Design and Evaluation of Nature-Like Fishways for 

Passage of Northeastern Diadromous Fishes 

Final Report 

Alex Haro, Abigail Franklin, Theodore Castro-Santos 

and John Noreika 

S.O. Conte Anadromous Fish Research Laboratory (CAFRL) 

U. S. Geological Survey, Biological Resources Division 

1 Migratory Way, P.O. Box 796 

Turners Falls, MA 01376 

Submitted to: NOAA National Marine Fisheries Service Office of 

Habitat Conservation 

September 2008 

Executive Summary 

Several nature-like fishway designs have been constructed in the northeastern US, but none of 

these fishways have been quantitatively evaluated for passage of northeastern diadromous 

species. This report summarizes data on passage performance from two studies of nature-like 

fishway designs for passage of river herring in the field (Town Brook, Plymouth, Massachusetts, 

and East River, Guilford, Connecticut), and from two years of tests of generic nature-like 

fishway designs (perturbation boulder and rock weir) in a semi-controlled laboratory 

environment. The field studies focused on passage of anadromous alewife (Alosa 

pseudoharengus); laboratory studies tested American shad (A. sapidissima), blueback herring (A. 

aestivalis), white sucker (Catostomus commersoni), white perch (Morone americana), striped 

bass (M. saxatilis), and smaller numbers of other nonanadromous riverine species. Nature-like 

fishways tested ranged in overall slope from 1:20 (laboratory and Town Brook site) to 1:15 (East 

River site). 

Overall passage performance through nature-like sections of fishways at the field sites was 

modest (40.6%; East River) to good (94%; Town Brook), and transit times through the fishways 

were relatively rapid (median transit times of 11 to 75 min). Most fish ascended the Town Brook 

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fishway in one attempt, but only 22% of fish at the East River fishway ascended in a single 

attempt; most other fish required two or three attempts to pass the entire East River fishway. 

In the experimental laboratory fishways, overall percent passage of American shad and white 

sucker over the two year test period ranged from 40% to 90%. There was no significant effect of 

fishway design, rock configuration, or flow depth on percent passage, although there may have 

been interactions between effects. Percent passage of alewife and river herring was lower (0% to 

40%) than for shad or suckers, and contrasted with results from the field sites; handling and 

transport may have affected motivation and performance of alewife and blueback herring. 

Passage performance of other species (smallmouth bass, yellow perch, black crappie, channel 

catfish, common carp, fallfish) tested was variable; however, low sample sizes (number of fish 

tested of each species) made these results statistically inconclusive. 

Introduction 

Upstream fish passage facilities have been constructed extensively throughout the northeastern 

United States, primarily for anadromous species such as American shad (Alosa sapidissima), 

alewife (A. pseudoharengus), blueback herring (A. aestivalis), sea lamprey (Petromyzon 

marinus), and Atlantic salmon (Salmo salar). Most pass designs are structural fishways of the 

baffle or “Denil” type (Denil or Alaska steepass) for small or low head (< 3 m height) dams, and 

pool-and-weir (i.e., Ice Harbor or vertical slot) type for larger rivers or higher head dams 

(Orsborn 1987, Larinier and Travade 2002). Although the baffle-type fishways can pass large 

numbers of some northeastern species at low head dams, many of both the Denil and larger 

structural fishways have poor or unknown overall effectiveness for passing larger anadromous 

clupeids, and their efficiency can decrease dramatically at dams of heights over 3 m (Sullivan 

2004). Structural fishways also frequently require substantial maintenance (e.g., regular debris 

removal, replacement of baffles) throughout the operational season. 

Recently, nature-like fishways (e.g., roughened ramps, bypass channels) have been developed 

and shown to pass a wide variety of species at low-head dams in Europe (FAO/DVWK 2002, 

Jungwirth et al. 1998). These fishways typically consist of a wide, low gradient channel (usually 

less than 1:20 slope) with a concave stream channel cross-section, and natural cobble or boulder 

substrates to dissipate hydraulic kinetic energy and reduce channel velocities to levels that are 

generally below sustained (i.e., aerobic) swimming speeds of target species. Nature-like fishway 

designs have typically included bypass channels around dams and roughened ramps constructed 

either immediately downstream of a dam or in association with a partially removed dam, creating 

a new hydraulic control upstream of the former dam. Fish are believed to find natural substrates 

more acceptable than concrete channels or channels with baffles in structural fishways 

(FAO/DVWK 2002). The lower velocities at the boundary layers and flow refugia resulting 

from high roughness of nature-like fishways (generally less than 0.3 m ·sec-1) also allow for 

greater potential passage of very small or weakly swimming species such as rainbow smelt 

(Osmerus mordax), juvenile American eel (Anguilla rostrata), and even benthic invertebrates. 

Although they show promise as effective fishway structures for low head dams, few nature-like 

fishways have been constructed in the northeastern US, and none of these fishways have been 

quantitatively evaluated for passage of northeastern diadromous species. Only a few evaluations 

of nature-like fishways have been performed in Europe, which have been shown to be 

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qualitatively efficient for passing larger-sized European species (Eberstaller et al. 1998, Mader et 

al. 1998), but quantitative data on passage efficiency for these structures is generally lacking, 

except for larger European salmonids (Aarestrup et al. 2003). 

In addition, some species such as American shad migrate and spawn in large rivers but rarely 

enter small tributaries, and thus may be reluctant to enter traditional nature-like fishway designs, 

which are relatively shallow with many obstructions (i.e., large boulders) and turbulent flow 

(Haro 2002). Design of nature-like fishways for shad thus presents a special challenge in that the 

fishway must possess sufficient depth (both over boulder weirs and within pools) and flow to be 

attractive to shad, yet velocities and turbulence must be low enough to allow shad to progress 

efficiently up the fishway within a reasonable timeframe. In addition, large eddies and pools of 

high volume may induce shad to mill or stall within the fishway, increasing transit time, as has 

been seen in large structural pool and weir fishways. These hydraulic characteristics also must be 

maintained over a reasonable range of operational flow to ensure functionality of the fishway 

under fluctuating headpond conditions, such that the fishway is not starved for flow, fish are not 

stranded or exposed to predators, and have sufficient flow depth for swimming . The design must 

also be able to withstand anomalous high storm flows without displacement of substrate or 

embedded large keystone boulders. 

We propose that current nature-like fishway designs can be advanced to accommodate the 

preferences and swimming behavior of American shad, river herring, and other species to derive 

one or more generic designs that will pass a variety of diadromous and resident fish species in 

the northeastern region and other localities, for sites with a variety of river sizes and hydraulic 

heads. Our studies aim to collect data on passage performance from existing nature-like fishway 

designs under a range of natural flow conditions, and to modify these designs to increase 

performance of passage for northeastern species. 

This report summarizes results from two studies of nature-like fishway designs for passage of 

river herring in the field (Town Brook, Plymouth, Massachusetts, and East River, Guilford, 

Connecticut), and from two years of laboratory tests of generic nature-like fishway designs river 

herring, American shad, and other species. 

This work is supported by NOAA National Marine Fisheries Service Office of Habitat 

Conservation. 

Study Objectives 

1. Evaluate passage performance of alewife and blueback herring in an existing naturelike fishway site at Town Brook in Plymouth, Massachusetts. 

2. Evaluate passage performance of alewife in an existing spillway bypass channel with 

nature-like fishway features site at the East River, Guilford, Connecticut. 

3. Evaluate two full-scale prototype nature-like fishway designs (perturbation boulder 

and rock weir; each 10 ft width) in the Conte Anadromous Fish Research Laboratory 

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(CAFRL) flume complex under varying flow depths or a variety of test species, 

including American shad, alewife, blueback herring, white sucker, and other species, 

over two study years. 

PART I - Field Studies 

I. 1. – Field Site Descriptions 

I. 1. 1. Town Brook Field Site 

Town Brook is a first order stream with a watershed of 10 km2 located in Plymouth, 

Massachusetts (Milone and MacBroom 2001). It flows 3 km from its source at a 109 ha 

freshwater lake called Billington Sea to its mouth at Plymouth Harbor in Cape Cod Bay (Fig. I1). In 2003 as part of an effort to reconnect the river corridor with the historic spawning grounds 

at Billington Sea, the fourth dam upstream from the mouth of the river was removed and a 32 m 

long, streamwide (8 m) nature-like fishway of a rock ramp design with an overall 1:20 slope was 

constructed at the site. Migrating fish must ascend three structural fishways (small pool-andweir, Denil and Alaska steeppass fishways) at the three lower dams and negotiate three small 

mill ponds before reaching the nature-like fishway at river kilometer 1.6. (Reback et al 2004). A 

short distance upstream (154 m) of the nature like fishway is the 0.91 m high “Off Billington 

St.” dam with a small 14 m long pool-and-weir fishway with a slope of 1:7. 

I. 1. 2. East River Field Site 

East River is a second order stream with a watershed area of 53.1 km2 located in Guilford, 

Connecticut. Its source is the first order Iron Stream which originates in the village of Rockwell 

and flows into three impounded ponds called Upper Lake, Middle Lake, and Lower Lake, 

collectively known as “Guilford Lakes”. East River then flows 10 km from Lower Guilford 

Lake Dam to the mouth at Guilford Harbor in Long Island Sound (Fig. I-2). The Lower Guilford 

Lake Dam is divided into two concrete spillway structures with an earthen “island” in between. 

The west spillway is 3.35 m high, includes three 2.74 m wide spill gates fitted with stoplogs and 

a 53.3 cm wide sluice gate. It has an elevation head of 3.66 m. The east spillway includes three 

3.05 m long spill gates fitted with stop logs, and has an elevation head of 0.61 m. The river 

below Guilford Lake Dam is therefore split by the two spillways into the passage channel below 

the east spillway and the overflow channel below the west spillway, which rejoin 60 m below the 

dam. 

 

In 2001 the passage channel was field-modified to include fish passage including structural 

fishway and nature-like fishway features to provide access to spawning habitat in the Lower and 

Middle Lakes. The passage channel is 60 m long and the fish passage structures within the 

channel collectively are 48 m long with an average slope of approximately 1:15. The nature-like 

portions are 7 to 9 m wide and constructed of 0.6-1.0 m (2-3 ft) diameter boulders that create 13 

step pools. The substrate is bedrock granite and gravel. Two 3.1 m long, 0.6 m wide Alaska 

steeppass fishway sections are located within a steep portion of ledge 20 m downstream of the 

base of the dam, and at the dam itself. One section of steeppass fishway is embedded in bedrock 

halfway up the fishway (this area presented difficulties in establishment of nature-like features 

due to the bedrock substrate and localized excessively steep slope). The other section of 

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steeppass fishway is located at the dam at the top of the bypass channel, and provides the final 

passage reach from the top of the bypass into the headpond, and maintaining passability under 

fluctuations in headpond level of approximately 0.5 m. Additional flow into the bypass channel 

comes from spill over the dam crest, which is regulated by 0.23 m (9 in) high stoplogs. Fish are 

unable to pass directly from the bypass channel over the dam crest due to the 0.61 m (24 in) 

vertical drop below the dam crest; all fish must exit the channel via the steeppass fishway section 

(which was installed to provide adequate passage conditions under varying headpond conditions 

from presence/absence of dam crest stoplogs). Downstream of the study area, migrating fish 

encounter two ponds and one structural (Denil) fishway before reaching the entrance to the 

Lower Guilford Lake Dam and passage channel at river kilometer 9. No fish passage is provided 

over the west spillway of the Guilford Lake Dam. 

I. 2. Methods 

I. 2. 1. PIT System 

Movements of alewife through the two study sites were quantified using passive integrated 

transponder (PIT) telemetry as described by Castro-Santos et al. (1996). Instream antennas were 

constructed with single loops of 4-gauge insulated welding wire and ranged from 4 to 8 m in 

length across each study passageway. Antennas inside the structural fishways were constructed 

with 12 gauge THHN insulated copper wire encased in PVC tubing. All antennas were tuned to 

resonate at 132.4 kHz to maximize read range and were connected to Texas Instruments Radio 

Frequency Identification System Series 2000 readers enclosed in a weatherproof box. Readers 

were configured to gather data at a rate of 10-12 reads per second and were powered by a DC 

power supply. The maximum distance a tag could be read from the antenna loop ranged from 30-

40 cm from the plane of the antenna loop. When a fish was detected by an antenna, the date, 

time, fish identification number, and antenna number was recorded by a data logging computer. 

Antennas were tested periodically with a test tag attached to the end of a hand-held pole.

Detection records for each fish were examined and missed detections were identified if a fish 

was known to have passed at an antenna upstream of the antenna in question. Efficiency was 

calculated for each antenna by dividing the number of fish known to have passed the antenna 

(determined by detections at other antennas) by the number of fish that were actually detected at 

the antenna. 

I. 2. 2. Antenna Placement 

At Town Brook a 180 m stretch of river was monitored with eight antennas. Four antennas were 

placed across the width of the nature-like fishway, two full-channel-width antennas were 

installed between the nature-like fishway and the Off Billington St. Dam and two antennas were 

placed at the entrance and exit weirs of the pool-and-weir fishway. (Fig. I-1). At East River the 

approach to the lower Guilford Lake Dam was similarly monitored with ten full-channel-width 

antennas. Antennas were placed across the entrances of the overflow channel and passage 

channel to monitor route choice. One antenna was placed at the entrance of the nature-like 

section and three others at other points along the nature-like section of the passage channel. Four 

antennas monitored the entrances and exits of the two steeppass fishways (Fig. I-2). 

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I. 2. 3. Fish Collection and Tagging 

At Town Brook, a total of 400 alewife were collected and tagged with 23 mm PIT tags (internal 

implantation; see Sullivan 2004 for methodology) at the commercial fish weir at Newfield Street 

Dam (914 m downstream from the entrance to the nature-like fishway) over a period of 27 d 

during daylight hours. Fish were netted from an enclosed area by hand and for each fish the fork 

length, sex, and percentage of scale loss was recorded. Fish with more than 50% scale loss were 

released without a tag. On April 19th 100 fish were tagged and released. Subsequent tagging 

events were completed in batches of 50 fish on 4/26, 5/1, 5/5, 5/8, 5/12, and 5/15. Tagged fish 

were immediately released into the headpond above the Newfield Street Dam and were allowed 

to enter the nature-like fishway volitionally. The PIT tags were numbered from 20063000 to 

20063399. 

At the East River site, a total of 393 alewife were collected and tagged with 23mm PIT tags 

using the same methodology as for Town Brook below the Capello Pond Dam over a period of 

38 days during daylight and evening hours. Collections were made using a weir constructed of 

1.9 cm square mesh Trical netting with steel rebar supports that was installed at a 45 degree 

angle across the full width of the river leading fish into a 4.57 m by 2.13 m trap box also 

constructed from netting and steel rebar supports . Trapped fish were then netted by hand, 

tagged, measured, examined for sex and scale loss, transported by bucket and released at the base 

of Capello Pond 762 meters below the entrance to the nature-like fishway. Fish with more than 

50% scale loss were released without a tag. Released fish were allowed to enter the nature like 

fishway volitionally. On March 30 seven fish were tagged and released. Due to weather 

conditions the next tagging event did not occur until April 21. Between April 21 and April 23, 

344 fish were tagged and released. An additional 34 fish were tagged on May 4 and 8 fish on 

May 7th. The PIT tags were numbered from 20073000 to 20073392. 

I. 2. 4. Data Collection 

Water level and temperature data were collected hourly at both sites using Onset HOBO Model 

U20-001-04 water level dataloggers. A total of three data loggers were installed at Town Brook 

at the entrance and exit of the nature-like fishway and above water in the weathertight box 

containing the PIT readers. The lower East River bypass channel was monitored by three data 

loggers installed in the headpond, at the entrance of the passage corridor, and in the weathertight 

box. The loggers installed in the weathertight enclosures were used to record atmospheric 

pressure that was later used to derive absolute water level. As a reference, water temperature and 

relative level were measured manually using a digital thermometer and staff gauges at weekly 

intervals. At East River hourly flow through the passage channel was calculated using a formula 

that incorporated the hourly water level measurements in the headpond and water level at the 

eastern and western weirs and the upper steeppass fishway. Hydraulic gradelines at both sites 

and elevations of individual antennas were measured with a rod and level. 

Tag detection data files produced by the datalogging computer were downloaded every few days. 

At Town Brook the system began monitoring on April 19, 2006 but due to a computer 

malfunction stopped recording data for 117 h from April 19, 2006 to April 24, 2006; antennas 

then operated continuously from April 24 to July 6, 2006. At East River the system began 

monitoring on March 23, 2007. Due to a computer malfunction the system stopped recording 

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data for 60 h from April 27 to April 30. The antennas then operated continuously from April 30, 

2007 to June 12, 2007. 

I. 2. 5. Data Analysis 

Telemetry data files from the PIT recording system were imported into a Microsoft Access 

database and condensed by converting consecutive reads at individual antennas of under a 

second to single presences. For each site passage performance was evaluated by examining 

passage efficiency, attraction efficiency, number of attempts, and transit time. Passage efficiency 

was quantified as the percentage of fish that entered a structure or river reach that successfully 

passed the entire structure or reach. Ninety-five percent confidence intervals for percent passage 

estimates at each antenna were calculated using the binomial distribution. Attraction efficiency 

for the East River passage channel was quantified as the percentage of fish that were detected at 

the first antenna of the passage channel (Antenna 2) that were subsequently detected at the 

entrance to the lower nature-like fishway section (Antenna 3). 

Detections of individual fish were grouped into “attempts” in order to quantify multiple efforts to 

ascend a fishway structure or reach as well as determine on what attempt the fish completely 

passed the entire structure or reach. At both sites movement data was sorted by individual fish 

and time and then the lags (amount of time elapsed) between presences at the antennas 

monitoring the nature-like fish passes were calculated. The distribution of these lag times was 

then examined. At Town Brook it was determined that because more than 50% of the lag times 

were under 15 minutes, a lag of 15 min or more between presences at antenna 1 indicated that a 

fish likely had left the area of the fishway entrance and then returned to make another attempt. 

At East River the lag time distribution was more right-skewed (longer average lag times), 

therefore a new attempt was assigned if a fish went undetected for more than 95 min between 

detections at Antenna 3, or antenna 4 to accommodate the possibility of being missed at Antenna 

3 (Figure 1-2). Transit times were then calculated within attempts. 

Transit times through fish passage structures or reaches were defined as the amount of time it 

took for a fish to travel through the structure or reach as delimited by upper and lower antennas, 

calculated by subtracting the time of the first detection at the lower antenna from the time of the 

first detection at the upper antenna. Transit times through passage structures or reaches were 

calculated only for fish that successfully completed the structure or reach. Because transit times 

were right skewed, median values are reported. A one-way analysis of variance (ANOVA) was 

used to test for differences between the natural log of transit times for males and females. 

Multiple linear regression analysis was used at each site to examine how transit times through 

the nature-like passes were affected by fish length, scale loss, time at liberty, water level, 

temperature, and the interaction between scale loss and length. The distribution of transit times 

was skewed so transit times were transformed to their natural log. Time at liberty is defined as 

the amount of time that elapsed between when a fish was tagged and released and when it was 

first detected at an antenna. Length and scale loss were standardized to a mean of zero and a 

standard deviation of one and the interaction term is the product of the two standardized 

variables. This was done to minimize the correlation between the single variables and the 

interaction of length and scale loss. An arcsine square root transformation was applied to the 

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proportion of scale loss. The top five models chosen by Aikake’s Information Criterion (AIC) 

are reported. 

First attempts of successful and unsuccessful fish through individual pairs of antennas were 

calculated by subtracting the last detection at the first antenna from the first detection at the next 

antenna. These are minimum times and can be representative of behaviors of fish traveling 

directly (without hesitation) or indirectly (hesitating, milling) from antenna to antenna. 

Horizontal and vertical (elevation gain) rate of travel was calculated by dividing the horizontal 

and vertical distance in meters between antennas by the amount of time it took for the fish to 

pass between those antennas. 

Estimates of survivor functions and hazard rates for passage through the fishways were 

calculated using the Kaplan-Meier method of event time analysis (Castro-Santos & Haro 2003). 

Cox’s proportional hazards regression analyses was employed to examine the effects of sex, 

scale loss, and length on the maximum distance of ascent (Castro-Santos & Haro 2003). In order 

to examine the effect of slope on hazard rates through individual sections of passage structures or 

reaches a linear regression analysis was performed.

For the data from East River multiple logistic regression analyses were performed to examine the 

probability of passing or failing to pass at Antennas 3 and 8 as a function of sex, length, 

proportion of scale loss, temperature at the time of first detection at the antenna, and flow at the 

time of first detection at the antenna. At each antenna analyses were performed for the first and 

second attempts. Models that included all covariates were compared to reduced models and the 

top models were chosen by lowest AIC scores. 

Downstream transit times were calculated by subtracting the time of the last presence at the most 

downstream antenna from the first presence at the most upstream antenna of the fishways. A 

fish was considered to be moving downstream if it was detected above at the uppermost antenna 

of a PIT antenna array and then detected in a downstream sequence at all of the antennas. 

I. 3. Results 

I. 3. 1. Town Brook 

Hydraulic gradeline data for the Town Brook study site are shown in Fig. I-3. Water 

temperatures at the Town Brook site during the study period ranged from 10.0 to 24.6 °C, and 

showed a diel fluctuation of approximately 2°C to 4°C on most days (Fig. I-4). Water levels at 

the upstream datalogger ranged from 0.23 to 0.34 m relative depth (Fig. I-4). 

Data were collected from 43% (175) of the 400 fish tagged. Fate of undetected fish is unknown; 

it is possible that they either stopped migrating once they reached the impoundment above 

Newfield Street Dam (from handling tagging effects or simply to spawn), lost their tags, or 

succumbed to handling/tagging mortality. However due to a monitoring system malfunction the 

movements of the first 100 fish tagged and released went unrecorded for 117 hours. One-way 

ANOVA analysis of the movements of the six later releases showed that the fish staged 

significantly more attempts in the first 117 hours than the subsequent 117 hours (df=158 

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F=102.45, p=<.0001). Because transit time and attempt rate data are dependent on complete 

histories of transits through the nature-like fishway, data from the first 100 fish released were 

omitted from further analyses. Results discussed from this point forward are based on the sample 

of 103 fish that were detected from the releases made on 4/26 through 5/15. 

Lengths of the 103 fish included in analyses ranged from 212 mm to 263 mm, scale loss from 0 

to 50% and the male to female ratio was 1:0.90. Forty days of movements were observed during 

the period between April 26, 2006 and June 4, 2006. Antenna efficiency during this period 

ranged from 99% to 100%. 

Passage success through the Town Brook nature-like fishway was high (Fig. I-5); 94% (N=97, 

95% CI 89.1% - 97.8%) of fish that entered successfully completed their ascent through it.

Sixty-six percent of the fish (N=68) reached their maximum distance of ascent above the naturelike fishway at Antenna 6. Only seven fish reached their maximum distance of ascent within the 

nature-like fishway. Survival estimates for intervals between antennas remained high until the 

section between Antennas 6 and 7, indicating a passage problem at the upstream pool-and-weir 

fishway. Cox’s proportional hazards regression indicated no significant relationship between 

sex, length, or proportion of scale loss on the maximum distance of ascent. Attraction efficiency 

could not be calculated for Town Brook because an antenna was not placed below the entrance 

of the nature-like fishway in order to detect the fish that were available to pass. 

Of the 97 successful fish, 93.8% (91) completed the nature-like fishway section on their first 

attempt (Fig. I-5). Five fish completed the section on their second attempt and one fish on the 

third attempt. On the first attempt Antenna 6 was the maximum distance of ascent for 63.11% 

(65) of the fish. Eighty-nine percent of all fish (N=92) began their first attempt during daylight 

hours. 

Transit times of successful fish through the entire nature-like section ranged from 4.85 min to 

44.08 min with a median time of 11.09 min (Fig. I-6). One-way ANOVA analysis found no 

significant difference in transit times between males and females (df=1, F=.29 p=.5903). The 

top multiple regression model (F=3.86, df=5 P=.0034) explained the variation in transit time as a 

function of standardized length, standardized scale loss, and temperature at the time the 

successful attempt was begun. Temperature and length were negatively correlated with transit 

time and scale loss was positively correlated with transit time. The model explained 13.84% of 

the variation and standardized partial regression coefficients indicate that length (b=-0.32) has 

the greatest effect and temperature (b=-0.21) and scale loss (b= 0.21) have equal effects. 

Transit times between antenna pairs in the nature-like fishway section were variable (Fig. I-7). 

Fish took the longest to swim between Antennas 3 and 4 but assuming a constant rate of travel, 

traveled the fastest horizontally through the first 17 m of the nature-like fishway section between 

Antennas 1 and 2 (median 4.07 m·min-1 -1 ) and Antennas 2 and 3 (median 4.04 m·min ). Fish 

traveled the slowest through Antennas 3 to 4 with a median of 2.85 m·min-1. Vertically, the fish 

ascended the fastest through the section between Antennas 1 and 3, which is the steepest part of 

the nature-like fishway section.

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At the upstream pool-and-weir fishway, 96 fish were detected at Antenna 6 and were considered 

available to pass. Twenty-eight of those fish found the entrance of the pool-and-weir fishway, 

resulting in an attraction efficiency of 29.17% for the pool-and-weir fishway. Six fish 

successfully completed the pool-and-weir fishway giving it a passage efficiency of 21.43%. 

Transit time from Antenna 7 to 8 ranged from 11.9 to 30.5 sec. Fish were visually observed 

congregating below the spillway of the dam and attempting to swim through the spillway flow. 

Downstream movement through the nature-like fishway was observed after two different events. 

If detections from the first release group of fish are included, ten fish were known to have passed 

upstream of the pool-and-weir fishway and then moved back downstream 8 to 27 d later. The 

downstream transit times of these fish through the nature-like fishway ranged from 17 to 96 sec. 

Downstream movements through the nature-like fishway were also observed from fish that only 

reached Antenna 6 and then moved downstream. This behavior was recorded for 86 fish and 

their transit times through the nature-like fishway ranged from 17.2 sec to 11.1 min with a 

median of 72.4 sec. Transit times from the last detection at Antenna 5 to the last detection at 

Antenna 4 ranged from 94 sec to 3.5 h with a median of 5.0 min. 

I. 3. 2. East River 

Hydraulic gradeline data for the East River study site are shown in Fig. I-3. Water temperatures 

at the East River site ranged from 11.1 °C to 26.4°C throughout the monitoring period, and 

showed a diel fluctuation of approximately 1°C to 2°C on most days (Fig. I-4). Water levels at 

the downstream datalogger (located in a deep pool at the downstream end of the bypass channel) 

ranged from 0.13 to 0.54 m relative depth. 

PIT data were collected from 59.5% (234) of the fish tagged. Their lengths ranged from 201 to 

271 mm, scale loss ranged from 0 to 40% and the male to female ratio was 1:0.55. Fifty-two 

days of movement were observed from April 22, 2007 to June 12, 2007. Antenna efficiency for 

this period ranged from 89.25 to 100%. 

The monitoring system did not operate for 60 h from April 27 to April 30 during a high flow 

event that inundated the antennas and tuning boxes. When the system was repaired and turned 

back on again at 12:03 on April 30th, no fish were detected at any antennas. The first detections 

of fish after this event occurred several h later and were in the lower portion of the antenna array 

at Antennas 1 or 2. The decision was made to retain all of the data from the 204 fish that were 

released before this high flow event. Over the entire monitoring period, of the 60 fish that did 

successfully ascend to the pond and were detected descending through the antenna array, only 

two fish spent less than three days in lower Guilford Lake before moving downstream. 

Considering this information it is unlikely that fish ascended and descended through the antenna 

array while the system was not operating. 

Attraction efficiency of the passage channel was high. Of the 231 fish detected at the entrance of 

the passage channel at Antenna 2, 90.6% (212) entered the lower nature-like fishway section at 

Antenna 3. Ninety-four percent of detected fish (221) were detected at the entrance to the 

overflow channel (Antenna 1) but only three of these fish were detected only at Antenna 1 and 

not in the passage channel. 

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Passage success through the entire passage channel was modest. Of the 212 fish that were 

detected at Antenna 3, 40.6% (N=86, 95% CI 34.4% - 47.5%) completed the nature-like and 

steeppass sections and reached Lower Guilford Lake (Fig. I-5). Seventy-eight percent (67) of 

successful fish were male and 22% (19) were female. For 25% (54) of fish that entered the 

passage channel, Antenna 3 was the maximum antenna ascended to. These fish successfully 

found the entrance to the lower nature-like fishway section but were either unable, or chose not 

to ascend further. Twenty-four percent (51) of fish reached their maximum antenna near the top 

of the upper nature-like fishway at Antenna 8. 

On the first attempt 64.62% (137) of fish ascended no further than the lower nature-like fishway 

section at Antenna 3 and only 8.96% (19) successfully ascended the entire passage channel. Of 

the 86 fish that successfully ascended to Lower Guilford Lake, 22.09% (19) of fish completed 

the passage channel on their first attempt, 36.04% (31) on their second, and 15.12% (13) on their 

third. The remaining 13 fish made between four and eight attempts to complete the passage 

channel. Seventy-two percent (153) of fish approached the passage channel during daylight 

hours. 

Transit times of successful fish (86) through the entire passage channel (both nature-like and 

steeppass sections) ranged from 19.6 min to over 3 d (Fig. I-6). The median passage time was 75 

min and 90% of the successful fish passed in 7 h. A one-way ANOVA analysis found no 

significant difference in transit times between males and females (df=1, F=0.0 p=.9611). Model 

1 (F=6.5 df=2 p=.0025) best explained the variation in transit time and included the time elapsed 

between release and detection and the positive interaction between scale loss and length. Release 

to detection time (p=.0009) and the interaction of scale loss and length (p=.0657) were positively 

correlated with transit times. The model explained 12.8% of the variation and standard partial 

regression coefficients indicated that release to detection time (b=0.39) is approximately twice as 

important as the length scale loss (b=0.21) interaction. 

Median transit times between individual pairs of antennas through the nature-like section ranged 

from 44 sec between Antennas 7 and 8 to 19 min between Antennas 8 to 9 (Fig. I-7). Fish 

travelled the fastest horizontally between Antennas 7 to 8 (median=7.94 m·min-1) and the 

slowest from Antennas 8 to 9 (median=0.099 m·min-1; Fig. I-7). Median times of elevation gain 

ranged from 0.328 m·min-1 -1 between Antennas 7 to 8 to 0.003 m·min at Antennas 3 to 4 (Fig. I7). Median transit times through the steeppass sections were 1.7 sec for the downstream 

steeppass and 3.02 sec for the upstream steeppass. 

Sixty-six percent (57) of the 86 fish that successfully ascended to Lower Guilford Lake were 

detected moving downstream through the passage channel. Time spent in the lake ranged from 1 

to 41 d with a median residence time of 16.5 d. Downstream transit times through the passage 

channel ranged from 1.7 min to 23.2 min with a median of 8.4 min. Downstream transit times 

through the two steeppass sections were 2.28 sec and 1.74 sec. Transit times for the nature-like 

sections ranged from 7.29 sec (Antennas 9 to 8) to 295.03 sec (Antennas 7 to 6). Six percent (5) 

of successful fish descended over the western spillway through the overflow channel and were 

detected at Antenna 1; one of those fish was initially detected at Antenna 10 (exit of upper 

steeppass fishway) but was later detected descending through the overflow channel 8 d later. 

This fish likely explored the steeppass fishway as an exit route from the lake, but ultimately did 

11
not enter the fishway and searched for other downstream passage routes from the lake before 

descending over the east spillway. Twenty-eight percent (24) of successful fish were not 

detected again after the last upstream presence at Antenna 10. 

I. 3. 3. Effect of Fishway Slope on Passage 

Linear regression analysis found a significant (p=0.0041) effect of inter-antenna slope on hazard 

rate for nature-like fishway sections pooled from both sites (Fig. I-8). However, this relationship 

was based on only 6 data points and was not significant when the data point from the highest 

slope section (East River, Antennas 3-4) was omitted from the dataset. 

12
Figure I-1. Upper panel: location of Town Brook study site, Plymouth, Massachusetts. Lower photos: left - 

Billington Street Dam and defunct structural (pool-and-weir) fishway prior to removal; right - nature-like fishway 

installation after removal of Billington Street Dam, at moderate spring flows. Note antennas (Antenna 3 and 

Antenna 4) spanning the fishway. 

Plymouth

Harbor

0 500 meters 

Nature-like 

fishway study 

site

Off 

Billington

St. Dam 

Gulf of 

Maine

Billington

Sea 

(freshwater lake)

Fish 

tagging 

site

Fish 

release 

site

0 15 m

A1

A2 A3

A4

A5

A6 A7

A8

Dam 

Pooland-weir 

fishway

0 50 km 

Nature-like 

fishway

N

Town 

Brook

N

N

Plymouth

Harbor

0 500 meters 

Nature-like 

fishway study 

site

Off 

Billington

St. Dam 

Gulf of 

Maine

Billington

Sea 

(freshwater lake)

Fish 

tagging 

site

Fish 

release 

site

0 15 m

A1

A2 A3

A4

A5

A6 A7

A8

Dam 

Pooland-weir 

fishway

0 50 km 

Nature-like 

fishway

N

Town 

Brook

N

N

13
Figure I-2. Upper panels: location and PIT antenna layout of East River study site, Guilford Lakes, Connecticut 

(not to exact scale). Lower photos: left photo - East River looking upstream towards at junction of overflow and 

passage channels; note locations of Antennas 1 and 2 (yellow ropes spanning channels with safety signage); right 

photo: bypass channel looking upstream from lower steeppass fishway.

Study Site

Capello

Pond

Fish trap & 

tagging site

Fish release 

site

Long Island 

Sound

0 1 km

N

DAM

PASSAGE 

CHANNEL

OVERFLOW 

CHANNEL

A1

A2

A3

A4

A6 A7

A8

A9

A10

Lower

NLF

Upper

Steeppass

Fishway

Long Island 

Sound

Atlantic Ocean

East River, 

Guilford

Overflow 

Channel

East

Firs

spillway

t Guilford Lake

West

spillway

Passage 

Channel

N

N

0 10 m

rock

ledge

Upper

NLF

Lower

Steeppass

Fishway

A5

Study Site

Capello

Pond

Fish trap & 

tagging site

Fish release 

site

Long Island 

Sound

0 1 km

N

DAM

A1

A2

A3

A4

A6 A7

A8

A9

A10

Lower

NLF

Upper

Steeppass

Fishway

Long Island 

Sound

Atlantic Ocean

East River, 

Guilford

Overflow 

Channel

East

Firs

spillway

t Guilford Lake

West

spillway

N

Passage 

Channel N

0 10 m

Upper

NLF

rock

ledge

A5 Lower

Steeppass

Fishway

14
Figure I-3. Hydraulic gradelines between antennas (numbers) and resultant slopes (%) for Town Brook and East 

River study sites. 

A - Town Brook

Horizontal Distance (m)

0 20 40 60 80 100 120 140 160 180

Vertical Distance (m)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

3

Horizontal Distance (m)

0 10 20 30 40 50 60

Vertical Distance (m)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

4

5

6

7 8

9

10

7.92%

4.77%

29.63%

5.43%

3.54%

18.52%

9.59%

B - East River

1

2

3

4

5

67

8

4.26%

5.08%

3.18%

1.01%

1.43%

.01%

14.29%

15
16

Figure I-4. Time series of water temperature and level recorded at the Town Brook site and water temperature and 

flow estimated from level data from the East River site. Temperature 

o

C

Town Brook 

8

10

12

14

16

18

20

22

24

26

28

Water Level (m)

East River 

Time

5/1 6/1 

Temperature °C

8

10

12

14

16

18

20

22

24

26

28

Flow m3 . sec-1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Temperature oC 

Nature-like Flow m3 . sec

-1

Temperature oC 

Water Level (m) 0.22

0.24

0.26

0.28

0.30

0.32

0.34

0.36
Figure I-5. Proportion of detected fish passing each antenna for Town Brook (left panels) and East River (right panels) sites. Upper p

reaching each antenna on their first attempt. Lower panel: proportion of fish reaching each antenna over all attempts. Vertical bars ind

intervals. Areas shaded in green are nature-like fishway (NLF) sections of the study reaches; blue shaded areas are pool-and-weir (P&W

(Town Brook) and yellow shaded areas are steeppass (SP) fishway sections (East River).

First Attempt

Proportion Passing

0.00.10.20.30.40.50.60.70.80.91.0

All Attempts

Vertical Distance (m)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

Proportion Passing

0.00.10.20.30.40.50.60.70.80.91.0

1 2 3 4 5 6

7

8

1 2 3 4 5 6

7

8

Nature-like 

fish pass

Nature-like 

fish pass

All A

Vertical Distance (m)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4

Proportion Passing

0.00.10.20.30.40.50.60.70.80.91.0

First A

Proportion Passing

0.00.10.20.30.40.50.60.70.80.91.0 3

4

5 6 7 8

9 10

3

4 5 6 7 8

9 10

SP

SP

SP

SP

Town Brook East River

NLF P&W NLF SP NLF SP

First Attempt

Proportion Passing

0.00.10.20.30.40.50.60.70.80.91.0

All Attempts

Vertical Distance (m)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

Proportion Passing

0.00.10.20.30.40.50.60.70.80.91.0

1 2 3 4 5 6

7

8

1 2 3 4 5 6

7

8

Nature-like 

fish pass

Nature-like 

fish pass

All A

Vertical Distance (m)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4

Proportion Passing

0.00.10.20.30.40.50.60.70.80.91.0

First A

Proportion Passing

0.00.10.20.30.40.50.60.70.80.91.0 3

4

5 6 7 8

9 10

3

4 5 6 7 8

9 10

SP

SP

SP

SP

Town Brook East River

NLF P&W NLF SP NLF SP

17
Figure I-6. Distributions of transit times through nature-like fishway sections at Town Brook and East River sites. 

East River transit times include time to pass both steeppass sections. Note difference in scales of x-axes. 

Minutes

0 5 10 15 20 25 30 35 40 45 50 55 60

Percent of Fish

0

5

10

15

20

25

30

35

40

45

50

Minutes

0 720 1440 2880 3600 4320 5040

Percent of Fish

0

5

10

15

20

25

30

35

40

45

50

Town Brook N=97

East River N=86

18
Figure I-7. Distribution of overall inter-antenna transit times for the nature-like fishway sections at the Town 

Brook (left panel) and East River (right panel) sites and resultant horizontal and vertical (elevation gain) rates of 

travel. Horizontal line within box = median; box = 25th and 75th percentiles; whiskers = 5th and 95th percentiles; dots 

= data points from individual fish (range). Note variation in y-axis scales. Minutes

0

2

4

6

8

10

12

14

16

18

20

22

24

Horizontal m·min-1

0

5

10

15

20

25

30

35

1-2

N=103

Vertical m·min-1

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

2-3

N=92

3-4

N=91

Minutes

0

60

120

180

240

300

360

420

480

540

Horizontal m·min-1

0

5

10

15

20

25

30

35

3-4

N=138

Vertical m·min-1

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4-5

N=121

6-7

N=125

7-8

N=142

8-9

N=86

19
Figure I-8. Regression of fishway slope on hazard rate. Data are combined from inter-antenna sections from Town 

Brook (TB) and East River (ER) nature-like fish passes. 

y=6.18x+ -.23

Slope

0.02 0.04 0.06 0.08 0.10

Hazard Rate

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

ER 

3-4

ER 

4-5

ER 

7-8

TB

2-3 TB

1-2

TB

3-4

20
PART II. Laboratory Studies 

II. 1. Experimental Design and Facility 

Two side-by-side nature-like fishway designs were tested in the 6.10 m (20 ft) width flume of the 

CAFRL flume complex; one in a rock weir design and the other in a perturbation boulder 

(randomized boulder placement) design (Figs. II-1, II-2). Each fishway was 3.05 m (10 ft) in 

width and 33.5 m (110 ft) in length, with a 1:20 slope. Design of the side-by-side fishways 

allowed us to evaluate two designs simultaneously, ensuring true replication of comparative tests 

and reducing down-time between tests required by repositioning of rock structures (larger 

boulders were fabricated from fiberglass, facilitating repositioning by hand). In 2006 tests, two 

rock placement designs were tested: for the perturbation boulder design, uniformly spaced rocks 

and rocks spaced to create a meandering central channel; for the rock weir design, low rocks in 

each weir were positioned to create a meandering channel (Configuration A) or an in-line 

channel (Configuration B). In 2007, only rock Configuration A was tested. Test flow depths 

were 0.42 m (16 in), 0.51 m (20 in), 0.61 m (24 in), and 0.76 m (30 in) (invert of base of rocks to 

water surface upstream of rocks; mean pool depths were slightly less). 

II. 2. Methods 

II. 2. 1. Hydraulic Measurement 

Point velocity measurements were taken over an 8 by 8 horizontal grid (0.38 to 0.46 m between 

points) in representative pools with total approximate dimensions of 3.05 m (10 ft) by 3.7 m (12 

ft) with developed flow. Measurements were taken at each point at four vertical depths 

distributed evenly over the total depth. A Marsh McBirney two dimensional electromagnetic 

velocity meter with a 3.8 cm diameter spherical probe was used for point velocity measurements. 

Flow ratings of the fishways at all test conditions were also measured using a sharp-crested 

rating weir at the downstream end of each fishway. Total flow (Q) and energy dissipation factor 

(EDF) were also calculated for each flow condition. 

II. 2. 2. Fish Collection and Passage Monitoring 

For both test years, American shad were collected and transported to the CAFRL facility from 

the Holyoke Dam fishlift; all other species (except alewife in 2006) were collected and 

transported from the lower Connecticut River mainstem and tributaries (Farmington River, 

Windsor Locks) by boat electrofishing. Alewife tested in 2006 were collected and transported 

from Town Brook (Plymouth, Massachusetts) at the Jenny Grist Mill Dam tailwater. Passage of 

fish through the fishways was monitored by passive integrated transponder (PIT) telemetry, with 

PIT tags attached externally to fish and eight antennas placed at regular intervals along the length 

of each fishway, using the method of Castro-Santos et al. 1996. Fish were allowed to select 

either fishway from a central tailwater pool. Trials were run for 3 to 6 h periods in 2006, and for 

24 h periods in 2007. 

II. 2. 3. Data Analysis 

PIT detection data were imported into a Microsoft Access database and condensed into presences 

by reducing consecutive reads at individual antennas of less than a second into single presences 

of individual fish at an antenna. Passage data were evaluated to determine fishway selection, 

21
passage attempts (detection by at least one PIT antenna), and maximum distance ascended in 

each fishway (Dmax) over all attempts. Data were pooled for individuals of each species to derive 

Dmax curves under each test (flow) condition. Data from species with low sample sizes and/or 

few detections (<5 per trial) were not analyzed with respect to Dmax. 

II. 3. Results 

II. 3. 1. Hydraulic Evaluation 

Summaries of hydraulic data from both fishway designs (two rock configurations at the three 

nominal flow depths) are given in Table II-1. No hydraulic data were collected from the 

fishways subject to the 0.41 m depth condition or Configuration B at the 0.51 m depth condition. 

Three-dimensional flow field plots from the two fishways under both configurations and 0.61 

and 0.76 flow depths are given in Appendix 1. 

Increasing flows increased maximum velocities within both fishway designs (with velocities 

highest at slots between rocks in the perturbation boulder design, or over low rocks in the rock 

weir design). Under the highest flow depths, these slot/weir velocities approached 3 m ·sec-1, 

exceeding maximum velocities permissible in some structural fishway designs. Reconfiguration 

of rocks to create a meandering central channel in the perturbation boulder fishway or an in-line 

configuration of low rocks in the rock weir fishway modestly increased maximum velocities. 

Energy dissipation factors in both fishways were high (range 166-319 watts · m-3 [3.5-6.7 ft-lbs · 

sec-1 · (ft3)

-1 ]); in all cases exceeding the 150 watts · m-3 (3.2 ft-lbs · sec-1 · (ft3 -1 ) ) maximum for 

shad pool-and-weir fishways recommended by Larinier and Travade (2002).

II. 3. 2. Biological Evaluation 

Numbers of tagged test fish detected at PIT antennas for the two fishways under different flow 

depths are given in Table II-2; note that sample sizes for some species are very low, largely due 

to limited numbers of fish collected. Not all species were tested at all depths; only American 

shad and blueback herring were tested at the 0.41 m depth. Graphical results of 2006 Dmax curves 

(Configurations A and B) with American shad and alewife are given in Fig. II-3; comparative 

2007 data (Configuration A only) for shad, alewife and other species are given in Fig. II-4. 

Both years of testing yielded percent passage of American shad generally over 50% throughout 

the total length of the experimental fishway under most conditions. There appeared to be no 

consistent preference of fishway type by shad, and upstream passage performance of shad was 

similar for both designs, regardless of flow depth or rock configuration. We noted that in the 

rock weir design, shad appeared to seek the deepest portion of pools as resting areas, especially 

under low flow conditions. 

Due to poor attempt and passage performance of alewives in 2006, we elected to test blueback 

herring in 2007 collected via electrofishing from the more local lower Connecticut River or its 

tributaries to minimize potential transport and interbasin transfer effects on migratory 

motivation. However, performance of 2007 blueback herring was roughly equivalent that of 

2006 alewives, with less than 50% of fish ascending to the top of the fishways. The cause of 

22
limited motivation in both species of river herring continues to be unknown, but collection 

method (including electrofishing) and handling/transport stress may be dominant factors. Effects 

of decrease in water temperature over ambient temperatures upon introduction into the CAFRL 

facility or other reaction to novel water seem to be less important based on 2007 results. 

No consistent trends in effect of fishway design, configuration, or flow depth were noted for 

alewife or blueback herring. However, the lowest test depth of 0.41 m (one trial in 2007) 

resulted in the best overall passage performance of blueback herring (~40%) recorded for this 

species or alewife under any condition. Effect of flow depth in passage performance of fish with 

larger sample sizes (American shad, blueback herring, white sucker, white perch) appeared to be 

relatively minor; slightly better performance was noted at the higher depths, but this trend was 

not consistent among species or fishway types. Observations in 2007 of shad behavior in the two 

fishways (fishway selection, reaction to shallow pool depth, general transit time) appeared to be 

similar to 2006. 

Passage performance of other species (smallmouth bass, yellow perch, black crappie, channel 

catfish, common carp, fallfish) tested was variable (a few individuals of some of these other 

species were able to ascend the entire fishway, while others did not even make attempts). 

However, low sample sizes of these other species that were tested make these results statistically 

inconclusive. 

PART III - Discussion and Summary 

Based on results from the field study, alewives appear to be able to pass nature-like fishways of 

the Town Brook design with little difficulty. Some questions remain about effects of fishway 

length; for most applications these fishway designs are best suited to low-head barriers, so 

typically nature-like fishways will be relatively short in total length. The East River fishway 

appeared to possess some specific bottlenecks possibly associated with its more pool-and-weir 

like design; overall gradient was higher (1:15) at East River than at Town Brook (1:20) and 

alewives may have had difficulty negotiating drops and/or high velocity zones between pools. 

Overall performance of the East River fishway is more difficult to interpret due to the integrated 

steeppass fishways, but the basic design may be appropriate for some sites as long as pool drops 

and plunging flows can be minimized and kept relatively uniform. Data pooled from both 

fishways indicated an overall relationship between slope and passage performance, but the 

correlation was based on minimal data and may not necessarily be linear. From this study, the 

East River design might be viewed as representative of the upper limit for design criteria (slope, 

length, number of and drop per pool) for nature-like fishways constructed for alewife passage. 

The Town Brook nature-like fishway offers more conservative design criteria: 1:20 slope, 

minimal drop per pool, and uniform slope. Both fishway designs appear to allow effective and 

rapid downstream passage of postspawning adult alewives. 

The bypass design of the East River introduced some delay in passage as arriving fish explored 

both the passage and overflow channels. Full-stream-width passage structures such as Town 

Brook may therefore some advantage over bypass designs in that there are no competing flow 

attraction delays associated with full-stream-width designs. 

23
The laboratory experiments permitted more extensive evaluation of fishway design, flow, and 

rock configuration effects. Results with American shad and white sucker indicated that these 

two species can negotiate the fishway designs/lengths relatively well, generally with over 50% 

passing under most of the test conditions. No specific trends in the effects of fishway flow and 

configuration were noted for these species, at least under the range of flows and configurations 

tested. Performance of both species would probably be limited under more extreme (higher and 

lower) test flow conditions. As with the field studies, effects of fishway length for these designs 

remain unknown. Given that overall passage success for both species rarely exceeded 80% to 

90%, there may be limits to overall total length of these fishway designs at this design slope, if 

failure rates throughout the fishway are cumulative. However, it should be remembered that the 

1:20 test slope is still relatively high for this fishway design; passage of these and other species 

may be even higher if slopes were reduced to the more nominal 1:30 to 1:40 slopes (but fishway 

length would also be proportionally longer). 

No species exhibited an obvious trend in preference for one type of fishway over another. 

However, these analyses are still pending, and there may be some interaction between fishway 

flow depth, rock configuration, and fishway selection. It should be noted that most individuals 

made more than one attempt to ascend a fishway, and many made attempts to ascend both 

fishways. Entry of fish into a particular fishway design probably is related to attraction to 

entrance configuration and hydraulics, which deserves further study. It is unclear whether EDF 

per se affects passage in nature-like fishways; EDF values in the experimental fishways were 

significantly higher than values recommended for structural fishways for American shad 

(Larinier and Travade 2002), yet shad appeared to negotiate the nature-like fishways well. If 

EDF is a factor, it can be effectively reduced by either increasing pool volume (length, width, or 

depth) or decreasing water velocity entering the pool (i.e., reducing drop-per-pool, or effectively, 

slope). 

Passage of other species in the laboratory studies was less efficient. Results from the Town 

Brook and East River field studies, which evaluated nature-like fishways of similar design and 

slope to the flume prototypes, indicated that alewives (and possibly morphologically and 

behaviorally similar blueback herring) should have had little difficulty ascending the prototype 

fishway structures in the flume facility. Although a transport-handling effect may be the cause of 

this difference, and attempt rate was low for both species, we noted increased performance of 

blueback herring under the lowest (0.41 m depth) flow condition, suggesting that passage of this 

species (and possibly alewives as well) may be higher under flow depths lower than were tested. 

Passage of striped bass and white perch was also modest in both designs and configurations, and 

both species appeared to have better passage performance under low flow depths. Although 

these species are known to use structural fishways, little is known about their passage 

performance and relative migratory motivation when ascending fish passage structures, so it is 

difficult to gauge these results against a structural fishway standard. It is possible that these two 

species again require shallower depths and lower velocities to ascend these and other fishway 

designs. 

24
Figure II-1. Perturbation boulder and rock-weir nature-like passes evaluated at the CAFRL flume facility, showing 

two rock configurations (A and B) for each pass type (flow direction from top to bottom). Low rocks in rock weir 

pass are white. Red lines and numerals indicate approximate position and number of PIT tag antennas. 2007 

biological evaluations tested configuration A of both fishway types only. 

Perturbation Boulder Rock Weir

8

1

2

3

4

5

6

7

Config.

A

Config.

B

Config.

A

Config.

B

0 5 m

25
Figure II-2. Left: installation of nature-like fishways in the CAFRL flume facility (dewatered). Right: nature-like 

fishways in operation at 0.76 m flow depth.

26
27

Table II-1. Hydraulic data for Rock Weir and Perturbation Boulder fishways under two rock configurations (2006 

tests) and three test depths. 2007 biological evaluations tested configuration A of both fishway types only 

 Rock Weir 

Perturbation 

Boulder 

Rock 

Configuration 

Test 

(Headpond) 

Depth, m 

(in) 

Q, 

m3

/sec 

(ft3

/sec)

Pool 

Depth, 

m (in) 

Pool 

Volume, 

m3

 (ft3) 

EDF 

watts/m3

((ftlbs/sec)/ft3

)

Maximum 

velocity, 

m/sec 

(ft/sec) 

Maximum 

velocity, 

m/sec 

(ft/sec) 

A 0.51 (20) 

0.44 

(15.4) 

0.43 

(16.8) 

4.53 

(160) 172.4 (3.6) 2.26 (7.4) 1.98 (6.5) 

A 0.61 (24) 

0.68 

(24.1) 

0.51 

(19.9) 

5.35 

(189) 228.4 (4.8) 2.68 (8.8) 2.19 (7.2) 

A 0.76 (30) 

1.26 

(44.5) 

0.67 

(26.4) 

7.08 

(250) 318.9 (6.7) 2.74 (9.0) 2.25 (7.4) 

B 0.51 (20) 

0.40 

(14.3) 

0.41 

(16.3) 

4.36 

(154) 166.1 (3.5) no data no data 

B 0.61 (24) 

0.63 

(22.2) 

0.50 

(19.6) 

5.27 

(186) 214.0 (4.5) 2.74 (9.0) 2.37 (7.8) 

B 0.76 (30) 

1.16 

(40.8) 

0.64 

(25.3) 

6.80 

(240) 304.5 (6.4) 2.80 (9.2) 2.37 (7.8) 
28

Table II-2. Numbers (N) of trials and fish of each species tested in 2006 and 2007, by test flow depths and fishway configurations. N 

trials; N Avail = total number of fish available to pass (introduced into flume); N Attempting = number of fish attempting to ascend a fion at least one antenna); PB = Perturbation Boulder; RW = Rock Weir. Because introduced fish can ascend either fishway, and some inascend both fishways during a trial, the total species N for both PB and RW columns under a given flow depth may exceed N Avail. E

trials run, no data collected. 

PB RW PB RW PB RW 

American shad 3 44 7 27 3 120 47 45 Alewife 6 437 7 121 3 220 0 55 Smallmouth bass 15221202American shad 3 126 19 86 Alewife 1 57 0 13 

American shad 1 33 31 32 2 125 102 120 4 186 100 101 Alewife 2 9 3 1 2 17 8 2Blueback herring 1 44 37 16 4 215 51 30 3 146 54 30 

Black crappie 1111

Channel catfish 1 1 1 0 1 4 2 4Common carp 1111

Fallfish 1 1 0 0 1 1 0 0 Smallmouth bass 11111443Striped bass 1 9 8 7 2 20 17 15 

White sucker 1 33 26 23 2 79 66 64 White perch 1 33 27 28 2 22 20 20 

Yellow perch 232225 0 0 

N Avail N Trials N Avail N Trials N Avail N Trial

Flow Depth 0.41 m (16") Flow Depth 0.51 m (20") Flow Depth 0.61 m (24")

N Trials

F

2006

N Attempting N Attempting N Attempting

Configuration B

2007

Configuration A

Year, Configuration, Species

Configuration A
Figure II-3. Proportion of fish (American shad and alewife only) passing each antenna position in 2006 tests in 

Perturbation Boulder and Rock Weir fishways, under three flow depths and two rock configurations. 

12345678

0.0

0.2

0.4

0.6

0.8

1.0

12345678

Rock Weir

0.0

0.2

0.4

0.6

0.8

1.0

0.0

0.2

0.4

0.6

0.8

1.0

0.51 m (20")

0.61 m (24")

0.76 m (30")

Proportion Succeeding

12345678

Rock Weir

0.0

0.2

0.4

0.6

0.8

1.0

12345678

Proportion Succeeding

Perturbation Boulder Rock Weir

American

Shad

Config. A

Alewife

Config. A

2006

Antenna Number

(47)

(19)

(68)

(20)

(61)

(97)

(9)

(45)

(86)

(44)

(121)

(55)

(13)

(7) (27)

0.51 m (20")

0.61 m (24")

0.0 0.76 m (30")

0.2

0.4

0.6

0.8

1.0

0.51 m (20")

12345678

0.0

0.2

0.4

0.6

0.8

1.0

0.61 m (24")

0.76 m (30")

(7)

(22)

(20)

American

Shad

Config. B

Alewife

Config. B

Antenna Number

29
Figure II-4. Proportion of fish passing each antenna position in 2007 tests in Perturbation Boulder and Rock Weir 

fishways, under varying flow depths. Total number of fish detected under each test condition in parentheses. Some 

passage performance curves may be based only on very few fish, and thus not accurately reflect true passage 

performance. 

0.0

0.2

0.4

0.6

0.8

1.0

0.41 m (16")

0.51 m (20")

0.61 m (24")

0.76 m (30")

Proportion Succeeding

Perturbation Boulder Rock Weir

American

Shad

2007

Antenna Number

0.0

0.2

0.4

0.6

0.8

1.0

0.0

0.2

0.4

0.6

0.8

1.0

12345678 12345678

0.0

0.2

0.4

0.6

0.8

1.0

0.0

0.2

0.4

0.6

0.8

1.0

0.0

0.2

0.4

0.6

0.8

1.0

Alewife

Blueback 

Herring

Striped 

Bass

White 

Sucker

White 

Perch

(31)

(102)

(100)

(57)

(51)

(7)

(2)

(5)

(5)

(12) (13)

(21) (20)

(32)

(101)

(120)

(8)

(3) (1)

(2)

(37)

(54)

(51)

(16) (30)

(30)

(17)

(8) (7)

(15)

(26)

(66)

(23)

(64)

(27)

(20)

(28)

(20)

30
Literature Cited: 

Aarestrup, K., M. C. Lucas, and J. A. Hansen. 2003. Efficiency of a nature-like bypass channel 

for sea trout (Salmo trutta) ascending a small Danish stream studied by PIT telemetry. Ecol. 

Freshw. Fish 12: 160-168. 

Castro-Santos, Theodore., Haro, Alex., Walk, Stephen. 1996. A passive integrated transponder 

(PIT) tag system for monitoring fishways. Fisheries Research 28: 253-261. 

Castro-Santos, T. and A. Haro. 2003. Quantifying migratory delay: a new application of survival 

analysis methods. Canadian Journal of Fisheries and Aquatic Sciences 60: 986-996. 

Eberstaller, J., M. Hinterhofer, and P. Parasiewicz. 1998. The effectiveness of two nature-like 

bypass channels in an upland Austrian river. Pages 363-383 in: Jungwirth, M., S. Schmutz, 

and S. Weiss, eds. Fish Migration and Fish Bypasses. Fishing News Books, Oxford. 

FAO/DVWK. 2002. Fish passes – design, dimensions, and monitoring. FAO, Rome. 119 pp. 

Haro, A. 2002. Passage of American shad through natural and experimental high velocity flow 

environments. Report to American Rivers, Washington DC. 17 pp. 

Jungwirth, M. , S. Schmutz, and S. Weiss. 1998. Fish migration and fish bypasses. Fishing News 

Books, Oxford 

Larinier, M. and F. Travade. 2002. The design of fishways for shad. Bull Fr. Péche Piscic. 364 

suppl. 135-146. 

Mader, H., G. Unfer and S. Schmutz. 1998. The effectiveness of Nature-like bypass channels in a 

lowland river, the Marchfeldkanal. Pages 384-402 in: Jungwirth, M. , S. Schmutz, and S. 

Weiss, eds. Fish Migration and Fish Bypasses. Fishing News Books, Oxford. 

Milone & MacBroom 2001. Final Environmental Impact Report. Billington St. Dam – Plymouth, 

MA. Anadromous Fish Restoration Town Brook. EOEA File # 12133 

Orsborn, J.F. 1987. Fishways – historical assessment of design practices. Am. Fish. Soc. Symp. 

1: 122-130. 

Reback, K. E., Brady, P. D., McLaughlin K. D., Milliken C.G. 2004. A Survey of Anadromous 

 Fish Passage in Coastal Massachusetts. 1-77. Pocasset, MA, Massachusetts Division of 

 Marine Fisheries. Massachusetts Division of Marine Fisheries Technical Report. 

Sullivan, T. J. 2004. Evaluation of the Turner's Falls fishway complex and potential 

improvements for passing adult American shad. M.Sc. Thesis, Department of Natural 

Resource Conservation, University of Massachusetts, Amherst, Massachusetts. 105 pp. 

31
APPENDIX 1 – Flow Field Data 

The figures below illustrate measured three-dimensional flow fields for the perturbation boulder 

and rock weir fishways in Configurations A and B, under flow depths of 0.61 and 0.76 m (24 

and 30 inches). Vectors indicate the direction and magnitude (coded by both color and vector 

length) of mean velocity at each depth point. See Section II.2.1. for methods of data collection. 

Pool and Weir

Configuration A

0.61 m flow depth

Velocity 

(m · sec-1)

Pool and Weir

Configuration A

0.61 m flow depth

Velocity 

(m · sec-1)

Pool and Weir

Configuration A

0.75 m flow depth

Velocity 

(m · sec-1)

Pool and Weir

Configuration A

0.75 m flow depth

Velocity 

(m · sec-1)

32
Pool and Weir

Configuration B

0.61 m flow depth

Velocity 

(m · sec-1)

Pool and Weir

Configuration B

0.61 m flow depth

Velocity 

(m · sec-1)

Pool and Weir

Configuration B

0.75 m flow depth

Velocity 

(m · sec-1)

Pool and Weir

Configuration B

0.75 m flow depth

Velocity 

(m · sec-1)

33
Perturbation Boulder

Configuration A

0.61 m flow depth

Velocity 

(m · sec-1)

Perturbation Boulder

Configuration A

0.61 m flow depth

Velocity 

(m · sec-1)

Perturbation Boulder 

Configuration A

0.75 m flow depth

Velocity 

(m · sec-1)

Perturbation Boulder 

Configuration A

0.75 m flow depth

Velocity 

(m · sec-1)

34
Perturbation Boulder

Configuration B

0.61 m flow depth

Velocity 

(m · sec-1)

Perturbation Boulder

Configuration B

0.61 m flow depth

Velocity 

(m · sec-1)

Perturbation Boulder

Configuration B

0.75 m flow depth

Velocity 

(m · sec-1)

Perturbation Boulder

Configuration B

0.75 m flow depth

Velocity 

(m · sec-1)

35