Recent evaluations of physical and behavioral barriers for

reducing ®sh entrainment at hydroelectric plants in the upper

Midwest

D.T. Michauda,*, E.P. Taft b

a

Wisconsin Electric Power Company, 333 W Everett St, Milwaukee, WI 53203, USA

b

Alden Research Laboratory, Inc., 30 Shrewsbury Street, Holden, MA 01520, USA

Abstract

Wisconsin Electric Power Company recognized the need to address ®sh protection options and commenced a proactive

applied research program in the late 1980s. Within a few years, the company began evaluation studies of promising physical and

behavioral alternatives. Stone and Webster Environmental Services and Alden Research Laboratory, Inc. played signi®cant roles

in identifying and evaluating the alternatives. The results from an evaluation of a barrier net installation at the Pine

Hydroelectric Project indicated that the technology was eective in preventing downstream passage of a wide variety of species

and sizes of ®sh, but was not as eective in preventing passage of YOY ®sh. The results of a separate Electric Power Research

Institute tailored collaboration study of sound, strobe light, and air bubble behavioral devices were discouraging. None of the

devices, either alone or in combination, were eective in signi®cantly reducing entrainment of native riverine ®sh species at the

White Rapids Hydroelectric Project. 7 2000 Elsevier Science Ltd. All rights reserved.

Keywords: Fish protection; Hydro plants; Barrier nets; Behavioral devices; Upper Midwest rivers

1. Introduction

During the 1970s and 1980s, utilities nationwide

were required to conduct extensive evaluations of ®sh

impingement and entrainment at steam electric power

plants. These requirements prompted development of

new screening technologies and intake designs. When

Congress passed the Electric Consumers Protection

Act in 1986, ®sh entrainment at operating hydroelectric power plants soon assumed a prominent position

on agency lists of environmental concerns that now

needed to be addressed by FERC and the licensees.

In response to agency concerns regarding ®sh

entrainment at hydroelectric projects, the Wisconsin

Electric Power Company (WE) commenced a ®sh protection research project. The initial phase of this project, identi®cation of feasible ®sh protection strategies

for the company's hydro plants, was aimed at screening the many known ®sh protection alternatives for

ones that could accommodate the  ̄ow, physical con-

®guration, and operational constraints characteristic of

small hydro plants in the upper Midwest. Based on the

results from this feasibility study, a barrier net was

installed and evaluated as a means to reduce ®sh

entrainment at the Pine Hydro Project on the Pine

River, a tributary to the Menominee River, which separates Wisconsin and the upper peninsula of Michigan.

Behavioral devices, such as sound deterrents and

lights, have the potential to reduce entrainment rates

with much less impact on project economics than

structural alternatives, and generally are considered to

be biologically benign. Relatively recent research and

®eld applications have demonstrated that behavioral

Environmental Science & Policy 3 (2000) S499±S512

1462-9011/00/$ - see front matter 7 2000 Elsevier Science Ltd. All rights reserved.

PII: S 1 4 6 2 - 9 0 1 1 ( 0 0 ) 0 0 0 7 7 - 0

www.elsevier.com/locate/envsci

* Corresponding author. Tel.: +1-414-221-2187; fax: +1-414-221-

2169.

E-mail address: dave.michaud@wepco.com (D.T. Michaud).
systems can be used eectively to repel or divert ®sh

from water intakes (Knudsen et al., 1994; Electric

Power Research Institute, 1994; McCauley et al.,

1996). However, behavioral devices have not been

evaluated to the extent that their range of biological

eectiveness is well understood or proven. Therefore,

the Electric Power Research Institute (EPRI), WE, and

Northern States Power Company (NSP) in a tailored

collaboration conducted a two-phased study of behavioral devices at two WE hydroelectric projects on the

Menominee River.

2. Methods

2.1. Pine barrier net study

2.1.1. Initial design and deployment

The Pine barrier net was initially designed by Stone

& Webster Environmental Services (SWES) and was

deployed in 1990 immediately downstream of a log

boom that had been modi®ed by WE to allow safe

deployment of the net (Fig. 1). The barrier net was approximately 79 m in length, with the height varying

between 0.6 m and approximately 11 m to match the

 ̄owage bottom contour as closely as possible. An initial survey performed with a lead line dragged across

the bottom indicated the presence of large debris projecting o the bottom in the vicinity of the log boom.

Prior to deployment, this debris was removed via

diver-assisted winching operations.

The barrier net was designed to extend from near

the water surface to the bottom with up to 0.6 m of

bow (Fig. 2). The net was originally installed with the

top line set 30±46 cm below the surface to allow surface debris (leaves, pine needles, sticks) to pass freely

over it. The net material was knotted nylon and the

mesh was 13 mm square (25 cm stretch). A 0.9-m wide

apron ®tted with a lead line was axed to the bottom

line of the net to improve the seal at irregularities

along the bottom. The top of the barrier net was tied

back at about 3 m intervals to the wire cable which

anchored the log boom. In ̄atable  ̄oats (18 kg buoyancy) were attached to the top of the barrier net.

Forces attributable to  ̄ow through the net were transferred to the log boom anchors.

The bottom of the barrier net was held in place by

iron blocks (36±45 kg each) spaced at 3±6 m intervals

depending on depth. Nylon lines, feeding from the log

boom down through an eyelet in each of the anchors,

were used to deploy and hold the bottom of the barrier net in place, similar to an upside-down  ̄agpole

line. These lines were tied o to the log boom superstructure (Fig. 2). In early November 1990, after completion of the ®rst sampling season, the barrier net was

dropped to the bottom of the reservoir and secured in

place for the winter by divers.

2.1.2. 1991 design and redeployment

As ice-out was occurring in April 1991, SWES and

WE personnel and several divers raised and re-secured

the net. A complete inspection of the net, support

lines, and log boom, was performed. Additional buoys

were attached to the top of the entire barrier net in

order to keep the net within approximately 15 cm of

the water surface. Based on the 1990 entrainment

monitoring results (Electric Power Research Institute,

1994), several modi®cations were made to the net's deFig. 1. Schematic layout of Pine barrier net study site.

S500 D.T. Michaud, E.P. Taft / Environmental Science & Policy 3 (2000) S499±S512
sign to further limit downstream passage of small ®sh,

as described below.

In 1990, hundreds to perhaps thousands of small

®sh were thought to have passed over the top of the

barrier net, especially in the area closest to the dam.

Therefore, a new surface net was used to supplement

the portion of the existing barrier net system in this

area. The surface net was positioned two feet upstream

of the original barrier net between the dam and the

log boom. The surface net was 2.7 m deep, about 27 m

long, and had toggle  ̄oats sewn into the top line every

0.6 m. The mesh size was the same as that of the main

barrier net, 13 mm square. The top of the surface net

was tied to the log boom and to a bracket mounted on

the dam face 0.6 m upstream of the main barrier net

bracket. The bottom of the surface net was stitched to

the top of the barrier net. This net deployed easily and

the net  ̄oated at the water surface and physically prevented ®sh passage.

The build-up of algae and other fouling material on

the original net in 1990 led to an evaluation of antifouling agents in 1991. Three portions of the new surface net were coated with one of three dierent types

of antifouling material. These coatings were Flexabar

Waterbase (the standard coating applied to the net by

the manufacturer), Flexabar Antifouling, and Seagrove

Soft Copper (Base ]1).

2.1.3. Net maintenance and inspections

The initial installation of the barrier net in June

1990 and the redeployment of the net in April 1991

took place with only minor diculties. However,

installations would not have been possible without

diver support. The integrity of the seal along the bottom and dam remained intact throughout the two-year

study. After the barrier net was deployed in both

years, the net was inspected by divers for snags, tears

or gaps between the net, dam face, and the impoundment bottom. The divers also swam along the face of

the net inspecting for any holes or debris in the net.

Finally, the surface of the net was inspected to check

all the connections to spring lines and buoys. In 1991,

the surface net was monitored to determine the degree

and nature of fouling.

Fig. 2. Cross section view of barrier net installation.

D.T. Michaud, E.P. Taft / Environmental Science & Policy 3 (2000) S499±S512 S501
During July 1990, a test was conducted to determine

the feasibility of back ̄ushing the barrier net by reversing  ̄ow direction. Flow through the power canal was

discontinued and a spillway tainter gate (Number 2)

was opened (see Fig. 1). This operation reversed the

 ̄ow through the net. Divers and surface personnel

observed small debris, including leaves, twigs, and

some algae,  ̄oating away from the net, primarily in

the area closest to the dam. These test results demonstrated that this method could be an eective and

economical way of cleaning the barrier net. During the

fall leaf period, Operations personnel back ̄ushed the

net one or two times a week in order to minimize leaf

build-up.

However, by September 1990, silt and algae had

built up to a 13- to 19-mm thickness along the top 3 m

of the net. In addition, sparse clumps of a lighter

green, long (20±30 cm) and stringy algae occurred on

the net. Holes were infrequently found and were generally small (13±20 cm). Organisms living on or near the

net had also increased. Sponges, hydroids, snails,

amphipods, larval insects and small ®sh were found

either on the nets, the buoys or in the surface layer

near the net. A back ̄ush during September did not

dislodge this biofouling.

In November 1990, the accessible portion of the net

along the log boom was cleaned with scrub brushes

attached to long poles. The amount of fouling growth

was not reduced from October, even though water

temperatures had reached 48C and there was reduced

photoperiod. A 2-h back ̄ush was performed to

remove leaves, during which time the remainder of the

net was scrubbed, both along the surface from a boat

and at greater depths by the divers with handheld

scrub brushes. With the plant shut down, the net was

detached from the dam, all buoys and spring lines

were removed, and as divers assisted, the net was lowered to the bottom.

When the barrier net was re-deployed in April of

1991, divers inspected it for snags, tears, or gaps

between the lead line seal and the bottom. Nearly all

of the algal growth and fouling present on the net at

the end of 1990 had been removed from the net, probably by microbial action.

In late October 1991, a quick inspection and cleaning of the net was performed prior to lowering the net

to the bottom for a second year of winter storage. The

net was in excellent condition although heavily fouled.

Following cleaning and back ̄ushing, the net was lowered to the bottom using the same methods employed

in 1990. The net material showed no visible signs of

degradation after two years in the water. The antifouling treatments on the surface net were eective: both

the Flexabar Antifouling and Seagrove Soft Copper

panels showed less fouling than the Flexabar Waterbase panel.

2.1.4. Velocity measurements

A Swoer Instruments Model 2100 velocity sensor

was used to measure velocities along the inside of the

Fig. 3. Standard locations of velocity measurements.

S502 D.T. Michaud, E.P. Taft / Environmental Science & Policy 3 (2000) S499±S512
barrier net, along transects between the barrier net and

the dam, and in the canal intake during each trap net

sampling period in both years. The locations of the

transects are shown in Fig. 3. The velocity information

was used to identify areas prone to debris loading and/

or subject to excessive hydraulic forces, and to assess

alternative net locations for possible future consideration.

Velocity mapping con®rmed earlier estimates that

velocities along the net would be less than 0.15 m/s

and even as low as 0.03 m/s. Velocities varied by plant

 ̄ow rate, depth, and location. Velocities behind the

barrier net were highest on the surface during low  ̄ow

periods (Fig. 4) and around the periphery (sides, bottom, shore, and dam) during the high  ̄ow periods

(Fig. 5). Flow velocities across the canal opening

under low  ̄ow and high  ̄ow conditions ranged from

generally less than 0.6 m/s to as high as 2.1 m/s.

2.2. Behavioral technology evaluation

In a tailored collaboration between EPRI, WE, and

NSP, a two-phased study was conducted at two Menominee River hydroelectric projects to evaluate the e-

cacy of behavioral protection technologies. The ®rst

phase of the study was conducted at WE's Kingsford

Project and consisted of cage tests during which several behavioral devices were evaluated for their ability

to repel or attract ®sh. The behavioral devices that

were tested included an acoustic sound system (100±

145 kHz), particle motion generators (10±60 Hz), overhead high-pressure sodium lights, underwater mercury

lights, and underwater strobe lights. The second phase

of the study involved a ®eld evaluation of the behavioral devices and signal parameters that were identi®ed during cage tests as having potential for repelling

®sh. Field tests were conducted at WE's White Rapids

Fig. 4. Flow velocities along the downstream side of the barrier net during a typical low  ̄ow period (August 1991).

Fig. 5. Flow velocities along the downstream side of the barrier net during a typical high  ̄ow period (September 1991).

D.T. Michaud, E.P. Taft / Environmental Science & Policy 3 (2000) S499±S512 S503
Project. Detailed descriptions of both study components (i.e., cage and ®eld tests) are presented in

Electric Power Research Institute (1998).

2.2.1. Cage tests

The goal of the cage tests was to determine whether

stimuli produced by the selected devices could elicit

avoidance or attraction responses that may be useful

for designing or enhancing the eectiveness of ®sh passage and/or ®sh protection systems. Tests were conducted with ®sh placed in a submerged cage that was

suspended from a modi®ed pontoon boat (Fig. 6). A

full compliment of test devices was located at either

end of the pontoon boat so that directional responses

could be elicited regardless of the ambient position of

®sh within the cage (Fig. 6). Fish responses were

observed using underwater video cameras and all tests

were recorded on VHS tapes. Avoidance to each stimuli was assessed by ranking ®sh responses based on the

level of startle reactions and directional movements

away from an active source.

Fish species evaluated in cage tests included walleye,

yellow perch, black crappie, smallmouth and largemouth bass, bluegill and/or other sun®sh species,

northern pike, rainbow trout, black bullhead, and

golden shiners or other minnow species. The target

size range for test specimens was 50±250 mm in length.

Test ®sh were obtained from fyke-netting in the Menominee River and from private hatchery sources located

in the state of Wisconsin.

2.2.2. Field tests

Field tests of selected behavioral devices including

sound and strobe light operating parameters were conducted at the White Rapids Hydroelectric Project

located at river km 84 on the Menominee River. The

project consists of a 219-m earth embankment dam

with a 73-m concrete spillway, and a 41-m long power

house with three vertical Francis units. Based on the

results of cage tests, strobe light and several acoustic

signals were selected for evaluation at White Rapids.

The ability of the selected stimuli to repel ®sh was

assessed by mounting the devices on the trash racks of

Unit 1 and monitoring ®sh entrainment through this

unit during treatment and control periods. Unit 1 has

two intake bays with trash racks that have 6.4-cm

clear spacing and are 9.0 m high by 11.0 m wide. The

Unit 1 intake opening is about 4.3 m high by 9.1 m

wide with the top of each opening about 3.0±3.4 m

below the normal headwater level. Discharge  ̄ow is

released through two draft tube bays and the maximum discharge  ̄ow for Unit 1 is 44 m3

/s. Fish

approaching the Unit 1 intake during testing could

either be entrained through the unit, be repelled and

pass through Units 2 or 3, or could be repelled and

swim upstream away from the powerhouse (White

Rapids has an open forebay with no canal or other

structure leading to the powerhouse).

Field tests were originally planned to be conducted

during 2-week periods in July and October. These test

periods were selected to coincide with times of the year

that ®sh abundance was most likely to be greatest

based on entrainment rates that were observed during

the entrainment study conducted at White Rapids in

1990 and 1991 (RMC Environmental Services Inc,

1992). An additional 7-day test period was conducted

at the beginning of September. This period was added

to the test program after the July ®eld tests were completed to allow greater assessment of any in ̄uence

that ®sh size (i.e., physiological development associated

with young-of-the-year ®sh) may have had on the ability of the selected behavioral devices to repel ®sh.

Fig. 6. Schematic of pontoon boat modi®ed for Phase 1 of the ®sh behavior study.

S504 D.T. Michaud, E.P. Taft / Environmental Science & Policy 3 (2000) S499±S512
After the September tests were completed, a decision

was also made to incorporate an air bubble curtain

into the evaluation of behavioral devices scheduled for

October. The air bubble curtain was added to the test

program in an attempt to increase the eectiveness of

the strobe light and sound systems based on similar

tests conducted at another hydro project in Michigan

(McCauley et al., 1996). The bubble curtain was

assessed in combination with the other behavioral

devices, as well as separately.

Twenty-four strobe lights (Flash Technology Model

AGL900) and four transducers (Navy Model G34)

mounted on two steel frames were placed over the

Unit 1 trash racks (Figs. 7 and 8). Strobe lights were

operated at 400  ̄ashes per minute. The sound signals

that were selected for ®eld testing included:

1. AM wave with center frequency of 2000 Hz and

modulation frequency of 20 Hz;

2. AM wave with center frequency of 5500 Hz and a

modulation frequency of 13.75 Hz;

3. FM wave with center frequency of 673 Hz and a

modulation frequency of 67.3 Hz;

4. AM wave with center frequency of 2000 Hz and a

modulation frequency of 50 Hz;

5. 2990 Hz sine wave (pure tone).

Fig. 7. Plan of White Rapids Hydroelectric Project and behavioral barrier evaluation equipment.

Fig. 8. Elevation view of behavioral barrier equipment deployed at the Unit 1 intake.

D.T. Michaud, E.P. Taft / Environmental Science & Policy 3 (2000) S499±S512 S505
Acoustic signals were presented in the order listed above

with a sound-on duration of 0.5 s for each signal and a

sound-o interval of approximately 0.1 s between signals. The entire ®ve signal sequence was played through

each transducer before moving on to the next transducer.

Light intensity and acoustic signal measurements indicated that both stimuli were produced at adequate levels

(based on cage test results) to distances of at least 7 m

from the intake. The air bubble curtain was produced

using 1.9-cm diameter galvanized pipe with 15-mm

diameter holes spaced 38 cm apart. Four 6.1-m lengths

of pipe were joined to form a squared U-shape around

the Unit 1 intake. The pipes were placed at a depth of

about 4.4 m and supplied with air at three locations at a

rate of 0.31 m3

/s and a pressure of 0.71 kg/cm2.

The ®eld evaluation consisted of sampling the Unit 1

discharge for entrained ®sh during speci®ed time blocks

with one or two devices operating (treatment periods) or

no devices operating (control periods). To account for

diel dierences in entrainment rates, each treatment and

the control were sampled during six 4-h time blocks

within a standard day (i.e., beginning at 12:00 am).

Based on the use of 4-h time blocks, a complete test

series (or replicate) spanned a 96-h time period [i.e., four

treatments (including control) multiplied by six time

blocks multiplied by 4 h per time block]. In July, three

replicates were conducted with strobe lights and sound

operating alone, in combination, and with both devices

o. The September evaluation included one test series

with no replication and with the same devices. In October, one test series with no replication was conducted

with the lights and sound, and a second set of tests with

two replicates was performed with lights, sound, and the

air bubble curtain. The second set of tests in October

included evaluation of the air bubble curtain alone and

in combination with strobe light and with sound.

A two-way ANOVA model with ®xed eects (treatment and time block) was used to test for dierences

in the number of ®sh collected among treatments and

the control, among time blocks, and to determine any

interaction between treatment and time block eects

(i.e., was the number of ®sh collected for any of the

treatments or control aected by the time of day the

sample was conducted). The ®sh collection data were

analyzed for all ®sh combined, by family, and by

species for ®sh that were less than 100 mm in length

(collection data were not analyzed for any family or

species group where less than 120 ®sh were collected).

3. Results

3.1. Pine barrier net study

3.1.1. Barrier net biological eectiveness

Fish entrainment into the power canal was monitored during both years of the study by use of a trap

net/live car system positioned near the mouth of the

power canal. Monitoring consisted of up to seven 24-h

periods per month during 1990; slightly less monitoring eort was expended during 1991. In 1991, tagged

®sh were also used to determine net eectiveness. A

complete description of the monitoring is presented in

Electric Power Research Institute (1994).

A comparison of the entrainment monitoring data

before and after the barrier net was installed demonstrates that the net was successful at reducing the number of ®sh passing into the intake canal (Fig. 9). The

few samples in which high numbers of ®sh were collected were, in most cases, due to young-of-the-year

®sh moving along the face of the dam and ultimately

over the barrier net. The low numbers of bottom and

mid-water adult species caught in the intake trap net

also indicated that the barrier net was eective in limiting ®sh passage into the power canal (Fig. 9).

3.2. Behavioral technology evaluation

3.2.1. Cage tests

During cage tests, an avoidance or agitation response was elicited by most species to at least one

behavioral stimuli, whereas no attraction responses

were observed to any of the stimuli that were evaluated. Most of the stronger responses to sound occurred

with FM and AM signals. The highest average responses were seen for frequencies in the 100±6400 Hz

range. Testing of dierent pulse duration and intervals

showed that sound signals with higher duty cycles

tended to result in higher response ratings. Testing

conducted with the particle motion generators (PMG)

resulted in weak avoidance by largemouth bass, yellow

perch, and walleye to frequencies in the 30±60 Hz

range. Rainbow trout exhibited extreme agitation

when exposed to the PMG at 40 Hz, but no directional movement was observed. For each species, the

response to the PMG decreased within several minutes,

indicating that acclimation occurred. Of the three light

sources tested, strobe light was the only source that elicited behavioral responses in any of the species tested.

Walleye demonstrated a consistent avoidance response

to  ̄ash rates of 400, 500, and 600  ̄ashes/minute.

These responses were maintained over repeated 5-min

exposures during sustained response tests. Weak avoidance reactions were noted for largemouth bass and yellow perch at 400  ̄ashes/minute, whereas no responses

were noted for these species at other  ̄ash rates.

3.2.2. Field tests

An estimated 81,685 ®sh comprising at least 27

species were collected during the July sample period.

Unidenti®ed catostomids, common carp, smallmouth

bass, walleye, and logperch comprised 93% of the

S506 D.T. Michaud, E.P. Taft / Environmental Science & Policy 3 (2000) S499±S512
total ®sh collected. Most of the ®sh averaged less than

50 mm in length (exception: walleye, mean length of

65.6 mm). Approximately 89% of all ®sh collected in

July (all treatments and control and replicates combined) were captured in the tailrace nets between 2000

and 0800 hours. Diel trends in entrained ®sh collection

were similar among the three treatments and control

(Fig. 10).

When all time periods for July tests are combined,

the greatest number of entrained ®sh occurred when

strobe lights were operating alone, and the least number of ®sh entrained occurred when strobe lights and

sound were operated together (Table 1). In July, there

were no statistical dierences in the number of ®sh collected among treatments for all ®sh combined or for

any of the family and species groups that were

assessed. There were statistical dierences in ®sh collection numbers among time blocks for all of the

groups analyzed, with the exception of four species

(white sucker, largemouth bass, mimic shiner, and yellow perch). The dierences among some of the time

blocks was most likely the result of the diel entrainment peaks which naturally occur at most hydroelectric projects.

A total of 1704 ®sh representing at least 15

species was collected during the September sampling

period. Black crappie, smallmouth bass, logperch,

and walleye were the most abundant species, comprising about 94% of the total ®sh collected. Average length of most species collected was between

70 mm and 125 mm. The diel distribution of

entrained ®sh diered from the trends observed in

July and there was more variability among test conditions within some time blocks. About 84% of all

®sh collected in September were captured between

midday and 0400 hours (Fig. 11). When all time

Fig. 9. Fish per hour catch rates, 1990 and 1991, for the Pine Barrier Net Study.

D.T. Michaud, E.P. Taft / Environmental Science & Policy 3 (2000) S499±S512 S507
periods for September are combined, there is little

dierence in the number of ®sh collected among the

three treatments and control (Table 2). However,

there are considerable dierences in the ®sh collection numbers during the 1200±1600 and 1600±2000

hour time blocks (Table 2). These dierences may

re ̄ect the variable nature of entrainment rates that

often is observed at hydro sites, as well as being indicative of sampling without replication.

The statistical analysis of the September ®sh collection data demonstrated signi®cant dierences among

treatment eects for percids less than 100 mm and for

logperch less than 100 mm and all sizes combined. The

number of percids collected during control periods was

Fig. 10. Number of ®sh collected during time blocks that were sampled for each treatment condition in July.

Table 1

Number of ®sh collected by treatment and time period (all replicates combined) during the July sample period

Treatment Time period (h) Total

0000±0400 0400±0800 0800±1200 1200±1600 1600±2000 2000±2400

Strobe light 7393 1847 485 617 1991 11,239 23,572

Sound 9341 1838 538 895 1547 8095 22,254

Strobe/sound 8438 1954 388 514 512 5956 17,762

Control 7281 2058 506 868 420 6964 18,097

Total 32,453 7697 1917 2894 4470 32,254 81,685

Fig. 11. Number of ®sh collected during time blocks that were sampled for each treatment condition in September.

S508 D.T. Michaud, E.P. Taft / Environmental Science & Policy 3 (2000) S499±S512
signi®cantly higher than the number collected during

strobe light and strobe/sound tests (Tukey's multiple

comparisons test, P < 0.05). For logperch, there were

signi®cantly fewer ®sh collected during strobe/sound

tests compared to control periods (P < 0.05). Only the

strobe/sound combination demonstrated any signi®-

cant reduction in reducing ®sh entrainment, and this

was limited mainly to logperch.

An estimated 6160 ®sh comprising at least 28 species

were collected during the October sample period.

Black crappie, logperch, yellow perch, and walleye

comprised about 94% of all ®sh collected, with black

crappie accounting for 67% of the total collected. The

average length of black crappie and yellow perch was

about 75 mm, and logperch and walleye averaged 104

and 151 mm, respectively. The other species that were

collected generally ranged from 50±150 mm in average

length. The diel distribution of entrained ®sh collected

in October exhibited a distinct trend that was characterized by a peak in abundance during the 1600±2000 h

time block for all treatment and the control periods

(Figs. 12 and 13).

For the ®rst test series in October, when all time

periods are combined, the total number of ®sh collected was greatest for the control tests (Table 3).

However, when the data are examined by time period,

the number of ®sh collected during control tests was

greatest only for the 0800±1200 and 1600±2000 h time

blocks. The lowest number of entrained ®sh during the

®rst test series was observed for tests with strobe lights

and sound operating together. During the second test

series, which included the air bubble curtain, the number of ®sh collected was greatest for air bubble curtain

tests and lowest for strobe light and air bubble combination tests. Overall, ®sh entrainment numbers for the

second test series were similar among the three treatments and the control when all the time periods are

combined.

Statistical analysis of the October ®sh collection

data from the ®rst test series demonstrated signi®cant

dierences among treatment eects for percids less

than 100 mm and all sizes combined. For percids less

than 100 mm, the number of ®sh collected during

sound tests was signi®cantly greater than the number

Table 2

Number of ®sh collected by treatment and time period during the September sample period

Treatment Time period (h) Total

0000±0400 0400±0800 0800±1200 1200±1600 1600±2000 2000±2400

Strobe light 62 27 26 50 182 41 388

Sound 72 66 26 206 28 69 467

Strobe/sound 37 30 24 22 235 48 396

Control 69 47 25 96 82 134 453

Total 240 170 101 374 527 292 1704

Fig. 12. Number of ®sh collected during time blocks that were sampled for each treatment condition in October (®rst series of tests with strobe

lights and sound).

D.T. Michaud, E.P. Taft / Environmental Science & Policy 3 (2000) S499±S512 S509
collected during strobe/sound tests (Tukey's multiple

comparisons test, P < 0.05); there was no statistical

dierence between the control and any of the three

treatments. For all percids combined, there was signi®-

cantly more ®sh collected during sound tests compared

to the other three treatments and the control (P <

0.05). All data groups, except yellow perch and logperch, demonstrated signi®cant dierences in the number of ®sh collected among time blocks. Statistical

analysis of the ®sh collection data for the second series

of tests conducted in October revealed no signi®cant

dierences in the numbers of ®sh collected among any

of the treatments and the control. Similar to the ®rst

October test series, signi®cant dierences were detected

in ®sh collection numbers among time periods for all

data groups except yellow perch and logperch.

4. Discussion

4.1. Barrier net

During the two-year study period, we found that:

. the modi®ed barrier net tested in 1991 was 85±100%

eective in reducing ®sh passage into the plant's power

canal, as implied by capture and release statistics;

monitoring of  ̄ow downstream of the modi®ed net

indicated continued presence of small (<100 mm) ®sh;

Fig. 13. Number of ®sh collected during time blocks that were sampled for each treatment condition in October (second series of tests with

strobe lights, sound, and air bubble curtain).

Table 3

Number of ®sh collected by treatment and time period (all replicates combined) during the October sample period

Treatment Time period (h) Total

0000±0400 0400±0800 0800±1200 1200±1600 1600±2000 2000±2400

Strobe light and sound tests (one replicate)

Strobe light 67 76 47 79 260 44 573

Sound 64 99 108 195 250 65 781

Strobe/sound 29 49 79 61 179 90 487

Control 33 89 172 55 554 60 963

Sub total 193 313 406 390 1243 259 2804

Strobe light, sound and air bubble curtain tests (two replicates)

Strobe/air 58 59 119 121 325 66 748

Sound/air 80 98 195 83 272 111 839

Air 55 103 103 234 333 100 928

Control 57 113 189 163 211 108 841

Sub total 250 373 606 601 1141 385 3356

Total 443 686 1012 991 2384 644 6160

S510 D.T. Michaud, E.P. Taft / Environmental Science & Policy 3 (2000) S499±S512
. maintaining the net near the surface is essential for

minimizing entrainment of YOY ®shes;

. the integrity of the net was maintained;

. the porosity of the barrier net was considerably

enhanced when it was periodically ``scrubbed

down'';

. the Flexabar Antifouling net coating reduced biofouling when compared with the standard net coating;

. back ̄ushing of the net was eective in reducing net

loading, particularly during the autumn leaf fall

period;

. storage of the net on the bottom for the winter

appears to be an appropriate technique;

. velocities along the barrier net remained well below

0.5 fps even under heavy fouling and maximum

plant  ̄ow.

4.2. Behavioral technology evaluation

During Phase 1 of this study, an avoidance or agitation response was elicited by most species to at least

one device, whereas an attraction response was not

observed with any device or species. The strongest

avoidance responses were observed in the species that

were provided from commercial hatcheries or rearing

ponds. The lower level of response observed in wildcaught ®sh may have been related to the stresses

imposed by fyke-netting collection procedures and

high water temperatures that occurred during the early

part of the test program.

It is important to note that the range of eective

sound frequencies identi®ed with the caged ®sh work,

generally covers the range of auditory threshold limits

that has been demonstrated for representative species

of ®sh (Popper and Fay, 1973). While it is logical that

®sh would respond to frequencies within their hearing

detection thresholds, some species respond to frequencies well beyond their threshold (most notably Alosa

species). However, the fact that those species which

reacted to sound responded to six speci®c signals (out

of 250 tested) at frequencies within their hearing

threshold range adds credibility to the observed results.

No strong or prolonged avoidance responses to the

PMG were observed for any of the species evaluated.

Strobe lights were the only light source that elicited

behavioral responses in any of the test species. Walleye

demonstrated a consistent avoidance response to  ̄ash

rates of 400, 500, and 600  ̄ashes/minute. These responses were maintained over repeated 5-min exposures during the sustained response tests. Weak

avoidance reactions were noted for largemouth bass

and yellow perch at 400  ̄ashes/minute, while no responses were noted for these species at other  ̄ash

rates.

The Phase 2 ®eld evaluation of behavioral barriers

at the White Rapids Project demonstrated that none

of the devices that were tested, either alone or in combination, were capable of eectively reducing entrainment of riverine ®sh through Unit 1. The only

evidence of deterrence was during the ®rst test series

that was conducted in October when the total number

of ®sh collected during control periods was 40%

greater than the number collected during strobe light

operation periods; 29% greater than sound operation

periods; and 50% greater than periods when both

devices were operated together. However, despite the

reductions in the number of ®sh collected during

device operation periods for this test series, no statistical dierences were detected between the treatment

and the control periods for all ®sh combined or for

any of the family, species, and size groups that were

analyzed.

It is unlikely that environmental or operational factors impacted the observed results because the behavioral stimuli were shown to be ineective during all

three sample periods (July, September, and October).

Also, most environmental (water temperature and turbidity) and operational (generation and approach velocities) factors remained relatively stable during each

sampling period. Daily high temperatures ranged from

20 to 258C in July, 17 to 198C in September and 10 to

168C in October. Water turbidity was highest in July

(range: 4.6±9.3 NTU) and lowest in September (range:

3.9±5.7). Generation levels for each unit remained

nearly constant within each sample period and Unit 1

generation was similar among the three months.

Approach velocities measured in front of the Unit 1

trash racks typically were between 0.15 and 0.27 m/s,

with the highest velocities near the water surface.

Based on these velocities, it is likely that the species

and size classes of ®sh that were entrained during all

three study periods were capable of actively avoiding

the behavioral stimuli if there was an aversive reaction.

If the environmental and operational parameters that

were measured in ̄uenced the eectiveness of the behavioral deterrents, dierences in eectiveness would

have been expected during what might have been considered optimal conditions for avoidance in September

and October when ®sh were larger (i.e., greater swimming capabilities), water temperatures were moderate,

and turbidity was low.

Despite the inability of the sound signals and strobe

lights to repel ®sh at White Rapids, both types of

behavioral barriers have eectively repelled riverine

and anadromous species during recent studies conducted at several types of water intakes (Electric

Power Research Institute 1992, 1994; Nestler et al.,

1992; Ross et al., 1993; Knudsen et al., 1994; McCauD.T. Michaud, E.P. Taft / Environmental Science & Policy 3 (2000) S499±S512 S511
ley et al., 1996). Most of these studies, however, have

demonstrated success with anadromous species, not

riverine ®shes. One study that has demonstrated avoidance responses by riverine ®sh to strobe lights was

conducted at the Four Mile Hydroelectric Project in

Michigan (McCauley et al., 1996). Tests conducted

with Flash Technology strobe lights produced avoidance responses from two abundant species groups,

bullheads (family Ictaluridae) and shiners (family

Cyprinidae) (McCauley et al., 1996). The reaction of

bullhead species to the strobe lights at White Rapids

could not be determined because they were not abundant during any of three sample periods. Cyprinids,

principally carp, did occur in large numbers in July,

but demonstrated no detectable response to the strobe

lights.

The general sampling design and analyses used at

the Four Mile Project were similar to those employed

for the White Rapids evaluation. However, at the

Four Mile Project, ®sh response was only evaluated

during a single 5-day period. The more extensive

sampling conducted at White Rapids was able to eliminate the possibility that behavioral barrier eectiveness changed with seasonal dierences in biological

and environmental conditions associated with this project. The considerable dierences in species composition and abundance also limits the ability to compare

results between the two studies. Additionally, there are

signi®cant project design and environmental dierences

that may be important as well.

Acknowledgements

Pine barrier study Ð The authors would like to

acknowledge the signi®cant assistance provided by the

entire Operations and Maintenance stas of Wisconsin

Electric's Hydro Division, located in Iron Mountain,

Michigan, but especially Richard Meinecke and

Charles Schmidt. We also gratefully acknowledge the

substantial eorts of SWES sta, especially Ned Taft,

Richard (``Ice Man'') Marks and Paul Martin. Without their dedication and sense of professionalism, this

project would not have succeeded.

Behavioral technology evaluation Ð The authors

would like to acknowledge the assistance of Steve

Amaral who artfully reduced a one-inch thick EPRI

report into a document that formed the basis for this

paper. The authors also acknowledge the ®nancial support of EPRI and Northern States Power Company

for this work.

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