COLUMBIA LAKE BURBOT POPULATION ESTIMATE PROGRAM, CANAL FLATS, BC

Transcription

1 COLUMBIA BASIN FISH & WILDLIFE COMPENSATION PROGRAM COLUMBIA LAKE BURBOT POPULATION ESTIMATE PROGRAM, CANAL FLATS, BC PREPARED BY J.E. Bisset, S.K.A. Arndt, R.S. Cope FOR Columbia-Kootenay Fisheries Renewal Partnership In Partnership with

2 Columbia Lake Burbot Population Estimate Program, Canal Flats, B.C. Prepared for: Columbia-Kootenay Fisheries Renewal Partnership 7468 Mission Road Cranbrook, BC V1C 7E5 Prepared by: th Avenue South Cranbrook, B.C. V1C 2W5 (250) AND Columbia Basin Fish & Wildlife Compensation Program Victoria Street Nelson, BC V1L 4K3 (250)

3 Columbia Lake Burbot Monitoring Program Executive Summary Columbia Lake burbot have been the subject of a number of investigations since These have included six years of spawner enumeration at a tributary, tracking of post-spawning movement, surveys of juvenile abundance and habitat use, and estimates of angler harvest. This study was designed to provide a population estimate of adult burbot in the lake to complement the earlier studies. In addition, information was obtained on the size distribution of lake-captured fish, and the depth and habitats used. The study took advantage of the fact that 995 burbot had been tagged as part of spawner enumeration early in 2001; these fish were used as the first phase of a mark-recapture population estimate. Sixteen cod traps were deployed at locations across Columbia Lake and the upper Columbia River from May 30 to June 7, and October 2 to October 11, The sites for the location of cod traps were chosen based on previous radiotelemetry surveys and suspected concentrations of prey in the autumn. These traps have been used very successfully to capture burbot in other lakes of the Kootenay Region. A total of 266 trap-days of effort were expended during the spring and autumn capture periods, resulting in a catch of 57 burbot of which three had been tagged in previous studies. There were zero recaptures for tags applied during this study. These catch rates were approximately one tenth of that expected based on other lakes, and resulted in a population estimate with wide 95% confidence limits (11,194 ± 9,557) that restrict its application to research and management questions. However, new information was obtained on aspects of life history and habitat use. Size distribution of burbot in the lake changed substantially between the spring and autumn periods, suggesting that a large number of adult burbot may have been absent from the lake during spring sampling. This contradicts an earlier radiotelemetry study and may indicate that post-spawning movement patterns differ from year to year. Also, when spring and fall size distributions in the lake are combined, it appears that the 1997 cohort was more abundant than the 1999 cohort. This contrasts with the relative abundance of these two cohorts in the tributary spawners of Depths occupied by lake-captured burbot were different from those determined in an earlier study that suggested a length of 39 cm as the size at which burbot moved from shoreline to deeper habitats. In this study, burbot less than 30 cm were captured at depths up to 6 m, and burbot over 50 cm were captured as shallow as 1 m. ii

4 Columbia Lake Burbot Monitoring Program If future population estimates are contemplated, consideration should be given to the following recommendations: Assume relatively low catch rates and plan for a longer, intensive collection period; Consider that autumn sampling coinciding with kokanee spawning migration (and spawning locations) may be more productive than spring sampling; Use fresh kokanee bait to improve capture rates if available; and Consider expanding the study area beyond Columbia Lake (e.g., Windermere Lake, Moyie Lake). iii

5 Columbia Lake Burbot Monitoring Program Acknowledgements Funding for the Columbia Lake Burbot Population Estimate was provided by Columbia- Kootenay Fisheries Renewal Partnership, Fisheries Renewal British Columbia (FsRBC) and Columbia Basin Trust (CBT), and administered by the Columbia Basin Fish and Wildlife Compensation Program (CBFWCP). CBFWCP also provided in kind support of the project for planning and design of the study, aspects of fieldwork, and reporting. The CBFWCP is a joint initiative between BC Hydro and the Government of British Columbia to conserve and enhance fish and wildlife populations in the Canadian portion of the Columbia River basin. The authors wish to acknowledge all the individuals that have contributed to bringing this project to a successful conclusion. Their contributions and on-going efforts are greatly appreciated. Marty Williams, Pat Nicholas (St. Mary s Band), Glen Smith, (), Kenton Andreashuk, Chris Beers (CKFRP), Harald Manson, Beth Woodbridge (CBFWCP), and Colin Spence (Ministry of Water, Land, and Air Protection) provided technical support. Dr. Carl Schwarz (Cooperative Resource Management Institute, Simon Fraser University) provided advice on the sampling design. Cod traps were loaned by the Ministry of Water, Land, and Air Protection. Suggested citation for this report: Bisset, J.E., Arndt, S.K.A. and R.S. Cope Columbia Lake Burbot Population Estimate Program, Canal Flats B.C. Report prepared for Columbia-Kootenay Fisheries Renewal Partnership, Cranbrook, B.C. Prepared by, Cranbrook, B.C. and Columbia Basin Fish and Wildlife Compensation Program, Nelson, B.C. 21 pp. + 2 app. iv

6 Columbia Lake Burbot Monitoring Program Table of Contents EXECUTIVE SUMMARY... II ACKNOWLEDGEMENTS... IV TABLE OF CONTENTS... V LIST OF TABLES... VI LIST OF FIGURES... VI 1 INTRODUCTION Background Project Rationale Study Area METHODS Sampling Design Spring Sampling Autumn Sampling RESULTS Water Temperature Fishing Effort and Catch v

7 Columbia Lake Burbot Monitoring Program 3.3 Burbot Size, Abundance, and In-lake Distribution DISCUSSION LITERATURE CITED APPENDIX A FIELD DATA FORMS - COD TRAP SET SUMMARIES FROM THE COLUMBIA LAKE BURBOT POPULATION ASSESSMENT, 2002 APPENDIX B FIELD DATA FORMS INDIVIDUAL FISH CAPTURE DATA FROM THE COLUMBIA LAKE BURBOT POPULATION ASSESSMENT, 2002 List of Tables Table 1. Summary of geographic information for Columbia Lake... 3 Table 2. Known species composition in Columbia Lake Table 3. Summary of data on previously tagged burbot captured during trapping in Columbia Lake and River in List of Figures Figure 1. Location of Columbia Lake in relation to communities of Canal Flats and Fairmont Hot Springs, BC. Source: BC Ministry of Forests, Forest Service Recreation Map, Invermere Forest District... 4 Figure 2. Typical baited cod trap used in Columbia Lake burbot population study being deployed Figure 3. Autumn sampling locations on the south end of Columbia Lake near Canal Flats, BC Figure 4. Autumn sampling locations on the north end of Columbia Lake and the upper Columbia River near Fairmont Hot Springs, BC Figure 5. Anesthetized burbot prior to checking for tags, and processing Figure 6. Burbot being checked for tags/marks prior to being measured Figure 7. Pit tag reader being used to check adult burbot for previous tags, Columbia Lake Figure 8. Pit tag being implanted in left cheek of adult burbot, Columbia Lake vi

8 Columbia Lake Burbot Monitoring Program Figure 9. Adult burbot in recovery cooler prior to release, Columbia Lake Figure 10. Adult burbot released into Columbia Lake following Pit tagging procedure Figure 11. Mean daily water temperatures recorded in trap T-12, Columbia Lake May 29 to June 7, Figure 12. Columbia River trap site R-1, October Figure 13. Columbia River trap site R-2, October Figure 14. Columbia River site R-3, October Figure 15. Typical cod trap location, Columbia Lake, October Figure 16. Typical cod trap location, Columbia Lake, October Figure 17. Northern pike minnow regurgitating kokanee following removal from a cod trap, Columbia Lake, October Figure 18. Length-frequency distributions for spring and autumn cod trap sampling in Columbia Lake and River, Figure 19. Burbot catch by depth, in relation to effort, for spring and fall trapping on Columbia Lake in Figure 20. Length-frequency distributions of burbot at the spawning tributary (January February) and in Columbia Lake and River (spring and fall sampling combined) in Dominant cohorts in the distribution peaks are based on otolith ages of tributary fish (Arndt 2002). Growth occurred between the spawning and the lake sampling Figure 21. Length of individual burbot and their depth of capture in cod-traps in Columbia Lake in spring and autumn During autumn, most trapping was done at depths less than 3 m. The dotted line shows the maximum length of shoreline residence found during backpack electrofishing in July (Taylor 2001) vii

9 Columbia Lake Burbot Monitoring Program 1 Introduction 1.1 Background Burbot Lota lota (also commonly referred to as ling-cod, or ling) are the only freshwater members of the cod family. They are generally nocturnal and feed primarily on other fish species. Burbot spawn in winter from January to March. Spawning occurs at night as individuals aggregate in spawning balls over suitable (sand and gravel) substrates (McPhail and Paragamian 2000). Burbot have a wide, Holarctic distribution (McPhail and Paragamian 2000), occupying suitable habitats north of 40ºN latitude (Scott and Crossman 1973). The Kootenay Region once supported large fisheries for burbot including popular angling locations such as Windermere and Columbia Lakes in the upper Columbia system, the Spillimacheen River, Moyie Lake, and Kootenay Lake at Balfour (Hutchinson 1996; Prince 2001). Burbot played an important role in the early settlement of the east and west Kootenays and provided important food resources for First Nations and early settlers (Prince 2001). Adult burbot were typically harvested at night through the ice during January and February, as large numbers of individuals congregated near the spawning grounds. Typical capture methods included setlines, spears, and angling. Some of the largest burbot on record from British Columbia have been reported from the Kootenay Region, including a kg burbot from Windermere Lake in 1923 (McPhail and Paragamian 2000). Large catches were reported in fishing derbies in some parts of the region. Creel data and angler surveys have since shown dramatic declines in the number and size of burbot captured in some locations (Prince 2001), particularly Kootenay Lake and the Kootenay River. A number of studies, funded by the Columbia Basin Fish & Wildlife Compensation Program (CBFWCP), have recently been completed on the burbot of Columbia Lake near Canal Flats, B.C. These have included: a study of early life history characteristics (Taylor and McPhail 2000; Taylor 2001), six years of adult spawner enumeration at a tributary spawning site (Arndt and Hutchinson 2000; Arndt 2000; Arndt 2002), an 18 month study of post-spawning movement patterns of adult burbot (Arndt 2001a), and 5 years of angler harvest assessment (Arndt 2001b). The present study was designed with intent to develop the first burbot population estimate for any lake in the Kootenay Region. Specific study objectives were to: Obtain a defensible estimate of the total number of adult burbot in Columbia Lake; 1

10 Columbia Lake Burbot Monitoring Program Compare the size distribution of lake-captured burbot to tributary spawners the previous winter; and Collect basic habitat use information for spring and autumn. 1.2 Project Rationale Burbot have become a species of concern in the Kootenay Region due to declines in certain areas and the relative lack of biological information about the species. The research at Columbia Lake was initiated due to concerns about local development proposals, as well as region-wide interest. So far it has resulted in two refereed publications (Arndt and Hutchinson 2000; Taylor and McPhail 2000) and several technical reports that have contributed to the understanding of burbot biology in western North America. The Columbia Lake studies have shown large fluctuations in juvenile abundance and tributary spawner numbers, as well as large fluctuations in angler harvest; however, several unanswered questions hinder the interpretation of the data. For example: 1) What proportion of Columbia Lake adult burbot spawn at the tributary (It is known that there are also spawning locations in the lake itself)? 2) What proportion of burbot switch spawning sites or skip spawning in some years? 3) Are tributary spawner counts a valid index of adult burbot abundance in the lake (based on the above two questions)? 4) What proportion of the total population is being harvested? 5) What was the survival of cohorts that were monitored at the juvenile stage? A population estimate of adult burbot in Columbia Lake would help answer the above questions, and allow fluctuations in tributary spawner numbers and harvest to be put into better ecological and management perspective. In addition, approximately 1000 burbot had already been marked with passive integrated transponder (PIT) tags as part of the sixth and last spawner count in the tributary in late winter of 2001 (Arndt 2002). Previous radiotelemetry work ( ) indicated that these burbot should be well distributed throughout the lake by spring 2001 (Arndt 2001a). Therefore they could serve as the first part of a two-stage mark-recapture population estimate (Begon 1979). A second phase of capture data in the lake was required to provide a ratio of marked/unmarked fish for a population estimate. 2

11 Columbia Lake Burbot Monitoring Program In summary, the rationale for the population estimate was as follows: 1) It was considered to be a very valuable addition to other long-term studies in Columbia Lake, and a key component for understanding the population dynamics of burbot in the lake. 2) It would take advantage of burbot already marked as part of another study, resulting in substantial savings in field effort and cost. 1.3 Study Area Columbia Lake is a ha waterbody (FISS 2002) located in the Rocky Mountain Trench, between the Purcell mountains to the west and the Kootenay Ranges of the Rockies to the east, between the communities of Canal Flats to the south, and Fairmont Hot Springs to the north (Table 1). Columbia Lake has a mean depth of 2.9m and a maximum depth of 6.0 m. Columbia Lake and its major tributaries (Marion Creek, Hardie Creek, Dutch Creek, and Warspite Creek) form the headwaters of the Columbia River, which drains to the north out of Columbia Lake (Figure 1). Surface total dissolved solids (TDS) are in the order of 230 ppm and the lake is slightly alkaline with a ph of 8.1 (FISS 2002). Table 2 lists the known fish species in Columbia Lake (FISS 2002). Table 1. Summary of geographic information for Columbia Lake. Geographic Information Surface Area 2,509.7 ha Approximate Distance to Nearest Town 1 km To Canal Flats, BC MoELP Region 4 MoELP Management Unit 4-25 FOC District Interior South East (#30) Ministry of Forests Region Nelson Ministry of Forests District Invermere NTS Map Reference 082.J05 Water body Identifier 00782COLR Watershed Code 300 3

12 Columbia Lake Burbot Monitoring Program Figure 1. Location of Columbia Lake in relation to communities of Canal Flats and Fairmont Hot Springs, BC. Source: BC Ministry of Forests, Forest Service Recreation Map, Invermere Forest District. 4

13 Columbia Lake Burbot Monitoring Program Table 2. Known species composition in Columbia Lake. Species Code Scientific Name Kokanee KO Oncorhynchus nerka Rainbow Trout RB O. mykiss Westslope Cutthroat Trout WCT O. clarki Bull Trout BT Salvelinus confluentus Mountain Whitefish MW Prosopium williamsoni Burbot BB Lota lota Largescale Sucker CSU Catostomus macrocheilus Longnose Sucker LSU C. catostomus Northern Pike minnow NSC Ptycheilus oregonensis Peamouth Chub PCC Mylocheilus caurinus Redside Shiner RSC Richardsonius balteatus Torrent Sculpin CRH Cottus rhotheus Pumpkinseed PMB Lepomis gibbosus 2 Methods 2.1 Sampling Design The population of interest was adult burbot in Columbia Lake. In February-March of 2001, 995 adult burbot ( 300 mm total length) were marked with PIT tags in a south end tributary during monitoring of the spawning run. An earlier radio-telemetry study of post-spawning movement ( ; 26 fish tracked) showed an initial northward movement followed by southward movement of some individuals so that fish were well distributed throughout the lake by May 12 (Arndt 2001a). Fish continued to move in the lake during June. Timing of the initial sampling was scheduled from late May to early June to coincide with the period when radiotelemetry studies indicated that fish were making substantial movements throughout the whole lake. Bernard et al. (1993) also found catch rates to be highest during the spring for Alaskan lakes. A rough approximation of the expected population number is needed to determine the amount of sampling required to obtain an estimate with a useful level of precision (Everhart and Young 1981). Based on juvenile densities and tributary spawner numbers from , it was expected that the adult burbot population in Columbia Lake should be in the range of 2,000 to 10,000 fish. Using the number of marked fish (995) and the expected range above, it was 5

14 Columbia Lake Burbot Monitoring Program determined that approximately 500 fish should be sampled in the lake for a population estimate with 95% confidence limits of +/- 20% of the estimate (Carl Schwarz, Simon Fraser University, personal communication). Cod traps (described in Spence 2000) baited with dead kokanee (frozen from the previous fall) were used as the main capture method for the study. The traps were borrowed from the Ministry of Water, Air, and Land Protection (MWALP). These traps are used by MWALP to capture burbot in other Kootenay Region lakes, and they typically have capture rates of up to 3 or 4 fish per 48 h set (Colin Spence, personal communication) using the same bait at the same time of year. Sixteen cod traps were available, with initial funding for up to 15 days of sampling, to obtain a capture target of approximately 500 fish (16 traps X 2 fish/24 h trap set X 15 days = 480 fish). The study was designed to allow use of two methods of population estimation. The first would be a simple Petersen estimate using the ratio of tributary-marked fish in the lake catch (Begon 1979). The second method would be based on successive days of mark and recapture in the lake trapping phase. Use of more than one estimation method with differing assumptions is advantageous because if the two estimates disagree, it may help indicate invalid assumptions; if the estimates agree, confidence in the estimates is increased. Spring trap placement was based loosely on an Alaskan study (Bernard et al. 1993). Columbia Lake is approximately 16 km long by 1.5 km wide. We used 16 transects, running east-west across the lake, spaced about 1 km apart from the north to south end. Transects were numbered from T1 to T16 starting from the north end of the lake. 1 Each transect had 15 sites 100 m apart. The starting site for each transect was chosen from a random number table. Traps were moved one site east every day, so that during the course of 15 days of sampling, all sites between the west and east side of the lake would be sampled. Moving traps each day has the advantage of averaging out incomplete mixing of tagged fish (simple Petersen estimate), and also helps avoid the potential of re-sampling the same fish if they are not moving after release (successive capture estimate). 1 Transect 1 (at the north end of the lake) was an exception in that it was comprised of two east-west crossings about 500 m apart because the lake narrows before the outlet. Transect 16 was also an exception; it ran north-south on the east side of the lake at the south end to cover area not reached by Transects (the lake is 2.5 km wide at this point). 6

15 Columbia Lake Burbot Monitoring Program 2.2 Spring Sampling Sixteen cod traps (Figure 2) were deployed on transects across Columbia Lake as described above from May 29 to June 7, Traps were checked daily starting at about 0930 hours, and moved 100 m east after each lift. All sets were 24 hr except for one 48 hr set (June 5-7). Kokanee bait was changed every 2 days or less. Traps were accessed by a boat launched at the south end of the lake via the Canal Flats Provincial Park boat launch. The boat used was a custom fabricated welded aluminum jet boat with Hummingbird depth sounder. Captured burbot were placed in a 45-liter plastic tub filled with water into which a solution of 3mg/l clove oil dissolved in 95% alcohol was added (Figure 3; Prince and Powell 2000). Once fish had been anesthetized with the clove oil mixture, they were checked for the presence of a previously applied PIT tag or other marks (Figures 4 and 5). The PIT reader was checked to ensure it was functioning prior to each use. All captured burbot that did not already have a PIT tag had a PIT inserted under the skin in the left cheek of the fish, just over the operculum (Figure 6). In addition to the insertion of a pit tag, a secondary mark (partial pectoral fin clip) was applied to each burbot. Once processed, burbot were placed in a plastic recovery cooler. Fresh water was circulated through the recovery cooler by means of an electric bilge pump, to facilitate rapid recovery (Figure 7). Once the fish had completely recovered, they were released back into the lake/river near the point of capture (Figure 8). Other species captured (i.e. kokanee, northern pike minnow) were documented and released. A 125 m hookless set line was also used over a 2-day period (June 3-5) in an attempt to increase the sample size. The rope had 8 monofilament lines, each baited with half of a kokanee, and was deployed at a depth of 2-3 m in the north end of the lake. This method has worked successfully to capture burbot in other lakes during the winter. Capture locations of individual fish were identified with a recreational grade handheld Global Positioning System (GPS) and documented on field data sheets provided by CBFWCP. Water depths were measured with a Hummingbird depth sounder, while air and water temperatures at the time of capture were recorded with a digital thermometer. Water temperatures in Columbia Lake were also collected at trap Number T-12 using a single Stowaway TidbiT temperature logger manufactured by the Onset Computer Corporation, submerged with the trap. The unit was factory calibrated to yield an error of 0.1 ºC to 0.2 ºC 7

16 Columbia Lake Burbot Monitoring Program and was programmed to record temperatures at 15-minute intervals. The unit was deployed from May 29 to June Spring sampling was terminated on June 7, prior to the planned 15 days, because catch rates were well below the expected 2 fish/trap day and inadequate for a population estimate. A decision was made to reserve remaining funds for a second capture attempt in the autumn during the kokanee spawning run. Figure 2. Typical baited cod trap used in Columbia Lake burbot population study being deployed. 8

17 Columbia Lake Burbot Monitoring Program Sample Areas Figure 3. Autumn sampling locations on the south end of Columbia Lake near Canal Flats, BC. 9

18 Columbia Lake Burbot Monitoring Program R3 R2 R1 Sample Sites Figure 4. Autumn sampling locations on the north end of Columbia Lake and the upper Columbia River near Fairmont Hot Springs, BC. 10

19 Columbia Lake Burbot Monitoring Program 2.3 Autumn Sampling Autumn trapping was targeted in areas where fish had been concentrated in autumn 1997 radiotelemetry surveys (Figure 3), and at locations where it was suspected that burbot might be feeding on spawning kokanee (UTM locations are summarized in Appendix A). This included sites in the Columbia River near the lake outlet (Figure 4). Additional funding was provided to allow up to 14 days of autumn field sampling. Sampling dates were chosen to coincide with the peak of kokanee spawning. Traps were checked daily between 07:30 and 19:00 hours October 2 October 11, Crews typically arrived at the upper river trap locations at 07:30 hours, and checked the traps on foot in waders. Lake traps were accessed by boat. Capture locations and other data were recorded as for the spring sampling. Figure 5. Anesthetized burbot prior to checking for tags, and processing. 11

20 Columbia Lake Burbot Monitoring Program Figure 6. Burbot being checked for tags/marks prior to being measured. Figure 7. Pit tag reader being used to check adult burbot for previous tags, Columbia Lake. 12

21 Columbia Lake Burbot Monitoring Program Figure 8. Pit tag being implanted in left cheek of adult burbot, Columbia Lake. Figure 9. Adult burbot in recovery cooler prior to release, Columbia Lake. 13

22 Columbia Lake Burbot Monitoring Program Figure 10. Adult burbot released into Columbia Lake following Pit tagging procedure. 3 Results 3.1 Water Temperature Columbia Lake is a long, wind swept lake. The large surface area relative to shallow depth suggests that it warms quickly during the summer and does not stratify. There may be however, some diversity of temperature conditions if there are areas of groundwater discharge into the lake similar to the spring-fed spawning tributary. Calm days were infrequent during the sampling period, which would suggest that the lake is constantly mixing and well oxygenated because of the frequent wave action. Mean daily water temperatures at Transect 12 ranged from ºC to ºC with an overall mean of 15.7 ºC during the spring sampling period (Figure 11). Minimum and maximum instantaneous temperatures were 8.69 ºC and ºC, respectively. Measured water temperatures during the fall sampling ranged from 3.9 ºC to 12.2 ºC. 14

23 Columbia Lake Burbot Monitoring Program Columbia Lake Water Temperatures Water Temperatures Water Temperature May 31-May 02-Jun 04-Jun 06-Jun Sample Date Figure 11. Mean daily water temperatures recorded in trap T-12, Columbia Lake May 29 to June 7, Fishing Effort and Catch A total of 128 trap-days were sampled during the spring period, with an additional 2 days sampled with baited set line. During the autumn period, there were 138 trap-days of effort. Sixteen traps were deployed initially, but one trap was stolen from the upper Columbia River early in the autumn period. No set lines were deployed during the autumn sampling. River and lake sampling sites are illustrated in Figures A total of 57 burbot were captured between May 30 and October 11, 2001; 19 during the spring period and 38 during the autumn period. Catch per unit effort was 0.15 burbot/trap-day in the spring and 0.28 burbot/trap-day in the autumn. The highest daily capture rates were observed following replacement of old baits with recently obtained kokanee in the traps. One adult burbot mortality, apparently unrelated to the trapping, was observed on October 5, Several 15

24 Columbia Lake Burbot Monitoring Program burbot were observed burrowing into the mud following release in the spring sampling (G. Smith, pers. comm.). In addition to burbot, northern pike minnow Ptychocheilus oregonensis, pumpkinseed Lepomis spp., mountain whitefish Prosopium williamsoni, sucker Catostomus spp., and kokanee Oncorhynchus nerka were also captured. Several of the captured fish had remnants of kokanee regurgitated from their mouths when retrieved from the traps (Figure 18). The baits used on the hookless set lines in the spring also appeared to have been chewed, although no fish were captured. Figure 12. Columbia River trap site R-1, October

25 Columbia Lake Burbot Monitoring Program Figure 13. Columbia River trap site R-2, October Figure 14. Columbia River site R-3, October

26 Columbia Lake Burbot Monitoring Program Figure 15. Typical cod trap location, Columbia Lake, October Figure 16. Typical cod trap location, Columbia Lake, October

27 Columbia Lake Burbot Monitoring Program Figure 17. Northern pike minnow regurgitating kokanee following removal from a cod trap, Columbia Lake, October Burbot Size, Abundance, and In-lake Distribution Only three of the 57 captured burbot had been previously tagged at the tributary spawning fence (Table 3); all three were captured in lake locations (i.e., none in Columbia River) during the autumn sampling. No burbot tagged during the lake sampling were recaptured in later sets. Biological data and capture information for individuals is summarized in Appendices A and B. Table 3. Summary of data on previously tagged burbot captured during trapping in Columbia Lake and River in Tag No. Sex Lake Capture Length in Lake (mm) Tributary Capture Length in Tributary 41363B4367 M 07-Oct Feb E37 M 07-Oct Feb C F 08-Oct Feb Comments First time captured in tributary Also spawned in the tributary in 1997 at 464 mm Also spawned in the tributary in 2000 at 532 mm 19

28 Columbia Lake Burbot Monitoring Program Captured fish ranged in length from 170 to 642 mm. There was a clear difference in the size distribution of the two sampling periods. In the spring, more than half of the burbot were less than 300 mm, whereas in the autumn most fish were over 325 mm (Figure 18). When both periods are considered together, the distribution of lake-caught burbot appears to be trimodal; peaks likely reflect the 2000, 1999, and 1997 cohorts based on age-length of tributary fish (see Arndt 2002). 6 Number of Fish Number of Fish Spring Autumn Length (mm) Figure 18. Length-frequency distributions for spring and autumn cod trap sampling in Columbia Lake and River, The low sample size precludes a population estimate with precise confidence limits, however, recapture data were used with Bailey s modification 2 of the simple Petersen estimate as follows (Begon 1979). Thirteen burbot <300 mm were excluded from the calculations because burbot less than 300 mm were not tagged at the tributary spawning fence: Nhat = r (n + 1) (m + 1) 2 Bailey s modification is recommended for small sample sizes. 20

29 Columbia Lake Burbot Monitoring Program Where: Nhat is the population estimate; r is the number of burbot marked at the tributary = 995; n is the total burbot in the lake sample = 44; and m is the number of marked burbot in the lake sample = 3. Standard error (SE Nhat ) was calculated as (Begon 1979): SE Nhat = square root {[r 2 (n + 1)(n - m)]/[(m + 1) 2 (m + 2)]} The resulting population estimate is 11,194 burbot, with 95% confidence limits (2 x SE Nhat ) of ± 9,557. It was not possible to use the second method of population estimation (successive days of mark-recapture) because no lake-caught burbot were recaptured. In the spring, burbot were captured throughout the lake, but the highest capture rates were in the north (transects 2 and 4). In the autumn, the most effective traps for capturing burbot were those situated in the north end of the lake near the outlet; two burbot were captured in the river outlet. Burbot were captured at depths from 1.0 to 6.5 m in the lake, and catch rates tended to follow the amount of effort at each depth except for slightly higher catches at 4 and 6 m during the spring sampling (Figure 19). Effort (trap-days) Spring Number of Burbot Captured Effort (trap-days) Autumn Effort Catch Depth (m) Figure 19. Burbot catch by depth, in relation to effort, for spring and fall trapping on Columbia Lake in Number of Burbot Captured 21

30 Columbia Lake Burbot Monitoring Program 4 Discussion The low rates of burbot capture in Columbia Lake were contrary to expectations based on experience with the same traps in other lakes of the Kootenay Region. The small sample resulted in a population estimate with wide confidence limits that restrict its application to management and research questions. However, the study still provides useful information for comparison with earlier research. There are several possible reasons for the low numbers of burbot captured, which include (but are not limited to): i emigration of adult burbot from the lake after spawning; i high annual mortality rates for adult burbot; and i ineffective traps (with ineffective bait). The numbers of burbot captured in the fall (n=37) were almost double those captured during the summer (n=19). In addition, the majority of spring burbot were smaller than spawning fish marked at the tributary. This apparent absence of larger burbot during the spring suggests that they may have left the lake (i.e., moved downstream into Columbia River or Windermere Lake) after spawning and returned later, possibly as prey species (i.e., kokanee) migrated up from the Columbia River to spawn near the outlet. In support of this, anglers regard Columbia Lake as a winter (January to March) fishery for burbot (Arndt 2001b; Cope 2001) and do not target burbot in Columbia Lake at other times of the year. However, none of the tributary-tagged fish were caught in the river trapping locations, so there is no direct evidence of tributary fish leaving the lake. Also, in the radiotelemetry study of post-spawning burbot in , no burbot were ever located outside of Columbia Lake (although not all fish were located every month; Arndt 2001a). It is possible that post-spawning movements change from year to year depending on conditions in the lake and river. The possibility of high annual mortality rates for adult burbot is supported by low percentages of repeat spawners at the tributary from 1996 to 2001 (<20%; Arndt 2002). In contrast, the radiotelemetry study of post-spawning fish in did not show any clear mortalities (Arndt 2001a). There were some tracked fish that showed relatively little movement later in the monitored period, and possibly some mortalities were disguised by imprecision in the locations or wind-induced movement of tags on the lake bottom. 22

31 Columbia Lake Burbot Monitoring Program Between 1996 and 2001, a total of 4071 burbot were implanted with PIT tags during enumeration of spawning escapement in a tributary to Columbia Lake. Of these previouslytagged fish, only three were captured in this study, and all three had been marked at the tributary in the winter of 2001 (995 fish total). We did not find evidence, in our small sample, that burbot from earlier tributary spawning events ( ) were still at large in the lake. Anecdotal reports suggest that avian predators may have an impact on burbot in Columbia Lake during the summer (Bill Green, pers. comm.), although further investigation is needed before any conclusions can be drawn. Annual harvest of the winter fishery ranged from about 50 to 500 burbot between 1996 and 2001, and the proportion of tributary-tagged fish in the catch was very low ( 3%; Arndt 2001b). Ineffective traps seems an unlikely explanation for the low catch rates because we were using the same traps and bait which was shown to be highly effective on other lakes. It may be, however, that burbot in Columbia Lake have other abundant sources of food that make baited traps less effective, particularly in the spring. Another explanation could be that post-spawning burbot do not actively feed until later in the summer, however, this seems unlikely, and again contradicts experience on other lakes. The length range of burbot in this study was similar (ignoring fish <300 mm and allowing for growth) to that of the tributary spawners in 2001, but the relative size of the 1997 and 1999 peaks suggests that the 1997 cohort was more abundant in the lake than it was in the tributary spawners. (Figure 20). This suggests that a substantial portion of the 1997 cohort either failed to mature in 2001, or spawned in locations other than the tributary. If so, the tributary spawner numbers and size distribution did not parallel spawning conditions or relative abundance in the lake for In most years, the catch-per-unit-effort (CPUE) and size distributions in the winter fishery have followed relative abundance and size of tributary spawners, but in 2001 CPUE was low while spawner returns were high (Arndt 2001b). Taylor (2001) found the 1997 cohort was about six times more abundant than the 1999 cohort at age-0; consequently, it would be expected to be more abundant now unless survival rates after the first summer were very different. 23

32 Columbia Lake Burbot Monitoring Program Frequency (%) Tributary Spawners Frequency (%) Lake Sampling Length (mm) Figure 20. Length-frequency distributions of burbot at the spawning tributary (January February) and in Columbia Lake and River (spring and fall sampling combined) in Dominant cohorts in the distribution peaks are based on otolith ages of tributary fish (Arndt 2002). Growth occurred between the spawning and the lake sampling. Taylor (2001) noted a length threshold of approximately 39 cm length above which he no longer found burbot in shoreline habitats (based on backpack electrofishing in July). However, in the spring and autumn trapping in this study, we found larger burbot (50-60 cm) at depths of only 1 m, and smaller burbot (20-30 cm) at depths up to 6 m (the maximum depth of the lake - Figure 21). Depths used by different size classes of burbot may differ depending on the season, or larger burbot may have avoided capture by the backpack electrofishing method of Taylor. 24

33 Columbia Lake Burbot Monitoring Program 6 Spring Autumn 5 Depth (m) Length (cm) Figure 21. Length of individual burbot and their depth of capture in cod-traps in Columbia Lake in spring and autumn During autumn, most trapping was done at depths less than 3 m. The dotted line shows the maximum length of shoreline residence found during backpack electrofishing in July (Taylor 2001). If future population estimates are contemplated, consideration should be given to the following recommendations: Assume relatively low catch rates compared to other lakes and plan for a longer, intensive collection period; Consider that autumn sampling, coinciding with kokanee spawning migration (and spawning locations), may be more productive than spring sampling; Use fresh kokanee bait if available, to improve capture rates; Do not use hookless set lines as they were ineffective in summer; and Consider expanding the study area beyond Columbia Lake (e.g. Windermere Lake, Moyie Lake). 25

34 Columbia Lake Burbot Monitoring Program 5 Literature Cited Arndt, S Data Summary for the 2000 Upper Columbia Burbot Study. Columbia Basin Fish and Wildlife Compensation Program technical report, File pp. Arndt, S. 2001a. Movements of burbot in Columbia Lake, British Columbia, for 18 months after spawning as determined by radio telemetry. Columbia Basin Fish and Wildlife Compensation Program technical report, File pp. Arndt, S. 2001b. Summary of Winter Creel Surveys for Columbia and Windermere Lakes from Columbia Basin Fish and Wildlife Compensation Program technical report, File pp. + appendices. Arndt, S Columbia Lake Burbot 2001 Data Summary, 2002 Observations, and Feasibility of Using Night Counts to Index Spawner Abundance. Columbia Basin Fish and Wildlife Compensation Program technical report. 14 pp. + appendices. Arndt, S.K.A. and J. Hutchison Characteristics of burbot spawning in a tributary of Columbia Lake, British Columbia over a four-year period. Pages in Burbot Biology, Ecology, and Management, edited by Vaughn L. Paragamian and Dave W. Willis. Publication Number 1. Fisheries Management Section of the American Fisheries Society. Spokane, Washington pp. Begon, M Investigating Animal Abundance: Capture-Recapture for Biologists. University Park Press, Baltimore, Maryland. 97 pp. Bernard, D.R., J.F. Parker and R. Lafferty Stock assessment of burbot populations in small and moderate-size lakes. North American Journal of Fisheries Management 13: Everhart, W.H. and W.D. Young Principles of Fishery Science. Cornell University Press, Ithaca. 349 pp. FISS Database Ministry of Fisheries provincial database. Hutchinson, J Upper Columbia Burbot Study. Prepared for the Ministry of Environment, Lands and Parks, Fisheries Branch. 29pp. McPhail, J.D. and V.L. Paragamian Burbot Biology and Life History. Pages in Burbot Biology, Ecology, and Management, edited by Vaughn L. Paragamian and Dave W. Willis. Publication Number 1. Fisheries Management Section of the American Fisheries Society. Spokane, Washington pp. Prince, A. and C. Powell Clove oil as an anesthetic for invasive field procedures on adult rainbow trout. North American Journal of Fisheries Management 20: , Prince, A Local knowledge of Columbia River fisheries in British Columbia, Canada. Report prepared for Columbia-Kootenay Fisheries Renewal Partnership, Cranbrook, B.C. Prepared by, Cranbrook, B.C. 50 pp. + 1 app. 26

35 Columbia Lake Burbot Monitoring Program Scott W. B. and E.J. Crossman Freshwater fishes of Canada. Fisheries Research Board of Canada. Bulletin pp. Spence, C A comparison of catch success between two styles of burbot traps in lakes. Pages in Burbot Biology, Ecology, and Management, edited by Vaughn L. Paragamian and Dave W. Willis. Publication Number 1. Fisheries Management Section of the American Fisheries Society. Spokane, Washington pp. Taylor, J.L The Early Life History and Ecology of Columbia Lake Burbot. M.Sc. thesis, University of British Columbia, Department of Zoology. 70 pp. Taylor, J. and McPhail Temperature, development, and behaviour in the early life history of burbot from Columbia Lake, British Columbia. Pages in Burbot Biology, Ecology, and Management, edited by Vaughn L. Paragamian and Dave W. Willis. Publication Number 1. Fisheries Management Section of the American Fisheries Society. Spokane, Washington pp. Personal Communications Green, B Program Director, Columbia-Kootenay Fisheries Renewal Partnership. Smith, G. Fisheries Technician,, October 5,

36 Columbia Lake Burbot Monitoring Program Appendix A Field Data Forms - Cod Trap Set Summaries From the Columbia Lake Burbot Population Assessment, 2002

37 DATE IN: DATE OUT: 29-May May-01 Columbia Lake Burbot Population Assessment - data sheet SITE TIME IN TIME OUT DEPTH (M) EASTING NORTHING COMMENTS T :30 9:29 1 Bait = 2 kokanee in all traps T :50 9:43 2 T :05 9: T :20 10: Tidbit logger attached to trap T : T :47 10: T9-1 17:00 10: just below powerlines T8-7 17:15 11: T7-3 18:12 11: T6-6 18:24 11: T5-1 18:40 11: T4-3 18:50 11: T3-5 19:00 12: T2-6 19:11 12: T1-2 19:23 12: burbot T :50 14: NFC - no fish caught; NPM (formerly NSC) - Northern Pikeminnow (formerly Northern Squawfish); CC - Torrent Sculpin; Comments: 29-May-01: w/t 15.5 C; a/t 20.6 C

38 DATE IN: DATE OUT: 30-May May-01 Columbia Lake Burbot Population Assessment - data sheet SITE TIME IN TIME OUT DEPTH (M) EASTING NORTHING COMMENTS T15-4 9:35 10: NFC T14-3 9:47 10: NSC - northern pikeminnow (NPM) T13-2 9:58 10: NFC T :16 11: NSC T :35 11:35 3 T :47 11: NSC T9-2 11:00 12: NFC T8-1 11:15 12: NFC T7-4 11:25 13: NFC T6-7 11:40 13: NFC T5-2 11:50 13: NFC T4-4 12:00 14: NFC T3-6 12:10 14: burbot T2-7 12:18 14: NFC T1-3 13:19 15: NFC T :05 15: NFC NFC - no fish caught; NPM (formerly NSC) - Northern Pikeminnow (formerly Northern Squawfish); CC - Torrent Sculpin; Comments: Trap 12-1 on its side when pulled - 1 burbot T11 trap recovered morning of May 31 & 11-1 *see May 29th - lost scotchman float, trap still fishing; NFC

39 DATE IN: DATE OUT: 31-May Jun-01 Columbia Lake Burbot Population Assessment - data sheet SITE TIME IN TIME OUT DEPTH (M) EASTING NORTHING COMMENTS :55 10: *located trap and reset - NFC :20 9: NFC - spawning suckers in area :40 9: NFC :45 10: NFC :10 10: tidbit present - NFC :05 10: adult NSC :30 10: NFC :40 10: NFC :30 11: NFC :45 11: burbot :00 12: NFC :20 12: NFC :40 12: burbot :05 13: NFC :10 13: NFC :25 13: NSC NFC - no fish caught; NPM (formerly NSC) - Northern Pikeminnow (formerly Northern Squawfish); CC - Torrent Sculpin; Comments: Fresh bait added (2 kokanee) to old traps *Trap recovered & set at new location

40 DATE IN: DATE OUT: 01-Jun Jun-01 Columbia Lake Burbot Population Assessment - data sheet SITE TIME IN TIME OUT DEPTH (M) EASTING NORTHING COMMENTS :35 9: NFC :45 9: NSC :09 9: burbot :19 10: NFC :27 10: NFC :40 10: NFC :53 11: NFC :00 11: NFC :10 11: NFC :00 11: NFC :15 11: NFC :23 12: NFC :56 12: NFC :05 12: NFC :13 12: NFC :40 13: NSC NFC - no fish caught; NPM (formerly NSC) - Northern Pikeminnow (formerly Northern Squawfish); CC - Torrent Sculpin; Comments: strong winds overnight - high turbidity

41 DATE IN: DATE OUT: 02-Jun Jun-01 Columbia Lake Burbot Population Assessment - data sheet SITE TIME IN TIME OUT DEPTH (M) EASTING NORTHING COMMENTS :40 9: NFC :53 9: NSC :27 9: CC - torrent sculpin :37 9: NSC :46 10: NFC :58 10: NFC :11 10: NFC :20 10: burbot :27 11: NFC :53 11: NSC :00 11: NFC :11 11: NFC :20 12: pumpkinseed :29 12: NFC :38 12: NFC :10 14: NFC NFC - no fish caught; NPM (formerly NSC) - Northern Pikeminnow (formerly Northern Squawfish); CC - Torrent Sculpin; Comments: Fresh bait added; partially overcast

42 DATE IN: DATE OUT: 03-Jun Jun-01 Columbia Lake Burbot Population Assessment - data sheet SITE TIME IN TIME OUT DEPTH (M) EASTING NORTHING COMMENTS :35 9: NFC :45 10: NFC :53 10: NFC :01 10: NFC :12 10: NFC :20 10: NFC :30 11: NFC :40 11: NFC :33 11: NFC :40 11: NFC :52 12: NFC :03 12: CC - torrent sculpin :15 12: NFC :30 12: adult NSC :35 12: NFC :07 13: NFC *T2-7 13:40 12:47 2 to NFC NFC - no fish caught; NPM (formerly NSC) - Northern Pikeminnow (formerly Northern Squawfish); CC - Torrent Sculpin; Comments: *Set Line - all bait had been chewed on but no fish were captured. Some bait appeared to have been swallowed, partially digested and then spit out

43 DATE IN: DATE OUT: 04-Jun Jun-01 Columbia Lake Burbot Population Assessment - data sheet SITE TIME IN TIME OUT DEPTH (M) EASTING NORTHING COMMENTS :01 9: burbot :16 10: NFC :35 10: NFC :27 10: NFC :47 10: NFC :56 10: NFC :08 10: NFC 8-6 1:18 11: NFC :52 11: NFC :58 11: NFC :07 11: NFC :16 11: burbot :23 12: NFC :31 12: burbot :41 12: NFC :16 13: NFC *T1-7 SL1 12:53 13:05 2 to NFC NFC - no fish caught; NPM (formerly NSC) - Northern Pikeminnow (formerly Northern Squawfish); CC - Torrent Sculpin; Comments: *set near outlet: bait chewed on but NFC