Stave River Project Water Use Plan

Transcription

1 Stave River Project Water Use Plan STAVE RIVER RISK OF ADULT STRANDING MONITOR (2006) SFLMON#5 Stave-WUP Adult Stranding 05 Study Period: Oct. Nov Report Date: March 2007 Written By: Troffe, P.M., and J. Ladell; InStream Fisheries Research 26 February 2007

2 STAVE RIVER RISK OF ADULT STRANDING MONITOR (2006) BC Hydro Reference No. : Stave-WUPAdultStranding05 Prepared by P.M. Troffe & J. Ladell March, 2007 InStream Fisheries Research Inc West Broadway, Vancouver, BC, V6K 2G8 Tel Fax

3 EXECUTIVE SUMMARY During late October and mid November, 2006 while the fall block loading operation was implemented a total of 16.1 kilometers of Lower Stave River shoreline was surveyed for stranded spawning salmon at a distance between 500 and 1000 m downstream of Ruskin Dam. A total of 1340 adult chum salmon were observed above the 100 m 3 s -1 watermark elevation. Each fish was examined for body condition, gonad condition and egg retention. The sex ratio of spawners was skewed towards females, averaging 1.37 females to every male, and ranged from a low of 1.14 at the start of the survey to a high of 1.59 on the last survey date. Of the female carcasses encountered, the majority were categorized as spawned out (87 % -100%), with fewer (0 % - 8.6%) identified as partially spawned out, and a smaller number (0 % %) classified as unspawned. During the Lower Stave River 2006 chum salmon spawning period, normal fall block loading operations were interrupted by two rainfall-induced spill events which resulted in peaking discharges greater than 600 m 3 s -1 ;a discharge well beyond the usual block load maximum of 325 m 3 s -1. Discharges were correlated to spawning ground tailwater elevations and the risk of stranding for unspawned, partially spawned, and spawned out adult female spawners increased with the magnitude of the operational drawdown during block loading operations. Analysis of covariance indicates the ratio of stranded spawner categories remains constant regardless of tail water elevation. An analysis of variance suggests the average stranding rate of unspawned and partially spawned fish were not significantly different, however, the stranding rate of spawned out fish is significantly higher. We suggest a performance measure be used to identify biologically significant levels of adult standing where the maximum yearly stranding rate of unspawned females is set at 0.39% of the total yearly female escapement 1 during normal fall block load operations. Should increases in stranding be observed above the performance measure in any survey year, evaluation of pre-spawn stranding rates of chum salmon on an unregulated watershed should be undertaken to assess if this value falls within typical natural variation, as published data on this subject area is limited. 1 Based on 2006 DFO escapement estimates ii

4 ACKNOWLEDGEMTS We would like thank the following people for their cooperation and help on this project: Dave Hunter, BC Hydro Coastal Generation James Bruce, BC Hydro Coastal Generation Kim Meidal, BC Hydro Operations Planning Miwako Nicol, InStream Fisheries Research Inc. Don McCubbing, InStream Fisheries Research Inc. Lynne Campo, Water Survey Canada CITATION Troffe, P.M., and J. Ladell Lower Stave River risk of adult salmon spawner stranding, Technical report for BC Hydro Coastal Generation. 26 p. iii

5 TABLE OF CONTENTS 1.0 INTRODUCTION METHODS FIELD METHODS DATA ANALYSIS CARCASS EGG RETENTION STRANDING AND BLOCK LOADING RESULTS DISCHARGE AND TAIL WATER ELEVATIONS CARCASS SURVEYS AREA SURVEYED AND PROPORTION OF SPAWNERS FEMALE BODY CONDITION AND EGG RETENTION EGG RETENTION AND OPERATIONAL DISCHARGES BIOLOGICAL SIGNIFICANCE OTHER SPECIES DISCUSSION LITERATURE TABLES FIGURES APPENDIX 19 iv

6 LIST OF TABLES Table 1 Chum salmon carcass data summary from 2006 Lower Stave River adult stranding survey. Table 2 The number and proportion of total female chum salmon assigned to each spawner and body condition category. v

7 LIST OF FIGURES Figure 1 Downstream representation of islands one, two and three surveyed during the 2006 adult spawner survey. Figure 2 Most common condition categories of chum salmon carcasses observed during the adult stranding survey. Figure 3 Spawned out female chum salmon carcass containing approximately 200 eggs observed during the adult spawner survey. Figure 4 Hourly averaged operational discharges observed during the adult spawner survey. Figure 5 Hourly averaged tail water elevations observed during the adult spawner survey. Figure 6 Linear regression of hourly averaged tail water elevation and operational discharges observed during the adult spawner survey. Figure 7 Hourly averaged Fraser River elevations as recorded by the Water Survey of Canada survey station at Mission B.C. Figure 8 Proportion of daily surveyed female chum spawner carcasses assigned to each spawner category during the adult spawner survey. Figure 9 Partially spawned out female chum salmon carcass observed entangled in angling monofilament during the adult spawner survey. Figure 10 Proportion of daily surveyed female chum spawner carcasses assigned to each body condition category during the adult spawner survey. Figure 11 Linear regression of the number of chum salmon carcasses per kilometer of survey shore versus tail water elevation. Figure 12 Linear regression of total number of eggs and eggs from unspawned carcasses enumerated per survey date versus tail water elevation. vi

8 1.0 INTRODUCTION The Stave River Water Use Planning (WUP) process was completed in 1999 and identified knowledge uncertainties dealing with the potential impacts of flow fluctuations on the reproductive cycle of salmonids downstream of Ruskin Dam (Failing 1999). Among the several operational changes adopted in the Stave River Water Use Plan is a limited block loading operating strategy that is implemented on two separate occasions, one of which is between October 15 to November 30 and is defined here as the fall limited block loading period (Failing 1999). The objective of this operating strategy in the fall is to limit the stranding of chum salmon redds at higher bank elevations by disrupting spawning activity in shoreline areas that lie above the 100 m 3 s -1 water level. The underlying premise of this strategy is that daily flow variations between 100 m 3 s -1 and 325 m 3 s -1 (maximum turbine release), undertaken to match peaking power demands, will disrupt redd excavation such that it forces most spawners into mid-channel areas to complete their spawning activity. Use of this strategy however, assumes that gravid spawners do not remain at their initial redd excavations and therefore put themselves at risk of stranding when water levels recede from 325 m 3 s -1 to 100 m 3 s -1. The validity of this assumption however, was uncertain and a monitor was designed to assess the risk of adult stranding during periods of this limited block loading operation. The success of the limited block loading strategy as a means of improving operational flexibly without negatively impacting spawning success hinges on a number of factors, one of which is that it does not result in the stranding of unspawned females. Significant stranding of gravid spawners could result in considerable egg loss and offset the potential reproductive gains of the strategy. Low stranding rates of gravid or partially spawned out females would validate a key assumption of the limited block loading strategy and thus support its continued use. If significant stranding of these fish occurs, the strategy may have to be modified where possible or be abandoned if the impact is deemed too great. The level of stranding that distinguishes biologically significant versus non-significant impact is to be determined by management committee in consultation with knowledgeable experts. The management questions addressed in this report are: 1. What is the rate of gravid chum salmon stranding during the limited block loading operations? 2. Is the level of stranding biologically important? This monitor is designed to test only one null hypothesis: Ho: The proportion of all stranded chum salmon that are gravid or only partially spawned out is less than a threshold value deemed to indicate significant egg loss. 1

9 2.0 METHODS 2.1 FIELD METHODS Shoreline adult stranding observations were conducted when fall block loading operations were in effect on three mid-channel islands between 500 m and 1000 m downstream of Ruskin Dam (Figure 1). Four hour spawner surveys were conducted at low tide while generation from Ruskin Dam was reduced to the minimum 100 m 3 s -1 discharge. Field crews investigated all new spawner carcasses encountered above the 100 m 3 s -1 water elevation during two observation periods comprising of a total of eight days through, October 31 November 2, and November 10 November 14, All carcasses encountered were identified to species, enumerated and their external condition classified based on a five point condition scale which was used to help estimate the likely time since stranding (Figure 2). Gonad condition was assessed by internal dissection and the number of eggs per female was recorded. Male testes were assessed on a three point condition scale with S1 males recorded as spent, S2 as intermediate and S3 as ripe with milt. It should be noted some carcasses might have become stranded many days after natural death due to normal tidal cycle and flushing. The condition of the carcasses was classified according to the following criteria: Condition 0 Carcass has likely just entered freshwater with no fin abrasion or body scarring present. Fish has likely become recently stranded due to fluctuating water levels. No evidence of avian predation. Condition 1 Carcass has little to no fin abrasion or body scarring and likely recently expired due to natural causes. Little to no avian predation. Condition 2 Carcass has some fin abrasion and body scarring and has likely been dead for more than 24 hours. Avian predation may have occurred. Condition 3 Carcass fins and body are heavily abraded and body is rigoured and bloated. Considerable avian predation. Condition 4 Carcass fins and body are markedly deteriorated and fungused. 2.2 DATA ANALYSIS CARCASS EGG RETENTION Following Chapman et al. (1984) female carcasses were classified as being spawned-out if containing less than 300 eggs, partially spawned-out if containing more than 300 eggs, but less than 1000 eggs, and carcasses that retain more than 1000 eggs will be classified 2

10 as being unspawned (Figure 3). Chi-squared contingency tests following procedures outlined in Zar (1984) was performed on the entire female dataset to assess whether female fish condition is independent of egg retention. The incidence of female adult stranding is reported as the number of unspawned and partially spawned out carcasses relative to the total female carcass count. It was assumed that unspawned and partially spawned-out females are equally likely to become stranded STRANDING AND BLOCK LOADING Daily estimates of unspawned, partially spawned and spawned female stranding rate were correlated to the previous 48 hours discharge and tail water elevation (tidal and block loading) to determine whether spawner stranding is independent of operational release. Comparison with literature data was used to help establish the normal variance that might be expected in pre-spawner mortality. To create a conservative proportional yearly estimate of female adult stranding we used 2006 DFO escapement data and the average observed sex ratio to calculate that some 219, 200 females returned to spawn during The maximum daily stranding rate is multiplied by total shoreline and spawning run time duration then the product is divided by total female escapement. 3.0 RESULTS 3.1 DISCHARGE AND TAIL WATER ELEVATIONS The hourly tail water elevations and discharges were recorded on site by BC Hydro operations during the October November, 2006 block loading period. Discharges ranged from a low of 63 m 3 s -1, with and associated 1.9 m tail water elevation, to a high of 696 m 3 s -1, with a tail water elevation of 4.0 m (Figures 4, 5). No peaking discharges were released during the early portion of the spawning season and flows were maintained near the minimum 100 m 3 s -1 due to un-seasonally dry weather. This dry period was followed by two extreme precipitation events during the last phase of spawning which resulted in two spill events, both with peaking discharges of over 600 m 3 s -1 (Figure 4). Tail water elevations during normal fall block loading operations ranged between 1.9 m and 3.0 m, depending on peaking discharge, however, during spill events tail water elevations between 3.0 m and 4.0 m were recorded (Figure 5). Figure 6 demonstrates the strong positive curvilinear relationship (R 2 = 0.98) between Lower Stave River tail water elevation and operational discharge during the fall 2006 block loading period. The Lower Stave River downstream of Ruskin Dam is in close proximity to the Fraser River confluence and the whole spawning area can be backwatered by seasonal variations in fluvial discharge and daily tidal phase (Troffe 2005; Leake and McLean 1998). During the 2006 block load period the range of hourly average variation in water elevations, as recorded at the Water Survey of Canada station at Mission, BC, spanned -0.5 to 3.25 m (Figure 7). 3

11 3.2 CARCASS SURVEYS 3.21 AREA SURVEYED AND PROPORTION OF SPAWNERS A total of 16.1 kilometers of shoreline distance was surveyed with a total count of 1340 adult chum salmon that were found at elevations above the 100 m 3 s -1 watermark (Table 1). The sex ratio of spawners was skewed towards females, averaging 1.37 females to every male and ranged from a low of 1.14 at the start of the survey to a high of 1.59 on the last survey date. (Table 1). Of the female carcasses encountered, the majority were categorized as spawned out (87 % -100%), with fewer (0 % - 8.6%) identified as partially spawned out, and some (0 % %) classified as unspawned (Figure 8). One partially spawned female carcass was observed entangled in angling monofilament (Figure 9). Appendix 1 contains the raw survey data with individual egg retention and condition assessments FEMALE BODY CONDITION AND EGG RETENTION The majority of females chum carcasses surveyed were assigned a Condition-2 or Condition-3 assessment value and over 65% (541/839) of the carcasses were classified as spawned out, Condition-3 females (Table 2). Condition-1, and Condition-4 fish comprised of 3.4 % (29/839) and 8.7% (73/839) of the female carcass population, respectively, and a general trend suggests a serial reduction in the proportional number of Condition-1 females with a concurrent increase in the number of Condition-4 females as spawning season progressed into its final phase (Figure 10). A Chi-square contingency analysis (3 x 4 format) was performed on the female dataset presented in Table 2 to address if carcass egg retention categories (spawned out, partially spawned, unspawned) were independent of carcass body condition (Conditions 1-4). Results failed to reject the null hypothesis with a χ 2 - value of 8.4, (0.10 < p < 0.25) suggesting that there might be equal recruitment among each egg retention category regardless of carcasses body condition EGG RETENTION AND OPERATIONAL DISCHARGES The number of spawned, partially spawned, and unspawned females encountered per river kilometer during each survey day was regressed against the maximum tail water elevation recorded during the 48 hours previous to the days survey period. A positive natural log linear relationship was demonstrated between maximum tail water elevation for each carcass category with r 2 values ranging from (Figure 11). Analysis of covariance (ANCOVA) on natural log transformed stranding rates demonstrates that the slope of the lines are similar suggesting stranding rates as a function of tailwater elevation do not differ between the spawner groups (F= 3.1, p= 0.15, α = 0.05). An analysis of variance (ANOVA) suggests that the average stranding rate of unspawned and partially spawned fish were not significantly different (p=0.81), however, the stranding rate of spawned out fish is significantly higher (p>0.001). 4

12 A similar positive linear relationship was found among the total number of eggs retained by all females surveyed per kilometer (R 2 = 0.61) and a weaker relationship (R 2 =0.38) for the number of eggs retained only by unspawned females (Figure 12). Unspawned female carcasses, observed at densities ranging from 0 to 4.4 per km versus 21 to 89 per km for spawned out carcasses, accounted for the majority of eggs retained by spawners per river kilometer as they were far more fecund than the other spawner categories. (Figures 11, 12). 3.3 BIOLOGICAL SIGNIFICANCE Based on historical escapement records the majority of chum spawning takes place in approximately 45 days (October 15 November 30) and the total estimated shoreline distance of the spawning reach in the Lower Stave River is 12.1 kilometers (Leake and McLean 1998; DFO data on file). The maximum daily stranding rate of unspawned females during normal block loading operations where tail water elevations are less than 3.0 m was 1.6 females per kilometer. During spill events, where tail water elevations are greater than 3.0 m, the stranding rate of unspawned females increased by more than a factor of two to 4.4 females per kilometer. A maximum yearly stranding rate for unspawned females of approximately 0.39% (864 / 219,200) of the total female escapement was observed during normal block loading conditions when tail water elevations were less than 3.0 m and the yearly stranding rate increased to 1.1% (2396 / 219,200) under spill conditions when tail water elevations were greater than 3.0 m. The average daily total number of eggs observed from partially and unspawned female chum carcasses per kilometer during the observation period was 4128 ± 4059 S.D. eggs Assuming egg loss was equal through the spawning reaches and season, on average, an estimated 0.40 % (2.48 million / million eggs spawned) of total egg production was lost to stranded fish, representing approximately 802 females 2, or 0.36 % (802/219,200) of the total yearly female escapement. 3.4 OTHER SPECIES The 2006 adult stranding survey was primarily focused on the numerous chum salmon spawners, however, during the eight day survey covering 16.1 km of shoreline, three chinook and four coho female spawners were also assessed. Two of the chinook and one of the coho females were spawned out and one of the chinook and three of the coho females were classified as unspawned. The body condition of the carcasses ranged Condition 2-3 and there were no obvious visual causes for their mortality (e.g. predation, angling). 2 Assumes average fecundity of 2800 eggs per female spawner (Bradford 1995) 5

13 4.0 DISCUSSION In a summary of chum salmon run timing, Salo (1991) reports that males typically predominate early in the spawning run followed by a dominance of females late in run. Also, when spawner densities are very high (as they are in the Lower Stave River) courtship and territorial defenses tend to break down and mass spawning occurs. The present adult stranding survey was conducted during the final phase of spawning and our data indicates that the sex ratio became increasingly skewed to females as the spawning season advanced. Troffe (2005) observed when spawner densities are high fish were taking advantage of access to high elevation sites to create redds and this may increase the risk of spawner stranding. A general trend indicates a reduction in body condition of female spawners with a proportional decrease in the number of Condition 1 fish, concurrent with increases in the number of Condition 4 fish as spawning season progressed into its final phase. Contingency analysis indicates that female carcass body condition appears to be independent of the number of eggs retained, suggesting that there might be equal recruitment among each spawner category regardless of carcasses body condition. During the Lower Stave River 2006 chum salmon spawning period normal fall block loading operations were interrupted by two spill events which resulted in discharges of greater than 600 m 3 s -1, well beyond the usual block load maximum of 325 m 3 s -1. Discharges were highly correlated to spawning ground tail water elevations and the risk of stranding unspawned, partially spawned, and spawned out adult female spawners increased with the magnitude of the operational draw down during block loading operations. Leake and McLean (1998) identified that 1.5% of the total chum fry population emerging in the Lower Stave River is exposed to stranding mortality during spring operations and the WUP CC s acceptance of the block loading operating conditions in 1999 was contingent on the condition that fry stranding mortality remain less than 1.5% of total production in subsequent years (Failing 1999). By extension, we suggest here that a similar performance measure be used to identify biologically significant levels of adult standing where the maximum yearly stranding rate during normal fall block load operations of unspawned females is set at 0.39% of the total female escapement. Further considerations should be given to acceptable spawner stranding under spill conditions but these events remain rare and are usually less than 36 hours in duration when the watershed receives unusually large amounts of precipitation. This study takes a conservative approach and assumes that all spawner stranding is the result of peaking operations and the threshold identifying an unspawned female was set at a conservative 1000 eggs, while, Salo (1991) reports mean fecundity of chum ranging eggs. Moreover, female carcasses counted as unspawned or partially spawned were assumed to have been stranded because of their persistence to remain on their redd despite dropping water levels and spent female carcasses found on shore were assumed to have passively washed up there because of water currents while discharge flows and resulting tail water elevations were high. It is important to remember that while we assume that all unspawned females have become stranded because of block load or spill operations there are many naturally occurring causes for egg retention and prespawning mortality in anadromous salmon and the subject has not been intensively 6

14 studied in chum salmon. Kolski (1975) and Schroder (1981) linked water temperature, time of freshwater entry, and density dependent population mechanisms to egg retention and pre-spawning mortality in female chum salmon in Big Beef Creek, Washington. Observations of carcasses during 2005 and 2006 field seasons suggest that hooking mortality due to heavy angling pressure at the Lower Stave River may contribute to the number of unspawned females found at high elevation site during stranding surveys. Should increases in stranding be observed above the proposed performance measure in any survey year, evaluation of stranding rates of chum salmon on an unregulated watershed should be undertaken to assess if this value falls within typical natural variation, as published data on this subject area is limited. 5.0 LITERATURE Bradford, M. J Comparative analysis of Pacific salmon survival rates. Can. J. Fish. Aquat. Sci. 52: Chapman, D.W., D.E. Weitkamp, T.L. Welsh, M.B. Dell, and T.H. Schadt Effects of river flow on the distribution of chinook salmon redds. Transactions of the American Fisheries Society. 115(4) Failing, L Stave River Water Use Plan: Report of the consultative committee. Prepared by Compass Resource Management Ltd for BC Hydro. October pp. + App. Kolski, K.V The survival and fitness of two stocks of chum salmon (Oncorhynchus keta) from egg deposition to emergence in a controlled-stream environment at Big Beef Creek. P.h.D. thesis. University of Washington, Seattle, Wa. 212 pp. Leake, A. C. and L. G. MacLean Assessment of chum fry stranding downstream of Ruskin Generating Station. BC Hydro Environmental Services Technical Report. 22 pp. + App. Schroder, S.L The role of sexual selection in determining overall mate choice in chum salmon. P.h.D. thesis. University of Washington, Seattle, Wa. 274 pp. Salo, E.O Life history of Chum Salmon. In: C. Groot, and L. Margolis (ed) Pacific Salmon Life Histories. pp Troffe, P.M Preliminary report on the Lower Stave River Limited Block Load as deterrent to spawning monitor. November 17, pp. Zar, J.H Biostatistical Analysis, 2 ed. Prentice-Hall, Inc., Englewood Cliffs, New Jersey. 7

15 6.0 TABLES Table 1 Chum salmon carcass data summary from 2006 Lower Stave River adult stranding survey. All carcasses found at high elevations were examined and species ID, sex, body condition, gonad condition (males), and number of eggs retained by females was noted. Date MALE N FEMALE N TOTAL N F:M SEX RATIO SPAWNED OUT (<300 EGGS) PARTIALLY SPAWNED (>300<1000 EGGS) UNSPAWNED (>1000 EGGS) TOTAL SHORELINE SEARCHED (KM) 31-Oct Nov Nov Nov Nov Nov Nov Nov TOTALS Table 2 The number and proportion (%) of total female chum salmon assigned to each spawner and body condition category during 2006 adult spawner stranding survey at the Lower Stave River. CONDITION 1 CONDITION 2 CONDITION 3 CONDITION 4 SPAWNED OUT 25 (2.9) 160 (19) 541 (65) 72 (8.6) PARTIAL SPAWNED 2 (0.2) 4 (0.4) 15 (1.8) 1 (0.1) UNSPAWNED 2 (0.2) 2 (0.2) 15 (1.8) 0 (0) TOTALS

16 7.0 FIGURES Figure 1 Downstream representation of islands 1, 2 and 3 surveyed during the 2006 adult spawner survey, Lower Stave River, B.C. (Source of image: Google Earth) 9

17 Figure 2 Most common condition categories of chum salmon carcasses observed during the Lower Stave River adult stranding survey. Fish assigned to body condition categories C2 (bottom), C3 (middle), and C4 (top) based on fin, external colour, and body deterioration assessment. 10

18 Figure 3 Spawned out female chum salmon carcass containing approximately 200 eggs observed during the 2006 adult spawner survey, Lower Stave River, B.C. 11

19 Discharge (CMS) /10/ /10/ /10/ /10/ /10/ /11/ /11/ /11/ /11/2006 Figure 4 Hourly averaged operational discharges (m 3 s -1 ) observed during the 2006 adult spawner survey, Lower Stave River, B.C. Normal block loading operations were interrupted by two spill events during November Tailwater (m) /10/ /10/ /10/ /10/ /10/ /11/ /11/ /11/ /11/2006 Figure 5 Hourly averaged tail water elevations (m) observed during the 2006 adult spawner survey, Lower Stave River, B.C. 12

20 4.5 4 Tailwater Elevation (m) y = x R 2 = Discharge (CMS) Figure 6 Power regression of hourly averaged tail water elevation (m) and operational discharges (m 3 s -1 ) observed during the 2006 adult spawner survey, Lower Stave River, B.C. NB observations greater than 325 m 3 s -1 are considered spill conditions. Figure 7 Hourly averaged Fraser River elevations (m) as recorded by the Water Survey of Canada survey station at Mission B.C. (49 07' 39" N ' 08" W). 13

21 100% SPAWNED OUT (<300 EGGS) 80% PARTIALLY SPAWNED (>300<1000 EGGS) UNSPAWNED (>1000) 60% 40% 20% SURVEY SUSPENDED 0% 31-Oct-06 1-Nov-06 2-Nov-06 3-Nov-06 4-Nov-06 5-Nov-06 6-Nov-06 7-Nov-06 8-Nov-06 9-Nov Nov Nov Nov Nov Nov-06 Figure 8 Proportion of daily surveyed female chum spawner carcasses assigned to each spawner category during the 2006 adult spawner survey, Lower Stave River, B.C. Carcasses were classified as: spawned out if they contained fewer than 300 eggs, partially spawned out if they contained more than 300 but less than 1000 eggs, and as unspawned if carcasses they contained more than 1000 eggs. 14

22 Figure 9 Partially spawned out female chum salmon carcass observed entangled in angling monofilament during the 2006 adult spawner survey, Lower Stave River, B.C. 15

23 90% 80% 70% 60% CONDITION 1 CONDITION 2 CONDITION 3 CONDITION 4 50% 40% 30% 20% 10% SURVEY SUSPENDED 0% 31/10/ /11/ /11/ /11/ /11/ /11/ /11/ /11/ /11/ /11/ /11/ /11/ /11/ /11/ /11/2006 Figure 10 Proportion of daily surveyed female chum spawner carcasses assigned to each body condition category during the 2006 adult spawner survey, Lower Stave River, B.C. 16

24 6 5 PARTIALLY SPAWNED UNSPAWNED SPAWNED OUT Linear (UNSPAWNED) Linear (PARTIALLY SPAWNED ) Linear (SPAWNED OUT) y = 0.83x R 2 = 0.53 ln (# of carcasses per km) y = 1.48x R 2 = y = 1.05x R 2 = Tailwater elevation (m) Figure 11 Natural log linear regression of the number of chum salmon carcasses per kilometer of survey shore versus the maximum Lower Stave River tail water elevation (m) observed in the 48 hours previous to the 2006 survey date. 17

25 14000 EGGS / KM TOTAL EGGS UNSPAWNED EGGS Linear (TOTAL EGGS) Linear (UNSPAWNED EGGS) R 2 = R 2 = TAILWATER ELEVATION (m) Figure 12 Linear regression of total number of eggs observed in all carcasses (solid with dashed line ) and eggs from unspawned (open with solid line) carcasses enumerated per survey date versus the maximum Lower Stave River tail water elevation (m) observed in the 48 hours previous to the 2006 survey date. 18

26 8.0 APPENDIX See attached electronic data file containing raw survey data. 19