S on October 8, 22. January 23 13

24 Table 2. Back-calculated lengths at successive annuli for rainbow trout in Echo Lake S. 95% confidence limits are shown in brackets. Age-group n Age Class I II III IV (12.11) (6.31) (13.7) (3.67) (18.83) (11.2) (9.2) (14.97) (14.58) (32.95) Grand Average Fork length (mm) = (Scale radius (mm)); r 2 =.83; n=12 4 Fork length (mm) Scale radius (mm x6) Figure 11. Body:scale relationship for rainbow trout in Echo Lake S. January 23 14

25 12 1 Numbers stocked 8 6 Pennask-Hath AF Pennask-Hath AF Pennask AF Pennask AF3N Pennask AF3N Pennask AF3N Blackwater AF3N Figure 12. Rainbow trout stock selection and stocking rate at Echo Lake S from 1996 to Log (W) = Log (FL); r 2 =.99; n=18 Weight (g) Fork length (mm) January 23 15

26 Figure 13. Length-weight relationship for rainbow trout sampled in Echo Lake S on October 8, Weight (g) Weight = Length ; r 2 =.97; n= (Length/1)^3 mm Figure 14. Length-weight plot showing rainbow trout condition factor (b=11.77) for Echo Lake S Edwards Lake The catch composition (n=56) from a single sinking gillnet set on October 9, 22 consisted of 57% rainbow trout, 3% kokanee and 13% redside shiner; a review of the FISS database currently lists rainbow trout as the only species known to occur in the lake (FISS database, Victoria, B.C.). Redside shiners were illegally introduced in the early 199 s (W.T. Westover, Ministry of Water, Land and Air Protection, Cranbrook, B.C.; pers. comm.) and hence the reason for Blackwater strain introductions of 1, fish per year in the recent past ( ; Fig. 15). The presence of kokanee is related to an unauthorized introduction of fish of unknown origin in the late 199 s although the close proximity of Lake Koocanusa and adjacent spawning tributaries seems a likely source. The kokanee population in Edwards Lake is supported by natural recruitment owing to the presence of a springfed inlet stream; spawning kokanee were observed in the inlet stream at time of survey and considerable redd construction had already taken place. Spawning January 23 16

27 12 1 Numbers stocked 8 6 Blackwater Genier Blackwater Genier Blackwater Genier Blackwater Genier Blackwater Blackwater 4 2 Pennask-Beaver Blackwater-Genier Figure 15. Rainbow trout stock selection and stocking rate at Edwards Lake from 1996 to 22. January 23 17

28 utilization by rainbow trout is also known to occur but the recruitment contribution to the lake has not been evaluated. The size distribution of rainbow trout ranged from mm and included agegroups ; an overlap in size between age-groups 2+ and 3+ was also evident (Fig. 16). Size-at-age information for rainbow trout is provided in Table 3 where incremental growth was more or less comparable between years. The body:scale relationship was again determined from a smaller sub-sample of individuals over the available size range; the intercept of the length axis (b=24.46) was used to backcalculate length at successive ages (Fig. 17). Differences in growth increment between year classes appear related to differences in size after the first year of hatchery rearing. The majority of fish observed in excess of 3 mm were maturing (gamete development in progress) and only 2 of the 32 fish sampled had consumed shiners. Stomach contents consisted primarily of freshwater snails, dragonfly larvae or other aquatic insect larvae Percent occurrence Size category (mm) Figure 16. Length frequency distribution of rainbow trout sampled in Edwards Lake on October 9, 22. January 23 18

29 Table 3. Back-calculated lengths at successive annuli for rainbow trout in Edwards Lake. 95% confidence limits are shown in brackets. Age-group n Age Class I II III (7.6) (4.81) (36.51) (11.71) (29.44) (25.15) Grand Average Growth was again isometric (b=3.18) based on the length-weight relationship (Fig. 18) and, collectively, individuals over the range of sizes provided were in good condition (b=12.13; Fig. 19; Plate 5); the higher variation in condition with age is 6 5 Fork length (mm) = (Scale radius (mm)); r 2 =.89; n=12 4 Fork length (mm) Scale radius (mm x6) Figure 17. Body:scale relationship for rainbow trout in Edwards Lake. January 23 19

30 1 Log (W) = Log (FL); r 2 =.99; n=32 1 Weight (g) Fork length (mm) Figure 18. Length-weight relationship for rainbow trout sampled in Edwards Lake on October 9, Weight = Length ; r 2 =.97; n=32 1 Weight (g) (Length/1)^3 mm Figure 19. Length-weight plot showing rainbow trout condition factor (b=12.13) January 23 2

31 for Edwards Lake. likely related to the smaller sample size for the oldest members and current state of individual maturity. The size distribution of kokanee (n=17) ranged from mm (Fig. 2) yet only those fish >2 mm were sexually mature; scales were not collected at this time. Kokanee were also observed in good condition (Fig. 21). The unauthorized presence of kokanee in the system has certain implications on future growth rates of rainbow trout. In consideration of their present size at maturity and potential for population expansion as well as their high desirability as a prey species, the partial substitution of Gerrard stock for Blackwater stock may be prudent to ensure that kokanee numbers are kept in check. Given the small size of kokanee observed, it is unlikely that a two-tiered fishery would develop at Edwards Lake when the size and abundance of fish in Lake Koocanusa is more attractive to the angling public Percent occurrence Size category (mm) Figure 2. Length frequency distribution of kokanee sampled in Edwards Lake on October 9, 22. January 23 21

32 Weight = Length ; r 2 =.94; 17 Weight (g) (Length/1)^3 mm Figure 21. Length-weight plot showing kokanee condition factor (b=11.97) for Edwards Lake Grundy Lake Rainbow trout was the only species encountered in both day time (sinking and floating gillnet) and over night (sinking gillnet) sets at Grundy (Sowerby) Lake on September 23, 22. Grundy Lake was the only water body sampled during day light hours but owing to the low capture rate, further day time sets were avoided. Despite an overnight set, the lowest sample numbers (n=1) were recorded at Grundy for those study lakes where rainbow trout were actually caught. The size distribution of fish ranged from mm and included age-groups 2+, 3+ and 5+ (Fig. 22). Pennask all female triploids have only been introduced in Grundy Lake over the last two years (Fig. 23) which explains the extent of gamete development of alternate stocks previously used; a single individual was egg bound and two other individuals in the sample were maturing. An examination of the stomach contents of all 1 fish revealed exclusive utilization of freshwater shrimp (i.e., Gammarus sp.). January 23 22

33 Percent occurrence Size category (mm) Figure 22. Length frequency distribution of rainbow trout sampled in Grundy Lake on September 23, 22. January 23 23

34 35 3 Numbers stocked Badger-Tunkwa NRT Genier Badger-Tunkwa Badger-Tunkwa Premier Pennask AF3N Blackwater AF3N Figure 23. Rainbow trout stock selection and stocking rate at Grundy Lake from 1996 to 22. Size-at-age information is provided in Table 4 and contrasts incremental growth differences between stocks. Caution is advised regarding growth interpretations due to back-calculations based on size-at-age averages that incorporate stocks with multiple growth patterns (Fig. 24). Therefore, the generic age information does not separate individual stocks since separation is difficult due to the low sample size. Notwithstanding, growth among members of the present population is isometric (b=2.95; Fig. 25) and individuals are reasonably fit (b=11.42; Fig. 26; Plate 6). Residual plots for each relationship are generally homoscedastic; the inclusion of the egg bound female artificially skews length-weight relationships and should be considered an outlier. This single individual has only been included in the present context owing to low overall sample size. January 23 24

35 Table 4. Back-calculated lengths at successive annuli for rainbow trout in Grundy Lake. 95% confidence limits are shown in brackets. Age-group n Age Class I II III IV V (1.29) (18.4) (8.89) (2.23) (97.55) (12.65) (73.55) Grand Average Fork length (mm) = (Scale radius (mm)); r 2 =.97; n=9 4 Fork length (mm) Scale radius (mm x6) Figure 24. Body:scale relationship for rainbow trout in Grundy Lake. January 23 25

36 1 Log (W) = Log (FL); r 2 =.99; n=1 Weight (g) Length (mm) Figure 25. Length-weight relationship for rainbow trout sampled in Grundy Lake on September 23, 22. January 23 26

37 Weight = 11.42(length) ; r 2 =.99; n= Weight (g) Length/1 (mm)^3 Figure 26. Length-weight plot showing rainbow trout condition factor (b=11.42) for Grundy Lake. January 23 27

38 3.2.6 Horseshoe Lake Rainbow trout (n=5) was the only species captured in a floating and sinking gillnet set on September 24, 22. Pennask all female triploids have been stocked in Horseshoe Lake since 1999 at a stocking rate of 3 fish per year (Fig. 27). Rainbow trout ranged from mm and included age-groups (Fig. 28). Age determination for the Horseshoe population is provided in Table 5; incremental growth was consistent at ~1 mm per year. The body:scale relationship displayed a wide degree of variation between individuals resulting in the lower correlation coefficient (Fig. 29). Similarly, growth is considered isometric (b=2.66) yet a high degree of scatter about the trend line was evident for the 2 year old age component (Fig. 3). Accordingly, the condition factor displayed the same amount of variation within the same age component and resulted in a lower overall condition factor (b=1.12; Fig. 31; Plate 7). There was no evidence of gamete development in the body cavity of representative fish and an examination of stomach contents showed rainbow feeding on a variety of aquatic invertebrates; again, freshwater shrimp were an important contribution to the fall diet of this population Numbers stocked Pennask-Hath AF Pennask-Hath AF Pennask AF Pennask AF3N Pennask AF3N Pennask AF3N Blackwater AF3N Figure 27. Rainbow trout stock selection and stocking rate at Horseshoe Lake from 1996 to 22. January 23 28

39 Percent occurrence Size category (mm) Figure 28. Length frequency distribution of rainbow trout sampled in Horseshoe Lake on September 25, 22. January 23 29

40 Table 5. Back-calculated lengths at successive annuli for rainbow trout in Horseshoe Lake. 95% confidence limits are shown in brackets. Age-group n Age Class I II III (8.28) (3.41) (18.2) (6.44) (2.16) (13.63) Grand Average Fork length (mm)= (scale radius (mm)); r 2 =.88; n=27 35 Fork length (mm) Scale radius mm (x6) Figure 29. Body:scale relationship for rainbow trout in Horseshoe Lake. January 23 3

41 1 Log (W) = Log (FL); r 2 =.97; n=5 Weight (g) Fork length (mm) Figure 3. Length-weight relationship for rainbow trout sampled in Horseshoe Lake on September 25, Weight = Length ; r 2 =.97; n=5 6 Weight (g) (Length/1)^3 Figure 31. Length-weight plot showing rainbow trout condition factor (b=1.12) for Horseshoe Lake. January 23 31

42 3.2.7 Jim Smith Lake The catch composition (n=2) from a single sinking gillnet set at Jim Smith Lake on September 3, 22 consisted of 85% yellow perch, 5% rainbow trout, 5% largemouth bass and 5% burbot. Species composition from FISS files indicates that eastern brook trout and Westslope cutthroat trout have also been planted historically (FISS database, Victoria, B.C.). Redside shiner is the only indigenous species known to occur in the lake. Although bass were intentionally stocked in the past, both yellow perch (mid-199 s) and burbot (recently) have been illegally introduced. Over the past six years, a variety of rainbow trout stocks have been planted in Jim Smith Lake at a stocking rate of ~6 fish per year (Fig 32). In 22, 5 catchable rainbow were substituted. Based on survey results to date, rainbow trout survival remains extremely low. This outcome is not surprising given the diversity of predators in the system and/or potential competitive interactions among species (particularly perch). 7 6 Numbers stocked Alymer 3N NRT Genier Badger-Tunkwa Badger-Tunkwa Fraser Valley (15.2 g) Blackwater-Dragon AF3N 2 1 NRT Genier Fraser Valley (5 g) Figure 32. Rainbow trout stock selection and stocking rate at Jim Smith Lake from 1996 to 22. January 23 32

43 The size distribution for yellow perch ranged from mm (Fig. 33) and the length-weight relationship suggests that growth is proportionate (b=2.7; Fig. 34; Plate 8). A review of the condition factor suggests a lower value that is likely associated with the high degree of scatter about the trend line (Fig. 35). 6 5 Percent occurrence Size category (mm) Figure 33. Length frequency distribution of yellow perch sampled in Jim Smith Lake on September 3, 22. January 23 33

44 1 Log (W) = Log (TL); r 2 =.9; n=35 Weight (g) Total length (mm) Figure 34. Length-weight relationship for yellow perch sampled in Jim Smith Lake on September 3, Weight = Length ; r 2 =.88; n=35 5 Weight (g) (Length/1)^3 (mm) Figure 35. Length-weight plot showing yellow perch condition factor (b=1.32) for Jim Smith Lake. January 23 34

45 3.2.8 Kaufman Lake The catch composition (n=28) from a single sinking gillnet set on September 25, 22 was 96% eastern brook trout and 4% rainbow trout. Owing to its relatively small size, only alternate year stocking has been practiced on Kaufman Lake; the release rate has been maintained at 5 fish per stocking although multiple strains have been utilized (Fig. 36). Low rainbow trout survival is apparent and may be related to competition with a self-sustaining population of eastern brook trout. The size distribution of eastern brook trout ranged from mm (Fig. 37); the single rainbow trout measured 225 mm. Scales were not collected from brook trout and therefore definitive ages are not included, however, representative age-groups up to 3+ seem plausible based on length frequency information. Proportional growth is indicated for eastern brook trout in Kaufman Lake at present densities (Fig. 38) and, overall, the fish are in good condition (b=11.32; Fig. 39; Plate 9). Residual plots for the latter two relationships were homoscedastic. 6 5 Numbers stocked 4 3 NRT Genier Badger-Tunkwa Premier Figure 36. Rainbow trout stock selection and stocking rate at Kaufman Lake from 1997 to 2. January 23 35

46 25 2 Percent occurrence Size category (mm) Figure 37. Length frequency distribution of eastern brook trout sampled in Kaufman Lake on September 25, Log (W) = Log (FL); r 2 =.99; n=27 Weight (g) Fork length (mm) Figure 38. Length-weight relationship for eastern brook trout sampled in January 23 36

47 25 Kaufman Lake on September 25, Weight (g) 15 1 Weight = Length + 1.5; r 2 =.98; n= (Length/1)^3 mm Figure 39. Length-weight plot showing eastern brook trout condition factor (b=11.32) for Kaufman Lake Larchwood Lake Forty-two rainbow trout were captured in a single sinking gillnet set on September 26, 22 at Larchwood Lake. Pennask all female triploids from Summerland Hatchery have been planted in Larchwood since 1999 at a stocking rate of 3 fish per year (Fig. 4). The size distribution ranged from mm and included age-groups (Fig. 41). Back-calculated ages are based on a body:scale relationship that displays a high degree of scatter (Fig. 42) however, average annual increments in growth of 82, 19 and 64 mm were estimated for age classes 2, 3 and 4, respectively (Table 6). The rather large size at their first year mark is related to the larger average size of fish produced at the Summerland hatchery where water supply temperatures are consistently warmer than that observed at Kootenay Trout Hatchery (R. Ek, Fish Culturist, Wardner, B.C.; pers. comm.). There was a low incidence of gonad development in the older members of the sample; one female was egg bound while 2 other females were maturing. Stomach content analysis indicated that a number of fish had fed heavily on Gammarus ; many stomachs of the fish examined had distended stomachs full of shrimp while others had fed January 23 37

48 extensively on leeches. Growth was isometric but slightly less than proportional (b=2.73; Fig. 43) and fish were generally in good condition (b=1.91; Fig. 44; Plate 1) although considerable scatter was observed about the trend line of the weight on length relationship. Outliers depicted in Figure 44 include either maturing females or the one individual that was egg bound. Table 6. Back-calculated lengths at successive annuli for rainbow trout in Larchwood Lake. 95% confidence limits are shown in brackets. Age-group n Age Class I II III IV (4.77) (12.79) (1.83) (29.34) (22.88) (8.86) (16.4) (18.91) (17.95) Grand Average Numbers stocked Pennask Hath AF Pennask Hath AF Pennask AF Pennask AF3N Pennask AF3N Pennask AF3N Blackwater AF3N Figure 4. Rainbow trout stock selection and stocking rate at Larchwood Lake January 23 38

49 25 from 1996 to Percent occurrence Size category (mm) Figure 41. Length frequency distribution of rainbow trout sampled in Larchwood Lake on September 26, Fork length (mm) = (Scale radius (mm)); r 2 =.78; n=15 4 Fork length (mm) Scale radius (mm x6) Figure 42. Body:scale relationship for rainbow trout in Larchwood Lake. January 23 39

50 1 Log (W) = Log (FL); r 2 =.95; n=42 Weight (g) Fork length (mm) Figure 43. Length-weight relationship for rainbow trout sampled in Larchwood Lake on September 26, weight = 1.91 (length) ; r 2 =.953; n=49 1 Weight (g) (Length/1)^3 (mm) Figure 44. Length-weight plot showing rainbow trout condition factor (b=1.91) for Larchwood Lake. January 23 4

51 3.2.1 Norbury Lake The catch composition (n=24) from a single sinking gillnet set on September 25, 22 consisted of 71% finescale sucker, 17% eastern brook trout, 8% redside shiner and 4% rainbow trout. Once again, the survival of yearling rainbow outplants appear to be marginal. Blackwater strain was introduced over the last two years while earlier introductions have utilized a variety of provincial stocks as well as Gerrard brood (Fig. 45). The limited amount of data collected on sportfish species precludes meaningful interpretation; the size distribution of eastern brook varied from mm (Fig. 46) while the single rainbow measured 3 mm (age 2+). Condition factors calculated for individual brook trout ranged from 7.45 to (mean = 1.77) while the condition factor for the rainbow trout was (refer to Plate 11) Numbers stocked NRT Genier NRT Genier Badger-Tunkwa Badger-Tunkwa Gerrard 1994 brood Gerrard 1996 brood Badger-Tunkwa Blackwater-Dragon AF3N Balckwater AF3N Figure 45. Rainbow trout stock selection and stocking rate at Norbury Lake from 1996 to 22. January 23 41

52 25 Rainbow trout 2 Percent occurrence Size category (mm) Figure 46. Length frequency distribution of eastern brook trout and rainbow trout sampled in Norbury Lake on September 25, Rosen Lake Rainbow trout (n=14) was the only species recorded in the catch during a single sinking gillnet set on October 9, 22. A review of the FISS files for Rosen Lake indicates the presence of natural populations of redside shiner and largescale sucker as well as previous introductions of Westslope cutthroat trout and Eastern brook trout. Both species of coarsefish were observed along the lake margin at time of survey. There is an earlier report of Dolly Varden (bull trout) in the basin that likely stems from a natural origin since Rosen Lake serves as the headwaters for the Little Sand Creek watershed. A variety of provincial rainbow stocks have been planted into Rosen Lake since 1996; most recently, catchable size fish from Abbottsford Hatchery were released in 22 (Fig. 47). The size distribution of rainbow trout in the catch varied from mm and all fish were comprised of age-group 2+ (Fig. 48). All fish in excess of 3 mm were determined to be catchables based on scale interpretation; individual circuli were evenly spaced over the distance of the scale radius suggesting even growth under constant temperature and food ration. An examination of the length-weight relationship reveals that growth is highly proportional (Fig. 49) and that individuals within the sample are reasonably fit (Fig. January 23 42

53 5; Plate 12). Stomach contents were also examined due to the presence of Blackwater all female stock planted in 21. No coarsefish species were found in any gut samples; stomach contents were restricted to aquatic invertebrates entirely. As an aside, kokanee were observed spawning in Little Sand Creek immediately downstream of Rosen Lake outlet. There was no evidence of kokanee in shoal areas at the lake outlet or along the lake margin in the vicinity of the gillnet set at time of survey. Further investigation is warranted however to determine if kokanee spawner distribution extends into localized shoal areas of the lake or attendant tributaries Numbers stocked NRT Genier NRT Genier Badger-Tunkwa Badger-Tunkwa Fraser Valley (15.2 g) Blackwater-Dragon AF3N Fraser Valley (13.7 g) Fraser Valley (5 g) Figure 47. Rainbow trout stock selection and stocking rate at Rosen Lake from 1996 to 22. January 23 43

54 yr old catchables 25 Percent occurrence Size category (mm) Figure 48. Length frequency distribution of rainbow trout sampled in Rosen Lake on October 9, 22. January 23 44

55 1 Log (W) = Log (FL); r 2 =.99; n=14 Weight (g) Fork Length (mm) Figure 49. Length-weight relationship for rainbow trout sampled in Rosen Lake on October 9, Weight = 1.7 Length - 5.1; r 2 =.98; n= Weight (g) (Length/1)^3 mm Figure 5. Length-weight plot showing rainbow trout condition factor (b=1.7) for Rosen Lake. January 23 45

56 Summit Lake Rainbow trout was the only species sampled in a single sinking gillnet set on October 21, 22. Summit Lake has been consistently planted with Pennask stock rainbow since 1996 although a reduction to 1, yearlings per year was instituted in 2 (Fig. 51). The size distribution of the catch ranged from mm and included age-groups (Fig. 52). The body: scale relation demonstrated limited scatter (Fig. 53) and annual growth increments averaged ~11 mm during their second and third years (Table 7). A review of the length-weight relationship shows isometric growth (Fig. 54) and the majority of fish were observed in good condition (Fig. 55; Plate 13); some scatter was again evident for the middle size classes however. Further examination of the body cavity indicated that the largest females were maturing and an analysis of the gut contents showed moderate to heavy feeding activity on aquatic invertebrates. In light of the potential for natural recruitment in this population due to tributary presence, two attendant tributaries were investigated. Bonanza Creek, a large outlet stream, was inspected for juveniles however none were observed. Rainbow trout fry were observed in a small inlet stream that bisects the local park, but in small numbers. The largest inlet stream was dry at time of survey. Further examination of the larger inlet and outlet streams is warranted to determine the contribution of natural recruitment to the lake. Table 7. Back-calculated lengths at successive annuli for rainbow trout in Summit Lake. 95% confidence limits are shown in brackets. Age-group n Age Class I II III (11.12) (8.12) (27.13) (5.78) (34.7) (28.87) Grand Average January 23 46

57 Pennask Pennask Pennask Pennask Numbers stocked Premier Premier Pennask-Premier Figure 51. Rainbow trout stock selection and stocking rate at Summit Lake from 1996 to Percent occurrence Size category (mm) Figure 52. Length frequency distribution of rainbow trout sampled in Summit Lake on October 21, 22. January 23 47

58 Fork length (mm) = (scale radius (mm)); r 2 =.93; n=17 35 Fork length (mm) Scale radius (mm x25) Figure 53. Body:scale relationship for rainbow trout in Summit Lake. 1 Log (W) = Log (FL); r 2 =.99; n=44 1 Weight (g) Fork length (mm) Figure 54. Length-weight relationship for rainbow trout sampled in Summit Lake on October 21, 22. January 23 48

59 Weight = Length ; r 2 =.97;n=44 Weight (g) (Length/1)^3 mm Figure 55. Length-weight plot showing rainbow trout condition factor (b=11.34) for Summit Lake. January 23 49

60 3.3 Condition factor, stocking density and angler use A comparison of rainbow trout condition factors across the 12 study lakes suggests a wide range of fitness from (mean = 11.11); the highest value was determined for Echo Lake N and the lowest value was confirmed at Kaufman Lake (Fig. 56). The only exception was Boundary Lake where rainbow trout were not encountered; the average condition factor for the self-sustaining population of eastern brook trout was substituted in this instance. The higher rainbow trout condition factors were generally associated with monoculture fisheries while the lower condition factors were generally associated with lakes with multiple species that may include coarsefish. With respect to fitness of individual populations, the importance of stocking density cannot be over-stated in consideration of density-dependent growth coupled with lake productivity. Moreover, stocking densities in combination with the appropriate 16 Condition factor % of theoretical stocking 7 Rainbow trout condition factor Eastern brook trout n= n=1 6 5 Echo N Edwards Boundary Echo S Grundy Summit Larchwood Jim Smith Norbury Horseshoe Rosen Kaufman Percentage of theoretical stocking (yearlings) Figure 56. A comparison of rainbow trout condition factors among representative study lakes. January 23 5

61 management regime are generally intended to meet a specific management objective. The array of management regimes can vary from high turnover put and take fisheries to low turnover quality fisheries; the latter option is generally associated with more restrictive regulations to meet quality angling objectives. In the present context, the 12 study lakes are representative of the above-mentioned array of angling opportunities and, as indicated in Figure 55, stocking densities are purposely set below the theoretical stocking rates of individual lakes to ensure that proportional growth is achieved. Management regimes that target special stocks of a higher growth potential, in combination with low stocking density, are intended to improve fishery quality. Further fine-tuning of stocking rates is dependent upon the amount of angler use and corresponding returns to the creel. As an example, both Edwards and Horseshoe fall in the middle range of lake productivity among the 12 study lakes (refer to Table 1). Based on the average of SLIM angler use estimates for 1989, 199, 1991 and 1996, Horseshoe Lake has ~one-third fewer angler days than Edwards Lake (Fig. 57). Higher angler use and anticipated catch at Edwards Number of angler days Echo North Echo South Edwards Horseshoe Larchwood Norbury Sowerby (Grundy) Figure 57. A comparison of angler use at selected lakes based on available SLIM data. Data summarized as the mean of 4 years (1989, 9, 91 and 96). may, in part, explain the higher condition factor if a higher removal in catch reduces January 23 51

62 intra-specific competition. At current stocking levels and lower annual catch at Horseshoe, the standing crop of fish may experience a lower condition factor due to higher competitive interactions. Further analysis of catch data is required, however, to substantiate these assumptions. Alternatively, Echo Lake N and Larchwood are representative of lakes with the highest productivity among study lakes and both are managed under special regulations. Despite the higher angler use at Larchwood, the condition factor is lower. In consideration of the single age class of fish encountered at Echo N, either winterkill or emigration to Echo S may explain the higher condition factor under the present stocking regime and assumed low competitive interaction, if the population fails to expand beyond a single year class. The slightly lower condition factor at Larchwood Lake may be an artifact of the fishery where representative anglers arbitrarily practice catch and release in order to maintain the quality aspects of the fishery. A reduced catch in the presence of continued stocking could increase intraspecific competition. This is not to suggest that the quality of fish at Larchwood Lake is poor, it merely provides a possible explanation for the contrast in condition factors between the two most productive monoculture lakes under special management. 4. Discussion The 12 study lakes have provided an opportunity to compare and contrast special stocks of rainbow trout in monoculture or coarsefish lakes across the region. For the most part, intended management strategies (i.e., special stocks and stocking rates) and objectives (i.e., quantity or quality fisheries) are being met under monoculture conditions where several years of continuous stocking with special all female triploid stocks has occurred. Examples include Echo North and South, Larchwood, Grundy, and Horseshoe lakes. Continued stocking at present levels is recommended to maintain present management objectives; a reduction to 25 yearlings per annum at Horseshoe Lake could be considered in the interest of improving the average condition factor under present levels of harvest. A follow-up assessment should ensue in two years to document changes under a reduced stocking regime if the above recommendation is pursued. Further assessment of Echo North is recommended with respect to over-winter survival. If the population is entirely represented by a single year class that succumbs to winterkill each year, then the present size limit may require adjustment to allow a harvest; it is doubtful that January 23 52

63 yearling fish will exceed the 4 cm size limit within a single growing season. Overall, hatchery operations to provide sterilized fish have been highly successful as evidenced by the low incidence of maturity among special stocks. Substitution of Pennask all females for Premier stock in Summit Lake should be considered if there is no intention of developing a self-sustaining population. If the objective is to continue planting with Premier, then, present levels of augmentation appear appropriate. Alternatively, management goals have not been achieved at a number of the coarsefish lakes nor have expectations been met at lakes supporting multiple sportfish species. The performance of Blackwater stock in coarsefish lakes that support sucker species such as Boundary, Norbury and Rosen lakes has been less than satisfactory; the results obtained at Norbury and Rosen, however, are likely confounded by introductions of multiple stocks or too short a time frame to effectively evaluate stock introductions. The apparent low survival however, may be linked to a downstream migration trait of this particular stock that has been observed in lakes with an attendant outlet stream (K. Tsumura, Head, Fish Culture Research Unit, Ministry of Water, Land and Air Protection, Vancouver, B.C.). This characteristic may be consistent with observations at Norbury and Boundary lakes that serve as the headwaters of the Little Bull and Corn Creek drainages; Edwards Lake is the only example of a coarsefish lake without an outlet stream. One of the virtues of this stock has been their ability to feed on coarsefish at later life stages, yet, the contribution of shiners in the diet of rainbow exceeding 3 mm was accordingly low in the Edwards Lake sample. The recent discovery of kokanee in Edwards Lake may require further consideration as to the nature of future special stock introductions. In the interest of controlling a naturalized population, the inclusion of Gerrard rainbow as a more effective kokanee predator may be required to achieve long-term management objectives. Edwards Lake should be considered as a candidate lake for both Blackwater and Gerrard strains to address both coarsefish and kokanee interactions, respectively. The performance of Blackwater rainbow trout at Boundary Lake remains uncertain. A complete absence in the gillnet sample suggests either poor competitive ability or a migratory trend. Further stocking of Boundary Lake with non-sterile rainbow is not recommended; future management should consider maintaining a naturalized population of brook trout that has proven its ability to co-exist successfully with January 23 53

64 finescale sucker. Brook trout in Boundary Lake displayed one of the highest condition factors among all study lakes and appears to have achieved a balanced population sustained by natural recruitment. Given the rather poor performance of Blackwater stock in Jim Smith, Norbury and Rosen lakes, and in consideration of their connectivity to downstream watersheds, further stocking practices should include sterilized females to avoid the potential release of non-native stocks to the Upper Kootenay drainage. Although the use of catchable rainbow is likely an advantageous method of sustaining a fishery in these coarsefish lakes, further utilization of this stock in lakes with connectivity to the remainder of the basin should only proceed where an effective rock drain at the outlet of each lake prevents potential downstream migration. Further introductions of Eastern brook trout should also be avoided for similar reasons relative to the exotic species argument. Alternative stock selection that considers the use of native cutthroat trout would overcome the issue of non-native introductions. With respect to the development of the bass fishery in Jim Smith Lake, further stocking of yearling rainbow should be discontinued in light of the high predation risk. Growth and survival of Premier stock in Kaufman Lake suggests that further outplanting of yearlings be abandoned. It is the present intention of management to carry forward with an alternate year cutthroat stocking program. Assessments within a two year period beyond the time of initial planting should be conducted to evaluate cutthroat trout performance and guide future management plans for this small lake. As a final note, the early 199 s introduction of redside shiner and more recent discovery of kokanee in Edwards Lake as well as yellow perch and burbot in Jim Smith Lake suggest the need for a news release that heightens public awareness as to the ecological and legal consequences of unauthorized introductions to provincial waterbodies. Disregard for the importance of maintaining current management strategies can severely compromise both management strategies and the long-term maintenance of the native species complex. Future efforts/actions are warranted to dissuade the public from further basin transfers. 5. Literature Cited Bagenal, T.B. and F.W. Tesch. Age and growth. Pages in T.B. Bagenal (ed.) Methods for assessment of fish production in fresh waters. Blackwell Scientific Publications Ltd., Oxford, England. January 23 54

65 Ryder, R.A., S.R., Kerr, K.H. Loftus, and H.A. Regier The morphoedaphic index, a fish yield estimator a review and evaluation. Journal of the Fisheries Research Board of Canada 31: APPENDIX 1 Bathymetric maps for selected lakes January 23 55

66 January 23 56

67 January 23 57

68 January 23 58

69 January 23 59

70 January 23 6

71 January 23 61

72 January 23 62

73 January 23 63

74 January 23 64

75 APPENDIX 2 Photographic plates January 23 65

76 Plate 1. Representative catch at Boundary Lake. Plate 2. Representative catch at Echo Lake North. January 23 66

77 Plate 3. Representative catch at Echo Lake South. Plate mm Pennask AF3N rainbow trout from Echo Lake South on October 8, 22. January 23 67

78 Plate 5. Representative catch at Edwards Lake (Blackwater rainbow and kokanee). Plate 6. Representative catch at Grundy Lake. January 23 68

79 Plate 7. Representative catch at Horseshoe Lake. Plate 8. Representative catch at Jim Smith Lake. January 23 69

80 Plate 9. Representative catch at Kaufman Lake. Plate 1. Representative catch at Larchwood Lake. January 23 7

81 Plate 11. Representative catch at Norbury Lake. Plate 12. Representative catch at Rosen Lake. January 23 71

82 Plate 13. Representative catch at Summit Lake. January 23 72