Abundance of Arctic Grayling in a 30-Km Reach of the Wapiti River, Alberta

Abundance of Arctic Grayling in a 30-km Reach of the Wapiti River, Alberta

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Abundance of Arctic Grayling in a 30‐km Reach of the Wapiti River, Alberta

John Tchir, Tyler Johns and Greg Fortier

Alberta Conservation Association Bag 900‐26 Peace River, Alberta, Canada T8S 1T4

Report Series Editor PETER AKU P.O. Box 40027 Baker Centre Postal Outlet Edmonton, AB, T5J 4M9

Conservation Report Series Type Data, Technical

ISBN printed: 978‐0‐7785‐5423‐3 ISBN online: 978‐0‐7785‐5424‐0 Publication No.: T/129

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: Tchir J.P., T.W. Johns, and G.N. Fortier. 2004. Abundance of Arctic grayling in a 30‐km reach of the Wapiti River, Alberta. Data report, D‐2004‐020, produced by Alberta Conservation Association, Peace River, Alberta, Canada. 13 pp.

Cover photo credit: David Fairless

Digital copies of conservation reports can be obtained from: Alberta Conservation Association P.O. Box 40027, Baker Centre Postal Outlet Edmonton, AB, T5J 4M9 Toll Free: 1‐877‐969‐9091 Tel: (780) 427‐5192 Fax: (780) 422‐6441 Email: info@ab‐conservation.com Website: www.ab‐conservation.com

EXECUTIVE SUMMARY

A total of 147 Arctic grayling were captured over the 30‐km stretch during our study. Mean (±SD) fish size (fork length) was 304 ± 38.1 mm and size composition was uniform throughout the study area.

Using the bias corrected Lincoln‐Peterson method, estimated total abundance of Arctic grayling in the 30‐km reach of the Wapiti River was 612 (95% CI = 281 ‐ 943). Estimated abundance of harvestable fish (≥ 350 mm total length (TL)) was 291 fish (95% CI = 34 ‐ 547). With the maximum likelihood estimate method, estimated total abundance was 670 fish (95% CI = 430 ‐ 1748) while that of harvestable fish was 408 (95% CI = 281 ‐ 2366).

ACKNOWLEDGEMENTS

This project was collaboratively developed between the Alberta Conservation Association (ACA) and Alberta Sustainable Resource Development (ASRD). We thank Mike Doran and Dave Jackson (ACA) for their help with field sampling. We also thank Paul Hvenegaard (ACA) and Travis Ripley (ASRD) for providing their expertise in site selection and sampling design. We acknowledge Garry Scrimgeour, Manager of Science and Research, ACA, for his guidance in statistical analyses.

iii

TABLE OF CONTENTS

EXECUTIVE SUMMARY...... ii

ACKNOWLEDGEMENTS...... iii

TABLE OF CONTENTS ...... iv

LIST OF FIGURES ...... v

LIST OF TABLES...... vi

1.0 INTRODUCTION ...... 1 1.1 General introduction...... 1 1.2 Study objectives...... 1

2.0 STUDY AREA...... 2 2.1 Description ...... 2 2.2 Ecoregion, forest cover and soils...... 4 2.3 Fish community...... 4

3.0 MATERIALS AND METHODS ...... 6 3.1 Abundance estimates...... 6 3.2 Size composition...... 8

4.0 RESULTS ...... 9 4.1 Arctic grayling abundance...... 9 4.2 Size composition...... 10 4.3 Summary ...... 12

5.0 LITERATURE CITED ...... 13

LIST OF FIGURES

Figure 1. Location of Arctic grayling mark‐recapture survey site on the Wapiti River, Alberta...... 3 Figure 2. Length‐frequency distribution of Arctic grayling from the 30‐km study site in the upper Wapiti River, Alberta...... 12

LIST OF TABLES

Table 1. Fish species captured in the Wapiti River watershed, Alberta...... 5 Table 2. Kolomogorov‐Smirnov (K‐S) two‐sample tests (z) for differences in length‐frequency distributions of Arctic grayling between sampling events in the upper Wapiti River, Alberta...... 9 Table 3. Descriptive statistics of Arctic grayling size composition from three sections in the upper Wapiti River, Alberta...... 10 Table 4. Summary of Kolomogorov‐Smirnov two‐sample tests (z) for differences in Arctic grayling length‐frequency distributions among sections in the upper Wapiti River, Alberta...... 11

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1.0 INTRODUCTION

1.1 General introduction

Arctic grayling (Thymallus arcticus) is an important sport fish species in several lakes and rivers in Alberta, including the Wapiti River. However, abundance and distribution of this species has declined throughout the province as a result of increased angling pressure and habitat destruction. Historically, the largest Arctic grayling spawning run in the Wapiti drainage occurred in the Beaverlodge River. However, this run has not existed for several years. Since the loss of this major run, the Redwillow River has been identified as an important spawning tributary to the Wapiti River (P. Hvenegaard, Alberta Conservation Association (ACA), pers. com). Although previous fish surveys have been conducted in the Wapiti River (Tchir et al. 2002), very limited quantitative data exist on the distribution and abundance of Arctic grayling in the river. Monitoring abundance of Arctic grayling in the Wapiti River is required by fisheries managers to ensure fishing regulations meet goals established in the provincial conservation guide “A fish conservation strategy for Alberta 2000‐2005 (Alberta Environment 1998)”. The present study was designed to determine abundance and size composition of Arctic grayling in a 30‐km reach of the Wapiti River. This study represents the first assessment of Arctic grayling abundance using mark‐recapture techniques on the upper Wapiti River.

1.2 Study objectives

The primary objectives of our study were to determine: i. Abundance of Arctic grayling using a mark‐recapture survey. ii. Size structure of Arctic grayling. iii. Abundance of the harvestable (≥ 350 mm total length (TL)) component of the Arctic grayling population.

2.0 STUDY AREA

2.1 Description

The Wapiti River enters Alberta approximately 90 km southwest of the City of Grande Prairie, where it flows 161 km northeast to its confluence with the Smoky River. The study reach started at 311700 Easting and 6069032 Northing UTM Zone 11 and ended at 328758 Easting and 6083536 Northing UTM Zone 11. The‐30‐km study reach was split into 3 equidistant sections (Figure 1).

Figure 1. Location of Arctic grayling mark‐recapture survey site on the Wapiti River, Alberta. The study reach started at 311700 Easting and 6069032 Northing UTM Zone 11 and ended at 328758 Easting and 6083536 Northing UTM Zone 11.

2.2 Ecoregion, forest cover and soils

The study area is located primarily within the Lower Boreal‐Cordilleran Ecoregion and to a lesser extent, the Upper Boreal‐Cordilleran, Mid Boreal Mixedwood and Alpine ecoregions, respectively (Strong and Leggat 1992). These areas typically have low annual precipitation with short summers and long, cold winters (Strong and Leggat 1992).

Forest cover is comprised of lodgepole pine (Pinus contorta), trembling aspen (Populus tremuloides), and white spruce (Picea glauca) with balsam poplar (Populus balsamifera), paper birch (Betula papyrifera), and balsam fir (Abies balsaimea) (Strong and Leggat 1992). Aspen and open stands of lodgepole pine occur on drier sites; black spruce and tamarack are associated with wet areas. Conifers are more prevalent on cooler, higher elevations in the foothills, whereas aspen is more dominant in its lower plains section (Strong and Leggat 1992).

Dominant soil types include well‐developed luvisolic soils with some bare rock ridges and Gleysolic and Organic soils. The ecoregion generally slopes and drains northeastward via the Peace, Athabasca, and Saskatchewan River systems (Strong and Leggat 1992).

2.3 Fish community

The fish community consists of 6 sport and 9 non‐sport fish species (Table 1). Mountain whitefish (Prosopium williamsoni) and Arctic grayling were the most prevalent sport species. Longnose sucker (Catostomus catostomus) is the most ubiquitous non‐sport species in the watershed (Tchir et al. 2002).

Table 1. Fish species captured in the Wapiti River watershed, Alberta (data from FMIS1 2003).

Common name Scientific name Sport fish Arctic grayling Thymallus arcticus Bull trout Salvelinus confluentus Mountain whitefish Prosopium williamsoni Walleye Sander vitreus Northern pike Esox lucius Burbot Lota lota

Non‐sport fish Longnose sucker Catostomus catostomus Largescale sucker Catostomus macrocheilus White sucker Catostomus commersoni Lake chub Couesius plumbeus Longnose dace Rhinichthys cataractae Redside shiner Richardsonius balteatus Slimy sculpin Cottus cognatus Trout perch Percopsis omiscomaycus Brook stickleback Culea inconstans

1FMIS is a provincial database containing comprehensive information on fish and fish habitat.

3.0 MATERIALS AND METHODS

3.1 Abundance estimates

Fish were captured with a raft‐mounted electrofisher consisting of a 4.3‐m inflatable raft shocking unit powered by a 5.0‐kWh generator that produced 60 pulses per second and between 4.0 and 6.0 amps. We conducted two marking runs over a 3‐day span (11‐ 13 August) during which we marked a total of 103 fish (size range 214 – 385 mm fork length (FL). Fish were measured for FL (±1.0 mm) and marked with t‐bar anchor tags below the dorsal fin to uniquely identify individual fish. A single re‐capture run was conducted on 18 August. All fish captured after the first tagging survey were examined for tags or the presence of wounds associated with tag loss. The mark‐recapture sampling design was adapted from Ripley (1997). Because only FL of fish was measured in the field, total length (TL) was estimated from FL using the relationship, TL = 2.474 + 1.0768 (FL) (Ripley 1997). Water discharge was at its lowest point of the summer during the sampling, conditions and water clarity remained consistent throughout.

The bias‐corrected Lincoln–Peterson method (Skalski and Robson 1992) and maximum likelihood estimation were used to estimate abundance and associated measures of dispersion.

3.1.1 Bias corrected Lincoln‐Peterson estimate

We estimated fish abundance using the following Skalski and Robson (1992) bias‐ corrected Peterson‐Lincoln equation:

[]1 += 2 + mnnN 2 + −1)1/()1)(1(

2 1 2 1 22 2 [ 2 mmmnmnnnNSE 2 ++−−++= )2()1(/))()(1)(1()( ]

95% Confidence Interval = NSE 96.1*)( where, N = Estimate of the population

n1 = Initial random sample (marked fish)

n2 = Number of captured fish from a second sample

m2 = Number of marked fish captured in second sample SE(N) = Standard error of the estimate

This estimator is unbiased and returns the correct average value if the study was repeated several times. Standard error (SE) of the estimate was calculated and used to determine confidence intervals. A separate abundance estimate was derived for the harvestable component (fish ≥ 350 mm TL) of the population.

3.1.2 Validation of the Lincoln‐ Peterson assumptions

Use of the Linclon‐Peterson estimator for mark‐recapture surveys requires that the following assumptions to be met:

Assumption 1: the population being sampled is closed. To address this assumption, the 30‐km study reach was split into three equal sections to assess the potential immigration and emigration of fish in the reach. During our study, all recaptured fish were found in the same sections that they were originally marked suggesting minimal movement out of the area. Based on this observation, coupled with the short duration between mark and recapture samples, we assumed the effects of immigration and emigration will be negligible.

Assumption 2: samples are randomly chosen from the population. To ensure all fish captured had the same probability of recapture the Kolmogorov‐Smirnov (K‐S) two‐ sample test (z), adjusted for multiple comparisons using the Bonferroni adjustment (Zar 1999), was used to examine differences in both the locations and the shapes of length frequency distributions between sampling events. The K‐S test is based on the maximum absolute difference between the observed cumulative distribution functions for both samples. When this difference is significantly large, the two distributions are considered different. We used a significance level of α = 0.017 based on the Bonferroni adjustment.

We indirectly tested assumptions that catchability was constant and all fish had an equal chance of being recaptured (Assumption 2). We tested for differences in Arctic grayling length‐frequency distributions between marking and recapturing events using the K‐S two‐sample test (Bonferroni adjusted α = 0.017).

Assumption 3: no marks are lost before the second sample is taken and all marked individuals are recognized as such. To satisfy this assumption, highly visible T‐bar anchor tags were used and all fish captured were examined for the presence of wounds associated with tag loss. If a puncture wound was noticed below the dorsal fin the fish was recorded as being recaptured. Marks were easily recognizable and since the same field crew participated in all sampling events we believe this assumption was met.

3.1.3 Maximum likelihood estimates

We also estimated population size of Arctic grayling using a maximum likelihood approach as per Haddon (2001). True probabilities were generated from the binomial probability density function

⎡ n! ⎤ m −mn )( ,| pnmP }{ =⎢ ⎥ − pp )1( ⎣ − mnm )!(! ⎦ where, n = the number of trails p = the probability of success in a trial m = the number of observed successes

Confidence intervals around the estimated population size were determined at α = 0.05 using the cumulative probability distribution. The same assumptions apply to this method of estimation of population size as the Peterson‐Lincoln method.

3.2 Size composition

We used length‐frequency distributions to examine size structure of the Arctic grayling population. We used the K‐S two‐sample test to examine differences in length‐ frequency distributions among the three sections in the 30‐km study reach and tested

for differences in average FL among the three sections using one‐way ANOVA (Bonferroni adjusted α = 0.017). Length‐frequency distributions were constructed for combined sections where differences were insignificant.

4.0 RESULTS

4.1 Arctic grayling abundance

A total of 147 Arctic grayling were captured over the 30‐km stretch during our study. Based on results of the K‐S two‐sample tests, fish size distribution did not differ among sampling events (two marking and one recapture sampling) (Table 2), suggesting that all samples were randomly chosen from the population as required under assumption 2.

Table 2. Kolomogorov‐Smirnov (K‐S) two‐sample tests (z) for differences in length‐ frequency distributions of Arctic grayling between sampling events in the upper Wapiti River, Alberta.

Differences in cumulative frequency Sampling event distributions Absolute Positive Negative z P Marking 1, Marking 2 0.165 0.040 ‐0.165 0.843 0.476 Marking 1, Recapture 0.239 0.239 ‐0.059 1.170 0.130 Marking 2, Recapture 0.175 0.175 ‐0.059 0.863 0.446

4.1.1 Lincoln–Peterson abundance estimates

A total of 103 fish were marked during the two capture surveys. During the recapture survey, 52 fish were captured, of which 8 were previously marked. Based on these numbers, the estimated population size of Arctic grayling in the 30‐km reach of the Wapiti River was 612 (95% CI = 281 ‐ 943). In total, 34 harvestable Arctic grayling (i.e., fish ≥ 350 mm TL) were marked during the capture surveys. During the recapture

survey, 24 harvestable fish were captured, of which 2 were previously marked, resulting in an estimated abundance of 291 (95% CI = 34 ‐ 547) harvestable fish.

4.1.2 Maximum likelihood estimate of abundance

The maximum likelihood estimate (MLE) of Arctic grayling population was 670 (95% CI = 430 ‐ 1748) while that of harvestable fish was 408 (95% CI = 281 ‐ 2366).

4.2 Size composition

Size (FL) of Arctic grayling captured in different sections did not differ significantly (One‐way ANOVA, F = 1.17, df = 2, 162, P = 0.182). Mean (±SD) fish size over the 30‐km stretch was 304 ± 38.1 mm FL (n = 147). Statistics describing length composition for each section are provided in Table 3 below. Although, statistically significant differences were not found, the greatest distinctions between mean lengths appeared to occur between upper and lower sections of the study reach.

Table 3. Descriptive statistics of Arctic grayling size composition from three sections in the upper Wapiti River, Alberta.

River Fork length (mm) section n Mean Range Median Mode Upper 47 297.68 126 ‐ 382 299 263 Middle 56 307.57 214 ‐ 385 313 261 Lower 44 311.36 214 ‐ 370 315 306

Based on our significance level of α = 0.017, results of the K‐S two‐sample tests indicate that fish size distributions generally did not differ among the three sections of the 30‐km stretch (Table 4). Although not statistically significant more small fish were captured in the Upper section than in the Lower section; with P = 0.02, the difference between these two locations may be considered statistically marginal (Table 4). To speculate, this may be a result of better upstream rearing habitat and subsequent

distribution of smaller fish being greater in upstream reaches of the Wapiti River than lower sections.

Table 4. Summary of Kolomogorov‐Smirnov two‐sample tests (z) for differences in Arctic grayling length‐frequency distributions among sections in the upper Wapiti River, Alberta.

Differences in cumulative frequency

River section distributions Absolute Positive Negative z P Upper, Middle 0.171 0.032 ‐0.171 0.947 0.332 Upper, Lower 0.291 0.291 ‐0.036 1.521 0.020 Middle, Lower 0.203 0.203 ‐0.063 1.106 0.173

The length‐frequency distribution is unimodal with a peak TL at the 360‐mm size class (Figure 2). Overall 64% of Arctic grayling were less than 350 mm TL (minimum harvestable size).

n = 147 20

(%) 15

10 Frequency

0 220 240 260 280 300 320 340 360 380 400 420 440

Predicted total length (mm)

Figure 2. Length‐frequency distribution of Arctic grayling from the 30‐km study site in the upper Wapiti River, Alberta.

4.3 Summary

In future studies, required precision of the estimate should be stated prior to sampling to ensure adequate results. Our results indicated little difference in size composition and relative abundance of fish between sections. Therefore, to reduce cost associated with increased precision the study area could be reduced to a single 10‐km reach comprised of three equidistant sections. For comparable results we recommend sampling during the same time of year (August) when flows are generally lowest and water clarity does not reduce capture efficiency.

5.0 LITERATURE CITED

Alberta Environment. 1998. A fish conservation strategy for Alberta 2000‐2005. Alberta Environment. Pub. No. I.698, Alberta. 23 pp.

Berry, D.K. 1998. Arctic grayling management and recovery plan. Pub. No. T/410 Alberta Environmental Protection, Fisheries Management Division, Alberta. 22 pp + App.

Haddon, M. 2001. Modeling and quantitative methods in fisheries. CRC Press, Washington, D.C. 405 pp.

Skalski, J.R., and D. S. Robson 1992. Techniques for wildlife investigation: Design and analysis of capture studies. Academic Press, San Diego. 237 pp.

Strong, W.L., and K.R. Leggat. 1992. Ecoregions of Alberta. Land Information Services Division. Alberta Forestry, Lands, and Wildlife. Edmonton, Alberta. 59 pp.

Tchir J., A.Wildeman, and P. Hvenegaard 2002. Wapiti River watershed study final report. Tech. Rep. Alberta Conservation Association, Peace River, Alberta. 59 pp.

Ripley T. 1997. A Stock Assessment of the Kakwa River Arctic Grayling (Thymallus arcticus) Population, Fall 1997. Tech. Rep. Alberta Conservation Association, Peace River, Alberta.

Zar, J.H. 1999. Biostatistical analysis. 4th ed. Prentice‐Hall, New Jersey. 663 pp + App.

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