Burbot Stock Status in Arrow Lakes Reservoir

35 Pages·2006·1.87 MB·English

by  Steve Arndt

Status of Burbot (Lota lota) in Arrow Lakes Reservoir

Steve Arndt1, M.Sc. and James Baxter2, M.Sc.

1Columbia Basin Fish & Wildlife Compensation Program
103-333 Victoria St., Nelson, B.C.

2BC Hydro, 601 18th St., Castlegar, B.C.

March 2006
Status of Burbot in Arrow Lakes Reservoir 2003-04

Executive Summary

The status of burbot populations in reservoirs is of interest with respect to evaluating both footprint and
operational impacts of BC Hydro dams. Arrow Lakes Reservoir (ALR) is located in the West Kootenay
and is located downstream of two other large impoundments. Prior to this study, no directed assessment
of burbot had been conducted on the reservoir. The primary objective of this study was to provide an
initial assessment of the status of burbot in ALR including distribution, relative abundance, and size and
age structure. Secondary objectives were to identify spawning locations and evaluate the use of an
underwater video camera for line transect or mark-recapture population estimates.

Distribution of burbot was determined using data from incidental catches during sturgeon set line
sampling in 1995. Relative abundance was determined using catch-per-unit-effort (CPUE) in cod traps
baited with dead kokanee. Traps were set in two widely separated locations (the narrows between the two
main basins, and Galena Bay) from late October to early November of 2003, and one location (narrows)
in late October 2004. Biological data were obtained from fish caught in the cod traps. All sampled fish
were marked with Floy tags applied posterior to the dorsal fin prior to release. Ten fish were surgically
implanted with radio tags during the trapping in 2003 and flights were conducted around the presumed
time of spawning in an attempt to locate spawning areas. Underwater video camera surveys were
conducted in the narrows area on 12-13 February 2004. Age was assessed using otoliths collected during
a creel survey.

Set line surveys indicated that burbot were widely distributed throughout the reservoir from Revelstoke
Reach to Hugh Keenleyside Dam. Average number of burbot per overnight trap set was 4.5 and 4.7 for
the narrows and Galena Bay respectively in 2003, and 8.5 for the narrows in 2004. Relative abundance, as
inferred from trap CPUE, was the highest reported in the province. Median CPUE for baited traps in the
ALR was more than 10 times higher than other B.C. lakes sampled to date with similar gear.

Burbot in the ALR were relatively large in comparison with other B.C. lakes, with more than 90% of the
trap catch exceeding 530 mm. Age structure showed some evidence of dominant and weak cohorts, but
suggested relatively stable recruitment compared to Columbia Lake in the East Kootenay. There was
large variation in length-at-age among individual fish; however, average growth rates in ALR were higher
than most other B.C. populations for which data are available. Mature males ranged from 598 to 875 mm
with two immature males at 510 mm. Mature females ranged from 630 to 860 mm and immature females
from 510 to 640 mm. These mature fish would be age-5 or older.

Flights located three of the radio-tagged fish after release. One was found near the mouth of Mosquito
Creek and this is a likely spawning area for burbot. Another was located near the release site, and the
third about 9 km north of the release site. Fish that were not detected may have spawned in deeper
locations, or may not have spawned during the surveyed period. No aggregations of spawning burbot
were observed in the narrows with the underwater video camera in February, however, the camera
showed the types of habitat occupied and the daytime behaviour of burbot. Most burbot were resting
inactive on the bottom and could be examined closely for the presence of a Floy tag. Therefore the
camera might be useful for mark-recapture population estimates, if it was used immediately after a period
of intense trapping and Floy tagging.

Key Words: burbot, Lota lota, fish, age, growth, maturity, cod, abundance, Floy tag,
radiotelemetry, spawning, stock density, habitat, depth, substrate

Columbia Basin Fish and Wildlife Compensation Program ii
Status of Burbot in Arrow Lakes Reservoir 2003-04

Acknowledgements

Funding and in kind support for this project was provided by the Columbia Basin Fish &
Wildlife Compensation Program (CBFWCP), BC Hydro (Castlegar), and the BC Ministry of
Environment (Nelson). Thanks to Colin Spence, Glen Olson, Matt Neufeld, Mike Hildebrand,
Demitria Burgoon, Bob Chapman, Dean den Biesen, Jeremy Baxter, Duncan Wassick, Dave
Mair, Josh Taylor, and Janice Arndt.

CBFWCP is a joint initiative between BC Hydro, the BC Government (Ministry of Environment)
and Fisheries and Oceans Canada to conserve and enhance fish and wildlife populations affected
by the construction of BC Hydro dams in Canada’s portion of the Columbia Basin.

Cover photo credit: Ernest Keeley

Columbia Basin Fish and Wildlife Compensation Program iii
Status of Burbot in Arrow Lakes Reservoir 2003-04

Table of Contents

Executive Summary................................................................................................................ii
Acknowledgements................................................................................................................iii
Table of Contents ..................................................................................................................iv
List of Tables ...........................................................................................................................v
List of Figures ..........................................................................................................................v

1.0 INTRODUCTION ...................................................................................................................1

2.0 METHODS ..............................................................................................................................1
2.1 Field Sampling ....................................................................................................................1
2.2 Radio Telemetry ..................................................................................................................6
2.3 Underwater Video ...............................................................................................................6
2.4 Lab and Data Analysis ........................................................................................................7

3.0 RESULTS AND DISCUSSION .............................................................................................7
3.1 Distribution and Depth of Capture ......................................................................................7
3.2 Relative Abundance ..........................................................................................................10
3.3 Growth, Condition, and Maturity ......................................................................................12
3.4 Size and Age Structure ......................................................................................................15
3.5 Movements and Spawning Locations ...............................................................................17
Radio Telemetry ...........................................................................................................17
Tag Returns ..................................................................................................................18
3.6 Underwater Camera Observations ....................................................................................19

4.0 CONCLUSIONS AND RECOMMENDATIONS ...............................................................21

5.0 REFERENCES .......................................................................................................................22

Appendix 1. Summary of burbot trapping data for the narrows south of Nakusp in 2003.
Appendix 2. Summary of burbot trapping data for Galena Bay in 2003.
Appendix 3. Summary of burbot trapping data for Nakusp area in 2004.
Appendix 4. Length-frequency of burbot used for ageing (A) and from 2003 (B) and 2004 (C)
trapping in the Nakusp area of Arrow Lakes Reservoir.
Appendix 5. Depth and habitat description for burbot observed by underwater camera on 12-13
February 2004.

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Status of Burbot in Arrow Lakes Reservoir 2003-04

List of Tables

1. Summary of burbot trapping effort and depths sampled on Arrow Lakes Reservoir in 2003 and
2004. Further details are provided in Appendices 1 to 3..............................................................2

2. Summary of burbot implanted with radio tags in the Arrow Lakes Reservoir in Oct,
2003.....................................................................................................................................17

3. Summary of tracking locations of radio tagged burbot in Arrow Lakes Reservoir during
the spring of 2004...............................................................................................................18

4. Summary of recaptures for burbot tagged in Arrow Lakes Reservoir in 2003 and 2004....18

5. Summary of sampling data for LBV underwater camera in the narrows area of Arrow
Lakes Reservoir in 2004.....................................................................................................20

List of Figures

1a. Locations of burbot traps set in the narrows between the upper and lower basins of Arrow
Lakes Reservoir in 2003. Set numbers correspond with Appendix 1................................................3

1b. Locations of burbot traps set in Galena Bay of Arrow Lakes Reservoir in 2003. Set numbers
correspond with Appendix 2..............................................................................................................4

2. Locations of burbot traps set in Arrow Lakes Reservoir in 2004. Trap numbers correspond with
Appendix 3........................................................................................................................................5

3. Locations (squares) where burbot were caught on set lines in Arrow Lakes Reservoir in 1995
(data from Ministry of Water, Land, and Air Protection, and Kootenay Wildlife Services Ltd .......9

4. Comparison of CPUE (number of burbot/trap hour) for cod traps in Arrow Lakes Reservoir in
2003 and 2004..................................................................................................................................10

5. Comparison of Arrow Lakes Reservoir CPUE to other British Columbia Lakes sampled with
baited cod traps................................................................................................................................11

6. Length-at-age of burbot from Arrow Lakes Reservoir.....................................................................13

7. Comparison of mean length-at-age of burbot in Arrow Lakes Reservoir to five other British
Columbia Lakes. .............................................................................................................................13

8. Length-weight relationships for Arrow Lakes Reservoir burbot captured by cod trap in 2003 and
2004.................................................................................................................................................14

9. Comparison of mean Wr by length category for Arrow Lakes Reservoir and four other British
Columbia Lakes. .............................................................................................................................14

10. Length frequency distributions for burbot taken in cod traps from Arrow Lakes Reservoir. ........15

11. Mean proportional and relative stock density of burbot from Arrow Lakes Reservoir compared to
four other British Columbia Lakes sampled with cod traps. Length frequency distributions for
burbot taken in cod traps from Arrow Lakes Reservoir. ................................................................16

12. Year class distribution of burbot sampled by cod traps and creel survey in Arrow Lakes
Reservoir..........................................................................................................................................16
Columbia Basin Fish and Wildlife Compensation Program v
Status of Burbot in Arrow Lakes Reservoir 2003-04

1.0 INTRODUCTION

Burbot have become a species of concern in Kootenay Region due to major declines of certain
populations. In Kootenay Lake and the lower Kootenay River, for example, burbot were very
abundant during the late 1960s and early 1970s, but currently these populations are red-listed
(British Columbia Conservation Data Centre). Fish habitats in the Canadian portion of the
Columbia River basin have been impacted substantially by the construction of several large
reservoirs from the 1960s through to the 1980s for flood control and hydroelectric power
production. In other parts of the world, creation of reservoirs has sometimes been accompanied
by increased burbot density (McPhail 1995). However, changes in flow regimes, temperature, or
nutrient loading may be detrimental to burbot downstream of impoundments (McPhail 1995;
Paragamian 2000; Paragamian et al. 2000; Ahrens and Korman 2002). Consequently, the status
of burbot populations is of concern from both footprint and operational hydroelectric
perspectives.

Arrow Lakes Reservoir (ALR) is located in the West Kootenay between the Selkirk and
Monashee mountain ranges. It is 230 km long with a surface area of 49,500 ha at full pool
(Sebastian et al. 2000). Two main basins at the north and south are separated by a shallower
narrows section approximately 30 km long near the midpoint of the reservoir. The reservoir is
located downstream of two other large impoundments (Kinbasket and Revelstoke Reservoirs).
Burbot assessments have occurred in a number of other lakes in the Kootenay Region (e.g.,
Arndt and Hutchinson 2000; Baxter et al. 2002a, 2002b; Bisset et al. 2002; Spence and Neufeld
2002; Neufeld and Spence 2004b), but prior to this study there was no directed stock assessment
of burbot in ALR. Some limited information was available from a creel survey and incidental
catches during sturgeon assessment. The creel survey indicated a small but apparently growing
fishery for burbot, most of which occurs in the narrows south of Nakusp (Arndt 2004). Catch
rates are high, and there was concern that the fishery might be based on an unusual concentration
of fish similar to that which is believed to have occurred in the West Arm of Kootenay Lake.

The primary goal of this study was to provide an initial assessment of burbot status in the ALR.
Key population parameters including distribution, relative abundance, and size and age structure
are described, with comparisons to other British Columbia lakes where data are available. A
second aim was to identify spawning locations, and the third was to evaluate the use of
underwater video camera in mark-recapture or line-transect population estimates (Bergstedt and
Anderson 1990; Edsall et al. 1993).

2.0 METHODS

2.1 Field Sampling

Distribution of burbot in the reservoir was inferred from incidental catches during sturgeon
sampling in 1995 (BC Ministry of Environment; data on file). In that study, the whole length of
the reservoir was sampled at roughly equal intervals using overnight set lines baited with dead
kokanee.

Cod traps were used in late October/early November of 2003 and late October 2004 to determine
relative abundance and size distribution. We used traps similar to those used in coastal
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Status of Burbot in Arrow Lakes Reservoir 2003-04

commercial cod fisheries, baited with dead kokanee collected the previous spawning season.
These traps are easy to deploy and effective for capturing burbot (Spence 2000). Resources were
not sufficient to allow a randomized survey covering the whole reservoir. Therefore we focused
on two areas in 2003. The first was in the narrows south of Nakusp between the two main basins
where the majority of known angling occurs; the second was in Galena Bay about 60 km to the
north. In 2004, trapping was done again in the area south of Nakusp as part of another program
to obtain fish for fish culture experiments. The majority of sets were in the narrows area but
three traps were also set close to the Town of Nakusp. The two years of trapping near Nakusp
allow a comparison of relative abundance over two years. All traps were left overnight before
lifting, with two exceptions (Appendices 1 and 3).

A total of 43 sets were made in 2003 and 15 in 2004 (Table 1; Figures 1a, 1b, 2). In order to
ensure an adequate sample of fish for size distribution data in 2003 and fish culture in 2004, a
number of traps were clustered around one of the more productive angling areas at Nakusp.
Possible influences of this on catch rates are considered in the Results and Discussion section.

Table 1. Summary of burbot trapping effort and depths sampled on Arrow Lakes Reservoir in
2003 and 2004. Further details are provided in Appendices 1 to 3.

Year Location No. Sets Depth (m) Time Fished (h)
Average Range Average Range
2003 Nakusp 27 24.5 10.0 – 31.0 21.5 4.8 – 28.3
2003 Galena Bay 16 19.1 10.0 – 31.0 19.8 17.3 – 50.0
2004 Nakusp 15 24.8 18.5 – 30.0 20.3 17.9 - 22.5

An overnight decompression procedure (Neufeld and Spence 2004a) was used to reduce
decompression trauma to burbot. This involved retrieving each trap and moving it quickly to a
depth of approximately half of the original pressure. The number of fish in the initial pull was
recorded as well as the number when the trap was processed on the following day. Most burbot
had gas accumulation in the abdominal cavity when retrieved, even after the decompression
period. This was relieved in the majority of fish by puncturing the body cavity with a hollow
needle so that fish were able to submerge to deeper water. Bruesewitz et al. (1993) found that
this did not affect survival of burbot.

Total length and weight were recorded and all fish were tagged with numbered Floy tags before
release. Ten fish were selected for radio tagging. These fish were assessed for sexual maturity
during the surgery, as well as a few fish that died during operations. Twelve otoliths were
obtained from burbot at Nakusp, six more were obtained from set line captures in a sturgeon
study, and 38 from the ALR creel survey at the Nakusp access point. All otoliths were stored dry
in envelopes.

Columbia Basin Fish and Wildlife Compensation Program 2
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16
Dog Creek
Upper Arrow
9
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17
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Figure 1a. Locations of burbot traps set in the narrows between the upper and lower basins of Arrow Lakes
Reservoir in October 2003. Set numbers correspond with Appendix 1.
Burbot Trap Locations - set October 2003
0.5 0.25 0 0.5Kilometers March 29, 2006
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Figure 1b. Locations of burbot traps set in Galena Bay of Arrow Lakes Reservoir in November 2003. Set numbers
correspond with Appendix 2.
Burbot Trap Locations - set November 2003
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Figure 2. Locations of burbot traps set in Arrow Lakes Reservoir in October 2004. Set numbers correspond with
Appendix 3.
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