Salmonid Escapement Estimates on the Deadman River, resistivity counter video validation and escapement estimates.
By
D.J.F. McCubbing and D.Ignace
Instream Fisheries Consultants 2-1883 West 3rd Ave Vancouver B.C. V6J 1K9 Tel 1-604-737-1510 Fax 1-604-737-1595 [email protected]
Project Report No. 2000
Executive Summary
An electronic resistivity counter was installed on the Deadmans River (Thompson River tributary near Kamloops) in the spring of 1999, to enumerate anadromous steelhead and rainbow trout. The resistivity fish counter, (Aquantic Ltd, Logie Counter 2100C) was installed approximately 3km upstream of the Deadman Rivers confluence with the Thompson River and was operational from the 22nd of April 1999.
The fish counter was validated using video equipment between August 28th and November 8th 1999 during the coho and chinook salmon migration. A total of 424 upstream and 120 downstream migrants were observed from video tape analysis of which 96% of the upstream and 89% of the downstream fish wee counted. Beaver activity caused some false upstream and downstream counts, although appeared restricted to the hours of darkness and skewed to November observations. Trace data indicated beaver activity could be manually removed with a very high degree of accuracy (98% or higher).
Fish sizing appeared accurate enough to determine rainbow trout from steelhead trout with little miss-classification of species, although a very small number of individuals weights/lengths may overlap based on data from the Boneparte River.
Using video validation data a minimum escapement estimate of 769 steelhead spawners was arrived at from counter data. Rainbow trout escapement was estimated at 2710 individuals, although some smaller fish may not have been counted as they were below the threshold size (20cm) as set-up in the counter firmware.
Observations of a significant upstream movement of fish under high flow conditions in June has resulted in a separate investigation to assess the species of fish utilizing this flow period. Whilst the analysis undertaken forms part of a separate study, without the installation of the resistivity counter this migration would not have been recorded.
The value of this method of data collection under medium and high flows, without delaying migration and without the need for handling fish is highlighted.
ACKNOWLEDGEMENTS
Funding for this project was provided by the Thompson Basin Trust through Fisheries Renewal B.C.. Development of the electronic counter was a joint venture between the Department of Fisheries and Oceans, Ministry of Environment Land and Parks, Ministry of Fisheries, Forest Renewal BC and the Skeetchestn Indian Band. Steve Maricle, Rob Bison and Don Ignace were helpful with their determination to develop this technology and in assisting with data interpretation.
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TABLE OF CONTENTS
page Executive Summary i
Acknowledgements i
Table of Contents ii
List of Figures iii
1.0 Introduction 1
2.0 Study Area & Methods 2 2.1 Fish Counter 3 2.2 Counter Operation 4 2.3 Video Validation 6
3.0 Results 7 3.1 Raw data analysis 7 3.1.1 "Ghost" counts 3.1.2 Kelt migration 3.1.3 Signal Sizes 3.1.4 Temporal Variation in counts 3.1.5 Migration, river discharge and temperature
3.2 Video validation 3.3 Counter Efficiency 3.4 Fish Sizing 3.5 Polulation Enumeration Esimates 3.5.1 Trace Assisted 3.5.2 Video Validation Assisted
4.0 Discussion
5.0 Summary.
6.0 References.
7.0 Appendix
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List of Figures
page Figure 1:Historical variability in wild steelhead populations over time in the Deadman River, based on fence counts. 1
Figure 2: Stylised channel design, Deadmans River 1999 Error! Bookmark not defined.
Figure 3. Counter construction, Deadmans River 1999 Error! Bookmark not defined.
Figure 4: Typical trace output of upstream fish event. 5
Figure 5: Video Validation Equipment 6
Figure 6. Screen measurement of total fish length, from video tape. 7
Figure 7: Daily fish count on the Deadmans River 1999 (corrected for ghost data) 9
Figure 8: Assigned species distribution classes, upstream migrants 1999. 10
Figure 9: Daily net upstream counts of steelhead trout and rainbow trout from he resistivity fish counter on the Deadmans River in 1999. 11
Figure 10. Daily time of migration, upstream fish, Deadmans River 1999. 12
Figure 11 Peak daily river discharge and up fish counts, Deadmans River 1999. 13
Figure 12 Peak daily water temperature and up fish counts, Deadmans River 1999. 13
Figure 13. Relationship of observed video length (cm) to PSS in salmon passing over the Deadman counter during video validation in 1999. 15
Figure 14. Boneparte River, steelhead and rainbow trout length 18 frequency histograms, 1998 data.
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INTRODUCTION
This report studies the effectiveness of electronic methods of assessing salmonid escapement to the Deadman River, (near Savona BC). The primary objective of the project was to assess the accuracy of count of upstream and downstream migrating adult salmonids, in particular steelhead trout, rainbow trout whilst utilizing coho/chinook salmon migration for video validation purposes and comparing these methods against more traditional fish fence operations.
This study assesses the effectiveness of the Logie 2100C resistivity fish counter on counting and sizing salmonids over a range of flow and escapement densities. This work will build on population dynamics data gathered from over 17 years of steelhead abundance using fence data, although the two methods of assessing escapement should not be taken as providing comparable data at this time.
Figure 1. Historical variability in wild steelhead populations over time in the Deadman River, based on fence counts.
1400 1200 1000 800 600
Spawners 400
200 n/a n/a 0 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000
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STUDY AREA AND METHODS
Study Area
The Deadmans River watershed is located within the Thompson and Fraser Plateau areas on the Interior Physiographic Region (Holland 1976). The river watershed covers an area of 1,490 km2 , with a peak gauged spring discharge of 60.6m3/s in 1990. Criss Creek it's largest tributary covers an area of 490km2. Elevation range from 350m asl at the Thompson River confluence to 1775m asl in the headwaters of Criss Creek. Peak floods occur in the spring and are generally snow melt dominated although rain-on-snow events are also reported (S.Maricle, Pers. Comm.).
Historic estimates of steelhead abundance have been undertaken using traditional full river fish fences, both below Highway 1 and more recently upstream of Criss Creek, due to the effect of this tributary on the flood levels in the main river stem.
Fish species present in the watershed include rainbow trout (both steelhead and Thompson/Kamloops Lake stock), brook trout, Chinook salmon, coho salmon, pink and sockeye salmon (lower reaches only), longnose dace, two species of sucker and pacific lampreys (Tredger 1980)
The method of assessment under examination in this report, is the Logie fish counter (Aquantic Ltd, Scotland, see Nicholson 1995, McCubbing 1998, McCubbing and Ward 1998, McCubbing et al 1999, McCubbing 1999), a method which electronically counts and sizes migrating fish.
Project Objectives
• Install and operate an electronic fish counter in the Deadmans River • Train local field staff in operation and maintenance of counter • Report on counter performance with calibration/validation of chinook and coho salmon passage in the summer of 1999. • Provide estimates of rainbow trout and steelhead escapement to spawning using the video validation data. • Provide correction factors for future fish counter escapement estimates, with confidence limits.
METHODS
Fish Counter.
The electronic counter is a resistivity counter, which detects the passage of fish across an array of three electrodes, placed across the river, or in a channel, in an insulated base (see fig 1.). The counter electronics continually monitors the resistance of the water above the counting array (bulk resistance) and calibrates for changes in this resistance ever 30 minutes. When a fish passes over the three electrodes, a change in resistance occurs, as a fish is more conductive than the water it displaces. This change of resistance is recorded and analysed by the counter using a firmware algorithm to determine if it fits a typical fish pattern. Should the counter assess that a fish has passed over the array (based on this comparison), the time, direction of travel and peak ______Instream Fisheries Consultants Deadman River Resistivity Counter – Video Validation Draft Page 2
signal size (change of resistance measurement) of the fish event is recorded and stored for later downloading and analysis (see Aprahamian et al 1996 for more details of counter design and operation).
Fig.2. Stylised channel design, Deadmans River 1999
The weir and channel design was a concrete lock-block base and bulkheads with mass concrete sill (DFO design, incorporating 3 channels of 1:2 upstream gradient and 1:5 downstream gradient; based on design by T.Carlson, on file). Alterations to initial design criteria included weir crests built at 30cm, 45cm and 55cm above bed level and cut-waters of increased width (50cm) to increase lateral strength.
To this sill HDPE insulating bases and side-walls were attached. Three stainless steel electrodes were placed in the base the HDPE sheets at 30cm centres to monitor fish passage. This structure was completed on the 22nd of April and the electronic monitoring device a Logie 2100C counter was plugged in.
Figure 3. Counter construction, Deadmans River 1999.
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Counter Operation
Our investigation considers four species of salmonids and two escapement estimates. Coho salmon and chinook salmon were enumerated through electronic counts whilst video validation was undertaken (although fence data was used for escapement estimation). Steelhead and rainbow trout were estimated from electronic counts only with a correction factor based on video validation work used to provide an escapement estimate.
Data collected was stored as buffer files (on the counter) and downloaded on a regular basis by field staff. An example of data derived from the counter is shown below;
04/29/1999 19:44:24 142 1 U 93 04/29/1999 19:46:32 142 1 U 43 04/29/1999 19:47:17 142 2 U 66 The data contains the date of download, settings of the counter, and dummy fish data, followed by fish records. The fish records contain a date, time, conductivity, channel of count (only one channel is operating), direction of travel (up or down) and estimated Peak Signal Strength (PSS) ______Instream Fisheries Consultants Deadman River Resistivity Counter – Video Validation Draft Page 4
Example fish record;
Date Time Conductivity. Channel. Direction PSS
04/29/1999 19:44:24 142 1 U 93
In addition graphical records were collected for migrating fish through much of the migration period. This data was logged direct to portable PC for storage, as the counter memory is insufficient for this purpose (fig 4). Graphical data was used for post data analysis and assisted in the assessment of fish behaviour and counter performance. In addition all variations in peal signal size above threshold values were recorded by the counter and in trace form for later analysis.
Fig 4. Typical trace output of upstream fish event.
150-
100-
50-
0-
-50-
-100- - - - -150- - 123 4
Time.(seconds)
Video Validation
The data obtained from the fish counter was analysed in relation to video footage recorded on channel 2 (deepest water flow, Figure 5) using a black and white video camera (Extreeme EX10S.604), linked to a time delayed video recorder (Pelco TLR2096) and illuminated by an infra light source(Extreeme UF100.401). Similar studies in the United Kingdom (Fewings 1987; Welton et al. 1987; Dunkley 1991; Aprahamian et al. 1995) have shown the value of this video validation methodology. Video footage was recorded for periods of up to 24hours per tape (4 hour tape set on time delay) from August 26th 1999 to November 11th 1999, the main period of chinook and coho salmon migration during which water clarity is suitable for video recording.
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Figure 5. Video Validation Equipment
Each detected event from video and counter records was assigned a code, based on the observed record. A total of 14 code types were used. These are tabulated (Table 1.)
Table 1 Codes used for event recognition and analsysis
Code Identification
UU Upstream fish recorded as upstream fish UE Upstream fish recorded as an event UM Upstream fish – no counter record DD Downstream fish recorded as downstream fish DE Downstream fish recorded as an event DM Downstream fish – no counter record EE Fish event recorded as an event U B Beaver movement recorded as upstream fish U BS Beaver with stick recorded as upstream fish D B Beaver movement recorded as downstream fish D BS Beaver with stick recorded as downstream fish E B Beaver recorded as an event E BS Beaver with stick recorded as an event Ghost No fish/event on video – ghost trace from a large event on a separate channel
Fish total length data from the video (screen length) was interpreted using a monitor (Panasonic) divided into screen sections; due to the sizing differential caused by the required wide angle lens of the video camera. Each screen section was assigned a multiplication factor based on the average screen distance measured between the inner edge of the upstream and downstream ______Instream Fisheries Consultants Deadman River Resistivity Counter – Video Validation Draft Page 6
electrodes (a known actual distance of 700mm) within that screen section. A total of four section were used (Fig. 6) with total fish lengths recorded by direct measurement from the screen (in mm) and then corrected for the appropriate screen section to give an estimated actual fish length.
Figure 6. Screen measurement of total fish length, from video tape.
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RESULTS
Raw Data Analysis.
Fish counter estimates of rainbow trout and steelhead escapement based on counter data in the Deadmans River in 1999 were initially calculated by the following process;
1) All obvious spurious debris or wave action data was removed from the raw data set.
2) All trace data was examined and ghost events removed.
3) All trace data was examined and “events” which were close to typical upstream or downstream based on comparative studies with other sites were altered to represent a true fish event.
4) A daily summary of up and down counts was examined to determine at what stage spawned out fish began dropping back over the counter.
5) A frequency histogram of "peak signal sizes was examined to determine the break point between rainbow trout (typically 1-5lbs in weight) and steelhead trout (typically 6-20lbs in weight) for species classification.
6) A value for net up counts was determined for steelhead and rainbow trout based on peak signal size distributions and the pattern of downstream counts.
Ghost Counts
Raw data was examined for spurious counts that could have been recorded when debris or wave action might have resulted in traces that mimicked fish events. Very few such events were observed during the steelhead migration period based on experience from other similar sites. However many events and some smaller up and down counts were observed to occur simultaneously on all three channels particularly at times of low conductivity when gain settings were high (Appendix 1). Discussion with the counter manufacturer identified these as "ghost traces" caused by linkage in the counters electrode drive board, which only occurs when high gain settings are used in an attempt to count small fish, i.e >30cm in length. Specifically, a large fish passing over one channel (upstream or downstream) causes a ghost image on the other two channels under high gain settings. Such events or upstream and downstream counts were easily identified and removed from the raw data prior to escapement estimates.
Kelt Migration
A daily summery of upstream and downstream counts indicated that downstream counts until the 20th of May were only 5.3% on average (range 0-10%) of the total daily count. After this date the percentage rose quickly with an average of 27% (range 7-56%) of total counts being in a downstream direction in the May 20th to June 3rd period, Figure 7. To establish a total upstream escapement, downstream counts prior to the 20th of May were removed from upstream counts to give a net upstream escapement. The assumption was made that prior to this date spawning was limited and downstream fish were simply milling and would eventually move upstream once more to spawn. After the 20th of May all downstream counts were assessed to be spawned fish and were not removed
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from the upstream counts, thus avoiding a reduction in total upstream escapement due to there outward migration.
Figure 7. Daily fish count on the Deadmans River 1999 (corrected for ghost data)
Up Counts Down Counts
250
200
150
100 Nos of counts 50
0 22-Apr 24-Apr 26-Apr 28-Apr 30-Apr 01-Jun 03-Jun 02-May 04-May 06-May 08-May 10-May 12-May 14-May 16-May 18-May 20-May 22-May 24-May 26-May 28-May 30-May Date
Signal Sizes
Peak signal size which (provided swim height over the electrodes is relatively constant) is a good indicator of the fishes mass (displacement) was analysed through several time periods and over the whole migration period. Data was examined as all channels combined and individual channels through the migration period to assess if variations in signal sizes between channels and across time could be detected. This analysis would highlight any differential sizing caused by channel selection and/or fish swimming height variation with changing water discharge (McCubbing 2000). Length frequency histograms were plotted and the possible break point between rainbow trout and steelhead trout was demonstrated, Figure 8. The low number of counts with PSS in the 110-120 range indicates the stability of the counter over a wide range of flow, temperature conductivity conditions, as it indicates the expected bimodal distribution of the target species, rainbow and steelhead trout. and Some overlap of larger rainbow trout and smaller steelhead trout may have occurred from this data but it probably represents a small percentage of the total count of either species (Maricle pers.comm). A "peak signal size" figure of greater than 110 was used to represent steelhead on this basis.
Figure 8. Assigned species distribution classes, upstream migrants 1999. ______Instream Fisheries Consultants Deadman River Resistivity Counter – Video Validation Draft Page 9
Rainbow Steelhead
600
500
400
300
Nos of Fish 200
100
0
e 10 30 50 70 90 110 or M Peak Signal Size
The final step in initial escapement enumeration estimates was to break down the daily net up count of fish using the size criteria as explained. This provides a raw daily estimated upstream count for steelhead trout and rainbow trout and assists in the interpretation of when the upstream migration run was coming to an end Figure 9.
Figure 9. Daily net upstream counts of steelhead trout and rainbow trout from the resistivity fish counter on the Deadmans River in 1999.
Rainbow Steelhead
180 80 160 70 140 60 120 50 100 40 80 30 60
Nos of Rainbows 20 40 Nos of Steelhead 20 10 0 0 22-Apr 24-Apr 26-Apr 28-Apr 30-Apr 01-Jun 03-Jun 02-May 04-May 06-May 08-May 10-May 12-May 14-May 16-May 18-May 20-May 22-May 24-May 26-May 28-May 30-May Date
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Temporal Variations in Fish Migration
Indications from an analysis of the time of passage over the counting weir, was for migration to be at it's greatest during the late afternoon. This co-incided with the peak of run-off due to daily snow melt. Fish appeared unconcerned over passing over the weir structure during daylight hours, Figure 11. No beaver activity was recorded during daylight hours and on examination of trace data, no signature traces of the type generated by beaver activity were observed either at night or during the day. It is thus reasonable to exclude beaver activity from efficiency estimates when considering steelhead and rainbow trout migration during the spring high water period of April- June.
Figure 10. Daily time of migration, upstream fish, Deadmans River 1999.
Steelhead Rainbow
250
200
150
100
Nos of Fsih 50
0
:00 :00 :00 :00 :00 0 2 4 6 8 0:00 2:00 4:00 6:00 8:00 0:00 2:00 1 1 1 1 1 2 2 Time Period of day
Fish Movement, River Discharge and Temperature.
Upstream migration of steelhead and rainbow trout was observed from the counters first day of operation, on April 23rd 1999. Flows of 5-30 m3s were recorded during steelhead migration although the majority of up counts attributed to steelhead and rainbow trout were observed in the flow range of 10-17.5 m3s . Notable reductions in steelhead migration and rainbow trout migration occurred when flows increased above 18 m3s, with over 80% of both escapements occurring before peak spring discharges of 25-45 m3s were recorded. Water temperatures rose throughout the migration period although peak migration of both rainbow trout and steelhead occurring after a maximum daily water temperature of 8oC was reached.
Figure 11. Peak daily river discharge and up fish counts, Deadman River 1999. ______Instream Fisheries Consultants Deadman River Resistivity Counter – Video Validation Draft Page 11
Nos of Counts (Up) Flow CMS
350 50.00 45.00
300 /s 40.00 3 250 35.00
200 30.00 25.00 150 20.00 Nos of Fish 100 15.00 10.00
50 Estimated discharge m 5.00 0 0.00
r r l y y y un un un ul J J J J - - 1- 6- 0 06-Ju 12-Apr17-Ap22-Ap27-Apr02-May07-Ma12-Ma17-Ma22-May27-May01 06 11-Jun16-Jun21-Jun2 Date
Figure 13 Peak daily water temperature and up counts, Deadman River 1999.
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Video validation Observations.
A total of 2176 discrete observations of fish, beaver and debris movement over channel two of the fish counter were recorded over the 28 days (approximately 672 hours) of viewed tapes stratified over the run from August 26th to November 11th (a total of 59 days, 1416 hours were recorded).
Counter Efficiency
Counter efficiency is generally measured as the number of up or down counts divided by the number of observed up or down fish movements (above threshold setting) and expressed as a percentage. Threshold length of fish was estimated as 25cm for a PSS of 20; all fish below this size were removed from video validation analysis as the counter was not set up to enumerate them.
During video validation of Deadman data it became apparent that downstream movement of beavers was in some cases registering as upstream counts with a variety of signal sizes (mean value 106). Beaver activity was restricted to the hours of darkness and peaked in late October and early November. No upward movement of beavers was detected on the video tapes, rather activity was passive downstream floating through the channel. In may cases this activity was rejected by the counter; 347 of 730 observations, being classed as events. However significant numbers of downstream beaver activity, particularly if the beaver was carrying a stick/branch were miss- classified as up counts. A total of 361 false up counts were recorded in this way, of which 82% were beaver/stick combinations. A small number of down counts were also created in this way, although less in number (22 in total), they inflated the down true down count by 15% before correction for counter efficiency. This beaver activity skewed the counter efficiency high resulting in an inflated upstream fish count. A range of 88-1550% of video upstream count was recorded in any 24hour period (average 233% of true upstream movement). This result was unexpected as non-fish activity is generally discarded by the counter as events. Examination of trace data indicated a distinct multiple peak “signature” trace was recorded by the counter during such events, (which was easily identified, Appendix 2) allowing manual removal of beaver activity.
Based on the manual removal of beaver traces (backed up by video observations), daily counter efficiencies of upstream fish movement, varied over the study period with a range of 78% to 100%. On average 94% of the 472 fish passing over the counter in an upstream direction were recorded correctly during the study period. In comparison some 81% of downstream migrants were correctly enumerated.
Some indication of ghosting was observed between counter channels as observed in the spring migration of salmonids, although with less frequency. This was only evident at low conductivity (unusual in summer flow conditions) and caused some small PSS upstream and downstream counts on channel 2 which could not be attributed to any video observation. This fault requires minor counter hardware redesign (which is underway) but can be removed from escapement estimates manually at present. Manual removal of ghost traces paired with video analysis increased average upstream counter efficiency to 96% (+/-6% 1 S.D.), for all sizes of fish observed, with a daily range of 83% to 100% count efficiency. Downstream count efficiency was increased to an average of 90%.
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Table 3. Range of counter efficiencies of upstream counts observed during video validation on the Deadman River 1999 (excluding ghost traces).
Date U-U U-E UG U-B U-BS % Efficiency % Efficiency * * # # Including Excluding Beavers Beavers
26-Aug 4 0 0 1 0 125.00 100.00 02-Sep 7 0 0 1 0 114.29 100.00 06-Sep 2 0 0 1 0 150.00 100.00 09-Sep 6 0 0 0 0 100.00 100.00 12-Sep 2 0 0 3 0 250.00 100.00 15-Sep 3 0 0 1 2 200.00 100.00 17-Sep 3 0 0 1 3 233.33 100.00 19-Sep 9 0 0 3 2 155.56 100.00 22-Sep 13 0 0 3 0 123.08 100.00 24-Sep 7 0 0 0 0 100.00 100.00 26-Sep 5 0 1 1 6 200.00 83.33 28-Sep 7 0 0 3 2 171.43 100.00 01-Oct 4 0 1 1 1 120.00 80.00 03-Oct 13 0 2 0 8 140.00 86.67 07-Oct 52 3 0 3 8 114.55 94.55 08-Oct 32 0 1 1 15 145.45 96.97 10-Oct 10 1 0 2 19 281.82 90.91 12-Oct 5 0 0 7 12 480.00 100.00 14-Oct 15 0 0 2 12 193.33 100.00 16-Oct 14 0 0 4 5 164.29 100.00 18-Oct 25 2 1 4 11 142.86 89.29 20-Oct 10 0 5 14 290.00 100.00 22-Oct 15 1 3 27 281.25 93.75 26-Oct 64 5 1 0 29 132.86 91.43 28-Oct 57 2 0 2 40 167.80 96.61 03-Nov 4 0 4 54 1550.00 100.00 08-Nov 21 1 7 28 254.55 95.45 09-Nov 30 3 2 4 40 211.43 85.71
Total 439 18 9 67 338 Average 15.68 0.64 0.38 2.39 12.07 235.46 95.88 S.D. 16.11 1.25 0.65 1.93 14.65 270.01 5.98
Note * These values denote upstream migrating fish that were incorrectly counted. # These values denote beavers miss-classified as up counts. ^ These values donate ghost traces created by large counts on channels 1 & 3.
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Several reasons for fish passing over the counter without being correctly counted were observed from video footage. These included, single upstream migrating fish logged as an event, 3.5% of the error (UE), single upstream migrating fish with no record, 0.5% of the error(UM), and ghost traces, 1.9% of the error. However these represented a small number of counts compared to the effects of beaver activity.
Fish sizing
The fish counter can be used to give an indication of fish length through the relationship of Peak signal size (PSS) and fish length/weight. When a fish passes over the electrode array, the larger the size of the fish the greater the volume of water displaced, so the greater the reduction in resistance which is measured by the counter. Factors which may affect the PSS include, water depth, conductivity, fish swim height above the electrode array, inter electrode distance and gain settings (sensitivity). Many of these are automatically calibrated for during standard counter operation, while inter-electrode distance is fixed. Thus two factors, fish size (measured as weight or length) and swim height contribute the greatest variance in PSS. A total of 208 observations of fish passage were of good enough resolution to be used for validation purposes. A strong relationship (Fig.10) was observed between video fish length data and PSS, with much of the variation in observed fish length explained by PSS, when data is transformed (equation 1, r2 = 0.74, n = 208, maximum signal sizes of 127 were excluded).
Figure 13. Relationship of observed video length (cm) to PSS in salmon passing over the Deadman counter during video validation in 1999.
70 65 60 55 50 45 40 35 Fish Length (cm) 30 25 20 20 40 60 80 100 120 140 Peak Signal Size
From this relationship equation 2, can be used with some precision to estimate the length frequency of pink salmon migration without the need to handle fish, (Fig.10.)
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. 1 log10 Fish Length = 0.388 •log10(PSS) + 0.921
where Fish Length = fish total length in cm (from video observations)
A total of 128 observations of fish passage were recorded where the signal size was recorded as 127, the maximum signal size recordable by the counter. The average size of fish producing this PSS was 57cm. The smallest fish that produced a PSS of 127 was 47cm in length.
Enumeration Estimates
Trace assisted population estimates.
A corrected population estimate of 860 steelhead and 2614 rainbow trout were assessed to have passed over the counter during the migration period under examination using trace data analysis. Data after June 4th was excluded as from radio tracking and fence counts as well as counter records, the steelhead migration appeared over. A few late fish and some rainbow trout were migrating after this date and Chinook salmon would possibly be entering the river by this time.
Video Validation assisted Steelhead Trout Population estimates
An alternate enumeration population estimate can be determined from the fish counter raw data, fish sizing information and observed counter efficiency, as recorded by the video validation study. A simple method of enumeration estimation includes taking a mean of all validation observations and raising the counter raw data to accommodate for this efficiency. For example a raw total of 748 steelhead trout were assessed counted by the fish counter, based on PSS of >109, which equates to a fish length in excess of 51cm from video sizing data. Using the average fish counted to fish observed ratio of all fish from all video validation observations, 96% (ghost fish were never sized above a PSS of 109) of upstream fish which passed over the counter were enumerated. A total upstream count of 779 steelhead trout can be derived from the equation,
E = c/e * 100 where E = escapement, c = total counter estimate, and e = mean efficiency from video validation.
This upstream migration figure requires correction for downstream migrants before May 20th, based on the raw up and down count daily ratios as previously explained. Given an average downstream count efficiency of 90%, and a recorded raw down count of 9 fish of PSS 109 or greater, then an adjusted total of 10 downstream strays were enumerated.
Using this data;
Net upstream Migrants = Upstream count – Downstream Count
A total escapement of steelhead trout of 769 spawners is thus estimated from counter data using summer video validation efficiency criteria. Confidence limits based on one standard deviation (of average daily efficiency) gives an upstream steelhead count range of 748 to 815 fish.
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Rainbow Trout
Upon examination of trace data, ghost counts can be manually eliminated. These events are characterised by counts/event on two or more channels simultaneously (or one second apart due to processing speed) where one count is a high PSS value, usually greater than 100 and the other count(s) are of low peak signal size, typically a PSS of less than 50. Many of these ghost traces are rejected by the counter, but at high gain settings some are counted as upstream or downstream fish (depending on the actual count direction). Video validation assisted in verifying this phenomena as some smaller up counts on channel 2 had no obvious trigger from the video tapes, but were associated with large counts on channel 1 or 3. Removal of these false counts is easy and accurate, and only likely to elevate counts of smaller fish if undetected. Indications from video validation work suggested under higher conductivity conditions only 2% of counter error is created by ghost fish. However detailed trace analysis in the spring indicated as much as 12% over count of smaller fish due to ghosting. Two correction factors are thus required to provide a rainbow trout escapement estimate. The first removes ghost traces, the second increases the escapement for fish miss-classified as events or undetected.
A total spawner escapement estimate of 2864 up stream migrants and 154 downstream migrants after ghost removal and video efficiency correction (pre spawning) resulting in a total escapement estimate of 2710 rainbow trout in 1999.
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DISCUSSION
Counter operation
The Logie 2100C fish counter was found to be a reliable method of estimating escapement of steelhead and rainbow trout and coho and chinook salmon (in the absence of beaver activity). Some problems were experienced with the counters operation at this site in 1999, relating largely to a debris laden flash flood on July 8th. Repair included minor modifications to design which should eliminate future problems of this nature.
Fish sizing.
Estimating fish sizes is vital to the definition of what constitutes a steelhead trout and what constitutes a rainbow trout in the absence of sub sampling the population and assuming no other species are migrating over the counter during the experimental period. Some overlap in larger rainbow trout and smaller steelhead does occur but this is known to be a small percentage of the overall stock. Thus fish size which is measured by the counter as a value of "peak signal size (PSS)" can be used for determining species provided the error in counter direct measurement is small. Other counters through video validation have been shown to produce PSS that equates to fish weight with better than a +/-20% accuracy (Nicholson et al 1997, McCubbing 1999, and McCubbing et al 1999). The variation is related usually to swim height, but may also be effected by fish condition and some stream environmental parameters such as temperature. Simple histograms of counter peak signal sizes were examined. These indicated two distinct patterns. The first was the noticeable break between fish producing a signal size of less than 110 and those producing a signal size of greater than 120. Only 2% of the overall up count data fell in the mid- range of 110 to 120 PSS. A fixed PSS of 110 was thus used for the definition of steelhead and rainbow trout stocks.
Figure 14. Boneparte River, steelhead and rainbow trout length frequency histograms, 1998 data.
Rainbow Trout Steelhead Trout
250
200
150
100 Nos of Fish
50
0 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 Fish length cm
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Video validation indicates this signal size for salmon to be around 51cm. Boneparte River data indicates a fish length of 50-55cm appears to be an accurate break-point to define rainbow trout and steelhead stocks, figure 14. For the purposes of this study a signal size of 110 or greater appears to work well for species separation, due in part to the limited number of counts with a signal size of 110-120.
A truncated PSS pattern at the lower end of the PSS histogram was observed. Such data may be indicative of two scenarios; that rainbow trout do not enter the Deadmans River before reaching a certain size (possibly in relation to maturity) or that the threshold set to avoid excessive noise due to debris and/or turbulence resulted in a number of smaller rainbow trout being excluded from the count. Data from the Boneparte fishway operation might at first glance indicate the counter is poor at sizing smaller rainbow trout. However bar width on the trap facility of the Boneparte fishway is selective to larger rainbow trout, allowing smaller fish to pass through the trap. . Some limited biological data is required to further define this classification on the Deadman River, as weight and length relationships will vary between species and the counter is actually measuring weight (or displacement) rather than fish length.
Population estimate and counter efficiency
Video validation was carried out under a variety of conditions through the migration period of chinook and coho salmon. No validation was undertaken on steelhead due to the high flows and turbidity during peak migration. Efficiencies during coho migration were applied to steelhead data. Counter efficiencies for salmon ranged from 84% to 100% (mean 96%). These are typical of Logie counter efficiencies observed in other studies on trout and salmon migration (Aprahamian et al 1996, Nicholson et al 1993, Fewings 1991).
During the analysis of video footage, only one fish (above threshold size), in 466 observations, was identified from video has having fully traversed the electrode without an associated counter record. This fish was small and may have passed high in the water column resulting in a signal below threshold settings. Thus almost all fish and fish created events produced a descriptive trace for later analysis had this been collected throughout the migration period. Post analysis of trace data can an effective method for assessing/confirming escapement efficiency corrections, based on blind tests of observer analysis compared to recorded video footage (McCubbing 1999 pers.obs), although it may tend to overestimate large fish when large numbers of smaller fish are migrating during a short time period.
A manually corrected initial in season population estimate of 860 steelhead and 2614 rainbow trout were assessed to have passed over the counter during the migration period under examination using trace data analysis. This compared to video validation corrected estimates of 769 steelhead and 2710 rainbow trout.
The differences between the two estimate methods are likely the effect of a combination of;
1) multiple fish passing over one channel simultaneously may look from trace data like one large fish (McCubbing et al 1999). and
2) counter efficiency may be slightly lower at increased water flows and escapement densities (McCubbing et al 1999)
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Based on these two factors the true steelhead escapement figure is likely to lie between 769 and 815 (the upper limit of escapement estimation based on video validation). It would seem prudent given the variation between assessing escapement by these two methods to collect efficiency data through video validation under higher flown conditions, but water clarity precludes such an investigation. In the absence of such information the lower population estimate for steelhead trout should be used as an escapement figure, as it is based on observed counter performance rather than the more subjective manual “trace analysis” and it follows the precautionary principle which should be adhered to in stocks with a conservation concern. However trace data should still be collected and analysed as it often indicates debris and other false or miss-classified counts such as was indicated by beaver activity and ghost fish.
Temporal Patterns in Fish migration
The time of daily passage of steelhead and rainbow trout was examined. A strong trend towards the movement of fish in mid to late afternoon and early evening was observed. Of the total up counted fish 73% of the steelhead trout and 74% of the rainbow trout migrated over the counter between 13:00hrs and 21:00hrs inclusive. This was likely the influence of water level which generally peaked late afternoon due to daily snow-melt. It may also be related to water temperature but no data is available at this time. Further investigation into daily fluctuations in water temperature and fish movement are required and will be compared to radio-tracking data in a future study.
Rainbow and steelhead trout movement was linked with the ascending limb of the spring snow melt hydro-graph. Typically upstream movement increased as river discharge increased to maximum of around 20cumecs. Flows in excess of this level appeared to result in reduced upstream migration.
CONCLUSIONS
The value of accurate and precise escapement estimates is well understood in escapement based fisheries management. The Pacific Fisheries Resource Conservation Councils in it’s first annual report highlights the need for improved and more accurate enumeration of salmon escapement to improve management, and specifically notes the potential of electronic enumeration techniques (Anon 1999). In addition recent evidence of poor ocean survival in steelhead trout and many salmon species (Ward 1999 and Welch pers.comm.) requires better monitoring methods if escapement estimates are to be accurate and the effects of climate change are to be fully understood.
Smolt enumeration historically and currently undertaken on the Deadman River may allow for marine and freshwater survival estimates by brood year to be developed in future studies, similar to studies currently undertaken on steelhead on the Keogh River (Ward and McCubbing 1999).
The fish counter operation on the Deadman River in 1999 provided acceptable escapement estimate of steelhead and rainbow trout adults. Video validation indicated the stability of the counter and the ability through counter sizing and visual observations of species composition at one site to determine escapement of salmonids without the requirement for the handling of fish.
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Some background data on the size distribution of steelhead and rainbow trout within the Deadman River should be collected to establish that Boneparte River data is an accurate indicator of fish size distribution and investigations on the species of fish producing significant numbers of upstream counts in June requires addressing.
In summary this project has demonstrated the usefulness and economic advantages of a resistivity fish counter on an interior B.C, during periods of medium and high water discharge when traditional fish fence operations may have been compromised.
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REFERENCES
Anon. 1999 Pacific Fisheries Resource Conservation Council 1998-99 Annual Report.
Aprahamian,M.W., S.M.Nicholson, D.J.F McCubbing, and I.Davidson. 1996. The use of resistivity fish counters in fish stock assessment. In Stock Assessment in Inland Waters ed I.Cowx Chapter 3, 27-43.
Crump, E.S. 1952. A new method of gauging stream flow with little afflux by means of a submerged weir of triangular profile. Proceedings of the institute of Civil Engineers Part 1: Design and Construction 1, 223-242.
Dunkley, D.A. 1991. The use of fish counters in the management of salmonid stocks: the example of the North Esk. Proceedings of the Institute of Fisheries Management. 22nd Annual Study Course, Aberdeen 1991, 153-158.
Fewings,G.A. 1987. The validation of two resistivity counters using infra-red telesurveillance at two sites in the North West of England. MSc Thesis, University College of North Wales, Bangor, Wales.
Gray,D. 1997. Instruction manual for the Logie 2100C fish counter.
McCubbing,D.J.F, and B.R.Ward. 1998. Development of a fishery worker escapement estimation method. Salmon enumeration estimates on the Keogh (SEEK). Habitat Restoration and Salmon Enhancement Program Report 1998.
McCubbing et al 1999
McCubbing 1999
Nicholson, S.A., M.W.Aprahamian, P.B.Best, R.A.Shaw, & E.T Kaar. 1995. Design and use of fish counters. NRA R&D Note 382. Foundation for Water Research. Liston. UK.
Ward, B.R., and D.J.F. McCubbing. 1999. Enumeration of adult steelhead trout and salmonid smolts at the Keogh River during spring 1998 in comparison to the historic record. Province of British Columbia, Ministry of Fisheries. Fisheries Technical Circular No. 102.
Welton,J.S, W.R.C.Beaumont, and I.C.Johnson. 1987. Experience of counters in the southern chalk-streams. Counters Workshop. Atlantic Salmon Trust, Montrose,Scotland, 15-16 September, 1987.
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