Okay Lake Stocking Assessment Report

Transcription

1 Okay Lake Stocking Assessment Report Region 1, Nanaimo Nanaimo/Cowichan Planning Unit Ministry of Water, Land and Air Protection Prepared by: Laura Cassin Scott Silvestri 2002

2 1.0 Introduction 1.1 Objective Okay Lake, in the Nanaimo/Cowichan planning unit, was assessed in the fall of 2002 as part of a stocking evaluation of Vancouver Island lakes. These assessments were carried out with the purpose of determining the overall effectiveness of past stocking efforts and/or to determine future actions in the lake stocking program. Results of the Williams Lake evaluation will focus on: 1.2 Background effectiveness of past stocking efforts by evaluating fish abundance and observing the level of natural recruitment of both stocked and non-stocked fish effectiveness of past stocking efforts by evaluating the current age structure of the population using fish aging techniques observations of the presence/absence of non-native fish future considerations for the fish stocking and lake management program A basic reconnaissance survey of Okay Lake was completed by provincial fisheries staff in The lake is located northwest of Nanaimo in Weyerhaeuser s North West Bay Division and lies in the Coastal Western Hemlock Biogeoclimatic Zone within the South Island Forest District. The lake is situated at an elevation of 450 m in management unit The surface area is 4.3 ha and the perimeter is 0.8 km. The lake attains a maximum depth of 6.9 m. The lake has been stocked 10 times from 1989 to 2002 (Table 1). Table 1. Stocking history of Okay Lake. Year Species (Stock) Number Stage Size (g) Mark 1989/08/24 Cutthroat Trout (Taylor) 2000 Fall Fry /04/25 Cutthroat Trout (Taylor) 1000 Yearling /10/29 Cutthroat Trout (Taylor) 500 Fingerling /04/06 Cutthroat Trout (PAQ) 500 Yearling /05/21 Rainbow Trout (Badger Tunkwa) 1000 Yearling /05/13 Rainbow Trout (Tzenzaicut) 1000 Yearling /05/27 Rainbow Trout (BlackWater) 1000 Yearling /05/10 Rainbow Trout (Tzenzaicut) 1000 Yearling /05/28 Rainbow Trout (Tzenzaicut) 1000 Yearling /05/07 Rainbow Trout (Tzenzaicut) 1000 Yearling

3 2.0 Methods and Materials The Vancouver Island lakes included in the evaluation were selected because they were previously stocked and needed assessment, or were potential candidates for future stockings. A list of over 45 lakes was compiled, and 18 were selected by the Region 1 Lakes Biologist to be sampled in the fall of Okay Lake had previous reconnaissance work completed and thus only temperature/oxygen profiles and fish sampling procedures were performed. The lake was assessed by boat, and a Lowrance X65 sounder was used to determine depth measurements. A bathymetric map of the lake was constructed, however, the outline of the lake as well as the position of the contour lines are rough estimates and are only intended to give a general overview of the lake (Figure 1). Upon locating the deepest part of the lake, the temperature/oxygen profile, as well as the secchi disk reading, was completed. The temperature/oxygen profile was obtained using a model 51B YSI meter. Figure 1. An unofficial bathymetric map of Okay Lake showing the survey site location and the positions of the floating and sinking gill nets.

4 Two gill nets, one sinking and one floating, were set in the lake overnight. The gill net sites were selected with the intention of sampling areas with evenly spaced contour lines on a bathymetric map. The floating gill net was set with the intent of covering more shoal area, where as the sinking gill net was set to sample a deeper part of the lake (Figure 1). The floating and sinking gill nets were 90m monofilament experimental gang nets of varying panel sizes. Both nets were anchored with the smallest mesh size panel nearest to shore and extended into the lake. Sampling of the gill net catch consisted of recording length (cm), weight (g), sex, maturity, and stomach contents of all fish captured. In addition, scale samples were taken from a representative sample of rainbow trout captured and mounted on slides. Columbia Environmental Consulting Ltd. aged the scales by counting the number of annuli that represent different growing seasons. Printed copies of each scale sampled can be seen in Appendix D. The ages of the fish that were not scale sampled were determined using a length-at-age comparison utilizing the known age data. 3.0 Results 3.1 Temperature-Oxygen Profile Okay Lake is a relatively shallow lake, less than 7 meters deep, with large shoal and flooded marsh areas all around the lake (Figure 1). The temperature-oxygen profile shows a lake that is well mixed from the surface to the bottom. Surface water temperatures are slightly warmer than subsurface water at 6.5 o C. Temperature values below the surface range from 6.1 o C at 1 m to 5.9 o C at the 6.5 m depth. Oxygen values remain constant at 11.8 mg/l for all depths. 0 Depth (m) Oxygen (mg/l) Temperature (C) Figure 2. Temperature-oxygen profile of Okay Lake. 3.2 Netting Data A total of 131 fish were captured in the two nets set in Okay Lake (Table 2). The results of the catch data can be seen in Appendix B and photographs of the catch can be seen in

5 Appendix C. The size distribution of rainbow trout in Okay Lake varied between 18.1 cm and 37.4 cm. The sex ratio between males and females was 57:70. Table 2. Summary of catch from the floating and sinking gill nets set in Okay Lake. Species Sample Size Size Range (cm) Ave. K Value K Value Std. Dev. Sex Ratio (M:F) Rainbow Trout :70 Cutthroat/Rainbow Trout Hybrids :0 Figure 3 shows the length-frequency distribution, by age, of all the rainbow trout and hybrids captured in Okay Lake. The age distribution appears normal, with only a small amount of overlap between some age classes. The largest number of fish captured (n=106) were seen in the 2+ age class. No fish of age 1+ were captured, while 19 age 3+ and 2 age 4+ rainbow trout were sampled. Only 4 cutthroat/rainbow trout hybrids were captured, of which 3 belong to the 2+ age class and 1 to the 3+ age class. The length at age data appears normal with a good distribution of sizes for each age class RB 2+ (N=106) RB 3+ (N=19) RB 4+ (N=2) CT/RB 2+ (N=3) CT/RB 3+ (N=1) # of Fish Length (cm) Figure 3. Length-frequency distribution by age for rainbow trout in Okay Lake in the fall of Figure 4 displays the length/weight relationship and the average condition factor for both the rainbow trout and cutthroat/rainbow trout hybrids captured in Okay Lake. The weight of the sampled population of rainbow trout and cutthroat/rainbow trout hybrids increase according to the formulas W = 7.807e L and W = e L where W represents weight in grams and L represents length in centimeters. The equations also have a

6 closeness of fit or R 2 value equal to and respectively. The calculated average condition factor for Okay Lake rainbow trout and cutthroat/rainbow trout hybrids was and Cutthroat/Rainbow Trout Hybrid (N=4) Rainbow Trout (N=127) Rainbow Trout y = 7.807e x R 2 = Ave. K = Weight (g) Cutthroat/Rainbow Trout Hybrid y = e x R 2 = Ave. K = Length (cm) Figure 4. Length-weight relationship of rainbow trout in Okay Lake in the fall of Presence/Absence of Non-Native Species The presence of both rainbow trout and cutthroat/rainbow trout hybrids in the gill nets set in Okay Lake suggests they are the only two species present in the lake. The BC Fisheries database states that both rainbow trout and cutthroat trout are present in the lake. No pure strain of cutthroat trout was noted in the gill net data during this sampling period. It should be noted that cutthroat were stocked historically, but haven t been added since The lake is not accessible to anadromous salmonids. 4.0 Discussion 4.1 Temperature-Oxygen Profile The temperature-oxygen profile for Okay Lake shows both temperature and dissolved oxygen levels ideally suited for fish development. Temperature values were fairly cold, however given the time of year it is not unexpected. The nearly uniform levels through all depths for temperature and oxygen show a lake that is well mixed with no presence of a thermocline. Oxygen values are consistent at all depths suggesting that mixing is occurring from the surface down to the bottom. Temperature values show minor

7 fluctuations, but it is likely due from daytime heating. Small shallow lakes are typically very productive and thus ideally suited for the growth of most trout species. High water temperature levels can, however, cause problems if values are in excess of 20 o C. Okay Lake is at a high enough elevation and is likely deep enough where temperature values are not likely to reach or exceed this critical level. Conversely, temperature values during winter periods are not likely low enough to cause extreme ice formation and/or oxygen depletion. 4.2 Netting Data The dominant age class in Okay Lake appears to be fish in the 2+ age class. This is likely a result of the stocking that occurred here in the spring. The drastic decline in the number of fish present in older age classes maybe partly due to the fishery on this lake. Another explanation is overcrowding, as the results from the gill nets show a lake that is overpopulated. The small overlap between age classes maybe the result of improper aging or incorrect ages inferred for those fish that were not scaled. The presence of a few hybrid fish suggest that some natural recruitment does occur, however it likely occurs when conditions are optimum. Spawning area is also extremely limited thus large amounts of natural recruitment are not possible in this lake without habitat modifications. The absence of juveniles from the gill net data supports the notion of little to no natural reproduction in Okay Lake. The length-weight relationships for both the rainbow trout and the cutthroat/rainbow trout hybrids appear normal with equations that are represented by good R 2 values. The mean condition factors of and are normal for these two species on Vancouver Island. The presence of a large sample size, especially of small fish (<25 cm), from the gill nets set in Okay Lake suggests that the lake maybe over populated. 4.3 Netting Data in Relation to Stocking History Stocking of Okay Lake has occurred annually since 1997, however no fish have been marked, thus verifying them as hatchery fish is difficult. Most fish sampled are likely from hatchery origin as natural recruitment seldom occurs as seen from the absence of juveniles in the gill net data. 4.4 Fish Health A matter of concern in Okay Lake fish is the presence of what appears to be yellow grub, an encysted parasitic fluke. The larval form of the fluke is released from snails and travels through the water column where it penetrates the skin of fish and embeds beneath, usually at the base of fins. The grub does no serious harm to fish, but if infection is heavy, the flesh is unsuitable for human consumption. The presence of these cysts was seen on all fish sampled from the gill nets, and in some cases infection was extremely prevalent

8 (Appendix C, Picture # 13). Little can be done about the infection, since no known efforts have resulted in the removal of the parasitic fluke larvae. 5.0 Conclusion The overall assessment of Okay Lake indicates good conditions for a healthy fishery. The level of natural recruitment in the lake appears extremely limited, however it is likely that annual stocking efforts have resulted in large numbers of trout in the lake. The gill net data shows a large portion of the fish less than 25 cm, thus suggesting the lake is overpopulated. The amount of use of Okay Lake by anglers is also unknown and maybe fairly low due to the restricted access by Weyerhaeuser. Road access is quite good to Okay Lake, but is fairly overgrown, suggesting limited use. The health concern, as a result of the parasitic flukes, may also reduce the angling pressure. 6.0 Recommendations The recommendations by the Regional Lakes Biologist is the scaling down of stocking from 1000 rainbow yearlings stocked annually to 500 rainbow yearlings stocked in even years. This would reduce the amount of competition for food, thus resulting in a higher number of larger fish. The resulting scale back would likely result in only minor changes to angler success rates as Okay Lake in only four hactares in size. If fishing pressure increases, the stocking program for this lake may have to be altered, thus it is recommended that fishing pressure be monitored to ensure a good quality fishery at Okay Lake. By reducing the stocking rate in Okay Lake, a reduction in parasitic infections may also occur. It is likely that overcrowding causes proliferation of the fluke, resulting in higher infection rates.

9 Appendix Appendix A Temperature-Oxygen Profile Locality: Okay Lake Date: November 4, 2002 Bottom Depth 6.9 m Secchi Depth > 6.9 m Weather: Sunny, few clouds, cool and calm Depth (m) O 2 (mg/l) Temperature ( o C) Surface

10 Appendix B Net Set Information and Catch Record Floating Gill Net Date Set : Time Set : Parameter Floating Gill Net 04-Nov-02 15:15 Date Lifted : 05-Nov-02 Time Lifted : 10:05 Shallow End Depth (m) : 0.5 Shallow End Substrate : Fine Organic Substrate Deep End Depth (m) : 5.1 Deep End Substrate : Fine Organic Substrate Max. Depth Along Net (m) : 5.1 Netting record key RB - rainbow trout CT - cutthroat trout DV - Dolly Varden EBT - eastern brook trout SMB - small mouth bass IMM MG MT R SP - immature - maturing - mature - ripe - spent LM RM AD NO - left maxillary - right maxillary - adipose - not marked Fish Characteristics Sample Stomach Contents Number Species Fork Length (cm) Weight (g) Sex Maturity Mark Age Type Bottom Organisms Plankton Terrestrial Fish Volume Comments 1 RB F MG No Scale Caddis and Casing Copepods 1/2 Parasitic Encysted Worms 2 RB M MG No Scale Digested Matter Copepods 1/4 Parasitic Encysted Worms 3 RB F MG No Scale Water Boatman 1/4 Parasitic Encysted Worms 4 RB F MG No Scale Copepods 1/8 Parasitic Encysted Worms 5 RB M IMM No Copepods Unident. Insect 1/4 Parasitic Encysted Worms 6 RB M IMM No Copepods 1/8 Parasitic Encysted Worms 7 RB F IMM No Scale Copepods 1/4 Parasitic Encysted Worms 8 RB M MG No Caddis and Casing 1/4 Parasitic Encysted Worms 9 RB M MG No Copepods 1/8 Parasitic Encysted Worms 10 RB F IMM No Copepods Unident. Insect 1/4 Parasitic Encysted Worms 11 RB F IMM No Scale Empty Parasitic Encysted Worms 12 RB F MG No Copepods 1/8 Parasitic Encysted Worms 13 RB M IMM No Empty Parasitic Encysted Worms 14 RB M IMM No Daphnia, Copepods 1/8 Parasitic Encysted Worms 15 RB F IMM No Empty Parasitic Encysted Worms 16 RB M IMM No Daphnia <1/8 Parasitic Encysted Worms 17 RB M MG No Empty Parasitic Encysted Worms 18 RB F IMM No Empty Parasitic Encysted Worms 19 RB F IMM No Daphnia <1/8 Parasitic Encysted Worms 20 RB F IMM No Daphnia 1/8 Parasitic Encysted Worms 21 RB M IMM No Scale Daphnia 1/8 Parasitic Encysted Worms 22 RB M IMM No Daphnia <1/8 Parasitic Encysted Worms 23 RB M MG No Daphnia, Copepods 1/8 Parasitic Encysted Worms 24 RB F IMM No Copepods 1/4 Parasitic Encysted Worms 25 RB M IMM No Copepods Unident. Insect 1/4 Parasitic Encysted Worms 26 RB F IMM No Empty Parasitic Encysted Worms 27 RB M MG No Daphnia, Copepods <1/8 Parasitic Encysted Worms 28 RB F IMM No Caddis Casing 1/8 Parasitic Encysted Worms 29 RB M IMM No Empty Parasitic Encysted Worms 30 RB F IMM No Scale Daphnia, Copepods 1/8 Parasitic Encysted Worms 31 RB F IMM No Scale Daphnia <1/8 Parasitic Encysted Worms

11 Appendix B Net Set Information and Catch Record Continued Sinking Gill Net Parameter Sinking Gill Net Date Set : 04-Nov-02 Time Set : 15:23 Date Lifted : 05-Nov-02 Time Lifted : 11:35 Shallow End Depth (m) : 1.8 Shallow End Substrate : Fine Organic Substrate Deep End Depth (m) : 5.6 Deep End Substrate : Fine Organic Substrate Max. Depth Along Net (m) : 6.5 Netting record key RB - rainbow trout IMM - immature CT - cutthroat trout MG - maturing DV - Dolly Varden MT - mature EBT - eastern brook trout R - ripe SMB - small mouth bass SP - spent LM RM AD NO - left maxillary - right maxillary - adipose - not marked Fish Characteristics Sample Stomach Contents Number Species Fork Length (cm) Weight (g) Sex Maturity Mark Age Type Bottom Organisms Plankton Terrestrial Fish Volume Comments 1 RB F MG No Scale Clams, Plant Matter Copepods 1/2 Parasitic Encysted Worms 2 RB M MG No Scale Clams Copepods 1/2 Parasitic Encysted Worms 3 RB F MG No 1/4 Parasitic Encysted Worms 4 RB F MG No Scale 1/8 Parasitic Encysted Worms 5 RB M MG No 1/4 Parasitic Encysted Worms 6 RB F MG No 1/4 Parasitic Encysted Worms 7 RB F IMM No 1/4 Parasitic Encysted Worms 8 RB F MG No Clams Copepods 1/2 Parasitic Encysted Worms 9 RB F MG No 1/4 Parasitic Encysted Worms 10 RB M MG No 1/8 Parasitic Encysted Worms 11 RB M MG No 1/4 Parasitic Encysted Worms 12 RB M MG No 1/2 Parasitic Encysted Worms 13 RB F MG No 1/8 Parasitic Encysted Worms 14 RB F MG No Scale <1/8 Parasitic Encysted Worms 15 RB F IMM No 1/8 Parasitic Encysted Worms 16 RB M MG No 1/8 Parasitic Encysted Worms 17 RB F MG No 1/8 Parasitic Encysted Worms 18 RB F MG No <1/8 Parasitic Encysted Worms 19 RB F IMM No Scale 1/4 Parasitic Encysted Worms 20 RB M MG No 1/4 Parasitic Encysted Worms 21 RB F MG No Empty Parasitic Encysted Worms 22 RB M MG No 1/4 Parasitic Encysted Worms 23 RB M MG No 1/4 Parasitic Encysted Worms 24 RB F MG No 1/4 Parasitic Encysted Worms 25 RB F IMM No 1/4 Parasitic Encysted Worms 26 RB M MG No 1/4 Parasitic Encysted Worms 27 RB F MG No 1/8 Parasitic Encysted Worms 28 RB F IMM No 1/4 Parasitic Encysted Worms 29 RB M MG No 1/4 Parasitic Encysted Worms 30 RB M MG No 1/8 Parasitic Encysted Worms 31 RB M MG No 1/8 Parasitic Encysted Worms 32 RB F MG No 1/8 Parasitic Encysted Worms 33 RB F IMM No 1/8 Parasitic Encysted Worms 34 RB F IMM No Scale 1/8 Parasitic Encysted Worms 35 RB M IMM No Empty Parasitic Encysted Worms 36 RB F IMM No 1/4 Parasitic Encysted Worms 37 RB M MG No 1/8 Parasitic Encysted Worms 38 RB F IMM No 1/8 Parasitic Encysted Worms 39 RB F IMM No Empty Parasitic Encysted Worms 40 RB M IMM No 1/8 Parasitic Encysted Worms 41 RB F IMM No 1/8 Parasitic Encysted Worms

12 Appendix B Net Set Information and Catch Record Continued Sinking Gill Net Continued Parameter Sinking Gill Net Date Set : 04-Nov-02 Time Set : 15:23 Date Lifted : 05-Nov-02 Time Lifted : 11:35 Shallow End Depth (m) : 1.8 Shallow End Substrate : Fine Organic Substrate Deep End Depth (m) : 5.6 Deep End Substrate : Fine Organic Substrate Max. Depth Along Net (m) : 6.5 Netting record key RB - rainbow trout IMM - immature CT - cutthroat trout MG - maturing DV - Dolly Varden MT - mature EBT - eastern brook trout R - ripe SMB - small mouth bass SP - spent LM RM AD NO - left maxillary - right maxillary - adipose - not marked Fish Characteristics Sample Stomach Contents Number Species Fork Length (cm) Weight (g) Sex Maturity Mark Age Type Bottom Organisms Plankton Terrestrial Fish Volume Comments 42 RB F IMM No 1/8 Parasitic Encysted Worms 43 RB F IMM No <1/8 Parasitic Encysted Worms 44 RB F IMM No 1/8 Parasitic Encysted Worms 45 RB F IMM No <1/8 Parasitic Encysted Worms 46 RB F IMM No 1/8 Parasitic Encysted Worms 47 RB F IMM No 1/2 Parasitic Encysted Worms 48 RB F IMM No <1/8 Parasitic Encysted Worms 49 RB M MG No 1/4 Parasitic Encysted Worms 50 RB F IMM No Scale 1/8 Parasitic Encysted Worms 51 RB M IMM No 1/4 Parasitic Encysted Worms 52 RB F IMM No 1/8 Parasitic Encysted Worms 53 RB M MG No 1/8 Parasitic Encysted Worms 54 RB F IMM No 1/8 Parasitic Encysted Worms 55 RB F IMM No 1/4 Parasitic Encysted Worms 56 RB F IMM No 1/8 Parasitic Encysted Worms 57 RB F IMM No 1/4 Parasitic Encysted Worms 58 RB M MG No 1/8 Parasitic Encysted Worms 59 RB F MG No 1/4 Parasitic Encysted Worms 60 RB M MG No <1/8 Parasitic Encysted Worms 61 RB M IMM No 1/8 Parasitic Encysted Worms 62 RB F IMM No 1/8 Parasitic Encysted Worms 63 RB M MG No 1/4 Parasitic Encysted Worms 64 RB M MG No Empty Parasitic Encysted Worms 65 RB M IMM No 1/8 Parasitic Encysted Worms 66 RB M IMM No 1/8 Parasitic Encysted Worms 67 RB F IMM No 1/4 Parasitic Encysted Worms 68 RB F IMM No 1/8 Parasitic Encysted Worms 69 RB F IMM No Empty Parasitic Encysted Worms 70 RB M IMM No 1/4 Parasitic Encysted Worms 71 RB F IMM No 1/8 Parasitic Encysted Worms 72 RB M IMM No 1/8 Parasitic Encysted Worms 73 RB M IMM No 1/8 Parasitic Encysted Worms 74 RB F IMM No Empty Parasitic Encysted Worms 75 RB F IMM No Empty Parasitic Encysted Worms 76 RB F IMM No 1/8 Parasitic Encysted Worms 77 RB F IMM No 1/8 Parasitic Encysted Worms 78 RB M MG No <1/8 Parasitic Encysted Worms 79 RB F IMM No <1/8 Parasitic Encysted Worms 80 RB M IMM No Daphnia 1/8 Parasitic Encysted Worms 81 RB M IMM No Empty Parasitic Encysted Worms

13 Appendix B Net Set Information and Catch Record Continued Sinking Gill Net Continued Parameter Sinking Gill Net Date Set : 04-Nov-02 Time Set : 15:23 Date Lifted : 05-Nov-02 Time Lifted : 11:35 Shallow End Depth (m) : 1.8 Shallow End Substrate : Fine Organic Substrate Deep End Depth (m) : 5.6 Deep End Substrate : Fine Organic Substrate Max. Depth Along Net (m) : 6.5 Netting record key RB - rainbow trout IMM - immature CT - cutthroat trout MG - maturing DV - Dolly Varden MT - mature EBT - eastern brook trout R - ripe SMB - small mouth bass SP - spent LM RM AD NO - left maxillary - right maxillary - adipose - not marked Fish Characteristics Sample Stomach Contents Number Species Fork Length (cm) Weight (g) Sex Maturity Mark Age Type Bottom Organisms Plankton Terrestrial Fish Volume Comments 82 RB M IMM No <1/8 Parasitic Encysted Worms 83 RB F IMM No 1/8 Parasitic Encysted Worms 84 RB M IMM No Scale <1/8 Parasitic Encysted Worms 85 RB M IMM No 1/8 Parasitic Encysted Worms 86 RB M IMM No 1/8 Parasitic Encysted Worms 87 RB F IMM No 1/8 Parasitic Encysted Worms 88 RB M MG No 1/8 Parasitic Encysted Worms 89 RB M MG No 1/8 Parasitic Encysted Worms 90 RB F MG No Newt/ Salamander 3/4 Parasitic Encysted Worms 91 RB M IMM No Daphnia <1/8 Parasitic Encysted Worms 92 RB M MG No 1/4 Parasitic Encysted Worms 93 RB M IMM No <1/8 Parasitic Encysted Worms 94 RB M MG No <1/8 Parasitic Encysted Worms 95 RB F IMM No Empty Parasitic Encysted Worms 96 RB F IMM No Daphnia 1/8 Parasitic Encysted Worms 1 CT/RB hybrid M MG No 1/8 Parasitic Encysted Worms 2 CT/RB hybrid M MG No 1/4 Parasitic Encysted Worms 3 CT/RB hybrid M IMM No 1/8 Parasitic Encysted Worms 4 CT/RB hybrid M MG No 1/8 Parasitic Encysted Worms

14 Appendix C Photos Picture 1. Okay lake looking northeast from the center of the lake. Picture 2. Okay Lake looking east from the center of the lake.

15 Picture 3. Okay Lake looking southwest from boat launch. Picture 4. Okay Lake looking west southwest from boat launch.

16 Picture 5. Okay Lake looking west from boat launch. Picture 6. Okay Lake looking west from center of the lake.

17 Picture 7. Looking west towards lake from the lake outlet. Note large flooded marsh area.

18 Picture 8. Outlet channel 100 m upstream of lake outlet. Note presence of cobble. Picture 9. Outlet channel 100 m upstream of lake. Note presence of logs and cobble.

19 Picture 10. Okay Lake floating gill net catch. Picture 11. Okay Lake sinking gill net catch.

20 Picture 12. Okay Lake sinking gill net catch close-up. Picture 13. Photo showing heavy infection of parasitic flukes inside the body cavity.

21 Picture 14. Comparison of rainbow trout and cutthroat/rainbow trout hybrids in Okay Lake. Note the presence of red hyoid slash. Fish also possessed vomer teeth. Picture 15. Close-up of cutthroat/rainbow trout hybrids of Okay Lake.

22 Appendix D Scale Readings Scale Sample #1 Sinking gill net RB 18.9cm 79g age 2+ Scale Sample #2 Sinking gill net RB 18.1cm 62g age 2+ Scale Sample #3 Sinking gill net RB 25.5cm 161g age 3+

23 Scale Sample #4 Sinking gill net RB 23.4cm 148g age 3+ Scale Sample #5 Sinking gill net RB 20.1cm 86g age 3+ Scale Sample #6 Sinking gill net RB 32.8cm 372g age 4+

24 Scale Sample #7 Sinking gill net RB 33.0cm 410g age 3+ Scale Sample #8 Sinking gill net RB 29.5cm 275g age 3+

25 Scale Sample #9 Floating gill net RB 20.3cm 85g age 3+ Scale Sample #10 Floating gill net RB 19.7cm 86g age 3+ Scale Sample #11 Floating gill net RB 18.9cm 73g age 2+

26 Scale Sample #12 Floating gill net RB 25.4cm 172g age 2+ Scale Sample #13 Floating gill net RB 24.6cm 153g age 2+ Scale Sample #14 Floating gill net RB 22.8cm 107g age 2+

27 Scale Sample #15 Floating gill net RB 37.4cm 571g age 4+ Scale Sample #16 - Floating gill net RB 27.8cm 208g regenerated scales

28 Scale Sample #17 Floating gill net RB 28.3cm 273g age 2+