Clowhom Project Water Use Plan. Fish Productivity Monitoring. Reference: COMMON-2. Fish Productivity Monitoring Year 2 Data Summary 2008

Transcription

1 Clowhom Project Water Use Plan Fish Productivity Monitoring Reference: COMMON-2 Fish Productivity Monitoring Year 2 Data Summary 2008 Study Period: August 25 to October 16, 2008 D.J. Bates Resource Management Sechelt First Nation 5555 Sunshine Coast Highway PO Box 740 Sechelt, BC, V0N 1Y January 31, 2009

2 Executive Summary The Clowhom Lake Fish productivity monitoring study was developed and initiated in 2006 to assess and track changes in fish productivity. Recently, it was noted that fish productivity has decreased following the impoundment of Clowhom Lake in the 1950 s. This decrease may be a direct result a loss in productive littoral habitat but little data exists to support this hypothesis. As a result a 20-year monitoring plan designed to track change in fish productivity through sampling of rearing populations was developed and implemented in 2006 with sampling to occur every 2 years throughout the 20-year study. In the fall of 2008, the second set of sampling data was collected. The upper and lower basin was gill netted using acceptable standards for collection of salmonids. The gill nets included sets with both sinking and floating nets and a drift net. In addition to the net samples the shoreline was trapped using baited minnow traps fished in groups of 5. All captured fish were identified, enumerated, measured and scales collected for aging. Salmonids caught in the gill net were retained and the stomachs examined for food items. Data was recorded and filed for comparison to future years. The results of the 2008 sampling revealed 3 salmonid species and 2 non-salmonids utilizing the lake. The salmonid samples included Rainbow and Cutthroat trout and kokanee salmon. The rainbow sample included 3 age classes (1+, 2+ and 3+) and the cutthroat trout sample yielded 4 age classes (1+, 2+, 3+ and 4+). Two age classes (1+ and 2+) of kokanee salmon were caught. In addition to the salmonids, sticklebacks and prickly sculpin were caught in the minnow traps. The total catch in 2008 was 24 salmonids. In addition to the sampling of fish a habitat assessment was completed on the lower reach of the Clowhom River. This assessment focused on spawning habitat suitable for species of salmonids found in the lake. A total of m 2 of available habitat was measured and of this 51% or m 2 was considered suitable spawning substrate. The 2008 sampling data provides the second year of this multi year project. As data continues to be collected it will be reviewed within the context of changes in population status and health and the results of littoral change. The littoral change is the subject of another continuing independent project examining the Effect Littoral Zones change (ELZ) 2

3 Table of Contents Page Table of Contents... 3 List of Tables Study Area Methods Fish Collection Fish Biometrics Scale Analysis Fish Data Analysis Lower Clowhom River Habitat Assessment Results Fish Capture Fish Biometrics Lower Clowhom River Habitat Assessment Discussion References Appendix

4 List of Figures Page Figure 1: Sample locations used during the gilllnet and minnow trap sets within the Clowhom Lake reservoir between August 25 and 26, Figure 2: Sample locations selected for the gill net and minnow trapping of fish within Clowhom Lake. Each location is identified along the shoreline with flagging tape and permanent metal tags... 8 Figure 3: Length versus weight relationships for salmonids captured in Clowhom Lake reservoir between August 25 and 26, Figure 4: Photos showing examples of the habitat found on the Clowhom River between the 16-km bridge and the lake. Assessment was conducted on October 16, 2008 during low summer flows List of Tables Table I: Type and set times for the sampling gear used to collect fish samples in the Clowhom Lake Reservoir Table II: Species captured in Clowhom Lake sampling, August 25 and 26, Table III: Summary of catch by gear type and sample location in Clowhom Lake between August 25 and 26, Table IV: Summary of length-at-age data for the salmonids caught in Clowhom Lake between August 25 and 26, Table V: Summary of wet weight data for the salmonids caught in Clowhom Lake between August 25 and 26, Table VII: Summary of available habitat from the 16-km bridge to the lake. Total available area and area suitable for spawning are summarized

5 1.0 Introduction In 2006, the Sechelt First Nation and BC Hydro began the first year of a 20 year monitoring program to document change in fish productivity in the Clowhom Lake reservoir. The monitoring program was implemented following recommendations made during the water use planning (WUP) process. Previous studies of the reservoir have noted a decrease in reservoir productivity since the impoundment of Clowhom Lake (Bruce 2004) and as a result the BC Hydro developed the fish productivity monitoring program address concerns and identify bottlenecks to production. The monitoring program addresses specific management questions that are summarized from the BC Hydro Terms of Reference for this project. They are: Does fish productivity change through time following the WUP implementation? Is any observed change correlated with changes in effective littoral zone changes? Is the population of salmonids in Clowhom lake recruitment limited and what role does the river play? If no change is observed what is the reason for the decline initially? Do operation based solutions exist for the reservoir that would benefit fish productivity? The purpose of this report is to present the data collected in the second sample year completed in the fall Study Area The Clowhom Lake reservoir is located at the head of Salmon Inlet northeast of Sechelt BC. The reservoir measures approximately 745 hectares and was first created in The study area for this project includes the entire basin and 9 pre-selected sampling sites. These sites correspond to locations selected by Bruce (2004) and Bates (2006) representing both the upper and lower basins of the reservoir. Figure 1 shows the location of Clowhom Lake in relation to Sechelt BC. 3.0 Methods 3.1 Fish Collection A two-person crew completed the fish sampling process between August 25 and 28, Fish collection was made using gill nets and Gee minnow traps. The gill net configuration was consistent with the mesh sizes recommended for lake inventory under the Resource Inventory Committee (RIC, 1998) and Bruce (2004). Three netting strategies were employed; floating; sinking and drift sets. The floating and sinking sets were anchor near shore and oriented perpendicular to the shoreline. The drift net set was released perpendicular to the lake and mid-line or e-line and allowed to move with the wind and lake currents(s). All gill net sample periods were restricted to 3-hours 5

6 Figure 1: Sample locations used during the gilllnet and minnow trap sets within the Clowhom Lake reservoir between August 25 and 26,

7 in an attempt to minimize the impact of the netting on salmonid mortality. All captured salmonids retained for detailed biometric data collection. In addition to gill nets, Gee minnow traps were used to sample near shore fish. Minnow traps were set in groups of 5, baited with borax preserved chum salmon roe housed in a perforated container to prevent consumption by the captured fish. All traps were set at mid-day and allowed to fish for a 24-hour period. The locations of the sample sites were approximately the same as sites sampled in Locations were determined from UTM coordinates determined with a Garmin handheld GPS receiver. Sample locations are illustrated in Figure 2 and details provided in Table I along with the set times and gear used for each location. Table I: Type and set times for the sampling gear used to collect fish samples in the Clowhom Lake Reservoir. Date Site UTM Gear Set Time Duration ID Northing Easting Type Deployed Retrieved (hr.) Aug 25 A Float GN Day 9:00 12:00 3:00 B Sink GN Day 9:30 12:15 2:45 Aug 25 C MT Night 9:35 11:45 26:10 D MT Night 9:45 11:30 25:45 Aug 26 E Float GN Day 10:00 13:00 3:00 F Sink GN Day 10:15 13:30 3:15 Aug 25 G MT Night 9:50 11:10 25:30 H MT Night 9:55 10:50 24:55 Aug 26 I - - Drift GN Day 11:30 13:40 3:05 Note: GN = gillnet and MT minnow traps (5) 3.2 Fish Biometrics All captured were enumerated and recorded by collection method. Captured salmonids were identified to species, and the fork length to the nearest millimeter (mm) and wet weight nearest 0.1 gms were measured (Bates, 2006). Scale samples were collected from representative size ranges of each species following standard scale collection methodology and placed on glass microscope slides. The scales were then compressed with another slide, labeled and stored for future reading. Live fish (those in the Gee traps), were also identified and enumerated then released unharmed. All dead fish collected in gill nets were retained and returned to the lab. Dead fish (gill net captures) were dissected and the sex identified based on presence of gonads. The stomachs of each fish was also removed and opened for examination and the contents reported. 7

8 Figure 2: Sample locations selected for the gill net and minnow trapping of fish within Clowhom Lake. Each location is identified along the shoreline with flagging tape and permanent metal tags. 8

9 3.3 Scale Analysis Scales from all salmonids captured were returned to the lab for reading. Each scale was reviewed under a compound dissecting microscope and a smear selected for clarity. The representative scale(s) was then photographed using a digital camera mounted on the dissecting microscope and the image stored as a JPEG file. The image was read on a desktop computer. The scale analysis was completed in a similar iterative fashion reported by Bruce (2004) and Bates (2006). The age is reported using the convention n+ values where the + denotes a partial year. 3.4 Fish Data Analysis All captured fish were reported by catch type and will be used to compare catch-per-unit effort as the data set increases. Biometric data is summarized by captured species with the age class and the condition coefficient (CC) for each species calculated using: Condition Coefficient (CC) = wet weight (gms) x length (cm) -3 x Lower Clowhom River Habitat Assessment Clowhom Lake supports salmonids that require accessible stream habitat to spawn. The Clowhom River enters the lake at the north end and is characterized by a low gradient reach. On October 16, 2008, a quantitative habitat assessment was completed on the lower reach of the river. The Assessment was completed from the bridge at the 16-km on the mainline to the confluence with the lake. The assessment was completed with a 2-man crew, one walking the edge and the other swimming in a dry suit. The stream was broken into macrohabitat units (riffles, glides, pools) and each unit measured and features recorded following a modified Johnston and Slaney (1996) process. Habitat features were summarized by macrohabitat units and presented in tabular form. 4.0 Results 4.1 Fish Capture A total of 96 fish were caught during the sampling period. The total catch was comprised of 3 species of salmonids (22.9%) and 2 non-salmonid species (77.1%) (Table II) with the gill nets accounting for 20.8% of the total catch and the minnow traps the balance (79.2%) non-salmonid species were caught along the shoreline in the minnow traps. 9

10 Table II: Species captured in Clowhom Lake sampling, August 25 and 26, Salmonids Non-salmonids Common Name Scientific Name Common Name Scientific Name Cutthroat Trout (CT) Oncorhynchus clarki Prickly sculpin (CC) Cottus asper Rainbow Trout (RBT) O. mykiss Three-spine stickleback (SB) Gasterosteus spp. Kokanee (KO) O. nerka The total catch was also separated by capture method and the catch reported by sample location (Table III). All dead fish caught in the gill nets were retained for dissection. Table III: Summary of catch by gear type and sample location in Clowhom Lake between August 25 and 26, Site Gear Type Species Number A Floating GN Rainbow Trout 3 Kokanee 1 B Sinking GN Cutthroat Trout 3 Kokanee 1 C MT Prickly Sculpin 6 Stickleback 5 D MT Prickly Sculpin 4 E Floating GN Rainbow Trout 9 Cutthroat Trout 2 F Sinking GN Cutthroat Trout 1 G MT Rainbow Trout 2 Prickly Sculpin 7 H MT Prickly Sculpin 52 I Drift GN Fish Biometrics. Nose to fork length and wet weight data were compiled and applied to the appropriate age classes determined from the scale reading results. The largest species caught was the cutthroat trout in the sinking gill nets. Table IV, V and VI summarize the length-at-age, weight and condition coefficient data for the three species of salmonids captured. Figure 3 shows the weight versus length relationship for each salmonid species caught. The total sample size was only 23 salmonids from all capture methods. 10

11 Table IV: Summary of length-at-age data for the salmonids caught in Clowhom Lake between August 25 and 26, Species specific fork length (mm) Rainbow Trout Cutthroat Trout Kokanee Age n Mean(SD) n Mean(SD) n Mean(SD) (12.6) (19.8) (14.6) (14.1) (41.9) Table V: Summary of wet weight data for the salmonids caught in Clowhom Lake between August 25 and 26, Species specific wet weight (gms) Rainbow Trout Cutthroat Trout Kokanee Age n Mean(SD) n Mean(SD) n Mean(SD) (5.91) (10.9) (13.5) (15.8) (79.7) In total 9 fish were retained for dissection. These fish were examined for gonadal development and sexed accordingly. The stomachs from each was then removed and dissected further. Food items found in the stomach were identified to broad categories and recorded for future analysis. Table VI: Summary of condition coefficients for the salmonids caught in Clowhom Lake between August 25 and 26, Species specific condition coefficient Rainbow Trout Cutthroat Trout Kokanee Age n Mean(SD) n Mean(SD) N Mean(SD) (0.08) (0.06) (0.06) (0.04) (0.19)

12 Figure 3: Length versus weight relationships for salmonids captured in Clowhom Lake reservoir between August 25 and 26,

13 4.3 Lower Clowhom River Habitat Assessment The habitat data from the lower Clowhom River is provided in Appendix I. Table VII summarizes the area of each habitat type and channel characteristics and the area available for spawning. Figure 4 shows the habitat found within the lower Clowhom River between the lake and the 16-km bridge. Table VII: Summary of available habitat from the 16-km bridge to the lake. Total available area and area suitable for spawning are summarized. Habitat Area (%) Length (%) Total Area (m 2 ) Mean Bankfull Width (m) Mean Gradient (%) Spawning Area of Total Available (%) Spawning Area (m 2 ) Riffle Glide Pool Total na na na Discussion The data summarized in this report represents the second year of the productivity monitoring under the present WUP. Results show similar numbers and species composition to results presented in Bates (2006). The 2008 results are again lower than those presented in Bruce (2004). Whether the 2006 and 2008 results are true reflections of change(s) in population dynamics or a result of spatial and temporal variation remains unknown. Subsequent sampling over the proposed project period should help to identify whether significant changes are in fact occurring within the reservoir. In addition to planned future sampling it is proposed that additional day and night time sampling be conducted in This sampling will specifically target kokanee salmon (O. nerka) in an attempt to better understand current capture results and diurnal movement of this species. The enclosed data and results of the 2008 season are provided in a summary form. Detailed analysis is not included at this time and will be attempted following subsequent sampling of lake populations. The next scheduled sampling of the lake is August/September

14 Figure 4: Photos showing examples of the habitat found on the Clowhom River between the 16-km bridge and the lake. Assessment was conducted on October 16, 2008 during low summer flows. 14

15 6.0 References Resource Inventory Committee (1998) Reconnaissance Fish and habitat inventory: Standards and procedures. BC Ministry of Fisheries, Victoria, BC. Bates, D.J Clowhom Lake Water Use Plan. Fish Productivity Monitoring Year 1. Shíshálh Nation and FSCI Biological Consultant. Bruce, James, Results of fish studies Clowhom Lake Water Use Plan. BC Hydro Technical Note Com-FTC-TN-001. Burnaby, BC. Johnston, N.T. and Slaney, P.A Fish habitat assessment procedures. Watershed Restoration Technical Circular No. 8. B.C. Ministry of Environment, Lands and Parks and Ministry of Forests, Victoria, B.C. 15

16 Appendix 16

17 Date October Reach: 1 Crew: D.P./J.J Stream Name: Clowhom River Weather: L. Rain Time: 8:58 WSC: Temp: 8 Reach: 1,772 m Unit # Total Mean Unit Type: Riffle Glide Riffle Glide Riffle Riffle Pool Glide Grad % Lgth (m) W. width (m) Ch. Width (m) Area Depth Bankfull Average Pools Max. depth Crest Ht Res. depth Pool type sc 0 LWD Total Lwd Func LWD LWD Area (m2) na na na na na na na na 0 Cover In. Boulder (%) In. Veg. (%) Ov. Veg (%) Canopy Cover (% Cutbanks (%) Off Channel Type na na na na na na na na Access na na na na na na na na Length na na na na na na na na Bed Type (%) Fines Sm. Gravel Lg. Gravel Cobbles Boulder Bedrock Total Velocity Sec Lgth in meters Spawning Spawning (%) Total Area Depths (Unit) Average Comments Start of 4 Braids wetland complex FSCi 2000