Tailed Frog WHA Monitoring - gov.bc.ca

Field Pilot for

Regional Effectiveness Monitoring of Tailed Frog

Wildlife Habitat Areas in the Cascades

Prepared by

Les W. Gyug, R.P.Bio. Okanagan Wildlife Consulting 3130 Ensign Way, West Kelowna, B.C. V4T 1T9 [email protected]

Prepared for

Ministry of Environment Ecosystem Protection and Sustainability Branch, Victoria, B.C. V8W 9M1

October 24, 2012.

CASCADES TAILED FROG WHA EVALUATION 2 OKANAGAN WILDLIFE CONSULTING

ABSTRACT

This field pilot project evaluated a proposed regional level monitoring program for tailed frog Wildlife Habitat Areas (WHAs). Forty-five random stream sites were sampled from 4 strata defined based first on tailed frog WHA status (WHA vs Non-WHA). Non-WHA strata was further stratified by basin area (i.e., N2 = 0.2-2 km2; N3 = 2-10 km2; N4 = 10-50 km2). Sampling at each site included 2 30-minute Time-Constrained Searches (TCS) (one upstream and one downstream), stream size measurements and Wolman pebble counts of 100 particles every 0.5 m on the flow centerline were made in a 50-m reach.

No tailed frogs were found in N2 streams and all were found to be dry. Tailed frogs were found at 14 of 17 N3 sites, 5 of 6 N4 sites and 16 of 17 WHA sites. Including incidental observations, tailed frog adults and/or larvae were found in every stream sampled that had a gradient >1% and had flowing water in it. There were no significant differences in larval abundance between strata. Only when sample sites were regrouped post-hoc by field-determined tailed frog reach type (unsuitable, frontier, core, and transient) could significant differences be shown between groups. A model for classification of streams and reaches into tailed frog reach type using GIS coverages is proposed for any future monitoring in the Cascades. Power analysis showed that 25 samples per stratum would provide a power of 0.8 to detect a significant difference in the observed difference in relative larval abundance in WHA and non-WHA core reaches. Detectability at a site using just one TCS was 0.86 (95% CI 0.74-0.93) using occupancy modeling and substituting space for time but was related to relative abundance.

Mean embeddedness was higher, mean and median particle sizes lower, percent of refuge-filling (fine) particles higher, and percent of refuge-forming (very coarse gravels and cobbles) particles lower in unsuitable reaches than other reaches, and in transient/frontier reaches than in core reaches. Unsuitable reaches were consistently higher in fines than core reaches but transient and frontier reaches were variable. Core reaches, both WHA and non-WHA, were very similar in all measurements and particle size characteristics. Within the metapopulations of this study, many of the core reaches not in WHAs would be suitable WHA candidates but may not have been proposed because of lack of previous surveys or because of fish presence so that there were already existing reserve zones.

Recommendations are made to refine the study design and methods for regional level tailed frog WHA monitoring. The tailed frog WHA identification process is still immature in the Cascades region with only 29% of the area having been considered for WHAs, and within those metapopulations WHAs contained only 21% of the relative larval abundance.


TABLE OF CONTENTS

List of Figures ........................................................................................................................... 4

List of Tables ............................................................................................................................ 4

Acknowledgements .................................................................................................................. 4

INTRODUCTION ........................................................................................................................ 5

METHODS ............................................................................................................................... 5

Study Area ................................................................................................................... 5

Sampling Design ............................................................................................................ 7

Field Methods ............................................................................................................... 8

Amphibian Sampling ........................................................................................... 9 Stream Measurements ........................................................................................ 10

Data Analysis ............................................................................................................... 11

RESULTS................................................................................................................................. 16

Sampling Logistics ........................................................................................................ 16

Relative Abundance ...................................................................................................... 17

Data Analysis .................................................................................................... 17 Power Analysis and Reliability ............................................................................... 20 Detectability ..................................................................................................... 21

Larval Cohort Ratios and Body Size .................................................................................. 21

Stream Measurements .................................................................................................. 23

Data Analysis .................................................................................................... 23 Power Analysis .................................................................................................. 26 Pebble Count Distributions ................................................................................... 27

Study Design ............................................................................................................... 27

Stream Characterization Model ...................................................................................... 29

Tailed Frog Larvae ........................................................................................................ 31

Pebble Counts .............................................................................................................. 32

RECOMMENDATIONS ............................................................................................................... 33

LITERATURE CITED ................................................................................................................... 34


List of Figures

Figure 1. Location of coastal tailed frog metapopulations sampled in the Cascades, August, 2012. ........ 6

Figure 2. Pebble count curves based on 100-particles per site using post-hoc groupings. .................... 28

List of Tables

Table 1. Sampling strata and number of sample sites defined by upstream drainage basin area or presence of tailed frog WHA for regional WHA monitoring in 9 Cascades metapopulations in 2012. . 8

Table 2. Developmental classes used to classify tailed frogs. ............................................................. 10

Table 3. Evaluation of channel disturbance from Dupuis and Friele 2003 and condition from FREP (2005). ..................................................................................................................................... 12

Table 4. Size classes used for pebble counts for tailed frog WHA evaluations. .................................... 13 Table 5. Tailed frog adult and larval counts on 30-minute Time-Constrained Searches (TCS) at sample

sites and regional relative abundance in the Cascades, 2012. ..................................................... 19

Table 6. Tailed frog larval cohort numbers detected on time-constrained searches, Cascades, 2012. ... 22

Table 7. Length of tailed frog larvae cohorts compared by stratum, Cascades, 2012 ............................ 22

Table 8. Water and air temperatures at tailed frog sample sites by stratum, Cascades, August 2012. .... 23

Table 9. Stream parameters by stratum at tailed frog sample sites, Cascades, August 2012. ............... 24 Table 10. Stream condition and substrate (particle size) parameters, Cascades, 2012, using different

post-hoc groupings by basin size and tailed frog reach classification. ........................................... 25

Table 11. Pebble count stream characteristics grouped to provide example data for power analysis. .... 26 Table 12. Proposed stream classification for tailed frog habitat stratification for regional WHA

effectiveness monitoring in the east slope of the Cascades. ........................................................ 31

Acknowledgements

Support for the author of this report was provided under contract to BC Ministry of Environment. Kathy Paige, BC Ministry of Environment, Ecosystem Protection and Sustainability Branch, served as contract monitor. Field crews were provided by the BC Conservation Foundation under contract to BC Ministry of Forests, Lands and Natural Resource Operations. I would like to thank Dennis Lynch, Alfredo Fernandez, Mike Dunn, Jess Findlay, Jared Hobbs, Kathy Paige and Donna Romaine for field assistance. Initiation and setup of this monitoring project including a number of other people including Darcy Pickard, ESSA Consulting, and Melissa Todd, BC Ministry of Forests, Lands and Natural Resource Operations.


INTRODUCTION

The Coastal Tailed Frog (Ascaphus truei) is a stream-breeding amphibian limited to the wet mountain areas of western North America. Within British Columbia the Coastal Tailed Frog is limited to the Coast and Cascade ranges, and has been designated as Identified Wildlife under the Forest and Range Practices Act (FRPA), due to concerns of the effects of forestry practices on the habitat and populations of this species. Under FRPA, Wildlife Habitat Areas (WHA) may be established along streams where tailed frogs occur, and typically provide no-timber-harvesting zones of 30-m on both sides of the streams, and an additional 20-m zone of managed forest adjacent to the 30-m reserve zone.

Development of monitoring strategies to determine the effectiveness of WHAs for tailed frogs has been underway since 2004. Maxcy (2004) began the process of drafting a generic tailed frog WHA effectiveness monitoring scheme, and protocols of a monitoring scheme more specific to the Rocky Mountain Tailed Frog were later drafted (Dupuis 2005, Dupuis and Friele 2006). Gyug (2005) conducted field trials to determine efficient methods for long-term population monitoring at the WHA level and assessed monitoring in general (Gyug 2005, 2006) but further assessments concluded that invasive and disruptive methods such as Area-Constrained Searches are not suitable for population monitoring (Friele and Pickard 2010) so that Time-Constrained Searches, even though highly variable, are the only tailed frog sampling choice.

This project was a field test of a possible regional monitoring scheme for tailed frogs. The field results are presented here and assessed for statistical and logistical effectiveness.

METHODS

Study Area

The study area was near the eastern edge of the Coastal Tailed Frog range in the Merritt and Lillooet Timber Supply Areas (TSA) of the Cascades Forest District on the eastern Cascade Mountain slopes east of the Fraser River (Figure 1). Nineteen tailed frog WHAs have been legally established and three are proposed along streams occupied by tailed frogs in this area based on sampling from 2000-2009 (Gyug 2000, Gyug 2001, Gyug 2002, Iredale 2009). Watershed assessment units, typically 3rd to 5th order basins, have been delineated where WHAs have been established or proposed. These watershed units, hereafter referred to as metapopulations, are believed to contain a spatially separated population of tailed frogs that interact with other populations through immigration and emigration. Units were approximated based on expert review of GIS data to identify likely tailed frog dispersal barriers (FREP In prep).


The 22 WHAs are contained within nine metapopulations, ranging in size from 36 to 122 km2(Figure 1). These nine metapopulations totalled 627 km2 and contained 29% of the core tailed frog range on the east side of the Cascades and east of the Fraser River (Gyug 2002). The metatpopulations included one (Mowhokam) in the Lower Mainland Region, five (Nicoamen, West Prospect, Upper Spius, Juliet and July-Coldwater) in the Thompson Region and three (Podunk, Britton and Upper Granite) in the Okanagan Region.

Figure 1. Location of coastal tailed frog metapopulations sampled in the Cascades, August, 2012


Sampling Design

The BC Freshwater Atlas Stream Network, which is based largely on the 1:20,000 TRIM water network, was used to define the sampling frame1 within the 9 tailed frog metapopulations (Pickard 2011). Sample points were randomly selected from established or proposed WHAs (the W stratum) and from non-WHA areas within metapopulations (the N stratum). The non-WHA strata was further stratified by basin area (Table 1) into three strata (N2, N3, N4). Basin area was used as a surrogate measure for tailed frog reach type (i.e, frontier, core and transient, as per Dupuis and Friele 2002). Frontier reaches are headwater reaches, are often ephemeral streams, are primarily adult non-breeding habitat, and are parts of probable migration routes across forested (or semi-forested) headwater basin divides. Core reaches contain natal reaches, are usually permanent streams, and are where the bulk of the tailed frog population occurs. Transient reaches are downstream reaches that are also often low-gradient fish streams, but where there may be significant downstream movement of tadpoles from core reaches. Tailed frog WHAs may include frontier, core, or transient reaches although not each type of reach is found in each WHA in the Cascades (Gyug 2007). Most WHAs in the east Cascades contain core reaches but some portions are frontier and transient reaches.

Most of the sampling effort was placed into the WHAs and Non-WHA N3 strata (i.e., core reaches) where most of the tailed frog population was expected to occur (Table 1). Sampling points were assigned a sampling order so that if some points could not be sampled, they were replaced by the next highest randomly numbered point within that stratum.

Only 1 10-day session by two field crews was available with 2-3 sites expected to be completed per day. Therefore sampling targets (Table 1) were considerably reduced for logistical reasons from the targets of 30 sites in each of the N3 and WHA strata, and 15 in N2 and N4 strata proposed by Pickard for tailed frog WHA monitoring (unpublished memo, July 14, 2012).

1 Complete list of possible sampling units within target population


Table 1. Sampling strata and number of sample sites defined by upstream drainage basin area or presence of tailed frog WHA for regional WHA monitoring in 9 Cascades metapopulations in 2012.

Stratum Name

Basin Area (km2)

Assumed Type of Tailed Frog Reach

Nominal Atlas

Stream length (km)

Stream length after removal

of non-streams

Number of Sample Sites, August 2012

Target* Actual N1 <0.2 Non-habitat (ephemeral) 186.2 178.5 0 0 N2 0.2-2.0 Frontier 621.7 602.3 6 5 N3 2-10 Core 176.9 169.1 17 17 (+1**) N4 10-50 Transient 114.3 112.2 6 6 N5 >50 Non-habitat (mainstem) 30.9 30.8 0 0

N (All) 29 28 (+1)

W (All) - WHAs - No Assumptions 48.6 48.6 17 17

Breakdown of WHA Sites by basin area W1 <0.2 Frontier*** <0.01 <0.01 - (0) W2 0.2-2.0 Frontier 14.7 14.7 - (5) W3 2-10 Core 33.9 33.9 - (12) W4 10-50 Transient <0.01 <0.01 - (0)

*Target number of sites for this pilot project

**One extra site was done out of sorted order because field crews were nearby but this was not included within the ANOVA analyses but was included in graphic representations of pebble counts.

***Any site within a WHA would be assumed to be frontier, core or transient rather than non-habitat.

Field Methods

Before field sampling began, stream lines that had been constructed to make a continuous flow network through lakes and open water were removed from the sampling frame because these were not actually streams. These were identified in the stream network database by their Feature Source listed as “lake” or “OP”. This reduced the stream length of the sampling frame by about 37 km of 1130 km or about 3%. One point was sampled fortuitously by the field crew because they happened to be close by even though not in the target group (see Table 1). This point (N3-33) was not included in the final analysis but did illustrate another case of a type of stream that should be removed from the sampling frame prior to sampling. It was on a mapped stream but was within a wetland polygon in the Freshwater Atlas wetland coverage. Marshes are not tailed frog habitat and can be removed from the sampling frame. In the future, the Freshwater Atlas lake and wetland polygons can be put over the stream network so that these “non-streams” can be identified in advance and removed.


Amphibian Sampling

The sample site center was the UTM location of the supplied random point on a stream. Because of inaccuracies with mapped streams in the Freshwater Stream Atlas, some random points were not actually on a stream. If the stream center was >5 m from the supplied location, then the co-ordinates at a point on the stream closest to the supplied random point were used as the sample site centre.

From the site center, two separate 30-minute Time Constrained Searches were conducted downstream and upstream from the point. At some sample sites upstream and downstream TCSs were conducted simultaneously (one person per search), taking care to avoid double-counting any larvae discovered near the center point. At other sites the 30-minutes of searching was shared among two or more people so the search could be finished in 15 minutes or less; the downstream TCS was done first to prevent double-counting of any dislodged larvae that floated downstream.

At the beginning of the first TCS at each site, time-of day, air temperature, water temperature, sky condition, wind (Beaufort scale) and current precipitation were recorded. Brita® water jugs were used to cut surface glare to view underwater. Most possible locations where tadpoles could be hiding within coarse gravels and under cobbles were searched by hand by lifting and replacing rocks. Boulders were searched by gently running a hand underneath to dislodge attached larvae. The total length covered from the center point during the search was estimated using GPS coordinates or by visual estimation based on location relative to the marked center point and other stream measurement points.

Whenever possible, tailed frog adults and larvae were caught and held for processing in tubs. If it took more than a few seconds to capture an animal, then this capture and handling time was added to the search time. Developmental stage was determined (Table 2), and length measured. Total length of larvae, and snout-vent length of adults and juveniles were measured with a ruler in mm. They were then released as near as possible to the point of capture. The cohort and total length of larvae that could not be captured were estimated if possible.

Equipment used was disinfected with 10% bleach when moving between watersheds.


Table 2. Developmental classes used to classify tailed frogs.

Code Developmental Class

Morphological Features

Egg H Hatchling Unpigmented with visible yolk sack C1 Tadpole Cohort 1 No leg buds C2 Tadpole Cohort 2 Rear leg buds C3 Tadpole Cohort 3 Well developed hind legs C4 Tadpole Cohort 4 Developing forelimbs with obvious knees and may have biting

mouth M Metamorph Well-developed forelimbs, biting mouth, and reabsorbing tail J Juvenile Small frog but with no nuptial pads AM/AF Adult Frog with nuptial pads and ‘tail’ in males

Stream Measurements

Stream measurements were taken using the random point as the center point or 25-m mark of a 50-m reach. At the center point, upstream and downstream gradient were recorded. At the 0, 10, 20, 30, 40, and 50 m marks, bankfull width and wet width were measured to the nearest 0.1 m, bankfull depth and wet depth to the nearest cm, and the stream flow type (pool, riffle or step) was recorded. For each 10-m reach between marks, the number of metres of pool, riffle and step were estimated.

Embeddedness, channel disturbance, channel condition, dominant and subdominant substrate type and general stream morphology were estimated for the 50-m sample reach. Embeddedness of cobbles in finer materials was estimated as None (free of fines to a depth of 160 mm), Low (25% buried in fines), Moderate (50% buried in fines) or High (>75% buried in fines) (Friele and Pickard 2010). Channel disturbance and channel condition were estimated using classes outlined in Table 3. The dominant and subdominant substrate types were estimated using the following categories: Fines (<2 mm), Gravels (2-64 mm), Cobbles (64-256 mm), Boulders (256-4096 mm), and Bedrock. The general stream morphology was recorded as cascade, step-pool, or riffle pool, and whether the steps were controlled by large organic debris (logs). The riparian buffer width was estimated only if it had changed since the most 2004 aerial photos, and only if it was about 50 m or less. This was only the case at one site. At most other sites one estimate was made of general stand type (deciduous, coniferous or mixed) and stand stage (initial, shrub, pose-sapling, young forest, mature forest or other). There was only


one case where there was a clearcut <50 m from a stream that was more recent than 2004. In that case the stream was a fish-bearing stream of >1.5-m width (S3) and therefore had a minimum 20-m reserve zone on it.

Wolman pebble counts (see Bunte and Abt 2001 for review of methods) with a sample size of 100, were conducted on the stream flow centerline or thalweg. Wentworth scale (Bunte and Abt 2001) was used for particle class sizes (Table 4). For every pace of approximately 0.5 m a surveyor picked up the particle at the point of his/her toe and measured the largest square opening on a gravelometer through which the particle would fit. Where steps were difficult to take, i.e., boulders or cobbles that were impossible to step upon without slipping, the place where the boot would have landed was estimated and the particle that would have been at the toe measured. A separate observer recorded the size of each particle and the channel type (pool, riffle or step). The class size of particle recorded was a “finer than” measurement. For example, a particle recorded as “64” would have an intermediate (b) axis in the 45-64 mm size class. For embedded particles, the shortest (c) axis was assumed to be vertical, and the shorter of the two visible axes was measured as the b-axis.

Data Analysis

The number of larvae or adults captured during 30-minutes of searching was an index of relative abundance. This was also converted to relative density by dividing by the stream length searched. This should be approximately equivalent to a “light-touch” Area Constrained Search relative density. Regional tailed frog larval relative abundance was estimated by multiplying the mean sample relative density times the length of stream in each stratum.

Since TCS counts were used as the basis for establishing most of the WHAs, there were prior TCS counts within 300 m of a number of sites, and prior population density estimates from Area Constrained Searches for a few sites. These were compared to the 2012 TCS counts to determine long-term reliability of counts, assuming that the true count had not changed over time.


Table 3. Evaluation of channel disturbance from Dupuis and Friele 2003 and condition from FREP

(2005).

Level or Score Field Evaluation Parameters

Channel disturbance

1=extreme Evidence of debris torrent within last 3 years

2=high Perpetual high intensity disturbances such as avalanches, high peak flows, and high bedload transport. Sidewalls may be unstable.

3=moderate Moderately disturbed with infrequent debris flow activity (>5 years). Channel units moderately to well developed.

4=low Stable flooding regime with low bedload transport (large substrates stable and often mossed over). Channel units are stable and well developed

Channel condition

Very poor Recent or chronic disturbance (scoured banks, debris levees, flood terraces, tree scars, seedling germinants, bright substrate, braided channel, high to moderate stone embeddedness

Few pools, low to negative scour depth, small D50, poor sorting, low to moderate stability

Poor Unstable sidewalls, flood terraces, braided channel, riparian brush, bright stone surfaces, moderate stone embeddedness)

Few pools, low to negative scour depth, small D50, poor sorting, instability

Moderate Moderate disturbance (immature to mature riparian vegetation, stable banks, vegetated flood terraces, old tree scars, steps moderately to well developed, moderate to low embeddedness, evidence of debris flow > 5 years old

Moderate number of pools, low to moderate scour depths, medium sized D50, moderate sorting, moderate stability

Good Stable flood regime, armoured bed, low bedload (mature riparian vegetation, no tree scars, coarse clean substrates, step-forming stones often mossed over, low to nil stone embeddedness

Numerous high steps, deep scour pools, large D50, good sorting, high channel stability


Table 4. Size classes used for pebble counts for tailed frog WHA evaluations.

Description of particle size Size class range (mm)

Upper end of size class

(mm)

Ø = -log2 Tailed Frog Larval function (Friele and Dupuis 2006)

[Bedrock] >4096 - Boulder very large* 2048 - 4096 4096 -12.0 large 1024 - 2048 2048 -11.0 medium 512 - 1024 1024 -10.0 Step-forming small 256 - 512 512 -9.0 Cobble

large 180 - 256 256 -8.0

128 - 180 180 -7.5

small 90 - 128 128 -7.0

64 - 90 90 -6.5 Refuge-forming Gravel

very coarse 45 - 64 64 -6.0

32 - 45 45 -5.5

coarse 22.6 - 32 32 -5.0

16 – 22.6 22.6 -4.5

medium 11 - 16 16 -4.0 Refuge-filling

8 - 11 11 -3.5

fine 5.6 - 8 8 -3.0

4 – 5.6 5.6 -2.5

very fine 2.8 - 4 4 -2.0

2 – 2.8 2.8 -1.5 Sand, silt or clay <2 2 -1.0

*Very large boulders were recorded on field sheets in the “finer than 4096” class as was bedrock. Bedrock should have been recorded separately as >4096.

Detectability was assessed by substituting space for time, and assuming that true occupancy (presence of larvae or adults) of each of the adjacent subsamples was the same. Software program PRESENCE (Hines 2006) was used to estimate detectability from encounter histories for each site. Encounter histories are expressed as binary results with 0 for non-detection and 1 for detection, and with one entry for each visit. The number of digits within the ellipses represents the number of visits to each site. Therefore, when there have been two visits, a history of (0,0) indicates an animal was detected on neither of two visits, (1,0) was detected only on the first visit, (0,1) was detection only on the second visit, and (1,1) was detected on both visits. The number of visits required to achieve a certain probability of detection at a site can be predicted by the 1-(1-pn) where p = detectability and n = the number of visits.


The planned contrasts of tailed frog relative abundance and stream measurements and were between the 4 sampled strata using ANOVA. It was recognized before choice of strata that WHA samples may represent a variety of basin sizes (Table 1), and that basin area alone may oversimplify status. However, available effort did not likely allow for sampling of two or more different WHA strata. Since many other factors contribute to tailed frog suitability and status, the effects of the decision to simplify strata to 4 classes based only on WHA occurrence and basin size only outside WHAs were examined during post-hoc analyses so that recommendations could be made to make future sampling and monitoring more efficient.

Relative abundance, relative density, larval cohort ratios and cohort body size contrasts were made using the original strata (N2, N3, N4 and WHA), and then with post-hoc groupings by basin area and by tailed frog reach type. For stream measurements, which were expected to vary with basin area, contrasts were made using the original strata dividing the WHA stratum by basin area, and then post-hoc groupings by tailed frog reach type. Stream water temperatures would be expected to vary with air temperature as an uncontrolled environmental variable, so correlation of water and air temperature was also examined.

ANOVA contrasts and power analyses were done using Statistica 8.0 software (StatSoft Inc. 2007). ANOVA statistics presented in tables for group contrasts were the F-statistic and α, the probability of a significant difference between groups. Where α <0.05, Scheffe’s test was used to test for differences between groups. Within tables, means of groups with the same following letter were not significantly different at the α = 0.05 level. Power analyses were used to predict sample sizes required in the future to show differences in group means based on the observed means and standard deviations, or for expected group mean differences. Differences in cohort ratios were examined using χ2 contingency tables.

Particles >512 mm were sometimes recorded twice if the next step 0.5 m away happened to also land on them. These should have been recorded as double counts and only tallied once for particle size analyses but we failed to recognize and include that before field sampling in 2012. Bedrock was not differentiated from very large Boulders when recorded in the field (although they should have been), so very large boulders were treated as if they were bedrock, i.e., were not included in particle size analyses.

Analyses of pebble count data included percent of particles that were refuge-filling (<32 mm), and refuge-forming (32 – 256 mm), graphic presentation of cumulative percent finer than Ø classes on a log scale, and calculation of median (D50) in phi units (and converted to mm), and its variance in phi units, and other percentiles (e.g. D5, D16, D25, D75, D84, D95) used in calculation of other metrics. Percentiles were calculated using equation 2.15 of Bunte and Abt (2001):


Øx = (x2– x1) · ((yx – y1)/(y2 – y1)) + x1

Where y2 and y1 are the two values of the cumulative percent frequency just below and above the desired cumulative frequency yx, and x2 and x1 are the particle sizes in Ø units associated with the cumulative frequencies of y2 and y1.

Sorting index (Folk and Ward 1957, from summary in Bunte and Abt 2001) was based on the particle size distribution using the following equation using percentiles finer than in Ø units:

SF&W = ((Ø84 – Ø16)/4) + ((Ø95 – Ø5)/6.6)

Only graphical comparisons of the cumulative frequency distributions were made. These distributions can be compared to each other by the χ2-statistic (Bunte and Abt 2001) but there were too many separate sample sites here to make single pairwise comparisons. This test would be appropriate when comparing a single site to itself in the future after a disturbance or change in condition. Analysis of Covariance could also be used to compare groups of distributions but was not done within this project.

Data has been submitted in the following excel files and ESRI shapefile sets in B.C. Albers projection:

• ASTR_Cascades_2012_RawData.xlsx The raw data as entered from the field sheets and including list of pre-sampling points including comments on points dropped from the sampling.

• ASTR_Cascades_2012_Location_Summary_Data.xlsx One-sheet summary of location data for TCS and tailed frog observations.

• ASTR_Cascades_2012_Data_Analysis.xlsx The raw data plus analyses including pebble count analyses and graphs, and larval cohort and length analyses.

• astr_2012_cascades_sampling_points.shp The final GIS generated sampling points including all possible sampling points minus any discarded as unsuitable, i.e. lakes, open water and points <300 m from other sampled points. Fields have been added for whether the point was sampled or not, comments on sampling, the upstream and downstream number of adults and larvae found, and the elevation (from GIS). The sampling points in this file are listed as they were derived from the Watershed Atlas – that is, they are not adjusted for any minor changes in location required in the field as this would move them off the watershed atlas network lines and make them difficult to re-associate with the watershed network. Final centerpoints of sampled points in UTM coordinates (NAD83) are in the excel files.


RESULTS

Sampling Logistics

Of the 45 sites sampled, 24 were at the planned location or within 10 m, 16 were within 25 m, 4 were within 50 m, and one was 90 m from the planned location. The stream was mapped quite incorrectly at the site that was 90 m from the planned location. The straight line on the map actually meandered within a >100-m wide valley bottom within a forest.

For independently randomly selected points that were on the same stream and within 300 m of each other, only the first selected point was sampled. This resulted in the replacement of 4 points that might otherwise have been in the target sample.

Other points were removed from the sampling frame prior to sampling for logistical reasons. Two points were removed because they were on cliff faces, i.e. slopes >80% in the general area, and >50% in the actual gully where sampling would have been done. One point was >5 km from the nearest road, and because of steep conditions in the area there was no guarantee that a field crew dispatched to the site could have ever got there safely.

Other points were removed for logistical reasons but only once sampling had started. The first 2 N2 (Frontier, non-WHA) points were sampled on the first day and both were found to be completely dry and not containing tailed frogs. For that reason, the next N2 point that was >1.5 km from a road and >500 m uphill was not sampled because it was also most likely to be dry. On the second last day, another N2 point was found to be >3 km from the end of the road that had been recently closed so the long walk to get to what was almost certainly to be a dry creek was not judged to be worth the time required, especially as the last two days were down to one crew of three as the fourth member (i.e. who would have been the second crew member of the second crew) had become sick and unable to participate in the last two days. This logistical constraint on the last 2 days also resulted in a N4 point being dropped in favour of the next random point up the list as it could not be sampled in the time available with only 1 crew remaining.

One point was reviewed on aerial photos while in the field and judged to be in a canyon that would have been very unsafe to traverse and was replaced with the next random point up the list in the same stratum.

Three points were dropped while in the field because the road required for access had overgrown with alder and was no longer drivable by truck. Accessing these 3 points would have required a 6.5 km walk on the old road plus 3 km through steep forest to two points, and then 5 km walk through steep forest to the other point, 2 km return to road, and then 6.5 km walk on


the old road. It would probably not have been possible to complete all these 3 points in one day.

When replacing points for logistical reasons while in the field, it was not always possible to replace with the next random point up the list when we had already passed that point by, i.e., it was in a metapopulation that had already been sampled and was too far away to re-sample with the limited time available. This sampling of points out of sequence resulted in 4 points not being sampled that should have been within the sample. The only way to remedy this type of situation is to have additional time available to go back to metapopulations to resampled such sites, i.e., to plan for extra sampling days.

In one case, the wrong stream was sampled. The randomly selected point (N3-04) was only 25 m from the downstream end of the stream. 200 m upstream of the sample site, this stream was a tailed frog WHA. However, the stream networks were not in the GPS units used in the field, we did not know the point was to be 25 m from the end of the stream, and the stream was in a cutover area with dense 3-m tall alder. When we arrived at the GPS point, we found a dry streambed. However, there was a “real” stream with water in it <25 m away. We assumed that the stream network had been mapped incorrectly (which is not unusual) and that the sample was supposed to be on the larger stream. The dense alder did not allow us to figure out which stream was actually which. Only after the fact once GPS points had been plotted, I realized the randomly selected point had a stream drainage area of 2.24 km2 but that our sampled stream had a drainage area of 8.36 km2. This point was retained in the sample for analysis, even though technically it was sampled in error. In the Cascades it is not unusual for tailed frog streams to go completely underground in late summer into deep coarse fluvio-glacial materials (mainly gravels) once they hit the main valley floors.

One of the N2 sites was not considered a stream as there was no detectable stream bed. It was possible to see where water had been flowing during freshet but it had not cut down through the forest duff layer and therefore would not be considered a stream.

Relative Abundance

Data Analysis

Mean length of stream searched per 30-minute TCS was 33.1 m (SD 29.7, range 5-218 m) and median length searched was 23.1 m. In total number 21 adults and 388 larval tailed frogs were detected at 35 of the 45 sites sampled. Tailed frogs were found at 14 of 17 N3 sites, 5 of 6 N4 sites and 16 of 17 WHA sites. Tailed frogs were not detected at any of the N2 non-WHA sites and all these sites were dry streambeds.


Of the 3 N3 sites where they were not detected, one larvae was found at one of the sites but only after the TCS had ended, and the other sites were ≤1% gradient streams where tailed frogs would not be expected. Tailed frogs were detected at 5 of the 6 N4 sites but were found at the sixth site only after the TCS had been completed. Tailed frogs were found at all but one of the 17 WHA sites. This one site was on a known frontier reach (Gyug 2005) but the 2012 sampling did find a larvae on the other site that happened to be on the same reach 315 m away. Tailed frog adults and/or larvae were found in every stream sampled that had a gradient >1% and had flowing water in it.

Even though tailed frogs were absent from N2 sites, there were no statistically significant differences among adult or larval relative abundance using the planned contrasts (Table 5). Only when the sites were grouped post-hoc based on tailed frog reach type could significant differences be shown: the dry N2 sites lacking tailed frog larvae were significantly different from the WHA Core sites (Table 5). However, no significant differences were found between any of the other groups, even between the dry N2 sites and the N3 and N4 sites.

Statistical comparisons of larval relative abundance excluding dry creeks and frontier sites where larvae could be expected to be lacking showed that the WHA Core reaches had almost twice the larval relative abundance and density of non-WHA Core reaches. The mean number of larvae found on TCS were significantly different (F = 6.1, p = 0.02) between WHA and non-WHA core reaches. However, when including non-WHA Transient reaches in the analysis there were no significant differences among the three groups. There were no WHA transient reaches sampled and very few have been proposed as WHAs because these are fish-bearing streams that already have reserve zones.

Extrapolating the larval relative density to a relative abundance in all streams in the nine metapopulations, total tailed frog larval relative abundance was 39703 (Table 5). The majority of the tailed frog larvae (69%) were in the 2.0-10.0 km2 basins (W3 and N3). The WHAs (W3) contained only 10% of the stream length in that basin size but contained 20% of the tailed frog larvae. In total, the WHAs were 21% of the total larval relative abundance, even though they only contained 5% of the potentially suitable stream length in basin sizes of 0.2 – 50.0 km2.


Table 5. Tailed frog adult and larval counts on 30-minute Time-Constrained Searches (TCS) at sample sites, and regional relative abundance in the Cascades, 2012. The result at each sample site was the average of 2 TCS, which were then grouped by sample stratum (first part of table), including drainage area of WHAs (second part of table) and according to tailed frog reach type determined from field sampling (third part of table).

Stratum n Adults/TCS Larvae/TCS Larvae/100

m

Total stream length

Total Larvae

Rel. Abund.*

95% Conf. Interval

Mean SE Mean SE Mean SE km N2 5 0.00 0.00 0.0 N3 17 0.24 0.15 4.41 1.48 11.5 4.8 N4 6 0.33 0.17 3.33 1.61 10.6 4.8 W 17 0.26 0.13 5.82 1.10 17.3 4.9 Average 0.23 0.08 4.31 0.76 12.3 2.7

F 0.42 1.89 1.24 p 0.74 0.15 0.31

N2 5 0.00 0.00a 0.0 602.3 0 0 N3 17 0.24 0.15 4.41a 1.48 11.5 4.8 169.1 19501 3560 - 35442 N4 6 0.33 0.17 3.33a 1.61 10.6 4.8 112.2 11847 1204 - 22489 W2 5 0.70 0.37 1.50a 0.82 4.0 2.3 14.7 584 0 - 1245 W3 12 0.08 0.06 7.63a 1.17 22.9 6.2 33.9 7771 3644 - 11898 Average 0.23 0.08 4.31 0.76 12.3 2.7 Total 39703

F 1.67 3.13 2.04 p 0.18 0.02 0.11

Unsuitable 7 0.00 0.00 0.00a 0.00 0.0a 0.0 N-Core 12 0.29 0.21 3.88ab 1.12 10.9a 5.7

N-Transient 9 0.28 0.12 5.39ab 2.53 14.2a 5.8

WHA-Frontier 4 0.88 0.43 0.13ab 0.13 0.2a 0.2

WHA-Core 13 0.08 0.05 7.58b 1.00 22.6a 5.6

Average 0.23 0.08 4.31 0.76 12.3 2.7

F 2.68 4.85 2.86 p 0.04 <0.01 0.04

*Total larval relative abundance is the product of (larvae/100 m) x (stream length in km x 10).


Power Analysis and Reliability

Based on the observed larval relative abundance group means (non-WHA core 3.9; non-WHA transient 5.4 and WHA core 7.6) and the pooled standard deviation (5.2), a sample size of 38 in each group would be required to show a significant difference at α = 0.05 between the groups with a power (1-β) of 0.8, and a sample size of 50 would be required for a power of 0.9. The standard deviation of the Transient reaches was very high with some lacking tailed frog larvae, and others having the highest relative density we observed in the 2012 sampling. The standard deviation of the Core reaches was smaller than for Transient reaches.

Comparing only core reaches within and outside WHAs, and using the observed mean TCS larval counts of 3.9 and 7.6 and the pooled standard deviation of 3.8, a very achievable sample size of 11 for a reasonable power of 0.8 and 14 for a power of 0.9 would be required to show a significant difference at α = 0.05. If comparing relative density adjusting for length of stream sampled (larvae/100 m), the standard deviations for the core reaches were much higher, being 100 to 200% of the mean instead of 50-100% of the mean. For relative densities a sample size of 25 for a power of 0.8 and 32 for a power of 0.9 would be required to show a significant difference at α = 0.05.

We examined how 2 TCS at each site affected variance for the simplest comparison of non-WHA core to WHA core reaches. When only comparing the first downstream reaches, the relative larval abundance was significantly different (p = 0.02), but using only the second upstream reaches, it was not significantly different (p = 0.06). Estimated sample size required to reliably show a significant difference at α = 0.05 with just one TCS using the upstream reach statistics was 17 for power of 0.8 and 23 higher for power of 0.9. These estimated sample sizes were 55-64% higher than if 2 TCS were done per site but were still relatively modest and logistically achievable in a typical two week sampling session with two field crews.

Prior TCS (Gyug 2000, 2001, 2002, Iredale 2009) and larvae population densities (Gyug 2005a) were available for 14 and 5 sites respectively that were also sampled in 2012. Where 1 site had been sampled in both 2000 and 2009, the average of the 2 counts was used. Prior TCS were significantly correlated with 2012 TCS mean counts (r2 = 0.19, p = 0.047) but not with just the single upstream or downstream counts (p = 0.11 and 0.10). Prior population density estimates were highly correlated with 2012 TCS mean site counts (r2 = 0.99, p < 0.001) and with single downstream or upstream counts (r2 = 0.96 p = 0.01; r2 = 0.91 p = 0.01 respectively), and with prior TCS counts (r2 = 0.97, p=0.01). It would appear that TCS counts are more reliable predictors if >1 is done per site, otherwise they may not be reliably repeatable over time at the same sites. Population density estimates from Area Constrained Searches appeared to be quite


reliable predictors of TCS counts, but given the small sample size (n = 5) further verification would be required before firm conclusions should be drawn.

Detectability

Tailed frog larvae encounter histories were 13 instances of no observations in either TCS (0,0); 4 instances of detection in only the second TCS (0,1); 4 instances of detections in the first TCS (1,0) and 25 instances of detection in both TCS (1,1) for a detectability estimate of 0.86 (95% confidence limits of 0.74-0.93). Therefore two TCS at a site would be expected to yield detection probabilities of 0.98 (95% confidence limits of 0.93-0.99).

Detectability was related to relative abundance as larvae were increasingly less likely to be detected at lower relative abundance. When the average relative abundance was >3 larvae per 30-minute TCS, detectability was 1.00 (n = 22 sites); when the average relative abundance was 2-3 larvae per TCS, detectability was 0.80 (n= 5 sites, SE = 0.13, 95% CI 0.46-0.95); and when the average relative abundance was <2 larvae per TCS, detectability was 0.17 (n= 18 sites, SE = 0.06, 95% CI 0.08-0.32). Based on the regression of ACS density estimates vs. 30-minute TCS counts (see previous section), these cutoff points of relative density would be equivalent to: >3 larvae/TCS =>50 larvae/100 m; 2-3 larvae/TCS = 30-50 larvae/100 m; and <2 larvae/TCS = 0-30 larvae/100 m. Where there were very few larvae (<2/TCS), it would take 9 TCS for an 80% probability of detection at a given site, and probably a similar sample size to reliably estimate relative abundance.

Adults were only detected at 12 of 45 sites compared to larvae found at 33 of 45 sites. Detection histories for adults were 1 (1,1), 6 (1,0), 5 (0,1) and 33 (0,0) giving an overall detection probability of 0.15 (SE 0.14, 95% CI 0.03-0.59). At this detectability, 10 visits would be required at a site to have a detectability of 0.80, i.e., an 80% probability of detecting adults, if present. TCS were designed to detect larvae and are generally inefficient at finding adults.

Larval Cohort Ratios and Body Size

Of the total 383 tailed frog larvae detected on TCS, 18% were not classified (Table 6), because they were not caught and not seen well enough when detected to classify. There were no significant differences in the ratio of C1:C2:C3 cohort numbers among the three original strata (χ2 = 5.57, 4 d.f., p = 0.23) not including the N2 stratum where no larvae were found. There was a significant difference in the C1:C2:C3 cohort ratio among the post-hoc groupings (χ2 = 10.35, 4 d.f., p = 0.03) with a higher proportion of C1 larvae within the WHA core reaches than in the non-WHA core or transient reaches. Larval length of each cohort did not differ significantly by either the original strata or the post-hoc groupings (Table 7).


Table 6. Tailed frog larval cohort numbers detected on time-constrained searches, Cascades, 2012.

Larval Cohort

Stratum Unclassified C1 C2 C3

Original Groups N2 0 0 0 0 N3 23 44 52 28 N4 11 9 14 6 WHA 33 77 57 29

Grouped by WHA and Reach Type N-Unsuitable 0 0 0 0 N-Core 20 30 30 10 N-Transient 14 23 36 23 WHA-Frontier 0 1 0 0 WHA-Core 33 76 57 29 Total 67 130 123 62

Total % 18% 34% 32% 16%

Table 7. Length of tailed frog larvae cohorts compared by stratum, Cascades, 2012

Larval Length

C1 C2 C3

Stratum n* Mean SD n Mean SD n Mean SD

Original Groups N3 8 35.8 4.0 7 43.1 5.0 7 50.2 4.6 N4 4 38.3 6.2 3 46.8 1.1 1 50.0 WHA 10 37.2 4.5 8 42.5 2.3 8 51.0 5.6

Total 22 36.9 4.5 18 43.4 3.7 16 50.6 4.8 F 0.41 1.72 0.05 p 0.67 0.21 0.94

Grouped by WHA and Reach Type N-Core 6 36.7 3.9 5 44.3 5.5 5 51.9 4.2 N-Transient 6 36.6 5.7 5 44.1 3.8 3 47.2 2.4 WHA-Core 9 36.8 4.5 8 42.5 2.3 8 51.0 5.6

Total 21 36.7 4.5 18 43.4 3.7 16 50.6 4.8 F 0.003 0.48 0.95 p 0.98 0.63 0.41

*n is the number of sample sites that had any larvae of that cohort. The mean larval length for each site was computed from all measured larvae at a site and then the grand mean presented as the Total in this table.


Table 8. Water and air temperatures at tailed frog sample sites by stratum, Cascades, August 2012.

Water Temp.

(°C)

Air Temp.

(°C)

Stratum n Mean SE N2* 1 8 - 10 - N3 17 8.9 0.6 12.8 1.1 N4 6 8.3 1.1 12.5 1.9 W2 5 8.0 0.4 10.6 1.8 W3 12 6.6 0.5 10.2 0.7 Average 41 8.3 0.4 11.6 0.6

F 1.54 1.14

p 0.22 0.34

*N2 not included in ANOVA of groups. The single temperature for an N2 site was from one small and shallow puddle found in one of the streams.

Stream Measurements

Data Analysis

Water temperatures at sampled sites during the survey period in late August ranged from 5 to 14°C, all well within the tolerances of tailed frog larvae and adults, and did not differ by stratum (Table 8). Air temperatures ranged from 5 to 24 °C. On a site-by-site basis water temperature varied significantly with air temperature (r2 = 0.20, F1,39 = 9.51, p = 0.003) but air temperature did not differ significantly between strata.

Stream widths and bankfull depths were significantly greater as basin drainage area increased, which was expected by design (Table 9). However, stream wet depths in late August did not vary as simply as widths. In these streams it would appear that most additional flow with larger basin sizes is handled by increased widths rather than depths. For the particular contrast of most interest (Non-WHA Core vs. WHA Core), there were no significant differences in any of the stream parameters presented in Table 9.

There were no significant differences in channel condition and channel disturbance parameters between any of the stream groups contrasted (Table 10). It may be that these qualitative assessments may be too variable or contain too many contributing factors to be consistently applied, or else they do not adequately describe tailed frog habitat or conditions.


Table 9. Stream parameters by stratum at tailed frog sample sites, Cascades, August 2012.

Stratum n Bankfull width (m) Wet Width (m) Bankfull

Depth (cm) Wet Depth

(cm) Gradient (%)

Mean SE Mean SE Mean SE Mean SE Mean SE N2* 4 1.2a 0.7 0.0a 20a 5 0a 8.6 1.7

N3 17 4.5b 0.4 2.4b 0.3 54bc 4 18bc 2 8.1 1.4 N4 6 7.3c 0.7 3.5bc 0.5 79c 12 26b 5 3.6 1.0 W2 5 2.8ab 0.3 1.1ab 0.3 42b 4 10ac 3 16.2 4.1 W3 12 4.9bc 0.6 2.6bc 0.2 51abc 5 16b 2 11.9 2.7 Average 4.5 0.3 2.2 0.2 52 3 16 1 9.3 1.2

F 10.37 11.08 7.38 9.52 2.66

p 0.00 0.00 0.00 0.00 0.05

Unsuitable 7 2.2a 0.7 1.3a 0.8 30a 7 8a 4 4.8a 1.9 Non WHA-Core 12 4.5ab 0.4 2.5a 0.3 51ab 5 18ab 2 10.5a 1.5 Non WHA-Transient 9 6.9b 0.6 3.2a 0.4 74b 8 23b 4 3.4a 0.7

WHA-Frontier 4 2.6a 0.4 0.9a 0.3 38ab 5 9ab 3 14.5a 4.2 WHA-Core 13 4.8b 0.5 2.6a 0.2 51ab 5 16ab 1 12.8a 2.7 Average 4.5 0.3 2.2 0.2 52 3 16 1 9.5 1.2

F 3.82 9.57 3.89 6.26 4.57

p 0.01 0.00 0.01 0.00 0.00

*Sample size differs because no measurements were taken at the N2 stream where there was no stream bed, and gradient was inadvertently not recorded at one other N2 site (n=3).

There were significant differences among groups in embeddedness, mean and median particle size, sorting index and refuge-forming and filling particle composition, all of which are related to each other (Table 10). Refuge-filling fine particles <32 mm diameter were a significantly higher proportion of particles in unsuitable streams than in core reaches whether these core reaches were in WHAs or not. Conversely, refuge-forming particles (32-256 mm diameter) were significantly more abundant in core reaches than in unsuitable streams. Transient and Frontier reaches were intermediate between the core and unsuitable groups, and not significantly different than either of them. Mean and median particle sizes were significantly smaller in unsuitable streams and larger in core reaches. D16 (the percentile below which the cumulative frequency is 16% or 1 SD from the median) showed the same pattern as for the median (D50), i.e., significantly lowest in unsuitable sites, intermediate in frontier and transient sites, and highest in core sites. Sorting was significantly lower in WHA core reaches than unsuitable reaches because fine particles were relatively lacking so that the overall particle size was more even.


Table 10. Stream condition and substrate (particle size) parameters, Cascades, 2012, using different post-hoc groupings by basin size and tailed frog reach classification.

Stratum n Embedded-

ness** (Rank)

Channel Disturbance

(Rank)

Channel Condition

(Rank)

Refuge-Filling Particles (%)

(<32 mm)

Refuge-Forming Particles (%) (32-256 mm)

Mean Particle Size

(mm)

Median Particle Size

(D50 mm)

D16 (mm) Sorting

Mean SE Mean SE Mean SE Mean SE Mean SE Mean SE Mean SE Mean SE Mean SE

N2* 4 2.8 0.3 3.5 0.5 1.5 0.5 56 13 39 11 27 11 27 10 6.2 3.6 2.0 0.2 N3 17 1.7 0.1 3.4 0.2 1.6 0.2 30 5 60 4 62 8 62 7 22.0 2.8 1.6 0.1 N4 6 2.0 0.4 3.0 0.3 2.0 36 10 55 7 56 19 56 19 19.8 7.1 1.7 0.1 W2 5 2.4 0.4 3.8 0.2 1.2 0.2 30 9 60 8 56 10 50 9 24.5 4.4 1.5 0.1 W3 12 1.6 0.2 3.5 0.2 1.6 0.2 17 3 71 2 78 7 72 6 32.1 3.3 1.4 0.1 Average 44 1.9 0.1 3.4 0.1 1.6 0.1 30 3 60 3 61 5 59 4 23.3 2.0 1.6 0.1 F 3.20 0.97 0.96 3.53 3.54 2.12 2.03 3.87 2.84 p 0.02 0.44 0.44 0.01 0.01 0.10 0.11 <0.01 0.04

Unsuitable 6 2.7a 0.2 3.7 0.3 1.5 0.3 59a 9 38a 7 23a 7 26a 7 5.2a 2.4 2.0a 0.2 Non WHA-Core 12 1.5b 0.2 3.4 0.2 1.6 0.2 22b 2 64b 3 75b 8 72b 7 26.7bc 2.2 1.6ab 0.1

Non WHA-Transient 9 2.0ab 0.2 3.0 0.2 2.0 0.2 37ab 8 57ab 6 51ab 13 53ab 13 18.4ab 5.1 1.7ab 0.1

WHA-Frontier 4 3.0a 0.0 3.8 0.3 1.3 0.3 38ab 9 55ab 9 45ab 8 43ab 9 17.0abc 2.5 1.7ab 0.1 WHA-Core 13 1.5b 0.1 3.5 0.2 1.5 0.2 16b 2 72b 2 79b 7 73b 6 33.8bc 3.8 1.4b 0.1 Average 44 1.9 0.1 3.4 0.1 1.6 0.1 30 3 60 3 61 5 59 4 23.3 2.0 1.6 0.1 F 10.85 1.37 1.08 9.45 6.99 5.67 4.53 9.93 4.33 p <0.01 0.26 0.38 0.00 <0.01 <0.01 <0.01 <0.01 0.01

*Sample size differs from other tables because no measurements were taken at the N2 stream where there was no stream bed.

**Embeddedness: 0 = None, 1 = Low, 2 = Moderate, 3 = High; Channel Disturbance 1 = Extreme, 2 = High, 3 = Moderate, 4 = Low; Channel Condition: 1 = Good, 2 = Moderate, 3 = Poor, 4 = Very Poor; Sorting: >4 = extremely poor, 2-4 = very poor, 1-2 = poor, <1 = moderate to very well.


Table 11. Pebble count stream characteristics grouped to provide example data for power analysis.

Stratum n Refuge-Filling Particles (%)

(<32 mm)

Refuge-Forming Particles (%) (32-256 mm)

Mean Particle Size

(mm)

Median Particle Size

(D50 mm)

D16 (mm)

Mean SE Mean SE Mean SE Mean SE Mean SE

Unsuitable 6 59a 9 38a 7 23a 7 26a 7 5.2a 2.4 Core 25 19b 2 68b 2 77b 5 72b 4 30.4b 1.8 Transient/Frontier 13 37c 6 56c 5 49a 9 50a 9 17.9c 3.6 F 18.9 13.0 9.2 11.6 17.7 p <0.001 <0.001 <0.001 <0.001 <0.001

Power Analysis

Taking refuge-filling particles as an example, in a two-way comparison between core reaches and transient/frontier reaches, mean % refuge-filling particles would be on the order of 19% and 37%, and SD on the order of 9% and 20% respectively. These variances (i.e., SD2) were significantly different (F-ratio test) and show that frontier and transient reaches have differing particle size distributions that are far more variable than core reaches. However, as long as sample sizes are similar, ANOVA is relatively robust to differences in variance. When sample sites were grouped by tailed frog reach type (i.e., unsuitable, core, and transient/frontier; Table 11), significant differences between groups could be shown between groups that could not be shown when dividing up reaches by WHA status because sample size was increased for each group.

Sample size required will depend on the magnitude of the difference expected. Just within core reaches, and examining them either over time or comparing WHAs to non-WHAs, differences on the order of 5% in refuge-filling particles (i.e., increase from 19 to 24%) would require a sample size of 27 for a power of 0.8 given α = 0.05, 4% would require sample size of 42, 3% a sample size of 73, 2% a sample size of about 160, and 1% a sample size about 650. Whether any significant difference could ever be shown with reasonable sample sizes at a regional level would require knowledge about the magnitude of expected impacts from lack or presence of streamside reserve zones. Potyondy and Hardy (1994) examined increase in fine sediments <6 mm using pebble counts finding increases from 40% to 60% 1 year after a high intensity burn in a heavily impacted watershed but no increase 2 and 3-years after because the fine sediments were flushed out. In a lower impacted watershed with a lower intensity fire, fines increased from about 10% to about 20% and persisted for up to 3 years after fire. Therefore, even with major forest impacts, fine input sediments are not always predictable and may be even more difficult to detect with less severe impacts.


Pebble Count Distributions

Computed particle size parameters (mean and median particle size) were compared in Table 10. The cumulative frequency distributions by particle size are graphed re in Figure 2. All unsuitable sites had left tails (more fines) on the curves that were much higher than +2 SD from the core WHA sites. Non-WHA core sites (N3 in Figure 2) had very similar curves to the WHA core sites with a few exceptions that had more fines. Some of the non-WHA transient sites had curves with far more fines than WHA core sites, but some curves were very similar. WHA frontier sites were generally had more fines than WHA core sites, but some sites were similar. Only 1 WHA core site was >2 SD from the mean WHA core curve.

DISCUSSION

Study Design

The target population did not include all tailed frog populations known to occur in the Merritt and Lillooet TSAs. In the Merritt TSA, 50-75% of the metapopulations known to be occupied by tailed frogs have yet to have any WHAs proposed (Gyug, unpublished data, 2002). Even within the basins where WHAs have been established there are many gaps in prior surveys and not all potential WHAs have even been surveyed yet. Priorities during previous surveys were based on likelihood of adjacent logging over the next forest development plan period (5 years), and on FRPA stream classification (fish-bearing streams >1.5-m width were low priority because they already had reserve zones equivalent to those applied under a tailed frog WHA).

Many of the non-WHA core reaches sampled in this study are also non-fish bearing reaches that would be excellent candidates for tailed frog WHAs, and WHAs will almost certainly be proposed on a number of them. Therefore it is not surprising that we could show no physical differences in WHA and non-WHA core streams. The WHA proposal process in the Cascades is still in the beginning stages with many sites not yet surveyed, and other sites surveyed but not yet evaluated for WHA potential. That includes a number of sites within the project study area.


Figure 2. Pebble count curves based on 100-particles per site using post-hoc groupings. The mean ± 2 SD for WHA Core sites has been shown in gray on

each graph. Upper left: Unsuitable (All N2; N3 if <1% gradient); Upper middle: Non-WHA core sites; Upper left: Non-WHA transient sites giving % stream gradient for N4 streams; Lower left: WHA frontier sites; Lower middle: WHA core sites.


This project has succeeded in highlighting the “immaturity” of WHA establishment in the Cascades. If the WHA identification process were “mature” and inclusive of all streams that should be included, then the only non-WHA streams that would be found to contain large populations of tailed frog larvae would be those protected by fish-stream reserve zones. The contrast of WHA core reaches and non-WHA core reaches would then become a contrast of tailed frog larval abundance in the presence of fish vs. the absence of fish. Therefore regional level comparisons in the Cascades may still be premature between WHA and non-WHA core reaches until more streams have been evaluated and WHAs proposed. While the intent may have been for this assessment to serve as a baseline, if and when more WHAs are established, then that baseline will have moved.

In 2002, I estimated that up to 75% of the basins in the Merritt TSA had yet to be evaluated for possible tailed frog WHAs. There is occurrence data for many tailed frog streams in those basins that have no WHAs yet, but proposals for WHAs must also include an evaluation of other factors including fish presence, the likelihood of timber harvest in the near future, and the presence of Category A approved cutblocks that would prevent changes in land status. At the regional level, the lack of any WHAs in a majority of the basins containing tailed frogs is a significant gap, and should be acknowledged in a regional level assessment.

Stream Characterization Model

A better model than just basin area is needed to distinguish ephemeral non-habitat, frontier, transient and core streams or reaches. Basin size is far too simple a measure that does not adequately characterize tailed frog distribution and habitat in the Cascades. Without an adequate model, only post-hoc analyses will be possible if streams can only be classified once they have been visited. The pebble count and other stream measurements showed that these streams are best compared based on their characterization to tailed frogs, i.e., as core or other reach type. A simple comparison of WHAs to other streams will always show WHAs with higher larval densities because they have been chosen as WHAs for their tailed frog populations and are not a random selection. Any random selection is bound to include some streams that are unsuitable habitat, and therefore relative densities will always be lower.

Streams ≤1% gradient should be removed from the sampling frame as these are generally not tailed frog habitat (e.g., Gyug 2001) and will not be included in WHAs. However, tailed frogs will occasionally occur in transient or mainstem reaches where gradient is <1% although we know of no case where a core reach was <1% gradient. The gradient field in the BC Freshwater Atlas stream networks is blank because of the coarseness of the underlying Digital Elevation Model, i.e., there were too many stream sections flowing “uphill” (Brehmer


2007). There is no simple or efficient solution to this problem on the provincial scale although larger streams (macro reaches) have had gradient mapped in a separate coverage (Wsa_mr_svw). These can be used to characterize larger streams and rivers but many low gradient non-habitat streams that are not parts of lakes or wetlands can only be removed after the field sampling. This would require oversampling beyond target levels since some sites will be expected to be discarded.

Data from previous tailed frog studies were combined with data from this study to attempt to better define and predict location of tailed frog reaches. From 2000 to 2002, 105 TCS were conducted within the project study area (Gyug 2000, 2001, 2002). Tailed frog adults were found in streams with drainage areas as small as 0.44km2, and larvae in streams with drainage areas as small as 0.72 km2. The smallest basin areas found that would have been classified as core reaches were 1.30 km2. Core reaches were found with gradients as low as 2.2% and drainage areas up to 9.6 km2. Transient reaches had basin sizes as small as 6.1 km2

with gradients from 0.5 - 6.5%. Along with basin area, the best predictor of whether a stream would be non-habitat (completely dry in late summer), frontier (partially dry in late summer or very narrow) or core appeared to be H90, the elevation below which 90% of the basin lies. The higher the H90, the more likely the stream would contain water in late summer.

I have proposed a classification for tailed frog streams that uses basin size, gradient, H90 and fish presence (Table 11). For small streams with basin areas <2.5 km2, a combination of basin area and H90 should characterize each stream. For streams with basin areas between 6 and 10 km2, the difference between core and transient reaches will be delineated by gradients of 5% and presence of salmonids, other than just bull trout. The macro reach coverage in the Freshwater Atlas provides gradients that cover most streams of this size for gradients. However, this will require manual attachment to the Freshwater Atlas stream network as the macro reach lines based on 1:50,000 do not match the stream network lines exactly. Fish presence and obstruction coverages are available publicly and if all forest licensee stream and fish inventories are included then perhaps 75% or more of all streams are covered. Educated guesses can be made for any remaining streams, and final characterization will have to be done post-hoc for any samples on those remaining streams.


Table 12. Proposed stream classification for tailed frog habitat stratification for regional WHA effectiveness monitoring in the east slope of the Cascades. Streams in WHAs or non-WHA locations with gradients <1% would be considered non-habitat.

Stratum Tailed Frog Reach

Characterization Basin Area (km2)

Gradient H90

1 Non-habitat dry in late summer <0.4 - - 0.4 - 1.3 - <1800 m

2 Frontier partially dry in late summer or very narrow

0.4 - 1.3 >1% >1800 m 1.3 - 2.5 >1% <1800 m

3 Core permanent stream in normal summers, cobble or very coarse gravels

1.3 - 2.5 >1% >1800 m 2.5 - 6 >1% - 6 - 10 >5% -

4 Transient Usually contains salmonids other than just bull trout, suitable cobble habitat very patchy and limiting

6 - 10 <5% - 10 - 50 - -

5 Mainstem Large rivers, non-habitat >50 - -

Tailed Frog Larvae

It was unclear why larval relative abundance was twice as high in WHA core reaches compared to non-WHA core reaches. It could be that high quality core reaches were unwittingly “hand-picked” as the most productive sites for initial surveys in 2000-2009 and that, of sites with tailed frogs present, only the most productive were put forward as WHA proposals. It is unlikely to be related to any protection that WHAs may have provided since establishment because there have been no cutblocks adjacent to any these WHAs since they have been established. The C1 (1-year old) larval cohort was significantly more common in core WHA reaches than in other reaches. It could be that most WHAs have been selected unwittingly on natal reaches (egg deposition sites) and other core sites may differ. We do not have a clear understanding of all the factors that may make only a portion of a core reach a natal reach, so it was not possible to analyze this possible cause further.

Whether one or two TCS should be completed at a site is a decision that must balance detectability, variance and access time vs. time on site. Where tailed frog abundance is high, they will be reliably detected with only one TCS. Where tailed frog abundance is not quite as high, and for detectability to be >0.9, 2 TCS are recommended per site. With no prior knowledge of what larval abundance may be at a site, there is a 14% probability of not detecting larvae when they are present with only one TCS. This can be reduced to a 2%


probability of not detecting larvae by one extra TCS per site, which would seem to be worth the extra minimal effort, especially given that this also significantly reduces within-site variance of relative abundance.. A crew of 2 can complete sampling of an average site (without interlocking alder or willow branches over the stream) in about 1.5 hours including 2 TCS, stream measurements, and pebble counts of 100 particles, and a crew of 3 can complete the sampling in about 1 hour. Sampling only 1 TCS at a site could reduce sampling time per site to about 1 hour for a crew of 2 and about 0.75 hour for a crew of 3. However, access time would not be changed. The slight savings in on-site crew time with just 1 TCS would not allow enough extra sample sites to be done overall to balance this reduction in detectability and variance per site.

Larval cohort length appeared to be quite consistent among site groups, and may not provide much basis for contrasting sites that may have different habitat quality. Length will also vary significantly as the larvae grow within the season which would complicate comparisons both within a single project, and with published data, or data from other projects.

Pebble Counts

Differences caused by clearcutting may be subtle rather than gross stream channel changes. In particular, a higher input of fine sediments might be expected. Two of the streams sampled in 2012 had major clearcuts 500 m to 1.2 km upstream but their pebble count curves appeared to be similar to other samples in the same reach type. However the field crew noticed very fine silts were easily raised into suspension with the slightest disturbance at these sites. These very fine silts are not measurable using the Wolman pebble count method. Finer suspended sediments and/or turbidity should also be quantified.

The fine sediment inputs that would be expected with land clearing and disturbance would include refuge-filling materials that would be counted in the sands and gravels <32 mm quantified by pebble counts. “Downstream fining” is a known phenomenon with the input of fine sediments (Bunte and Abt 2001). Bunte and Abt (2001) suggest that “a study which focuses on the supply of fine sediment should sample the bankfull width, whereas sampling for a computation of stream roughness is usually restricted to the low flow bed.” It may be appropriate to alter the pebble count methodology (i.e., 0.5-m spacing on the thalweg) to include the entire stream width if we wish to quantify fine accumulations in particular. Bunte and Abt (2001) assess and provide appropriate methods.


RECOMMENDATIONS

The following recommendations are made for regional-level tailed frog WHA monitoring:

1. Workplans and study designs need to expressly state the contrasts to be made and the expected outcome, i.e., the hypothesis, so that sample sizes required can be estimated.

2. Use the tailed frog t reach type classification proposed here to classify stream reaches as the basis for any contrasts to be made, and evaluate that classification after application.

3. Physical constraints on sampling of some sites and the difficulty in pre-characterizing some types of sites will require extra time to be allotted to return to metapopulations already sampled so that replacement sites can be selected in the correct random order.

4. 2 separate 30-minute Time Constrained Searches should continue to be done at each sampling site to more reliably characterize relative abundance of larvae at each site, and to reduce between-site variance within strata.

5. A two-week field session by two crews can provide adequate sample size (≥11 per stratum) with reasonable power (≥0.8) to show a significant difference when tailed frog larval relative abundance is twice as high in WHA core reaches than in non-WHA core reaches. Any other contrasts, or when expected differences in relative abundance are not as high, will require higher sample sizes because of higher variation or will need to be assessed separately.

6. Pebble count field methods should be continued as one of the best methods available to characterize tailed frog habitat quantitatively but should consider entire bankfull width assessments since fines may be expected to collect elsewhere than just on the flow centerline.

7. The expected outcome of pebble counts with disturbance, i.e., possible downstream fining accompanied by increases in refuge-filling particles, should be defined by targeted research so that sample sizes required to show differences in groups with different reserve zones or cutting strategies can be determined.

8. Channel condition and channel disturbance ranks were found to be too general and not useful for comparing tailed frog reaches or non-WHAs to WHAs. Quantitative measures are preferred but, except for pebble counts, these were not evaluated in this project.

9. A regional level assessment should include the basins that are known to contain tailed frogs but have yet to have any WHAs proposed. I estimate that 3 10-day sessions by 2 field crews, i.e., 60 field days, in August and September could provide a complete field assessment of potential WHAs in the Merritt TSA and include many potential sites in the Lillooet TSA as


well. This would be preceded by an analysis of all streams by FRPA Stream Classification status and the tailed frog reach classification proposed here in co-ordination with licensees who may hold stream classification and fish inventory data, and would take about 20 biologist-days.

LITERATURE CITED

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Bunte, K., and S. Abt 2001. Sampling surface and subsurface particle-size distributions in wadable gravel-and cobble-bed streams for analyses in sediment transport, hydraulics, and streambed monitoring. Gen. Tech. Rep. RMRS-GTR-74. Fort Collins, CO. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 428 p. Available at URL: http://www.fs.fed.us/rm/pubs/rmrs_gtr074.pdf

Dupuis, L.A. 2005. Protocol for conducting routine and extensive effectiveness evaluations for tailed frog wildlife habitat areas: Version 1. Report prepared for the Forest and Range Resource Evaluation Program. Ministry of Water, Land and Air Protection and Ministry of Forests. Victoria, B.C.

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