CLBMON-37 | Arrow Lakes Reservoir Amphibian and Reptile Life History and Habitat Use ...

46 Pages·2013·1.87 MB·English

Columbia River Project Water Use Plan

ARROW LAKES RESERVOIR: AMPHIBIAN AND REPTILE LIFE
HISTORY AND HABITAT USE ASSESSMENT

Reference: CLBMON 37

Interim Analysis

Study Period: 2008 - 2012

LGL Limited
Environmental research associates
Sidney, BC

December 2013
EA3303B
KINBASKET AND ARROW LAKES RESERVOIRS
Monitoring Program No. CLBMON-37
Arrow Lakes Reservoir: Amphibian and Reptile Life
History and Habitat Use Assessment
Comprehensive Report 2013
Prepared for

BC Hydro Generation
Water Licence Requirements
6911 Southpoint Drive
Burnaby, BC
BC Hydro Reference # RFP 735
Prepared by
Virgil C. Hawkes, MSc., RPBio.
and
Krysia N. Tuttle, MSc.

LGL Limited
environmental research associates
9768 Second Street
Sidney, British Columbia, V8L 3Y8
December 12, 2013
Arrow Lakes Reservoir - Amphibian and Reptile Study
Comprehensive Report 2008–2012

Suggested Citation:
Hawkes, V.C., and K.N. Tuttle. 2013. CLBMON-37. Arrow Lakes Reservoir: Amphibian
and Reptile Life History and Habitat Use Assessment. Comprehensive Report –
2013. LGL Report EA3303B. Unpublished report by LGL Limited environmental
research associates, Sidney, BC, for BC Hydro Generations, Water License
Requirements, Burnaby, BC. 33 pp.
Cover photos:
From left to right: Common Garter Snake (Thamnophis sirtalis) © Krysia Tuttle; Western
Toad tadpoles (Anaxyrus boreas); Western Toad; and Painted Turtle (Chrysemys
picta); © Virgil C. Hawkes, LGL Limited.
© 2013 BC Hydro.
No part of this publication may be reproduced, stored in a retrieval system, or
transmitted, in any form or by any means, electronic, mechanical, photocopying,
recording, or otherwise, without prior permission from BC Hydro, Burnaby, B.C.
Arrow Lakes Reservoir - Amphibian and Reptile Study EXECUTIVE SUMMARY
Comprehensive Report 2008-2012
EXECUTIVE SUMMARY
An amphibian and reptile life history and habitat use monitoring study has been
underway in the drawdown zones (DDZs) of Kinbasket and Arrow Lakes
Reservoirs since 2008. Over a 10 year period, six years of data are to be
collected. This study is intended to address the relative contribution and
importance of the current reservoir operating regime (i.e., timing, duration and
depth of inundation) on the life history (e.g., abundance, distribution and
productivity) and habitat use of amphibians and reptiles occurring in the DDZs of
each reservoir. The lack of data on the relative abundance, distribution, life
history and seasonal patterns of habitat use by amphibians and reptiles
precluded incorporation of concerns for these species in the Columbia River
water use planning process. The results of CLBMON-37 provide general
information on operation-related impacts on some of these species and possible
mitigation strategies. The effectiveness of soft constraints implemented in Arrow
Lakes (target reservoir levels between 437 m and 439 m from May 24 to
September 30) is also considered.
Nine management questions are addressed, with the primary objective being to
provide information on how amphibian and reptile communities at the landscape
scale are affected by long-term variations in water levels and whether changes to
the reservoir’s operating regime may be required to maintain or enhance these
communities or the habitats in which they occur.
Through a variety of survey methods (egg mass surveys, visual encounter
surveys, auditory surveys) we documented the presence of four amphibian and
six reptile species in Arrow Lakes Reservoir. Western Toads (Anaxyrus boreas),
Pacific Chorus Frog (Pseudacris regilla), and Common Garter Snakes
(Thamnophis sirtalis) were the most commonly encountered species. Most
amphibian and reptile detections were distributed between 435 and 441 m ASL.
The influence of reservoir operations on the availability of habitat in the DDZ is
evident: as reservoir elevations increase throughout the season, the total amount
of available habitat decreases. Habitats situated between 435 and 441 m ASL
are generally inundated beginning in early to mid-June, with inundation lasting
through the end of August or mid-September. As such, the utilization of the
drawdown zone by amphibians and reptiles is a function of reservoir elevation.
The timing of inundation of ponds at critical times of the year may have
implications on amphibians using the drawdown zone for breeding (e.g., growth
and development of anuran larvae). However, the implications may not be
realized for many years due to ecological time lags and the longevity of some
species. This means that multiple generations of some species (e.g., Western
Toads) may need to pass before an effect is evident.
Monitoring in Arrow Lakes Reservoir will continue in 2014 and it is recommend
that subsequent sampling occur annually (i.e., in 2015 and 2016) to remove
uncertainties about the relationship between reservoir operations and amphibian
and reptile abundance, diversity, and productivity. Moreover, the Arrow Lakes
study should focus on fewer monitoring locations and on two species: Western
Toads and Common Garter Snakes. The other species detected in the drawdown
zone occur at such low frequencies that assessments of change would be
meaningless or difficult to assess. Narrowing the focus of the study to these two
species and to fewer monitoring locations may increase the frequency at which
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Arrow Lakes Reservoir - Amphibian and Reptile Study EXECUTIVE SUMMARY
Comprehensive Report 2008-2012
study sites are sampled, which will improve the data sets and increase the
probability of addressing the management questions.
Of the nine management questions, one has been answered (Management
Questions 1), three are not answerable at this time (MQs 7, 8, and 9), two have
been partially answered (MQs 2 and 3) and questions 4, 5, and 6 may be
answered as more data are collected.
The following tables summarize the status of CLBMON-37 at the end of 2012
with an emphasis on our ability to test specific hypotheses, to answer
management questions, and to meet the management objectives.
Management Management Status (at the end of 2012) & Summary
Management Objective
Questions Hypotheses Points
 4 species of amphibians and 6 species of
reptiles documented to date.
 Western Toads ubiquitous (all study sites).
 Columbia Spotted Frogs ad Pacific Chorus
Frogs are found from Edgewood north to
Revelstoke Reach, but in much lower
frequencies than Western Toads.
H1A
Determine reptile and amphibian MQ#1  Long-toed Salamanders are abundant in
H1B
use of the drawdown zones of the MQ#2 Revelstoke Reach and likely occur at all sites.
H1C
Arrow Lakes and Kinbasket MQ#3  Western Terrestrial and Common Garter
H1D
Reservoirs. MQ#4 Snakes are abundant at all sites.
H1E
 Northern Alligator Lizards are most abundant
in Revelstoke Reach, but also occur in Lower
Inonoaklin Road and Edgewood.
 Rubber Boa and Western Skink have been
observed in Edgewood only.
 Western Painted Turtles have only been
documented from Revelstoke Reach.
 Too soon to assess.
 Longer-term data sets required.
Inform BC Hydro on how reservoir MQ#1
 Decreased habitat availability in DDZ
operations affect reptile and MQ#2 H1A
beginning in early to mid-June and persisting
amphibian populations by MQ#3 H1B
though mid-September may have long-term
monitoring their abundance, MQ#4 H1C
impacts.
diversity, distribution, productivity, MQ#5 H1D
 Inundation of amphibian breeding ponds prior
and patterns of habitat use over MQ#6 H1E
to metamorphosis, which begins (usually) in
time.
mid-August may affect reproductive success,
but too soon to tell.
 Difficult to assess at this point;
 Longer-term data sets required
 Data collected in 2014 to 2018 will help but
this will still be difficult to measure.
Determine whether minor  Implementation of physical works to protect,
adjustments can be made to H1A enhance, or create wetland habitat in the
reservoir operations to minimize MQ#5 H1B drawdown zone of Arrow Lakes Reservoir
impacts on reptile and amphibian MQ#6 H1C will likely mitigate the impacts
populations or determine if H1D  Maintaining elevations at or below ~435 m
mitigation strategies can be H1E ASL until mid-August would minimize
developed to reduce these impacts? possible reservoir impacts on certain life
stages of amphibians.
 Probably easier to assess for amphibians
than reptiles (i.e., snakes and lizards)
because of known habitat requirements.
 Physical works (yet to be completed) to
Inform BC Hydro on how physical
create habitat in the higher elevations of the
works and revegetation can be
MQ#7 H2A DDZ would help to minimize the impacts of
designed and implemented to
MQ#8 H2B inundation and loss of habitat.
mitigate adverse impacts resulting
MQ#9 H2C  Revegetation is likely important for
from reservoir operations on
amphibians/reptiles especially in barren
amphibian and reptile populations.
areas surrounding the DDZ breeding ponds.
Provide the data necessary to MQ#7 H2A  Data gathered from 2008 to 2012 provide
evaluate whether physical works MQ#8 H2B baseline data (before the physical works are
projects or revegetation initiatives MQ#9 H2C initiated).
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Arrow Lakes Reservoir - Amphibian and Reptile Study EXECUTIVE SUMMARY
Comprehensive Report 2008-2012
Management Management Status (at the end of 2012) & Summary
Management Objective
Questions Hypotheses Points
benefit amphibian and reptile  Data collected after physical
populations through increased works/revegetation projects (2014-2018) will
abundance, site occupancy, species help evaluate benefits to amphibian and
diversity, or increases to habitat reptile populations
availability or quality.

What is the biological significance of
Management Hypothesis What is the effect size (ES)?
the ES?
H1: Annual and seasonal variation in water levels in Arrow Lakes Reservoir and the implementation of soft
operational constraints and potential effects of Revelstoke Unit 5 in Arrow Lakes Reservoir (“reservoir
operations”) do not directly or indirectly impact reptile and amphibian populations.
 Amphibians populations are
inherently variable. Any change in the
relative abundance of amphibians
from one year to the next may not be
biologically significant.
 However, if a downward trend is
observed over multiple consecutive
 No specific effect size has been years, a conclusion of overall decline
determined for either reptiles or in the local population of those
amphibians. The minimum detectable species might be made. Reptile
difference could be defined as populations (garter snakes and
H1A: Reservoir operations do not
changes of less than 1 standard lizards) have not been studied in the
result in a decreased abundance of
deviation of the mean of given detail required to make a
amphibians or reptiles in the
response variable as likely not determination of the biological
drawdown zone.
biologically important. However, this significance of a decline of these
change may not be statistically populations.
significant, so context and  The biological significance of any
interpretation are required. effect on amphibian abundance is not
known and difficult to assess at this
point.
 A 1 SD change may or may not be
statistically significant, but may be
indicative of a biological effect, so
context and interpretation are
required.
 Under the current operating regime,
the timing of inundation impacts the
larval stage of amphibians at a critical
time in their development
(metamorphosis); however, it is
H1B: Reservoir operations do not
unknown if this contributes to
increase the stage specific (e.g.
increased rates of mortality
larval, juvenile, or adult) mortality  See above
 The biological significance of any
rates of amphibians or reptiles in
effect of reservoir operations on
the drawdown zone.
amphibian and reptile mortality rates
is not known and difficult to assess at
this point because we don't know how
reservoir operations are related to
population-level changes.
 Site occupancy has remained
relatively constant over the first 5
years
 Reservoir operations do result in
decreased site occupancy at certain
times of the year. When lower
H1C: Reservoir operations do not elevation (e.g., 433 m to 435 m ASL)
result in decreased site occupancy ponds are inundated in the spring,
 See above
of amphibians or reptiles in the they become unavailable, and site
drawdown zone. occupancy is reduced.
 All ponds in the drawdown zone
below 440.1 m ASL are inundated in
most years. As such, site occupancy
changes as a result of inundation,
and the degree to which site
occupancy decreases is a function of
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Arrow Lakes Reservoir - Amphibian and Reptile Study EXECUTIVE SUMMARY
Comprehensive Report 2008-2012
What is the biological significance of
Management Hypothesis What is the effect size (ES)?
the ES?
reservoir operation.
 The biological significance of any
effect of reservoir operations on
changes in site occupancy is not
known and difficult to assess at this
point.
 Amphibian productivity was assessed
using a catch per unit effort
calculation and egg mass counts.
With the exception of Western Toads,
too few data exist for the other
H1D: Reservoir operations do not species of amphibians to discuss how
result in decreased productivity of reservoir operations might affect their
 See above
amphibians or reptiles in the productivity.
drawdown zone.  Reptile productivity is not being
assessed via CLBMON-37
 The biological significance of any
effect of reservoir operations on
productivity is not known and difficult
to assess at this point
 Reservoir operations do affect habitat
availability and quality. The number of
observations in the DDZ per species
H1E: Reservoir operations do not
generally declines throughout the
reduce the availability and quality of
summer, which is directly related to
breeding habitat, foraging habitat
 See above habitat availability.
and overwintering habitat for
 The variable manner in which Arrow
amphibians or reptiles in the
lakes Reservoir has been operated
drawdown zone.
makes it difficult to quantify the
relationship between reservoir
operations and habitat availability.
H2: The physical works projects and revegetation efforts do not increase the utilization of habitats by amphibians or
reptiles in the drawdown zone.
H2A: Revegetation and physical
works do not increase species
diversity or seasonal
(spring/summer/fall) abundance of
amphibians or reptiles in the
drawdown zone.
These management hypotheses require
H2B: Revegetation and physical  Effect size has not yet been assessed
data collection after physical works are
works do not increase amphibian or as physical works are not completed.
implemented.
reptile productivity in the drawdown
zone
H2C: Revegetation does not increase
the amount or improve habitat for
amphibians and reptiles in the
drawdown zone.

Can it be
Management Questions Summary points to back answer
answered?
 The data collected to date provide a good understanding of the
distribution of amphibians and reptiles in the drawdown zone
1. Which species of reptiles and
 Currently, large populations of Western Toads and Common
amphibians occur (utilize habitat) within
Yes Garter Snakes occur in ALR. Pacific Chorus Frogs are
the drawdown zone and where do they
abundant in some locations.
occur?
 Numbered and mapped breeding ponds give an overall
distribution of use for breeding and foraging in the DDZ
 Detection rates (CPUE) provide a measure of relative
2. What is the abundance, diversity, and abundance over the 4 year period
productivity (reproduction) of reptiles  Species diversity can be calculated for each location
and amphibians utilizing the drawdown Partially  Productivity measured by # egg masses per pond per year
zone and how do these vary within and (Western Toads only)
between years?  Productivity of reptile populations cannot be determined
without more intensive research.
3. During what portion of their life history  Site occupancy has been determined for each species
Partially
(e.g., breeding, foraging, and  For most species we can only assess how the drawdown zone
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Arrow Lakes Reservoir - Amphibian and Reptile Study EXECUTIVE SUMMARY
Comprehensive Report 2008-2012
Can it be
Management Questions Summary points to back answer
answered?
overwintering) do reptiles and is used for breeding and foraging. We don’t have any data to
amphibians utilize the drawdown zone? assess how the drawdown zone might be used during the
winter period..
 Garter snakes are present in the drawdown zone in the spring
and summer and forage there. We do not know where females
give birth or where they overwinter. One species of reptile
(Northern Alligator Lizard) uses habitats adjacent to the
drawdown zone, but it is unknown to what extent it uses the
drawdown zone to fulfill its life history requisites.
 We can correlate species presence to vegetation communities
4. Which habitats do reptiles and
mapped in each drawdown zone, and have characterized the
amphibians use in the drawdown zone
water chemistry of ponds with amphibians; however, the current
and what are their characteristics (e.g., Probably
vegetation mapping for Arrow Lakes Reservoir is difficult to
pond size, water depth, water quality,
correlate to wildlife habitat use. Refinements are required to the
vegetation, elevation band)?
mapping to answer this question.
 Direct impacts of reservoir operations on amphibians and
reptiles have not been observed in the drawdown zone of Arrow
Lakes Reservoir. We have not observed desiccation at
breeding ponds nor do we have any data to suggest that
5. How do reservoir operations influence inundation results in direct impacts or increase rates of
or impact reptiles and amphibians predation.
directly (e.g., desiccation, inundation, Maybe  Reservoir operations do impact habitat and habitat availability
predation) or indirectly through habitat varies by month and year relative to reservoir operations and
changes? the correlation between reservoir elevation and habitat
availability is negative.
 Although inundation affects habitat availability, we do not know
if this indirectly affects amphibian and reptile populations using
the drawdown zone of Arrow Lakes Reservoir.
 Some operational changes can be implemented to maintain
the existing amphibian and reptile communities (e.g., keep
6. Can minor adjustments be made to
reservoir elevations below 433 m ASL through the end of
reservoir operations to minimize the Possibly
August)
impact on reptiles and amphibians?
 A lack of control on inundation precludes us from correlating
the use of the drawdown zone by amphibians to inundation.
7. Can physical works projects be  At this stage we are unable to assess the relationship between
designed to mitigate adverse impacts on Not at this physical works and the impacts on amphibian and reptile
reptiles and amphibians resulting from time populations because physical works have not been
reservoir operations? implemented in ALR
 It is unlikely that revegetation will contribute to an increase in
the amount or improvement of habitat for amphibians or reptiles
8. Does revegetating the drawdown as the revegetation prescriptions have been applied at a scale
Not at this
zone affect the availability and use of unlikely to elicit a population-level response. The type of
time
habitat by reptiles and amphibians? revegetation is also more consistent with upland vs. wetland
revegetation and therefore not likely to influence the use of
most areas of the drawdown zone by amphibians or reptiles.
9. Do physical works projects
implemented during the course of this
Not at this  This cannot be assessed at this time because the physical
monitoring program increase reptile or
time works have not been implemented in ALR.
amphibian abundance, diversity, or
productivity?
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Arrow Lakes Reservoir - Amphibian and Reptile Study ACKNOWLEDGEMENTS
Comprehensive Report 2008-2012
ACKNOWLEDGEMENTS
The authors express their appreciation to the following individuals for their
assistance in coordinating and conducting this study: Margo Dennis (BC Hydro),
Guy Martel (BC Hydro), Doug Adama (LGL Limited), Jamie Fenneman (LGL
Limited), Jeremy Gatten (LGL Limited), Janean Sharkey (LGL Limited), Robin
Tamasi (LGL Limited), Charlene Wood (LGL Limited), Patrick Gregory (University
of Victoria), Kelly Boyle (University of Victoria), Leigh Ann Isaac (Nupqu), and
Pascale Gibeau (Ripple Environmental).
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Arrow Lakes Reservoir - Amphibian and Reptile Study TABLE OF CONTENTS
Comprehensive Report 2008-2012
TABLE OF CONTENTS
EXECUTIVE SUMMARY .................................................................................................. i
ACKNOWLEDGEMENTS............................................................................................... vi
LIST OF TABLES ........................................................................................................... ix
LIST OF FIGURES .......................................................................................................... x
1.0 INTRODUCTION ................................................................................................. 1
1.1 Study Area ....................................................................................................... 2
2.0 METHODS........................................................................................................... 3
2.1 Addressing Management Questions ................................................................ 3
2.2 General Survey Methods ................................................................................. 3
2.3 Data Analyses .................................................................................................. 4
3.0 RESULTS ............................................................................................................ 4
3.1 H1 : Reservoir operations do not result in a decreased abundance of
A
amphibians or reptiles in the drawdown zone. ....................................... 5
3.2 H1 : Reservoir operations do not increase the stage specific (e.g. larval,
B
juvenile, or adult) mortality rates of amphibians or reptiles in the
drawdown zone. .................................................................................... 8
3.3 H1 : Reservoir operations do not result in decreased site occupancy of
C
amphibians or reptiles in the drawdown zone. ....................................... 9
3.4 H1 : Reservoir operations do not result in decreased productivity of
D
amphibians or reptiles in the drawdown zone. ..................................... 12
3.5 H1 : Reservoir operations do not reduce the availability and quality of breeding
E
habitat, foraging habitat and overwintering habitat for amphibians or
reptiles in the drawdown zone. ............................................................ 12
3.6 H2 : Revegetation and physical works do not increase species diversity or
A
seasonal (spring/summer/fall) abundance of amphibians or reptiles in
the drawdown zone. ............................................................................ 15
3.7 H2 : Revegetation and physical works do not increase amphibian or reptile
B
productivity in the drawdown zone. ...................................................... 16
3.8 H2 : Revegetation does not increase the amount or improve habitat for
C
amphibians and reptiles in the drawdown zone. .................................. 16
4.0 CONCLUSIONS AND RECOMMENDATIONS .................................................. 17
4.1 MQ1: Which species of amphibians and reptiles occur (utilize habitat) within
the drawdown zone and where do they occur? .................................... 18
4.2 MQ2: What is the abundance, diversity, and productivity (reproduction) of
amphibians and reptiles utilizing the drawdown zone and how do these
vary within and between years? .......................................................... 19
4.3 MQ3: During what portion of their life history (e.g., breeding, foraging, and
over-wintering) do amphibians and reptiles utilize the drawdown zone?
............................................................................................................ 20
4.4 MQ4: Which habitats do amphibians and reptiles use in the drawdown zone
and what are their characteristics (e.g., pond size, water depth, water
quality, vegetation, elevation band)? ................................................... 21
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