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A Creel-based Assessment of SportFisheries in Sturgeon Lake, Alberta, 2007

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The Alberta Conservation Association is a Delegated Administrative Organization under Alberta’s Wildlife Act.

A Creel‐based Assessment of Sport Fisheries in Sturgeon Lake, Alberta, 2007

Nathan Carruthers1, Greg Fortier1, Tyler Johns1, and John Tchir2 1Alberta Conservation Association

Bag 900‐26 96 Ave Peace River, Alberta, Canada

T8S 1T4 2Alberta Sustainable Resource Development

P.0. Box 23 Slave Lake, Alberta, Canada

T0G 2A0

Report Editors PETER AKU KELLEY KISSNER Alberta Conservation Association 50 Tuscany Meadows Cres. NW #101, 9 Chippewa Rd Calgary, AB T3L 2T9 Sherwood Park, AB T8A 6J7 Conservation Report Series Type Data ISBN printed: 978‐0‐7785‐7733‐1 ISBN online: 978‐0‐7785‐7734‐8 Publication No.: T/200 Disclaimer: This document is an independent report prepared by the Alberta Conservation Association. The authors are solely responsible for the interpretations of data and statements made within this report. Reproduction and Availability: This report and its contents may be reproduced in whole, or in part, provided that this title page is included with such reproduction and/or appropriate acknowledgements are provided to the authors and sponsors of this project. Suggested Citation: Carruthers, N., G. Fortier, T. Johns, and J. Tchir. 2008. A creel‐based assessment of

sport fisheries in Sturgeon Lake, Alberta, 2007. Data Report, D‐2008‐007, produced by the Alberta Conservation Association, Peace River, Alberta, Canada. 18 pp + App.

Cover photo credit: David Fairless Digital copies of conservation reports can be obtained from: Alberta Conservation Association #101, 9 Chippewa Rd Sherwood Park, AB T8A 6J7 Toll Free: 1‐877‐969‐9091 Tel: (780) 410‐1998 Fax: (780) 464‐0990 Email: info@ab‐conservation.com Website: www.ab‐conservation.com

i

EXECUTIVE SUMMARY

Recent population growth in northwestern Alberta has raised concerns about the

potential impacts of increases in angling pressure on regional populations of sport fish.

To guide fisheries management at Sturgeon Lake, the Alberta Conservation Association

(ACA) conducted shoreline creel surveys between 11 May and 26 August 2007. We

used observations collected from two locations, and computer modeling and

bootstrapping procedures, to provide whole lake estimates of angling parameters. We

also conducted test angling to verify catch rates reported by sport anglers.

We interviewed a total of 2,514 anglers at Sturgeon Lake. Anglers reported a total

effort of 7,187 angler‐h or 1.77 angler‐h/ha. We estimated that (over the entire angling

season and lake) 11,400 anglers fished at Sturgeon Lake in 2007 (95% CI = 9,300 –

14,400). In addition, we estimated that angling effort was 36,000 angler‐h (95% CI =

27,500 – 47,000) or 9.00 angler‐h/ha (95% CI = 6.75 – 11.50).

Anglers reported catching 2,774 walleye during the survey, of which 528 were

harvested. Total catch‐per‐unit‐effort (CPUE) of walleye by sport anglers was 0.386

fish/h, whereas total CPUE by test anglers was 0.436 fish/h. Total harvest‐per‐unit‐

effort (HPUE) of walleye by anglers was 0.073 fish/h. We estimated that the total

angler catch of walleye in the lake was 14,500 fish (95% CI = 10,500 – 19,300) and total

angler harvest of walleye was 2,800 fish (95% CI = 2,500 – 3,500).

The mean weight of harvested walleye was 0.86 kg/fish (95% CI = 0.82 – 0.90). Using

the mean weight and number of harvested walleye, we estimated that the total weight

of the harvest was 2,405 kg (95% CI = 2,127 – 3,007) or 0.59 kg/ha (95% CI = 0.53 – 0.74).

Walleye harvested by anglers ranged in size from 319 to 540 mm total length (TL), with

a mean (± SD) TL of 452 ± 41 mm (n = 121). Age of angler‐harvested walleye ranged

from 3 to 16 y, with a mean age of 8.9 ± 3.6 y (n = 116). Based on von Bertalanffy

growth estimates, it would take approximately five years to produce a harvestable

walleye (> 43 cm TL).

Anglers reported a total catch of 2,905 northern pike and a harvest of 276 northern pike

during the survey. Total CPUE of northern pike by sport anglers was 0.404 fish/h,

ii

iii

whereas total CPUE of northern pike by test anglers was 0.410 fish/h. Total HPUE of

northern pike was 0.038 fish/h. We estimated that the total angler catch of northern

pike in Sturgeon Lake was 13,500 fish (95% CI = 10,000 – 18,000) and that the total

angler harvest in the lake was 1,650 fish (95% CI = 1,250 – 2,100).

The mean weight of harvested northern pike was 1.66 kg/fish (95% CI = 1.46 – 1.87) and

that the weight of the total harvest was 2,747 kg (95% CI = 2,081 – 3,497) or 0.678 kg/ha

(95% CI = 0.514 – 0.864). Northern pike harvested by anglers ranged in size from 553 to

903 mm TL, with a mean of 653 ± 76 mm (n = 51). Age of harvested northern pike

ranged from 4 to 14 y, with a mean age of 6.8 ± 2.0 y (n = 51). Based on von Bertalanffy

growth estimates, it would take four to five years to produce a harvestable northern

pike (> 55 cm TL).

Key words: walleye, northern pike, angler survey, catch‐per‐unit‐effort, Sturgeon Lake, harvest rates, sport fisheries.

ACKNOWLEDGEMENTS

This work was funded by the Alberta Conservation Association (ACA). In addition,

ACA received in‐kind support from Alberta Sustainable Resource Development,

Fisheries Management Division, in Grande Prairie and Alberta Tourism, Parks,

Recreation and Culture in Grande Prairie. We thank creel clerks, Faye Cotton, Jason

Leathem, Chad Lyttle, Jesse McNabb and Amanda Nunn who interviewed anglers at

Sturgeon Lake and all volunteer test anglers for donating their time and personal

expense to this project. We also thank Melissa Poirier for ageing fish samples and

Craig Johnson for reviewing earlier drafts of this report.

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TABLE OF CONTENTS

EXECUTIVE SUMMARY.......................................................................................................... ii

ACKNOWLEDGEMENTS....................................................................................................... iv

TABLE OF CONTENTS ............................................................................................................ v

LIST OF FIGURES..................................................................................................................... vi

LIST OF TABLES...................................................................................................................... vii

LIST OF APPENDICES ..........................................................................................................viii

1.0 INTRODUCTION .......................................................................................................... 1 1.1 Study objectives .........................................................................................................2

2.0 STUDY AREA................................................................................................................. 2

3.0 MATERIALS AND METHODS ................................................................................... 4 3.1 Survey design.............................................................................................................4 3.2 Biological fish data ....................................................................................................4 3.3 Test angling ................................................................................................................4 3.4 Data management analysis ......................................................................................5 3.5 Population structure and harvestable fish .............................................................6

4.0 RESULTS ......................................................................................................................... 7 4.1 Angler survey.............................................................................................................7 4.2 Walleye catch and harvest........................................................................................8 4.3 Walleye population structure and growth.............................................................9 4.4 Northern pike catch and harvest ...........................................................................12 4.5 Northern pike population and growth.................................................................13 4.6 Angler exaggeration ................................................................................................16 4.7 Other sport fish ........................................................................................................16

5.0 LITERATURE CITED .................................................................................................. 17

6.0 APPENDICES............................................................................................................... 19

v

vi

LIST OF FIGURES Figure 1. Map of Sturgeon Lake showing creel sites surveyed in 2007........................... 3

Figure 2. Length‐frequency distributions of walleye captured and harvested during the survey of Sturgeon Lake, 2007. .................................................................... 10

Figure 3. Age distributions of walleye captured by gill nets and by sport anglers during the survey of Sturgeon Lake, 2007. ....................................................... 11

Figure 4. von Bertalanffy plot for walleye harvested by anglers from Sturgeon Lake, 2007......................................................................................................................... 11

Figure 5. Length‐frequency distributions of northern pike captured during the survey of Sturgeon Lake, 2007............................................................................ 14

Figure 6. Age distributions of northern pike captured during the survey of Sturgeon Lake, 2007. ............................................................................................................. 15

Figure 7. von Bertalanffy plot for northern pike harvested by anglers from Sturgeon Lake, 2007. ............................................................................................................. 15

LIST OF TABLES

Table 1. Summary of walleye and northern pike daily limit harvest regulations for Sturgeon Lake, 2007 – 2008. .................................................................................. 1

Table 2. Summary of observed and estimated angler parameters from summer angler surveys conducted at Sturgeon Lake, 2007............................................. 8

Table 3. Summary of walleye catch and harvest estimates from summer angler surveys conducted at Sturgeon Lake, 2007......................................................... 9

Table 4. Summary of northern pike catch and harvest estimates from summer angler surveys conducted at Sturgeon Lake, 2007....................................................... 13

vii

LIST OF APPENDICES

Appendix 1. Example of a creel survey data form ....................................................... 19

Appendix 2. Daily summaries of observed walleye and northern pike sport fishery parameters from Sturgeon Lake, 2007..................................................... 20

Appendix 3. Biological information collected from walleye and northern pike harvested by anglers from Sturgeon Lake, 2007.................................... 23

viii

1.0 INTRODUCTION Recent population growth in northwestern Alberta, specifically Grande Prairie and

surrounding area, has fisheries managers concerned about the potential impacts on

local sport fish populations that may result from increased angling efforts. Current

strategies implemented by Alberta Sustainable Resource Development (ASRD) to

maintain populations of walleye (Sander vitreus) and northern pike (Esox lucius) include

implementation of angling regulations that are designed to reduce fish mortality and

increase recruitment (Berry 1995, 1999). Annual surveys of angler use, effort, catch and

monitoring of sport fish populations are critical for evaluating the effectiveness of

regulations and adaptively managing the sport fishery.

Sturgeon Lake is currently being managed as a ‘stable’ fishery for both walleye and

northern pike (Tchir and Sawdon 2002), with a ‘higher‐risk’ angling regulation (smaller

allowable harvest size) being implemented for walleye (Table 1). However, the July

daily limit regulation of one walleye over 43 cm TL and one walleye under 43 cm TL,

combined with potential increases in angling pressure, may increase the risk of

unacceptable declines in the walleye population (C. Johnson, ASRD, pers. comm.).

Further, the results of the 2005 stock assessment (Schroeder and Tchir 2005) suggested

that the 2007 ‐ 2008 regulation for northern pike of two fish over 55 cm TL daily may

place the northern pike population at a high level of risk of unacceptable decline.

Results of the 2007 creel survey will help determine whether more conservative

regulations are needed (C. Johnson, ASRD, pers. comm.).

Table 1. Summary of walleye and northern pike daily limit harvest regulations for Sturgeon Lake, 2007 – 2008.

1 April 1 – 30 June 1 – 31 July 1 August – 31 March

Walleye > 43 cm TL 2 fish 1 fish 2 fish < 43 cm TL ‐ 1 fish ‐ Northern Pike > 55 cm TL 2 fish 2 fish 2 fish < 55 cm TL ‐ ‐ ‐

1

1.1 Study objectives

Alberta Conservation Association conducted a creel survey on Sturgeon Lake between

11 May and 26 August 2007. Our objective was to provide fisheries information that

can be used to guide management regulations for walleye and northern pike. Our

specific objectives were to:

i. Quantify harvest and catch rates using creel surveys and modeling

methods;

ii. Conduct test angling to assess the accuracy of data collected by creel

surveys;

iii. Describe length‐frequency distributions of fish captured by sport and test

angling; and

iv. Calculate the number of years required to produce a harvestable fish in

Sturgeon Lake.

2.0 STUDY AREA

Sturgeon Lake is located approximately 90 km east of Grande Prairie, Alberta (Figure

1). Access to the lake is via a paved highway (Highway 43), followed by all‐weather,

secondary roads that access several locations around the lake. The most commonly‐

used points to access the lake are located at Williamson Provincial Park, at the

southwest end of the lake, and Young’s Point Provincial Park, at the northwest corner

of the lake. Both parks offer camping and boat launches and are relatively easily

accessed from Highway 43. The lake has a surface area of 4,049 ha, a mean depth of 6.1

m and a maximum depth of 9.1 m.

2

Figure 1. Map of Sturgeon Lake showing creel sites surveyed in 2007. Inset is map of

Alberta indicating the location of the lake within the province.

3

3.0 MATERIALS AND METHODS 3.1 Survey design We conducted a reduced effort creel survey (Pollock et al. 1994) at two access points at

Sturgeon Lake to collect angler effort and sport fishery data. Between 0800 and 2300 h,

two creel clerks interviewed returning anglers at Young’s Point Provincial Park and

Williamson Provincial Park. We conducted surveys on a schedule of ten days on and

four days off from 11 May to 26 August 2007. The ten‐day shifts were split such that

five consecutive days were spent at each access point. We sampled both access points

with equal effort.

As part of creel surveys, we asked angling parties a series of questions regarding the

number of anglers, number of hours fished, number of each fish species kept and

released, and angler residence. A copy of the survey form used by creel crews to

record angler data is presented in Appendix 1.

Boat counts were used to determine a ratio‐of‐use (ROU) for each of the surveyed

access sites. The ROU was used to extrapolate the information collected from anglers

at the access sites to all the anglers on the lake.

3.2 Biological fish data When possible, we collected biological data from fish harvested by anglers. Data

included fork length (FL), weight (± 10 g), ageing structures, sex, and state of maturity.

We dissected fish to determine sex and maturity through inspection of the gonads. We

determined age of fish using otoliths and the left cleithrum for walleye and northern

pike, respectively, as well as the first three rays of the left pelvic fin for both species

(Mackay et al. 1990).

3.3 Test angling We conducted test angling throughout the survey period to collect data on size and age

of fish that could not be legally harvested by anglers (i.e., most walleye < 43 cm and

northern pike < 55 cm TL). Test anglers included creel clerks, fisheries staff, and

volunteers, all with varying skill levels, attempting to catch walleye and northern pike

4

using techniques that anglers would normally use (Sullivan 2003). Test anglers

recorded the number of hours fished, number of fish captured per species and the FL of

all fish caught. To assess the rate of angler exaggeration (inaccurate reporting of

released fish by anglers), we compared the ratio of legal‐length fish to protected‐length

fish sampled during test angling to the corresponding ratio reported by anglers

(Sullivan 2003). We also used the ratio of legal‐length fish to protected‐length fish from

test angling and the number of legal‐length fish captured by anglers to estimate the

number of protected‐length fish.

3.4 Data management analysis

All data collected during angler interviews and sampling of anglers’ catch (number

caught, FL, sex, maturity and weight) was submitted to the Alberta Government

Fisheries Management Information System (FMIS) database, Project Location ID 7682.

We used data from gill netting surveys on the lake in September 2007 to supplement

length and age distributions of northern pike and walleye (FMIS Project Location ID

7640).

We reported standard metrics used for angler surveys (Pollock et al. 1994). Harvest‐

per‐unit‐effort (HPUE) and catch‐per‐unit‐effort (CPUE) were calculated using data

from angler surveys. We also calculated a suite of parameters (and 95% confidence

intervals, CI) using both data from angler surveys and bootstrapping methods

(Haddon 2001) to account for temporal and spatial strata that were not surveyed.

Parameters included number of anglers, number of hours, angling pressure (h/ha),

harvest and yield (kg/ha) of walleye and pike. Our statistical procedure followed

Sullivan (2004). First, we re‐sampled the original data set 10,000 times per temporal

strata (weekend, weekday, July, non‐July months) and spatial strata (two access

points), and then calculated a mean that represented the distribution of possible means

having the same scale of variation as observed in the original data set. Next, we

multiplied the estimated means by the number of weekdays (or weekends) not

surveyed, and then added the total observed value (e.g., angling hours, number of

anglers). We combined the projected estimates from each weekend and weekday

stratum representing values for each sampling period (July versus May, June and

August). To account for spatial strata not surveyed, we multiplied values by ratio‐of‐

5

use estimates (ROUs): the number of boats from the boat count divided by the number

of boats using the surveyed sites. We randomly generated ROUs from values within

the binomial confidence interval for ROU.

3.5 Population structure and harvestable fish

We described length‐frequency distributions to allow fisheries managers to compare

current versus historical population structures of sport fish in Sturgeon Lake. We used

total length (TL) in assessments. Total length was not measured for all fish, so we

estimated lengths for fish for which TL was not measured using the following linear

regression relationships established from fork and total lengths collected during 2005

index netting at Sturgeon Lake (Tchir and Schoeder 2005):

Walleye (mm): TL = 1.05 * FL+ 3.34; R2 = 0.999, n = 287. Northern pike (mm): TL = 1.04 * FL + 10.29; R2 = 0.995, n = 72.

In addition, we used age and length (TL) data from the gill netting, sport, and test

angling to assess growth rate using the von Bertalanffy growth function (von

Bertalanffy 1938):

)e‐(1L L )t‐(t‐K t

0∞=

where:

Lt = length at age t,

L∞ = the asymptote or final maximum size,

K = the rate at which the growth curve approaches the asymptote,

t = age, and

t0 = a time scaler, the hypothetical time when the fish was size zero

The von Bertalanffy growth function is a non‐linear equation that explains growth

using K, the rate at which the fish approaches maximum size (L∞). Higher values of K

represent faster growth and are usually associated with a lower L∞. Due to small

sample sizes of small fish, we fixed t0 at zero to reduce bias in the growth function. We

calculated growth curve parameters through iteration using Sigma Plot 8.0, and then

6

used the estimates for L∞ and K to calculate the time for a fish to reach a harvestable

length (i.e., > 43 cm TL). Parameter values will be considered by fisheries managers

when making decisions regarding future harvest regulations for Sturgeon Lake.

4.0 RESULTS 4.1 Angler survey Between 11 May and 26 August 2007, we interviewed 2,514 anglers at Sturgeon Lake

(Table 2). Anglers that visited Sturgeon Lake were primarily from Grande Prairie

(66.0%). The majority of remaining anglers came from Valleyview (13%) and

Edmonton (4%). Anglers reported a total of 7,187 angler‐h of effort or 1.77 angler‐h/ha

(Table 2). Based on modeling, the estimated total number of anglers at Sturgeon Lake

during the survey was 11,400 (95% CI = 9,300 – 14,400; Table 2). Estimated total effort

was 36,000 angler‐h (95% CI = 27,500 – 47,000) or 9.00 angler‐h/ha (95% CI = 6.75 –

11.50). Estimates were pooled for the months of May, June and August. Estimates for

July were treated separately because different sport fishing regulations were in effect

that month.

7

Table 2. Summary of observed and estimated angler parameters, with 95% confidence intervals (CI), from summer angler surveys conducted at Sturgeon Lake, 2007.

May / June / August July* Total

Number of anglers Observed 1,628 886 2,514 Estimated 7,850 3,620 11,400 95% CI 5,600 – 10,600 3,080 – 4,100 9,300 – 14,400 Angler‐h Observed 4,683 2,504 7,187 Estimated 27,000 9,875 36,000 95% CI 17,000 – 37,000 8,475 – 11,275 27,500 – 47,000 Effort (h/ha) Observed 1.16 0.62 1.77 Estimated 6.50 2.45 9.00 95% CI 4.25 – 9.00 2.10 – 2.75 6.75 – 11.50 *Higher‐risk angling regulation season 4.2 Walleye catch and harvest The total observed catch rate (CPUE) reported for walleye by anglers was 0.386 fish/h.

Total CPUE for test anglers was 13% higher than that for sport anglers. Sport fish

CPUE for the May, June and August period was 0.397 fish/h and was approximately

9% higher than the CPUE calculated for July.

Total observed harvest rate (HPUE) was 0.073 fish/h. July HPUE was 0.092 fish/h, and

was approximately 1.5 times higher than the pooled rate for May, June and August

(0.063 fish/h). The higher harvest rate in July may be a result of the different harvest

regulation in that month (see Table 1).

We determined that anglers caught 2,774 walleye during the survey, of which 528 were

harvested. Based on modeling, we estimated that the total angler catch of walleye was

14,500 fish (95% CI = 10,500 – 19,300; Table 3). We estimated that approximately 19% of

these fish were harvested for a total angler harvest of 2,800 walleye (95% CI = 2,500 –

8

3,500; Table 3). The mean weight of harvested walleye was 0.86 kg/fish (95% CI = 0.82 –

0.90). Estimated total harvest weight was 2,405 kg (95% CI = 2,127 – 3,007) or 0.59 kg/ha

(95% CI = 0.53 – 0.74).

Table 3. Summary of walleye catch and harvest estimates, with 95% confidence

intervals (CI), from summer angler surveys conducted at Sturgeon Lake, 2007.

May / June / August July* Total

Walleye caught

Observed 1,860 914 2,774 Estimate 11,000 3,750 14,500 95% CI 6,500 – 15,500 3,225 – 4,350 10,500 – 19,300

Walleye kept

Observed 297 231 528 Estimate 1,750 1,060 2,800 95% CI 1,200 – 2,400 920 – 1,220 2,500 – 3,500

Walleye harvested (kg)

Observed 271 178 453 Estimate 1,596 818 2,405 95% CI 1,094 – 2,189 709 – 940 2,147 – 3,007

Walleye harvested (kg/ha)

Observed 0.07 0.04 0.11 Estimate 0.39 0.20 0.59

95% CI 0.27 ‐ 0.54 0.18 ‐ 0.23 0.53 ‐ 0.74 *Higher‐risk angling regulation season 4.3 Walleye population structure and growth Walleye harvested by sport anglers ranged in size from 319 to 540 mm TL with a mean

(± SD) TL of 452 ± 41 mm (n = 121; Figure 2), whereas fish captured by test anglers

ranged in size from 262 to 561 mm TL with a mean TL of 394 ± 59 mm (n = 161; Figure

2). In contrast, walleye captured by gill nets in September 2007 ranged in size from 106

to 590 mm with a mean size of 379 ± 84 mm (n = 904; Carruthers et al., unpubl. data).

The length distribution of fish captured by test anglers had greater representation of

9

smaller fish compared to those harvested by sport anglers (Figure 2). The distribution

resulting from gill netting appears to be similar to that of the test fishery (Figure 2).

0

5

10

15

20

25

90 150 210 270 330 390 450 510 570

Predicted Total Length (mm)

Frequency (%

)

Gill Netting (n = 904)

Test Angling (n = 161)

May, Jun and Aug Angler Harvest (n = 77)

July Angler Harvest (n = 44)

Figure 2. Length‐frequency distributions of walleye captured and harvested during the survey of Sturgeon Lake, 2007.

Age of angler‐harvested walleye ranged from 3 to 16 y with a mean of 8.9 ± 3.6 y (n =

116; Figure 3). Fish sampled from gill netting ranged in age from young‐of‐the‐year

(yoy) to 24 y with a mean age of 5.9 ± 3.6 y (n = 830; Figure 3). We did not examine ages

of walleye captured by test anglers.

Based on the von Bertalanffy function (Figure 4), the theoretical maximum length (L∞)

of walleye was 474 mm TL, with a growth coefficient (K) of 0.456 (n = 115). With these

growth characteristics, it would take approximately five years to produce a harvestable

walleye (> 43 cm TL; Figure 4).

10

0

5

10

15

20

25

30

35

40

45

0 3 6 9 12 15 18 21 24

Age (y)

Freque

ncy (%

)

Gill Netting (n = 830)Angler Survey (n = 116)

Figure 3. Age distributions of walleye captured by gill nets and by sport anglers during the survey of Sturgeon Lake, 2007.

Age (y)

0 2 4 6 8 10 12 14 16 18

Total L

ength (m

m)

0

100

200

300

400

500

600

430 mm

Min. harvest length

L∞ = 474, K = 0.456, R2 = 0.342

Figure 4. von Bertalanffy plot for walleye harvested by anglers from Sturgeon Lake, 2007.

11

4.4 Northern pike catch and harvest Total CPUE for northern pike reported by anglers was 0.404 fish/h, whereas total CPUE

for test anglers was marginally higher (by 1%) at 0.410 fish/h. Observed CPUEs for the

sport fishery were similar between the combined May, June and August sampling

period and the July period (i.e., 0.407 versus 0.399 fish/h), whereas CPUE for test

angling was almost 1.4 times higher in July (i.e., 0.36 versus 0.5 fish/h). Observed total

HPUE of northern pike was 0.038 fish/h. HPUE showed marginal variation between

regulation periods (0.039 to 0.037 fish/h). Anglers reported a catch of 2,905 northern pike and a harvest of 276 northern pike

during the 2007 survey (Table 4). We estimated that the total angler catch of northern

pike (for the complete duration of the angling season and whole lake) was 13,500 fish

(95% CI = 10,000 – 18,000; Table 4). We determined that approximately 12% of the total

catch was harvested resulting in an estimated total angler harvest of 1,650 fish (95% CI

= 1,250 – 2,100; Table 4). The mean weight of harvested northern pike was 1.66 kg/fish

(95% CI = 1.46 – 1.87) resulting in an estimated total harvest of 2,747 kg (95% CI = 2,081

– 3,497) or 0.678 kg/ha (95% CI = 0.514 – 0.864).

12

Table 4. Summary of northern pike catch and harvest estimates, with 95% confidence intervals (CI), from summer angler surveys conducted at Sturgeon Lake, 2007.

May / June / August July Total

Northern pike caught

Observed 1,907 998 2,905 Estimate 9,400 4,040 13,500 95% CI 5,800 – 13,400 3,560 – 4,600 10,000 – 18,000

Northern pike kept

Observed 183 93 276 Estimate 1,200 410 1,650 95% CI 800 – 1,650 350 – 490 1,250 – 2,100

Northern pike harvested (kg)

Observed 317 147 459 Estimate 2,082 650 2,747 95% CI 1,396 – 2,862 555 – 777 2,081 – 3,497

Northern pike harvested (kg/ha)

Observed 0.08 0.04 0.11 Estimate 0.51 0.16 0.68

95% CI 0.35 – 0.71 0.14 – 0.19 0.51 – 0.86

4.5 Northern pike population and growth Northern pike harvested by anglers ranged in size from 553 to 903 mm TL, with a mean

(± SD) TL of 653 ± 76 mm (n = 51; Figure 5), whereas those captured by test anglers

ranged from 338 to 894 mm TL with a mean TL of 564 ± 97 mm (n = 103; Figure 5).

Northern pike captured in gill nets in September 2007 ranged from 358 to 1,117 mm,

with a mean size of 561 ± 129 mm (n = 76; Carruthers et al., unpubl. data). The length

distribution of fish captured by test anglers had greater representation of larger fish

when compared to those captured by gill nets.

13

0

5

10

15

20

25

325

375

425

475

525

575

625

675

725

775

825

875

925

975

1025

1075

1125

Predicted Total Length (mm)

Freq

uenc

y (%

)

Gill Netting (n = 76)Test Angling (n = 103)Angler Survey (n = 51)

Figure 5. Length‐frequency distributions of northern pike captured during the

survey of Sturgeon Lake, 2007. Age of angler‐harvested northern pike ranged from 4 to 14 y with a mean of 6.8 ± 2 y (n

= 51; Figure 6), whereas those captured by gill nets ranged from 1 to 13 y with a mean

age of 4.2 ± 2.4 y (n = 74; Figure 6). We did not age northern pike captured by test

anglers.

Based on the von Bertalanffy function, we determined that the theoretical maximum

length (L∞) of northern pike was 834 mm TL and that the growth coefficient (K) was

0.236 (n = 51). With these growth characteristics it would take between four and five

years to produce a harvestable northern pike (> 55 cm TL; Figure 7).

14

0

5

10

15

20

25

30

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Age (y)

Frequency (%

)

Gill Netting (n = 74)

Angler Survey (n = 51)

Figure 6. Age distributions of northern pike captured during the survey of Sturgeon Lake, 2007.

Age (y)

0 2 4 6 8 10 12 14 16

Total L

ength (m

m)

0

100

200

300

400

500

600

700

800

900

1000

Min. harvest length

550 mm

L∞ = 834, K = 0.236, R2 = 0.7127

Figure 7. von Bertalanffy plot for northern pike harvested by anglers from Sturgeon Lake, 2007.

15

4.6 Angler exaggeration

Our assessment of angler exaggeration indicated that it was occurring. The predicted

number of small‐sized walleye (< 43 cm TL) that were released differed from the

reported number by 21.7% (1,557 estimated vs. 1,988 reported). In addition, the

estimated number of protected‐length northern pike (< 55 cm TL) that were released

differed from the reported number by 65.5% (685 estimated vs. 1,986 reported).

4.7 Other sport fish

In addition to walleye and northern pike, Sturgeon Lake anglers reported catching a

total of 33 yellow perch (Perca flavescens). Of yellow perch caught, 15 were harvested.

16

5.0 LITERATURE CITED Alberta Sustainable Resource Development. 2007. 2007 Alberta guide to sportfishing

regulations. Sports Scene Publications, Edmonton, Alberta. 92 pp.

Berry, D.K. 1995. Alberta’s walleye management and recovery plan. Alberta

Environmental Protection, Natural Resources Service, Number T/310,

Edmonton, Alberta. 32 pp.

Berry, D.K. 1999. Alberta’s northern pike management and recovery plan. Alberta

Environmental Protection, Natural Resources Service, Number T/459,

Edmonton, Alberta. 22 pp.

Haddon, M. 2001. Modeling and quantitative methods in fisheries. Chapman and

Hall/CRC, Boca Raton, Florida. 406 pp.

Mackay, W.C., G.R. Ash, and H.J. Norris (eds.). 1990. Fish ageing methods for Alberta.

R.L. & L. Environmental Services Ltd., in association with Alberta Fish and

Wildlife Division and University of Alberta, Edmonton, Alberta. 113 pp.

Patterson, B. 2004. An assessment of the summer sport fishery for walleye and

northern pike at Pigeon Lake, 2003. Data report, D‐2004‐015, produced by the

Alberta Conservation Association, Edmonton, Alberta, Canada. 26 pp + App.

Pollock, K.H., C.M. Jones, and T.L. Brown. 1994. Angler survey methods and their

applications in fisheries management. American Fisheries Society Special

Publication 25. 371 pp.

Sullivan, M.G. 2002. Exaggeration of walleye catches by Alberta anglers. North

American Journal of Fisheries Management 23: 573‐580.

Sullivan, M.G. 2004. Computer simulation of sport fishery parameters. Alberta Fish

and Wildlife Division Memorandum, Edmonton, Alberta. 16 pp.

17

18

Schroeder D.G., and J.P. Tchir. 2005. Fall walleye index net assessment of Sturgeon

Lake. Unpublished data report, produced by Alberta Sustainable Resource

Development, Fish and Wildlife Division, Fisheries Management Branch, Peace

River, Alberta, Canada. 23 pp + App. (DRAFT)

Tchir, J.P., and L. Sawdon. 2002. Angler survey of Sturgeon Lake, 2002. Unpublished

data report produced by Alberta Conservation Association, Peace River,

Alberta, Canada. 18 pp + App.

von Bertalanffy, L. 1938. A quantitative theory of organic growth. Human Biology 10:

181‐213.

6.0 APPENDICES Appendix 1. Example of a creel survey data form.

19

Appendix 2. Daily summaries of observed walleye and northern pike sport fishery parameters from Sturgeon Lake, 2007. Codes: WALL = walleye; NRPK = northern pike; capt = captured; R = released; K = kept.

Date Anglers Effort

(angling‐h)

Total WALL Capt

WALL > 43 cm

WALL < 43 cm

WALL R

WALL K

Total NRPK Capt

NRPK > 55 cm

NRPK < 55 cm

NRPK R

NRPK K

Totals 2514 7,187 2774 786 1988 2246 528 2905 919 1986 2629 276 12‐May 5 21.75 0 0 0 0 0 1 0 1 1 0 13‐May 16 24.75 0 0 0 0 0 8 3 5 7 1 14‐May 6 27 0 0 0 0 0 0 0 0 0 0 15‐May 5 12.5 0 0 0 0 0 2 1 1 2 0 16‐May 18 59 2 0 2 2 0 27 10 17 24 3 17‐May 14 33.5 1 0 1 1 0 8 1 7 8 0 18‐May 8 11 0 0 0 0 0 2 1 1 1 1 19‐May 52 165.5 11 6 5 5 6 28 10 18 22 6 20‐May 87 229.5 6 3 3 3 3 86 17 69 78 8 21‐May 24 74 2 2 0 2 0 18 18 0 18 0 25‐May 21 59.5 2 2 0 2 0 9 2 7 8 1 26‐May 44 112.5 6 2 4 4 2 14 5 9 12 2 27‐May 33 104.5 22 9 13 21 1 29 13 16 26 3 28‐May 2 10 0 0 0 0 0 0 0 0 0 0 29‐May 11 24.5 12 3 9 10 2 1 1 0 0 1 30‐May 8 30.5 1 0 1 1 0 7 1 6 7 0 31‐May 24 97.25 22 5 17 22 0 124 26 98 123 1 1‐Jun 47 152 45 30 15 36 9 47 10 37 40 7 2‐Jun 123 386.25 120 39 81 89 31 147 48 99 139 8 3‐Jun 30 76 13 5 8 10 3 49 9 40 45 4 8‐Jun 4 12 0 0 0 0 0 2 0 2 2 0 9‐Jun 14 63.75 4 2 2 2 2 33 7 26 29 4 10‐Jun 32 86 2 1 1 1 1 15 4 11 13 2 11‐Jun 8 20.5 0 0 0 0 0 26 4 22 22 4 12‐Jun 4 12 2 0 2 2 0 2 2 0 0 2 13‐Jun 16 45.5 54 20 34 46 8 21 8 13 19 2

20

Appendix 2. Continued.

Date Anglers Effort

(angling‐h)

Total WALL Capt

WALL > 43 cm

WALL < 43 cm

WALL R

WALL K

Total NRPK Capt

NRPK > 55 cm

NRPK < 55 cm

NRPK R

NRPK K

14‐Jun 36 99.25 24 15 9 16 8 40 24 16 32 8 15‐Jun 28 62 15 5 10 10 5 61 16 45 52 9 16‐Jun 158 492.75 117 53 64 87 30 212 85 127 178 34 17‐Jun 63 172.5 55 13 42 46 9 114 56 58 110 4 22‐Jun 18 46.5 36 6 30 32 4 32 4 28 29 3 23‐Jun 35 109 44 17 27 30 14 71 24 47 60 11 24‐Jun 44 117 79 22 57 61 18 96 17 79 91 5 25‐Jun 18 63 18 5 13 13 5 28 11 17 27 1 26‐Jun 18 54 32 8 24 24 8 47 15 32 39 8 27‐Jun 32 49 7 0 7 7 0 14 7 7 12 2 28‐Jun 36 121.5 7 4 3 6 1 17 7 10 15 2 29‐Jun 43 103 36 10 26 28 8 26 6 20 23 3 30‐Jun 76 144 86 18 68 75 11 37 12 25 36 1 1‐Jul 142 459 255 82 173 193 62 178 41 137 164 14 2‐Jul 46 110 95 25 70 76 19 48 19 29 44 4 6‐Jul 4 10 4 1 3 3 1 10 0 10 10 0 7‐Jul 58 138.75 39 3 36 26 13 55 22 33 52 3 8‐Jul 51 139.5 42 10 32 29 13 80 31 49 69 11 9‐Jul 9 18 45 6 39 41 4 34 0 34 34 0 10‐Jul 14 52 32 14 18 17 15 21 5 16 19 2 11‐Jul 38 118 31 8 23 21 10 78 27 51 64 14 12‐Jul 16 29.5 7 2 5 3 4 26 5 21 22 4 13‐Jul 50 122.5 29 11 18 22 7 32 9 23 28 4 14‐Jul 59 168.75 30 7 23 28 2 50 26 24 48 2 15‐Jul 24 58 18 2 16 16 2 25 14 11 25 0 20‐Jul 36 118.5 23 4 19 14 9 27 9 18 21 6 21‐Jul 70 187.5 29 15 14 15 14 66 48 18 55 11

21

22


Date Anglers Effort

(angling‐h)

Total WALL Capt

WALL > 43 cm

WALL < 43 cm

WALL R

WALL K

Total NRPK Capt

NRPK > 55 cm

NRPK < 55 cm

NRPK R

NRPK K

22‐Jul 94 375 100 20 80 73 27 155 47 108 147 8 23‐Jul 27 74.75 32 9 23 29 3 20 5 15 20 0 24‐Jul 13 19 6 2 4 2 4 7 2 5 6 1 25‐Jul 34 83.5 22 4 18 10 12 21 3 18 19 2 26‐Jul 28 71.25 39 10 29 33 6 22 6 16 18 4 27‐Jul 22 43.5 18 1 17 16 2 17 2 15 16 1 28‐Jul 46 97.25 13 2 11 11 2 21 5 16 19 2 29‐Jul 5 9.5 5 5 0 5 0 5 5 0 5 0 3‐Aug 8 18.25 2 0 2 2 0 4 0 4 4 0 4‐Aug 46 97 20 7 13 18 2 15 6 9 13 2 5‐Aug 68 228.5 254 80 174 219 35 119 22 97 113 6 6‐Aug 43 171 190 36 154 173 17 89 14 75 84 5 7‐Aug 2 10 11 0 11 11 0 1 0 1 1 0 8‐Aug 9 31 11 2 9 9 2 15 4 11 11 4 9‐Aug 19 49 111 24 87 98 13 26 1 25 25 1 10‐Aug 35 89.5 110 41 69 100 10 31 12 19 31 0 11‐Aug 29 72.5 15 1 14 14 1 9 5 4 7 2 17‐Aug 31 114 13 5 8 12 1 12 7 5 8 4 18‐Aug 22 37 17 2 15 15 2 4 3 1 4 0 19‐Aug 41 122.5 135 28 107 122 13 55 24 31 52 3 20‐Aug 6 22 16 0 16 16 0 3 1 2 2 1 21‐Aug 6 23 53 8 45 45 8 5 1 4 4 1 22‐Aug 2 13 19 4 15 15 4 18 3 15 15 3

Appendix 3. Biological information collected from walleye and northern pike harvested by anglers from Sturgeon Lake, 2007. Species code: WALL = walleye; NRPK = northern pike.

Sample # Species Fork length (mm)

Weight (g) Sex Maturity

Age (y)

1 WALL 418 740 M Mature 9 2 WALL 433 890 M Mature 11 3 WALL 412 780 M Mature 10 4 NRPK 846 4,330 F Mature 13 5 NRPK 589 1,160 F Mature 6 6 WALL 410 720 M Mature 9 7 NRPK 620 1,400 F Mature 7 8 NRPK 855 3,570 F Mature 11 9 NRPK 550 1,076 F Mature 5 10 WALL 407 ‐ M Mature 13 11 WALL 427 ‐ M Mature 14 12 WALL 425 ‐ M Mature 13 13 NRPK 580 1,276 F Mature 6 14 WALL 422 ‐ M Mature 13 15 WALL 417 800 M Mature 13 16 WALL 445 920 M Mature 6 17 WALL 428 690 M Mature 13 18 NRPK 550 1,160 F Mature 5 19 WALL 413 750 M Mature 14 20 WALL 437 830 F Mature 6 21 WALL 427 860 M Mature 13 22 WALL 432 880 M Mature 14 23 WALL 445 ‐ F Mature 11 24 WALL 400 650 M Mature 7 25 WALL 412 740 M Mature 13 26 WALL 457 980 M Mature 14 27 WALL 437 780 M Mature 13 28 NRPK 685 2,120 F Mature 8 29 WALL 477 1,400 F Mature 13 30 NRPK 655 2,013 F Mature 8 31 NRPK 740 1,650 F Mature 9 32 NRPK 640 1,420 F Mature 7 33 WALL 427 1,000 F Mature 6 34 WALL 431 870 M Mature 11 35 WALL 430 740 M Mature 10 36 WALL 415 940 F Mature 6

23




Age (y)

37 WALL 510 1,180 F Mature 13 38 WALL 420 760 M Mature 11 39 WALL 427 1,000 F Mature 7 40 WALL 430 950 M Mature 13 41 WALL 430 880 M Mature 12 42 WALL 440 940 F Mature 6 43 NRPK 624 1,473 F Mature 6 44 WALL 420 850 M Mature 13 45 WALL 441 780 F Mature 6 46 WALL 423 860 F Mature 6 47 WALL 412 760 F Mature 9 48 WALL 495 1,180 F Mature 13 49 WALL 477 1,110 F Mature 13 50 WALL 417 800 F Mature 6 51 WALL 418 778 M Mature 6 52 NRPK 520 1,425 F Mature 6 53 NRPK 577 1,410 F Mature 6 54 NRPK 545 960 F Mature 6 55 NRPK 580 1,250 F Mature 9 56 WALL 428 830 M Mature 13 57 WALL 430 810 F Mature 6 58 WALL ‐ 820 M Mature 11 59 WALL 414 740 F Mature 6 60 WALL 427 920 F Mature 11 61 WALL 445 940 M Mature 12 62 NRPK 599 1,350 F Mature 7 63 NRPK 650 1,450 F Mature 8 64 NRPK 567 1420 M Mature 6 65 NRPK 636 1,680 F Mature 6 66 NRPK 563 1,340 F Mature 5 67 NRPK 654 1,630 F Mature 7 68 NRPK 625 1,470 F Mature 8 69 WALL 427 870 M Mature 13 70 WALL 407 780 F Mature 6 71 WALL 443 980 F Mature 7 72 NRPK 610 1,700 F Mature 6 73 WALL 424 910 M Mature 12 74 WALL 440 820 F Mature 12

24




Age (y)

75 WALL 443 920 F Mature 6 76 WALL 445 1,010 F Mature 12 77 WALL 451 950 F Mature 13 78 WALL 435 810 M Mature 12 79 WALL 431 850 M Mature 12 80 WALL 455 1,110 F Mature 13 81 WALL 420 840 F Mature 12 82 WALL 413 740 F Mature 6 83 NRPK 741 3,800 M Mature 14 84 WALL 449 860 F Mature 11 85 WALL 478 929 F Mature 6 86 WALL 422 820 F Mature 4 87 WALL 439 810 M Mature 5 88 WALL 426 800 M Mature 6 89 WALL 360 500 M Mature 3 90 WALL 410 750 M Mature 6 91 WALL 434 760 M Mature 5 92 WALL 427 880 F Mature 6 93 WALL 380 580 M Mature 5 94 WALL 430 810 F Mature 5 95 WALL 349 510 M Mature 4 96 WALL 500 1,290 F Mature 10 97 NRPK 650 1,920 F Mature 8 98 NRPK 560 1,210 F Mature 7 99 NRPK 675 2,190 F Mature 8 100 NRPK 627 1,620 F Mature 7 101 WALL 418 770 M Mature 4 102 WALL 349 440 M Mature 4 103 NRPK 596 1,450 F Mature 6 104 WALL 431 910 F Mature 6 105 WALL 447 930 F Mature 6 106 WALL 423 870 M Mature 9 107 NRPK 684 2,090 F Mature 8 108 NRPK 635 1,600 F Mature 8 109 NRPK 564 1,180 F Mature 6 110 WALL 435 850 F Mature 14 111 WALL 421 750 F Mature ‐ 112 WALL 352 480 F Mature 5

25




Age (y)

113 NRPK 731 2,430 F Mature 10 114 WALL 390 631 F Mature 5 115 NRPK 610 3,500 F Mature 8 116 WALL 510 ‐ M Mature 16 117 WALL 446 1,050 M Mature ‐ 118 WALL 430 930 F Mature 13 119 NRPK 676 1,870 F Mature 6 120 NRPK 554 1,020 F Mature 5 121 NRPK 574 1,300 F Mature 5 122 NRPK 550 1,210 F Mature 5 123 WALL 300 320 F Mature 4 124 WALL 437 930 F Mature 7 125 WALL 420 800 F Mature 6 126 WALL 510 1,370 F Mature 10 127 WALL 324 350 M Mature 4 128 WALL 380 530 M Mature 5 129 WALL 416 790 F Mature 6 130 WALL 355 490 M Mature 5 131 WALL 412 730 F Mature ‐ 132 WALL 418 770 F Mature 5 133 WALL 452 880 F Mature 14 134 WALL 332 830 F Mature ‐ 135 WALL 369 560 F Mature 5 136 NRPK 630 1,660 F Mature 7 137 NRPK 527 1,310 F Mature 4 138 NRPK 550 1,140 F Mature 5 139 NRPK 541 1,290 F Mature 4 140 NRPK 570 1,420 F Mature 6 141 NRPK 564 1,340 F Mature 5 142 NRPK 523 1,040 F Mature 4 143 NRPK 600 1,480 F Mature 7 144 WALL 423 820 F Mature 6 145 WALL 414 717 M Mature 6 146 WALL 325 640 F Mature 4 147 WALL 330 820 F Mature 4 148 WALL 346 900 F Mature 4 149 WALL 410 700 F Mature 6 150 WALL 500 1,170 F Mature 13

26

27




Age (y)

151 NRPK 550 1,190 F Mature 5 152 NRPK 600 1,570 F Mature 7 153 WALL 415 750 F Mature 6 154 WALL 445 1,000 M Mature 13 155 WALL 426 860 F Mature 5 156 WALL 506 1,400 F Mature 12 157 WALL 510 1,420 F Mature 10 158 WALL 467 1,300 M Mature 14 159 WALL 504 1,470 F Mature ‐ 160 WALL 440 1,000 F Mature 6 161 WALL 455 1,190 F Mature ‐ 162 WALL 423 780 F Mature 5 163 WALL 451 860 M Mature 6 164 WALL 411 790 F Mature 5 165 WALL 436 930 M Mature 10 166 WALL 429 880 M Mature 12 167 WALL 425 900 M Mature 10 168 NRPK 614 ‐ F Mature 6 169 WALL 433 ‐ F Mature 12 170 WALL 436 ‐ M Mature 14 171 WALL 444 962 F Mature 5 172 WALL 438 953 F Mature 13 173 NRPK 626 ‐ F Mature 7

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