Clowhom Lake Water Use Plan Fish Productivity Monitoring
CLOW-WUP-Fish Productivity Year 1 – Data Summary Study Period: September 13 to 19, 2006
D.J. Bates Resource Management Sechelt First Nation 5555 Sunshine Coast Highway PO Box 740 Sechelt BC, V0N 1Y1 604-885-2273
January 31, 2007
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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 has, for the purposes of the Water Use Planning, been attributed to a loss in productive littoral habitat but little data exists to support this hypothesis. As result a monitoring plan that track change in fish productivity through sampling of rearing populations was developed and implemented in 2006. This plan referred to as the Fish Productivity Monitoring has been designed to test the premise that observed and measured reduction in fish productivity is attributed to reservoir operations. Metrics used for measurement include fish abundance, composition and general condition of rearing salmonids. The specific questions to be addressed throughout this study will include: • • • • • Does fish productivity, measured as relative abundance and size at age and condition change through time? If change occurs is it correlated to change in littoral area? Is the population of salmonids in Clowhom Lake limited by juvenile recruitment? If no change is found why? Is there another cause for the reduction in fish productivity post impoundment? Do alternatives exist to reservoir operations that would help reduce or mitigate the influence on fish production.
In the fall of 2006, the first 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 sample. 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 lake and its fish populations will be sampled every 2 years. The results of the 2006 sampling revealed three 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 4+) while only 2 age classes (3+ and 4+) of cutthroat were noted. Only one age 1+ Kokanee was caught. In addition to the salmonids, sticklebacks and prickly sculpin were caught in the minnow traps. The total catch in 2006 was only 19 salmonids. In addition to the sampling of fish using scientific collection methods a creel census was implemented to determine the sport catch within the reservoir. This was implemented through the Clowhom Lodge and during the sampling period no angler days were reported.
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The 2006 sampling data provides the first 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 independent project that examines the Effect Littoral Zones change (ELZ)
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Table of Contents Executive Summary ............................................................................................................ 2 Table of Contents................................................................................................................ 4 List of Figures ..................................................................................................................... 4 List of Tables ...................................................................................................................... 4 1.0 Introduction................................................................................................................... 6 2.0 Study Area .................................................................................................................... 6 3.0 Methods......................................................................................................................... 6 3.1 Fish Collection .......................................................................................................... 6 3.2 Fish Biometrics ......................................................................................................... 8 3.3 Scale Analysis......................................................................................................... 10 3.4 Data Analysis .......................................................................................................... 10 3.5 Creel Survey............................................................................................................ 10 4.0 Results......................................................................................................................... 12 4.1 Fish Capture ............................................................................................................ 12 4.2 Fish Biometrics. ...................................................................................................... 13 4.3 Creel Survey............................................................................................................ 14 5.0 Discussion ................................................................................................................... 15 6.0 References................................................................................................................... 15
List of Figures Figure 1: Sample locations used during the gilllnet and minnow trap sets within the Clowhom Lake reservoir between September 18 and 19, 2006. ................................ 7 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............................................................................................ 9 Figure 3: Sport fishing zones assigned to the Clowhom Lake reservoir. Zone boundaries are assigned based on local topography. ................................................................. 11 Figure 4: Length versus weight relationships for salmonids captured in Clowhom Lake reservoir between September 18 and 19, 2006 ......................................................... 14 List of Tables Table I: Type and set times for the sampling gear used to collect fish samples in the Clowhom Lake Reservoir. .......................................................................................... 8 Table II: Species captured in Clowhom Lake sampling, September 18 and 19, 2006. .... 12 Table III: Summary of catch by gear type and sample location in Clowhom Lake between September 18 and 19, 2006. ....................................................................... 12 Table IV: Summary of length-at-age data for the salmonids caught in Clowhom Lake between September 13, and 19, 2006. ...................................................................... 13 Table V: Summary of wet weight data for the salmonids caught in Clowhom Lake between September 13, and 19, 2006. ...................................................................... 13
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Table VI: Summary of condition coefficients for the salmonids caught in Clowhom Lake between September 13, and 19, 2006. ...................................................................... 14
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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 methods employed during the first sampling season and data collected Year 1. 2.0 Study Area The Clowhom Lake reservoir is located at the head of Salmon Inlet northeast of Sechelt BC. The reservoir measures approximately xx hectares and was first created in 19xxx. 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 represent 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 September 18 and 19, 2006. 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 mid-line of e-line and allowed to move with the wind and lake current(s). All gill net sample periods were restricted to 3-hours
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Figure 1: Sample locations used during the gilllnet and minnow trap sets within the Clowhom Lake reservoir between September 18 and 19, 2006.
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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. The minnow traps were set in groups of 5 traps baited with borax preserved chum salmon roe. The bait was housed in a perforated container to prevent consumption by the captured fish. The traps were set at mid day and allowed to fish for a 24 hour period. The locations of the sample sites were fagged along the lake shoreline and UTM coordinates determined with a Garmin handheld GPS receiver. Sample locations are provided on Figure 2 and Table I reports 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.
Site UTM ID Northing Easting Sept 18 A 5508579 461286 B 5509613 461887 Sept 18 C 5509915 461774 D 5510722 462958 Sept 19 E 5510961 464552 F 5511065 467434 Sept 18 G 5510897 467399 H 5512518 467991 Sep 19 I Note: GN = gillnet and MT minnow traps (5) Date Gear Float GN Sink GN MT MT Float GN Sink GN MT MT Drift GN Type Day Day Night Night Day Day Night Night Day Set Time Deployed Retrieved 11:20 14:30 11:45 14:50 13:30 14:00 10:30 13:30 11:30 14:30 16:30 16:45 12:00 15:15 Duration (hr.) 3:10 3:05 24:00 24:00 3:00 3:00 24:00 24:00 3:15
3.2 Fish Biometrics All captured were enumerated by collection method. Captured salmonids were identified to species, fork length to the nearest millimeter (mm) and wet weight nearest 0.1 gms on a portable Scout Ohaus electronic balance. Scale samples were collected from all salmonids following standard scale collection methodology. The scales were scraped from the “preferred” area and applied as a scale smear to a glass microscope slide. The scales were then compressed with another slide, labeled and stored for future reading. Live fish (those in the Gee traps), were released unharmed. The fish collected in the gill nets were retained and returned to the lab. All dead fish 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.
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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.
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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. Scales from the smear were selected for their clarity and photographed using a digital camera and appropriate adapter. The image was saved and read on a desktop computer. The scale analysis was completed in a similar iterative fashion reported by Bruce (2004). Each year of growth was determined from the focus of the scale outward using: 1. Determination of widely versus closely spaced circuli bands to determine growth seasons. 2. Area devoid of circuli 3. Incomplete circuli 4. Irregular circuli 5. Breaks and/or spawning checks in circuli patterns. The age is reported using the convention n+ values where the ‘+’ denotes a partial year. 3.4 Data Analysis All Captured fish were reported by catch type and may be used to compare catch-per-unit effort as the data set increases. Biometric data summarized by species and age class if possible. The condition coefficient of each group is also calculated using: Condition Coefficient (CC) = wet weight (gms) x length (cm)-3 x 100
3.5 Creel Survey A creel census will consist of angler interviews as the fishing trip is concluded. The staff at the Clowhom lodge will conduct and record census data as fisherman return to the dock. In order to narrows lake utilization and angler success the lake (reservoir) is broken into 4 arbitrary zones and is shown on Figure 2. Anglers fishing the lake will be asked to provide the following information by zone. The standard will used in subsequent years. • • • • • • Total hours of actual fishing Type of gear used Number of fish caught by species Number of fish released Biometric data for harvested fish (weight, length and scale) Stomach contents of fish harvested.
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Figure 3: Sport fishing zones assigned to the Clowhom Lake reservoir. Zone boundaries are assigned based on local topography. .
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In addition to biometric and catch effort data the following information will also be collected: • Date • Fishing ability (beginner, intermediate, advanced) • Start and finish times of trip 4.0 Results 4.1 Fish Capture A total of 159 fish were caught during the sampling period. The total catch was comprised of 3 species of salmonids (11.3%) and 2 non-salmonid species (88.7%) (Table II) with the gill nets accounting for 5.7% of the total catch and the minnow traps the balance (94.3%). All non-salmonid species were caught along the shoreline in the minnow traps. Table II: Species captured in Clowhom Lake sampling, September 18 and 19, 2006.
Salmonids Common Name Scientific Name Cutthroat Trout (CT) Oncorhynchus clarki Rainbow Trout (RBT) O. mykiss Kokanee (KO) O. nerka Non-salmonids Common Name Scientific Name Prickly sculpin (CC) Cottus asper Three-spine stickleback (SB) Gasterosteus spp.
The total catch was also separated by capture method and the catch reported by sample location (Table III). All 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 September 18 and 19, 2006. Site
A B 1 C D E F G
Gear Type
Floating GN Sinking GN MT MT Floating GN Sinking GN MT
Species
Cutthroat Trout Rainbow Trout Prickly Sculpin Stickleback Prickly Sculpin Rainbow Trout Cutthroat Trout Rainbow Trout Prickly Sculpin Stickleback Rainbow Trout Prickly Sculpin Stickleback Rainbow Trout Kokanee
Number
0 2 1 20 1 30 2 2 6 17 1 4 70 3 1 1
H
MT
I
Drift GN
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4.2 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 19 fish from all capture methods.
Table IV: Summary of length-at-age data for the salmonids caught in Clowhom Lake between September 13, and 19, 2006. Species specific fork length (mm) Rainbow Trout Cutthroat Trout Kokanee n Ave±SD n Ave±SD n Ave±SD 0 0 0 7 112±6.6 0 1 177 4 167±14.8 0 0 0 1 282 0 3 243±8.2 3 334±39.3 0 0
Age 0+ 1+ 2+ 3+ 4+ 5+
Table V: Summary of wet weight data for the salmonids caught in Clowhom Lake between September 13, and 19, 2006. Species specific wet weight (gms) Rainbow Trout Cutthroat Trout n Ave±SD n Ave±SD 0 0 7 14.9±2.45 0 4 48.1±12.9 0 0 1 189.4 3 155.5±28.51 3 386.8±105.8 0 0
Age 0+ 1+ 2+ 3+ 4+ 5+
Kokanee n Ave±SD 0 1 62.2 0 0 -
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.
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Table VI: Summary of condition coefficients for the salmonids caught in Clowhom Lake between September 13, and 19, 2006. Species specific condition coefficient Rainbow Trout Cutthroat Trout Kokanee n Ave±SD n Ave±SD n Ave±SD 0 0 0 7 1.05±0.12 0 1 0.84 4 1.01±0.08 0 0 0 1 1.12 0 3 1.08±0.10 3 1.04±0.17 0 0 -
Age 0+ 1+ 2+ 3+ 4+ 5+
4.3 Creel Survey There were no recorded recreational fishermen utilizing the reservoir during the summer and fall of 2006. The lodge did not report and fishing clients.
600 Cutthroat Trout Rainbow Trout Kokanee
400
Wet weight (gms)
200 0 100 200 300 400
Nose to fork length (mm)
Figure 4: Length versus weight relationships for salmonids captured in Clowhom Lake reservoir between September 18 and 19, 2006
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5.0 Discussion The data summarized in this report is the represents the first year of the productivity monitoring under the present WUP. Results appear to show a “significant” decline between data presented by Bruce (2004) where 47 salmonids were captured within a similar time period. Whether this is a true reflection of changes 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. The enclosed data and results of the 2006 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. 6.0 References Resource Inventory Committee (1998) Reconnaissance Fish and habitat inventory: Standards and procedures. BC Ministry of Fisheries, Victoria, BC. Bruce, James, 2004. Results of fish studies – Clowhom Lake Water Use Plan. BC Hydro Technical Note Com-FTC-TN-001. Burnaby, BC.
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