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Anthropogenic barriers to fish passage, such as culverts and dams, are major factors impeding the persistence and recovery of aquatic species. Considerable work has focused on mitigating these impacts; however, activities associated with measuring and restoring connectivity of aquatic ecosystems often face challenges in determining the passability of barriers by aquatic species. Hydrological modeling software that incorporates biological aspects of a focal species is often used as a relatively inexpensive method for assessing barrier passability for restoration decisions. However, the biological relevance of these approaches remains to be rigorously tested. We assessed passage rates of PIT-tagged Brook Trout Salvelinus fontinalis through four road culverts and adjacent reference sites (unaltered areas of the streams) on the island of Newfoundland to determine whether upstream passage through road culverts was more restrictive than unaltered reference areas of the stream. Next, we examined the usefulness of barrier passability predictions derived from FishXing software by comparing them with in situ movement data for this species. Brook Trout passage for three of the four reference sites had a significantly higher range of passable stream flows compared with that for culverts, indicating the presence of velocity barriers in culverts. However, FishXing predictions of suitable fish passage discharges were conservative, and tagged fish successfully navigated partial barriers that were at least 2–3 times the upper limits of stream flow predicted to allow successful passage. The results of our study show a clear need for an improved understanding of fish movement through these structures so that barrier assessment techniques can be refined. The implications of not doing so may lead to restoration actions that result in limited biological benefit.Received February 6, 2013; accepted July 2, 2013
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Content may be subject to copyright.
This is an Author's Accepted Manuscript of an article submitted for consideration in Transactions of the
American Fisheries Society [copyright Taylor & Francis]; TAFS is available online
at http://www.tandfonline.com/[Article DOI: 10.1080/00028487.2013.825641].
a Corresponding author
b Current address: P.O. Box 92, Glovertown, NL, A0G 2L0, Canada.
Title:
Evaluating the Barrier Assessment Technique FishXing and the Upstream Movement of Brook
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Trout through Road Culverts
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Authors:
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Shad Mahluma: Department of Biology, Memorial University, St. John’s, NL A1B 3X9, Canada.
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Email: skm311@mun.ca
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David Coteb: Parks Canada, Terra Nova National Park, Glovertown, NL. P.O. Box 92,
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Glovertown, NL, A0G 2L0, Canada.
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Yolanda F. Wiersma: Department of Biology, Memorial University, St. John’s, NL A1B 3X9,
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Canada.
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Dan Kehler: Parks Canada, 1869 Upper Water St., Halifax, NS, B3J 1S9, Canada.
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Keith D. Clarke: Science Branch, Fisheries and Oceans Canada, St. John’s, PO Box 5667, NL
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A1C 5X1, Canada.
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a Corresponding author
b Current address: P.O. Box 92, Glovertown, NL, A0G 2L0, Canada.
Abstract:
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Anthropogenic barriers to fish passage, such as culverts and dams, are major factors
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impeding the persistence and recovery of aquatic species; and considerable work has focused on
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mitigating these impacts. However, activities associated with measuring and restoring
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connectivity often face challenges in determining the passability of barriers for aquatic species.
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Hydrological modeling software that incorporates biological aspects of a focal species is often
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used as a relatively inexpensive method for assessing barrier passability for restoration decisions.
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However, the biological relevance of these approaches remains to be rigorously tested. We
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assessed Passive Integrated Transponder (PIT) tagged Brook Trout Salvelinus fontinalis passage
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rates through four road culverts and adjacent reference sites on the island of Newfoundland,
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Canada, to determine if upstream passage through road culverts was more restrictive than
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unaltered reference areas of the stream. Next, we examined the usefulness of barrier passability
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predictions derived from FishXing software by comparing them to in-situ movement data for this
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species. Brook Trout passage for three of the four reference sites had a significantly higher range
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of passable stream flows compared to culverts, indicating the presence of velocity barriers in
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culverts. However, FishXing predictions of suitable fish passage discharges were conservative,
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with tagged fish successfully navigating partial barriers at least 2 to 3 times the upper limits of
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stream flow that were predicted to allow successful passage. The results of our study show a
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clear need for an improved understanding of fish movement through these structures so that
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barrier assessment techniques can be refined. The implications of not doing so may lead to
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restoration actions that result in limited biological impact.
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Introduction:
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This is an Author's Accepted Manuscript of an article submitted for consideration in Transactions of the
American Fisheries Society [copyright Taylor & Francis]; TAFS is available online
at http://www.tandfonline.com/[Article DOI: 10.1080/00028487.2013.825641].
a Corresponding author
b Current address: P.O. Box 92, Glovertown, NL, A0G 2L0, Canada.
The re-establishment of natural processes is a critical step in restoring and maintaining
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diverse biological communities (Roni et al. 2002, Palmer et al. 2005). Aquatic connectivity is
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increasingly recognized as an important characteristic of aquatic ecosystems and has gained
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considerable attention in recent years (Fullerton et al. 2010, Olden et al. 2010). Unlike terrestrial
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landscapes that may have multiple pathways between habitat patches, riverscapes have a single
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movement corridor among habitat patches for obligate aquatic species. Consequently, the
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obstruction of these pathways by culverts, dams, and other barriers can alter community
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assemblages, impede the completion of life history stages, and limit the dispersal of aquatic
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species within meta-communities (Fagan 2002, Fahrig 2003, Schick and Lindley 2007, Fullerton
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et al. 2010, Perkin and Gido 2012). Recent advancements in connectivity models have developed
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riverscape approaches to measure the fragmentation of dendritic ecosystems (Cote et al. 2009,
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Padgham and Webb 2010, O’Hanley 2011) since terrestrial metrics of fragmentation (e.g.,
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Kindlmann and Burel 2008) are of limited utility in riverine systems.
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Barrier location and passability are two components routinely used in assessing the
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degree of fragmentation in watersheds. The first component helps determine the maximum
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amount of total habitat that could be gained by restoring or removing a single barrier (Cote et al.
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2009, O’Hanley 2011). For the second component, determining how a focal species navigates
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past a barrier can indicate the degree to which an obstacle impedes stream movement for an
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aquatic species. This is often difficult to resolve because of the complex and dynamic nature of
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passability (Cote et al. 2009, Padgham and Webb 2010, Bourne et al. 2011). Furthermore,
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accurate measures of connectivity are sensitive to barrier assessment methods (Bourne et al.
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2011) and thus it is critical to know whether barrier assessment methods are representative of
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fish movements.
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a Corresponding author
b Current address: P.O. Box 92, Glovertown, NL, A0G 2L0, Canada.
Various methods exist to analyze the passability of barriers (Kemp and O'Hanley 2010).
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Common methods used to calculate culvert passability include flow charts (Taylor and Love
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2003, Clarkin et al. 2005, Coffman 2005) and computer simulations (Hotchkiss et al. 2008).
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These barrier assessment methods are particularly appealing because of their simplicity and
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affordability to gather and process the required information. However, hydrological data needed
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to assess barriers are often missing or the data can be difficult to obtain (Kemp and O'Hanley
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2010) and only a few studies have examined the accuracy of barrier assessment methods using
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in-situ field experiments (Coffman 2005, Burford et al. 2009).
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FishXing is one commonly used method that was originally designed to assist in the
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evaluation and design of culverts to promote upstream fish passage (Furniss et al. 2006). By
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incorporating species-specific metrics (e.g., species length and swimming capabilities) and
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hydrologic properties of the culvert (e.g., culvert slope, length, and roughness), FishXing is able
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to estimate the stream flow that a particular individual is able to pass. In theory, this should lead
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to a more accurate passability estimates than simpler, rule-of-thumb type assessments. FishXing
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has been used extensively to model culverts for fish passage (Flanders and Cariello 2000, Taylor
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and Love 2003, Standage 2007, Davis and Davis 2008, Hendrickson et al. 2008). However,
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remarkably few studies have analyzed the effectiveness of FishXing as a barrier assessment tool
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(Burford et al. 2009), despite the widespread perception that FishXing produces conservative
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outputs (Poplar-Jeffers et al. 2009, Bourne et al. 2011).
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Poplar-Jeffers et al. (2009) found that outputs from FishXing appear to categorize most
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barriers as completely impassible, when in reality some form of intermediate passability may be
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more appropriate (Anderson et al. 2012). Potentially, default swim speeds in FishXing are
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underestimated since they are calculated in laboratory settings through forced swim performance
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methods (Castro-Santos 2006, Peake and Farrell 2006). Furthermore, culvert hydrological
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This is an Author's Accepted Manuscript of an article submitted for consideration in Transactions of the
American Fisheries Society [copyright Taylor & Francis]; TAFS is available online
at http://www.tandfonline.com/[Article DOI: 10.1080/00028487.2013.825641].
a Corresponding author
b Current address: P.O. Box 92, Glovertown, NL, A0G 2L0, Canada.
properties, used for FishXing, are modeled after maximum stream flow characteristics within the
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culvert (Burford et al. 2009, Bourne et al. 2011), which have been shown to overestimate the
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severity of a barrier (Lang et al. 2004). In reality, culverts rarely exhibit the flows that are
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predicted by FishXing default parameters. Several studies have focused on the accurate
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calculation of hydrological properties in hopes of improving predictions of fish movement. For
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instance, Burford et al. (2009), following the approach of Karl (2005), adjusted the roughness
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coefficient but found only modest changes in their error rate between observed and actual flow
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depths. Moreover, Bourne et al. (2011) did extensive culvert modeling using methods from
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Straub and Morris (1950a, 1950b) to adjust the roughness coefficients of barriers. Although they
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could not always predict water flow through culverts, the use of the more precise entrance loss
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and roughness coefficients improved the accuracy of the stream flow predictions (Bourne et al.
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2011). However, even with the increased precision of the hydrological modeling by Bourne et al.
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(2011) it is still unknown if the stream flows predicted by FishXing as passable are
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representative of what fish can navigate under natural conditions.
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We monitored Brook Trout Salvelinus fontinalis upstream passage across four culverts
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over three years in the Terra Nova National Park area of Newfoundland, Canada, using passive
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integrated transponder (PIT) tags. The use of PIT tags to study fish movement allows an
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opportunity to analyze, under natural flow conditions, whether culverts alter fish movement and
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if so, to test if the predictions of a commonly used barrier assessment technique are accurate. We
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first evaluated whether there were differences between upstream fish passage in culverts
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compared to reference sites. If culverts influence the movement of Brook Trout we expect to see
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a wider range of stream flows that Brook Trout are able to pass in reference sites when compared
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to culverts. We also determined the accuracy of FishXing estimates with the use of in-situ fish
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a Corresponding author
b Current address: P.O. Box 92, Glovertown, NL, A0G 2L0, Canada.
movements. Verifying the accuracy of FishXing with in-situ Brook Trout movements will
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provide direct empirical support for the efficacy of FishXing for use in barrier assessments.
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Study area:
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The study was conducted in the boreal stream systems of the Terra Nova National Park
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area (TNNP) of Newfoundland, Canada. TNNP is a low productivity system with low species
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richness dominated by salmonids (Cote 2007). Native Brook Trout exhibit both anadromous and
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diadromous life histories in the study area.
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Methods:
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Field Data Collection:
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We used a portable Smith Root Inc. electroshocker (model 12-B) to capture fish for
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tagging at the 4 study sites (~150 meters upstream and downstream of the culverts of interest).
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Sampling intervals occurred yearly in May and June from 2009 to 2011 after the installation of
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fish tracking arrays. We attempted to tag sea run brook trout in some systems but these were not
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well represented in our study area. As a result we focused on juveniles. All fish were measured
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(fork length; mm) and weighed (wet mass; g). Fish greater than 95 mm were implanted with PIT
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tags (model RI-TRP-WRHP; Texas Instruments Inc.; 23.1 mm in length and 3.9 mm in diameter,
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mass in air of 0.6 g; tag-to-fish ratio: 0.95.7%) through a small ventral incision made anterior to
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the pelvic girdle. One suture (4-0 SoftSild TM) was used to close the incision and the fish were
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then placed in flow-through holding pens within the capture area to recover for 24 hours before
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release.
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Fish passage was monitored using detection arrays (Oregon RFID, www.oregonrfid.biz)
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placed near culverts and reference sites (unaltered areas of the stream) from May to November
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This is an Author's Accepted Manuscript of an article submitted for consideration in Transactions of the
American Fisheries Society [copyright Taylor & Francis]; TAFS is available online
at http://www.tandfonline.com/[Article DOI: 10.1080/00028487.2013.825641].
a Corresponding author
b Current address: P.O. Box 92, Glovertown, NL, A0G 2L0, Canada.
during the sampling years. At culvert locations, arrays were established across the stream with 2
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antennae deployed upstream of the culvert (at the culvert entrance and 2-3 m upstream) and 2
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deployed downstream (at the culvert outlet and 2-3 m downstream; see Figure 1). The order of
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detection on the antennae allowed the direction of movement to be determined and the success or
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failure of an upstream passage attempt. We considered a pass attempt successful if a fish
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registered at one of the downstream antennae followed by a detection at either upstream
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antennae. Conversely, it was considered a failed attempt if the individual moved upstream past
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the two downstream antennae, did not register at either of the upstream antennae prior to being
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recorded a second time at the furthest downstream antennae. Reference sites were established
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with detection arrays in unaltered adjacent areas of the stream approximately 50 m from the
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culvert and in a manner that mimicked culvert lengths. The reference sites for culverts A, B, and
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C were located downstream of the culvert while the reference site for culvert D was located
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upstream due to the proximity of culvert D to the ocean.
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Discharge was derived from water level loggers (Solinst Levellogger Gold) deployed in
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each study stream to record hourly water temperature and depth during the study period. Each
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site was visited across a broad range of discharges to establish a rating curve with which
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discharge could be modeled on an hourly basis based on water depth (Riggs 1985). To determine
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the temporal availability of suitable stream flow we calculated the cumulative frequency of
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stream discharge for each culvert.
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We chose three partial barriers (culverts A, B, and C) based on a previous assessment in
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conjunction with a cost-benefit analysis of all barriers in TNNP that suggested improving
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passage at these locations would provide the most ecological benefit. Culvert D was an
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opportunistic addition to the study after Hurricane Igor washed it out in 2010. We used culvert
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a Corresponding author
b Current address: P.O. Box 92, Glovertown, NL, A0G 2L0, Canada.
measurements collected from various sources (Table 2). Detailed characteristics of culverts A, B,
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and C were summarized in Bourne (2013) and culvert D was resurveyed after it was replaced.
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Analysis:
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We used FishXing to predict the stream flows for each culvert that 50 to 250 mm Brook
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Trout were able to pass. We used sustained and burst speeds for Brook Trout defined by Peake et
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al. (1997; Table 1). Minimum depths were based on 2/5 body length. This is less than earlier
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studies that used minimum depths between 9 to 24 cm (Bates et al. 2003, Burford et al. 2009,
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Bourne 2013). Previous work in TNNP used a value of 3/4 body length (Bourne et al. 2011),
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which was considered conservative given prior field observations of fish movements within the
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study area. We therefore selected a lower value of 2/5 body length. Lastly, jumping height was
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based on 2 times the length of the Brook Trout (Bourne 2013). Using methods outlined by
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Bourne et al. (2011), we calculated Ke values from Straub and Morris (1950a, 1950b) and back
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calculated the Manning’s roughness coefficient (n) using data from the culvert surveys. Finally
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we modeled tail-water depth using the channel cross section method outlined by the FishXing
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User Manual (Furniss et al. 2006). For a given range of water flow values, FishXing predicts the
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range at which a fish will experience i) passable flows, ii) a depth barrier (insufficient water
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depth for fish to navigate), iii) a leap barrier (perched culvert elevation too high), or iv) a
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velocity barrier (water velocity is too great for an individual to pass).
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Fish movements in unaltered systems are temporally variable. For example, it might be
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expected that fish movement rates would be impacted by discharge and/or seasonal life history
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demands (Gowan and Fausch 1996, Klemetsen et al. 2003). To isolate the effects of culverts on
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fish movement, reference sites were monitored to compare fish movement in relation to stream
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discharge in the absence of anthropogenic barriers. We compared the range of discharges
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associated with successful passage across culverts and reference sites. To limit the influence of
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This is an Author's Accepted Manuscript of an article submitted for consideration in Transactions of the
American Fisheries Society [copyright Taylor & Francis]; TAFS is available online
at http://www.tandfonline.com/[Article DOI: 10.1080/00028487.2013.825641].
a Corresponding author
b Current address: P.O. Box 92, Glovertown, NL, A0G 2L0, Canada.
outliers, passage range was defined as the 25th percentile minus 1.5 times the inter-quartile range
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(IQR) and the 75th percentile plus 1.5 times the IQR. A permutation test was used to determine
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significance. Specifically, we randomly re-assigned the stream discharges associated with
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passage events to either reference or culvert locations and recalculated the range for the
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permuted reference and culverts sites (10,000 permutations). The distribution of permuted values
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was compared to the observed value to evaluate whether there were significant differences in the
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discharge range where Brook Trout passability occurred ( = 0.05).
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We also tested to see if observed fish movement was consistent with predicted movement
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as calculated with FishXing, by using a generalized linear mixed effects model (GLMM) with a
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binomial distribution (Bates et al. 2011, R Development Core Team 2012) as follows:
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Eventijk = intercept + individuali + sitek + predictedijk
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where Eventijk was binary (successful passage / failed passage) for individual i at site k. We
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included individuali and sitek as random effects to account for variation associated with repeated
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observations at the same levels of these variables. The final term, predictedijk variable, was also a
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binary event (successful passage / failed passage) that represented the FishXing prediction, given
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the associated culvert and flow parameters. To test the significance of the fixed effect, we used a
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likelihood ratio test ( = 0.05). All statistical analyses were carried out with the package R
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(version 2.15.2; R Development Core Team 2012).
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Results:
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We captured and tagged 462 Brook Trout across the four culverts in the study. Seventy of
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these trout were later observed in the culvert and reference arrays, which generated a total of 415
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a Corresponding author
b Current address: P.O. Box 92, Glovertown, NL, A0G 2L0, Canada.
upstream passage attempts in culverts (69% success rate) and 1,123 passage attempts at reference
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sites (56% success rate). Furthermore, 26 individuals of the 70 individuals were observed in both
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reference and culvert sites. Brook Trout that successfully moved through the culvert and
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reference sites did not differ significantly in size when compared to the population of Brook
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Trout caught and tagged (χ2 = 0.9576 , df = 1, p-value = 0.33). Moreover, lengths of successful
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Brook Trout migrants did not significantly differ (χ 2 = 0.1312 , df = 1, p-value = 0.72) between
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culvert and reference sites. Timing of the passage events occurred throughout the day with peaks
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in the early morning and afternoon. Three of the four culverts were predicted by FishXing to
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have passable stream flows (grey zones Figure 2). Only culvert D was predicted to be an
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impassable barrier by FishXing. Predicted passable stream flows increased with increases in
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Brook Trout size (grey zones in Figure 2). Stream flows that were considered barriers were
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classified by FishXing as either depth or velocity barriers with depth barriers observed during
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low flows and velocity barriers observed during high flow periods. No jump barriers were
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observed across the four culverts in this study regardless of stream flows.
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Comparing the range of passable flows between reference sites and stream culverts
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indicate a decreased range of passable flows through culverts. Permutation tests showed that
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culverts A, B, and C had a significantly smaller range of passable flows compared to their
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respective reference stream sections (Figure 3). However, culvert D had a significantly higher
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range of passable flows compared to its reference stream site (Figure 3). The decreased range of
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passable flows in culverts A, B, and C support the presence of a velocity barrier. Failed attempts
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were more frequent at lower flows but often corresponded to at least one successful passage at
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similar flows (Figure 2).
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The prediction from FishXing regarding whether the fish would pass was not a
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significant explanatory variable in observed passage events. We were unable to accurately
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This is an Author's Accepted Manuscript of an article submitted for consideration in Transactions of the
American Fisheries Society [copyright Taylor & Francis]; TAFS is available online
at http://www.tandfonline.com/[Article DOI: 10.1080/00028487.2013.825641].
a Corresponding author
b Current address: P.O. Box 92, Glovertown, NL, A0G 2L0, Canada.
predict fish passage with FishXing across the four culverts (χ 2 = 0.9192, df = 415, P = 0.338;
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Figure 2). In each culvert, with the exception of culvert A, fish were able to pass stream
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discharges that exceeded two or three times the upper discharge threshold predicted using
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FishXing. We also observed fish passage at flows that were considered depth barriers to Brook
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Trout movement (Figure 2A). To identify the minimum water depth and maximum water
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velocity that Brook Trout successfully passed, we used FishXing to calculate hydraulic
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characteristics at observed flows. Brook Trout were recorded successfully passing estimated
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water depths as low as 3 cm (135 mm Brook Trout in culvert A at 0.009 cms-1) and a maximum
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water velocity of 1.56 ms-1 (135 mm Brook Trout in culvert D at 0.628 cms-1) which were
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respectively predicted as depth and velocity barriers to Brook Trout movement.
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Discussion:
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The frequency of fish movement is temporally variable and fluctuates according to
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season, environmental factors, and life history stages (Riley et al. 1992, Gowan and Fausch
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1996, Klemetsen et al. 2003). It is therefore important to assess fish passage through barriers
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within the context of when fish are moving under natural conditions. The use of reference sites
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allowed us to isolate the effects of culverts from other confounding influences. Comparison of
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movements of PIT tagged Brook Trout in reference sites and culverts indicated that culverts
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impair fish passage. Because stream discharge is the same in paired reference and culvert sites,
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disparities in fish movement indicate that barriers exist in culverts due to low water depth or
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increased velocities (Cote et al. 2005). This supports previous studies which found barriers
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impaired movement of Brook Trout through culverts when compared to reference sites (Belford
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and Gould 1989, Thompson and Rahel 1998, Burford et al. 2009). It is therefore important to
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recognize that non-perched culverts can also be problematic and create conditions that limit the
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a Corresponding author
b Current address: P.O. Box 92, Glovertown, NL, A0G 2L0, Canada.
upstream movement of fish (see also MacPherson et al. 2012). This underscores the complexity
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of connectivity in many systems as barriers may not always be easily characterized as fully
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passable or impassable (e.g., Park et al. 2008, Burford et al. 2009, O’Hanley 2011).
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We were unable to accurately predict the movement of fish passage through culverts
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using FishXing. With increased effort to improve hydrological modeling of culverts, it was
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expected that FishXing predictions would be useful in determining fish passage. Unfortunately,
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FishXing is a complex model that incorporates physiological information of the species and
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hydrological information associated with the culvert. While qualitative assessments of barriers
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from FishXing remain useful (they were accurate for three of the four barriers), the severity of a
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barrier is an important element for quantifying connectivity or prioritizing restoration.
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Beyond refining hydrologic parameters, the predictive shortcomings of FishXing might
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be associated with an incomplete knowledge of fish physiology and/or behavior. The
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underestimation of fish swimming abilities can account for the conservative estimates by
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FishXing. Past studies that have derived swim speeds from forced swimming methodologies
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have been criticized because they do not reflect conditions in natural systems (Castro-Santos
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2006, Peake and Farrell 2006). Haro et al. (2004) analyzed swim speeds of several species of fish
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exhibiting anadromous, amphidromous and potamodromous life histories using an open channel
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flume. In that study, fish were allowed to transverse the flume under their own volition, which is
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different from past studies that used forced swim speeds. They found that by allowing fish to
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mimic their natural tendencies (multiple pass attempts, movement under own volition) to
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navigate the flume, they were able to record speeds that were well above those previously
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observed. However, Haro et al. (2004) used a smooth channeled flume with relatively constant
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flow regimes and recommended that these swim speeds should be used in situations that mimic
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these flow profiles (e.g., box culverts). Such improvements in understanding species swim
278
This is an Author's Accepted Manuscript of an article submitted for consideration in Transactions of the
American Fisheries Society [copyright Taylor & Francis]; TAFS is available online
at http://www.tandfonline.com/[Article DOI: 10.1080/00028487.2013.825641].
a Corresponding author
b Current address: P.O. Box 92, Glovertown, NL, A0G 2L0, Canada.
performance would enhance fish passage methods like FishXing that rely on swimming
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performances.
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Many obstacles to fish movement, both natural and anthropogenic, incorporate non-
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uniform flow characteristics with areas of velocity refugia consisting of lower velocity flow
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patterns (e.g., culvert boundary layers). For instance, in this study, fish were observed idly
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resting in the boundary layers of culverts (low velocity zones near the edge of the culvert) with
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little or no effort to maintain their position. Clearly, laboratory settings that replicate the
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turbulent conditions found in nature would be useful in understanding of how fish optimize
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passage (Haro et al. 2004, Castro-Santos 2006, Neary 2012) and will benefit future assessments
287
and restoration practices by allowing us to focus on velocity zones that are critical to fish
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passage.
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Behavior plays an important role in how fish move past barriers. Minimum depth is a
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biological parameter incorporated into FishXing that determines whether individuals are able to
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successfully navigate a culvert at low stream flows. Water depth remains an important aspect of
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culvert passage as predictions of depth barriers can be common in studies using FishXing
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(Gibson et al. 2005). However, Burford et al. (2009) indicated that this parameter had very little
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influence on determining the upstream movement of fish. Inconsistencies with FishXing
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predictions from previous work (Bourne 2013) and field observations of fish movements led us
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to reduce the models minimum depth measurement. Our results indicate that this threshold
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remains conservative. We defined the minimum depth as 2/5 the body length (minimum depth
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from 4 to 8 cm) of an individual which was more liberal than the 9.1 cm used by Burford et al.
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(2009). Both the values in this study and in Burford et al. (2009) are considerably lower than
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recommended minimum depth values (Bates et al. 2003). However, we found that using 2/5 body
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length was accurate in three of the culverts in this study (only culvert A was considered a depth
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a Corresponding author
b Current address: P.O. Box 92, Glovertown, NL, A0G 2L0, Canada.
barrier). Unfortunately, we were unable to capture in-situ measurements of culvert hydrologic
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characteristics to calculate minimum depth, and thus we used FishXing outputs to derive
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minimum depth for culvert A. While it is useful to know at what depth fish are able to pass, it is
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unclear whether the precision of FishXing is accurate enough to back calculate such parameters.
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Therefore, further work is needed to continue to refine how depth influences fish movements and
307
how individuals interact with anthropogenic structures in low flow situations.
308
The installation and replacement of stream crossings is an expensive endeavor (Bernhardt
309
et al. 2005) and using inaccurate barrier assessment methods to prioritize culvert restoration
310
could unnecessarily burden limited financial resources when no action is needed to promote fish
311
passage. However, the conservative outputs of FishXing, when predicting fish movement, may
312
be advantageous as a precautionary tool. FishXing was created to help in the design of culverts
313
to promote fish passage, and within this framework, a precautionary approach is beneficial.
314
Designing culverts in excess of what is needed for fish passage will ensure fish movement
315
throughout the range of flows encountered by fish. However, at what point does designing
316
culverts for fish passage based on a conservative FishXing output become too costly when a less
317
conservative design can have the same effects on the aquatic community? Continued
318
advancements in the understanding of fish passage should lead to a balance that will promote
319
effective culvert designs without accruing unneeded expenditures.
320
An alternate approach to FishXing would be to focus on identifying specific physical
321
thresholds that create a pass/no pass scenario and would continue to capitalize on the simplicity
322
and affordability of commonly used barriers assessment methods. Past methods such as flow
323
chart methods, have calculated culvert passabilities but few have been rigorously tested as to
324
whether these predictions match actual fish movement (Kemp and O'Hanley 2010). In spite of
325
this, one flow chart model developed by Coffman (2005) uses several easy-to-calculate
326
This is an Author's Accepted Manuscript of an article submitted for consideration in Transactions of the
American Fisheries Society [copyright Taylor & Francis]; TAFS is available online
at http://www.tandfonline.com/[Article DOI: 10.1080/00028487.2013.825641].
a Corresponding author
b Current address: P.O. Box 92, Glovertown, NL, A0G 2L0, Canada.
measurements based on culvert slope, length, and tail-water area to calculate the passability of a
327
culvert. Although the methods used by Coffman (mark recapture using fin clips; 2005) likely
328
produce conservative results, it is still appealing in that model estimates were based on
329
observations of fish movement to determine thresholds. The benefit of using a model like that of
330
Coffman (2005) is that it allows the user to quickly and easily assess a culvert and assign a
331
passability value to it with an associated degree of confidence. However, Anderson et al. (2012)
332
postulated that binary responses likely over-simplify culvert passage of many fish species. Using
333
Bayesian belief networks (BBN), Anderson et al. (2012) concluded that the inclusion of two and
334
three levels of criteria would distinguish partial barriers that were previously labeled as complete
335
barriers with a pass/no pass analysis. But not unlike other barrier assessment methods, the use of
336
BBNs to calculate probabilities of culvert passage is still dependent on accurately defining
337
thresholds, a trait shared by other culvert assessment techniques (Haro et al. 2004, Coffman
338
2005, Furniss et al. 2006, Kondratieff and Myrick 2006, Kemp and O'Hanley 2010, Anderson et
339
al. 2012).
340
Barrier assessments are an integral part of understanding and maintaining riverscape
341
connectivity. Passability metrics are one measurement that can be difficult to assess but which
342
have been shown to influence connectivity models (Bourne et al. 2011). Our results isolate the
343
effects of culvert impacts on fish movements and provide support to previous studies that
344
speculated on the conservative nature of FishXing (Burford et al. 2009, Bourne et al. 2011) and
345
highlight the need to continue to validate the effectiveness of common barrier assessment models
346
and how fish interact with barriers. The implications of using inaccurate barrier assessment
347
techniques could lead to misidentifying barriers as impassable and result in costly management
348
actions that have little or no ecological impact on the focal species.
349
350
a Corresponding author
b Current address: P.O. Box 92, Glovertown, NL, A0G 2L0, Canada.
Acknowledgements:
351
The authors are grateful to M. Langdon, T. Mulrooney, and R. Collier (PC) and C. Pennell and C.
352
Kelly (DFO) for tagging fish and maintaining telemetry stations. Furthermore the authors would
353
like to acknowledge the input and guidance from I. Gidge, R. Randall, M. Underwood and the
354
Landscape Ecology & Spatial Analysis Lab at Memorial University for valuable feedback
355
throughout the study. Funding to support the research was provided by Parks Canada Action on
356
the Ground Funding and by a Canadian Foundation for Innovation and NSERC Discovery grants
357
to YFW.
358
359
360
This is an Author's Accepted Manuscript of an article submitted for consideration in Transactions of the
American Fisheries Society [copyright Taylor & Francis]; TAFS is available online
at http://www.tandfonline.com/[Article DOI: 10.1080/00028487.2013.825641].
a Corresponding author
b Current address: P.O. Box 92, Glovertown, NL, A0G 2L0, Canada.
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a Corresponding author
b Current address: P.O. Box 92, Glovertown, NL, A0G 2L0, Canada.
TABLES:
505
Table 1: Brook Trout Salvelinus fontinalis biological parameters used for FishXing. Burst
506
(maintaining swim speeds for 20 s; BS) and sustained (maintaining speeds for 600 s; SS) swim
507
speeds based on swim speed models by Peake et al. (1997). Minimum depth was calculated as
508
2/5 of fish length, while Jump Height was calculated as 2 times fish length.
509
Length (mm) BS(m/s) SS (m/s) Min depth (m) Jump height (m)
510
50 0.374 0.266 0.02 0.1
511
100 0.599 0.491 0.04 0.2
512
150 0.824 0.716 0.06 0.3
513
200 1.049 0.941 0.08 0.4
514
250 1.274 1.166 0.1 0.5
515
516
517
Table 2: FishXing hydrologic input parameters used for each culvert in TNNP (see Fig. 1). Culvert roughness was back calculated
518
using the entrance loss coefficients of Straub and Morris (1950a, 1950b).
519
Measurement Culvert A Culvert Ba Culvert C Culvert Da
520
Shape (unit less) Circular Circular Circular Circular
521
Diameter (cm) 87 75 78 240
522
Material (unit less) CMPb CMPb Concrete CMPb
523
Entrance type (unit less) Projecting Projecting Projecting Projecting
524
Entrance loss (Ke) 0.7 0.9 0.9 0.9
525
Culvert roughness (n) 0.01 0.024 0.16 0.015
526
Length (m) 14 12 6.2 36
527
Inlet bottom elevation (m) 147.32 67.18 98.6 10.10
528
Slope (%) 2.29 1.50 1.77 1.83
529
Outlet bottom elevation (m) 147 67 98.6 9.44
530
Outlet pool surface elevation (m) 147.07 67.22 99.05 9.64
531
Velocity reduction factors
532
inlet/barrel/outlet (unit less) 0.8/0.6/0.8 0.8/0.6/0.8 0.8/0.6/0.8 0.8/0.6/0.8
533
Channel bottom slope (%) 3.4 4.6 3.1 2.1
534
Outlet pool bottom elevation (m) 146.75 67.146 98.66 9.3
535
Tail-water roughness (unit less) 0.2 0.05 0.46 0.04
536
Tail-water cross section
537
station (elevation) (m) 0.00 (146.95) 0.00 (67.57) 1.0 (98.96) 1.50 (10.33)
538
1.70 (146.82) 0.45 (67.53) 2.0 (98.73) 1.95 (9.83)
539
1.90 (146.78) 1.05 (67.15) 3.0 (98.77) 3.80 (9.82)
540
1.95 (146.82) 1.40 (67.22) 4.0 (98.80) 5.25 (9.69)
541
2.10 (146.75) 1.80 (67.20) 5.0 (98.86) 6.00 (9.45)
542
2.40 (146.75) 2.15 (67.20) 6.0 (98.73) 6.30 (9.40)
543
2.70 (146.80) 2.45 (67.23) 7.0 (98.78) 6.60 (9.30)
544
2.80 (146.77) 2.70 (67.29) 8.0 (98.77) 6.90 (9.30)
545
3.05 (146.79) 3.66 (67.75) 9.0 (98.83) 7.20 (9.30)
546
3.50 (146.77) 4.45 (67.69) 10.0 (99.0) 7.50 (9.36)
547
4.20 (147.02) 7.80 (9.43)
548
8.30 (9.64)
549
9.10 (9.75)
550
9.90 (9.98)
551
10.70 (9.92)
552
12.00 (10.33)
553
a Culverts A and D had secondary overflow culverts that were not modeled in FishXing; b Corrugated Metal Pipe
554
555
FIGURES:
556
557
Figure 1: Antennae setup for all culvert sites. Antennae II and III are on the inlet and
558
outlet of the culvert respectively. Antennae I and IV are located at the outlet and inlet
559
pools approximately 2 to 3 meters from the culvert respectively.
560
561
Figure 2: Successful and failed passage of Brook Trout based on length and discharge at
562
the time of the pass attempt. Grey zones indicated the conditions under which Brook
563
Trout are predicted to be able to pass at each culvert based on FishXing. Open squares
564
respresent successful pass attempts and black triangles represent unsuccessful pass
565
attempts. Panels A-D correspond to data from the 4 culverts, and culvert parameters (A-
566
D) are given in Table 2.
567
568
Figure 3. Timing of Brook Trout passage relative to the cumulative distribution of stream
569
discharge (black line), observed culvert and reference site passage (box plots), and
570
predicted passage as determine by FishXing (grey zone). Predicted passage was based on
571
FishXing passable flows outputs for 100 to 150 mm Brook Trout. The boxes represent the
572
inter-quartile range (IQR), solid dark line is the median, whiskers are 1.5 times the IQR.
573
Outliers are represented by open circles. Sample size (n) is the total number of successful
574
pass events for a given site, which consists of a reference and culvert telemetry array.
575
Trt is the difference of the range (represented by the whiskers) of passable flows
576
between the reference site and culvert site. Positive numbers indicate that culverts had a
577
smaller range of passable discharges compared to reference sites.
578
579
... Empirical evaluation of fish passage at culverts has often utilized mark-recapture with batch marks (Warren and Pardew 1998;Coffman 2005;Burford et al. 2009;Norman et al. 2009), short-range telemetry with PIT tags (Solcz 2007;Mahlum et al. 2014;Goerig et al. 2015), or both in combination (e.g., Roghair et al. 2014). These methods are effective but may be expensive in terms of labor (field crews) or specialized equipment (PIT tags and readers), and they can be plagued by small numbers of recaptures (Dunham et al. 2011;Hoffman et al. 2012). ...
... We used multiple monitoring methods at a few culverts (see also Roghair et al. 2014), whereas other studies have used a single method at a dozen or more culverts judged to differ in their passability (e.g., Coffman 2005;Burford et al. 2009). The "false culvert" or reference reach (e.g., Dunham et al. 2011) design has been used to quantify the barrier effect of a culvert or contrast the fish passage rates between a reference point in a natural stream channel (i.e., false culvert) and one or more culverts exhibiting a range of hydraulic or physical characteristics or passability ratings (e.g., Burford et al. 2009;Norman et al. 2009;Mahlum et al. 2014). Our choice to focus intensively on a few sites and not use a reference reach reflects the likelihood that a biologist implementing such monitoring faces significant time and cost constraints and might stop sampling at a site once passage is confirmed. ...
... This study measured passive movement, where fish are released at their original capture location after marking or tagging and their subsequent behavior is monitored (e.g., Norman et al. 2009;Mahlum et al. 2014). Others have captured fish in one location (upstream of a culvert) and released them in another (downstream from the culvert) and presumed that the fish would be motivated to move (translocation-displacement; e.g., Burford et al. 2009;Goerig et al. 2015). ...
Article
The removal or remediation of thousands of culverts at road‐stream crossings to restore connectivity is a major conservation investment in aquatic systems in North America. Effectiveness monitoring is necessary to confirm that passage has been restored for the species of interest and justify project costs. We compared the performance of (1) recapture of batch‐marked fish by backpack electrofishing, (2) recapture of PIT‐tagged fish by electrofishing, (3) detection of PIT‐tagged fish by mobile antennas, and (4) detection of PIT‐tagged fish at stationary antennas to verify upstream passage of native Westslope Cutthroat Trout (Oncorhynchus clarki lewisi, WCT) and nonnative Brook Trout (Salvelinus fontinalis) at remediated culverts in four Rocky Mountain streams. Generally, detection probability at stationary antennas was higher (range 0.74–0.97) than capture by electrofishing (range 0.24–0.77) or detection by mobile antenna (range 0.47–0.66). All four methods confirmed upstream passage by trout originally marked or tagged below the culvert, though overall recapture rates were low (≤20%). During summer and early fall, the continuously‐sampling stationary antennas detected more than twice as many PIT‐tagged trout moving upstream through the culvert than either the mobile antenna or electrofisher. Upstream movement by PIT‐tagged trout was first detected by stationary antennas 1–10 d after tagging. For all methods, upstream passage was most frequently detected by fish marked or tagged in the 100m reach adjacent to the culvert. We compared the relative cost of the four mark‐recapture methods to evaluate upstream passage of age‐1 and older WCT to a genetic method based on pedigree analysis, sib‐split, that was used previously to evaluate passage of age‐0 WCT in the study streams. Stationary antennas, mobile antennas, and sib‐split were comparatively expensive for a single‐year study because of PIT equipment and laboratory costs, respectively, and electrofishing was at least half the cost. This article is protected by copyright. All rights reserved.
... Potentially, many managers are satisfied with restoration techniques that improve physical habitat attributes (e.g. water velocities, outflow drops) but such assumptions that physical improvements will predictably improve fish passage may not always be valid (Pretty et al. 2003;Mahlum et al. 2014b). Consequently, understanding the usefulness of restoration approaches relies heavily on empirical data of fish community responses. ...
... The first was the inclusion of baffles on three of the sites to alter the stream flows to reduce discharge velocities through the culvert and the second was the placement of a secondary overflow culvert next to the barrier on Spracklins Brook (Table 1). We collected culvert measurements and characteristics from Bourne (2013) and Mahlum et al. (2014b) (summarized in Table 1). ...
... Restoration type consisted of the inclusion of baffles or the installation of a second adjacent culvert. tributaries where it served as a reference site for the culvert in this study and a nearby culvert in the connecting tributary (not included in the current study; Mahlum et al. 2014b). Furthermore, the upper and lower boundaries of the reference sites were selected to mimic the corresponding culverts. ...
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The restoration of four partial stream barriers was evaluated in watersheds of Terra Nova National Park, Newfoundland, Canada from 2009 to 2011. Brook trout (n = 462) were tagged and tracked moving through our study sites using PIT telemetry and the restoration actions were assessed using three different measures: passage success rates; the range of passable flows; and the availability of passable flows. We considered the observed results within a Before-After Control-Impact (BACI) design that included reference reaches and pre-restoration observations. The conclusions of BACI analyses were also contrasted with those that would have been obtained from commonly used Before-After (B-A) or Control-Impact (C-I) study designs. While the restoration actions changed hydrological conditions in a way that should facilitate fish passage, our biological measures indicated that success was variable across culverts and within culverts depending on the measure evaluated. Furthermore, the natural temporal and spatial variability of fish movements often resulted in different conclusions between the more robust BACI design and the more commonly used B-A and C-I designs. Our results demonstrate that restoration of partial barriers may not always yield dramatic improvements. Furthermore, without suitable controls, the chances of drawing false conclusions regarding restorations in temporally and spatially dynamic systems are substantial.
... When assessing the effect of barriers on aquatic biological communities, the Dendritic Connectivity Index (DCI) is widely used and modified to quantify longitudinal connectivity [1,3,[20][21][22][23]. In previous studies, anthropogenic barriers include dams, culvert, and roads, and natural barriers include waterfalls and beaver dams [22,[24][25][26]. Combined with field investigation, barriers are defined as anthropogenic or natural deposits that block river flow in the river channels in this paper. ...
... The proposed model is a pure structural connectivity metric based on the structures of the river channel and barriers. In contrast, when considering barriers, previous hydrological longitudinal connectivity researchers prefer to set the river flow and aquatic biological communities as the study object [1,21,26]. The Dendritic Connectivity Index (DCI) is a popular assessment index when setting aquatic biological communities as the study object. ...
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A large variety of barriers can affect longitudinal connectivity, which leads to shipping blocking and even flood hazard. However, few existing methods can quantify physically the river channel connectivity from the barrier’s details perspective in a watershed. This paper establishes a new model of the River Channel Connectivity Index (RCCI) to quantify the unobstructed degree of river flow in river channels within geographic information system (GIS ) platforms based on the modified concept of time accessibility. A comprehensive classification system of barriers is setup before these barriers are identified by the remote sensing technology. The model is applied to Dashi Watershed in suburban Beijing, China. Results show that submersible bridges and sediment siltation are the main barriers in the watershed. RCCI values in the mountainous areas are generally higher than that of the plains. The assessment results verified by two historical flood events show that the RCCI can reveal where the river channel connectivity is impaired, how serious it is, and what the reason is for managers. Through scenarios’ results, the best restoration measure for each tributary is obtained from the perspective of reducing flood hazards. The new RCCI method not only has methodological significance, but also helps policymakers to enhance river flooding reduction and determine restoration priorities of the river channel.
... Additionally, research in firstand second-order streams in central Michigan, USA, showed that even in culverts not indicated as obvious barriers by the FishXing model, fish passage can still be limited (Briggs and Galarowicz 2013). Using tagged fish, Mahlum et al. (2014) demonstrated that brook trout had a significantly higher range of passable flows in natural streams than in culverts, showing the presence of velocity barriers in culverts. In this case, fish successfully passed through barriers that were two to three times the upper stream flow limits predicted by FishXing. ...
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... Consequently, the barrier severity scores used here should not be interpreted as direct measures of passability, but instead relative condition of crossings. Crossings with low barrier severity scores are likely impassable by most organisms, and future research linking barrier severity scores to organism movement might identify such relationships (e.g., Mahlum, Cote, Wiersma, Kehler, & Clarke, 2014). In the meantime, the barrier severity score represents an excellent measure of relative condition across barriers, shows correlation with landscape variables, and allows use of optimization modeling for conservation planning. ...
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... For example, FishXing (developed in the late 1990s) has become a common software package used by fish passage practitioners (Furniss et al., 2006), even though it relies on overly simplified representations of flow (e.g., 1-D hydraulic models) and assumes swimming performance is constant for all fish of a given species. These simplifications can result in conservative estimates of fish passage which can lead to designs with limited biological benefit (Mahlum et al., 2014;Furniss et al., 2006). More robust models pairing steady state, three-dimensional flow simulations with fish energetics have been used in contemporary analyses of fishway designs (Khan, 2006;Khan et al., 2008). ...
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Despite the popularity of barrier removal as a habitat restoration technique, there are few studies that evaluate the biological effects of restored stream crossings. An extensive post‐treatment study design was used to quantify fish populations (e.g. species, life stage, abundance) and habitat attributes (e.g. gradient, geomorphic channel units) at 32 culvert removal or replacement projects to determine their effectiveness in restoring habitat access for juvenile salmon, Oncorhynchus spp., and steelhead, O. mykiss (Walbaum), in the Columbia River Basin, USA. Anadromous fish (steelhead, Chinook salmon O. tshawytscha [Walbaum]) abundance, juvenile steelhead abundance and habitat conditions were not significantly different between paired reaches (i.e. upstream and downstream of former barrier sites), suggesting these sites are no longer full barriers to movement. This suggests that barrier removal projects on small Columbia Basin streams provide adequate fish passage, increased habitat availability and increased juvenile anadromous fish abundance immediately upstream of former barriers.
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The distance fish can swim through zones of high-velocity flow is an important factor limiting the distribution and conservation of riverine and diadromous fishes. Often, these barriers are characterized by nonuniform flow conditions, and it is likely that fish will swim at varying speeds to traverse them. Existing models used to predict passage success, however, typically include the unrealistic assumption that fish swim at a constant speed regardless of the speed of flow. This paper demonstrates how the maximum distance of ascent through velocity barriers can be estimated from the swim speed–fatigue time relationship, allowing for variation in both swim speed and water velocity.
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Combinations of watar vclocity and passape length in highway culvarts were evaluated to datermine conditions that enabled or prevantad the passaga of nonnnadromous rainbow Eout Oncorhynchus mykiss. brown trout Salmo truttu, cutthroat -out 0, clarb, and brook trout Sal- velinus fontlnalis. Fish paasagc throa six culverta 45-93 m long was datermined by trapping and elcctrofishinb Water velocities wem mcaeurcd 5 cm above tha bottom (bottom vtlodty) and at 0.6 of tha water depth at intervals batwttn rest sitae throughout the bnpfhs of tha culverts. Nonlinear ragmeion linm epaci6c to species and state of mxual maturity wart fit to the wmbinationa of mean bottom velocity and paasage length represanthg tha most atrenuow conditions that allowed the upstraarh paneage of trout. Bccausc of the similarity of the stranuoua pasap relations among specits, the spawning rainbow trout relation could ba used M the general critarion for pmwe of the trout studied. This relation indicated that fish could swim distances of 10, 30, 50, 70, and 90 m with mean bottom valocitit~ up to 0.96, 0.8KO.74, 0.70, and 0.67 mh, respectively. Highway culverts often impede or block fish movements. The steep slopes and low roughness coefficients of culverts frequently cause high water velocities to develop that have prevented the pas- saga of Arctic grayling Thymallus arcticus. long- nose suckers Catostomus catostomus, northern pike Esox lucfus (Derksen 1980), staclhcad (anadro- mous rainbow trout) Oncorhynchus mykiss, coho salmon 0. kisutch, chinook salmon 0. tshawytscha (Kay and Lewis 1970), and cutthroat trout 0. clar- ki (Huston 1964; Berg 1975).