# Recent evaluations of physical and behavioral barriers for reducing ®sh entrainment at hydroelectric plants in the upper
Midwest

D.T. Michaud a, 

## *, E.P. Taft b

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

bAlden 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 ProtectionAct 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 strategiesfor 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 PineRiver, 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 tailoredcollaboration 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 safedeployment 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 acrossthe 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 whichanchored 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  ̄agpoleline. 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. D.T. Michaud, E.P. Taft / Environmental Science & Policy 3 (2000) S499±S512 S500sign 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 andthe net  ̄oated at the water surface and physically prevented ®sh passage. The build-up of algae and other fouling material onthe 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 withoutdiver 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, tearsor 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 S501During July 1990, a test was conducted to determinethe 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 onthe 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 4 8 C 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 lineswere 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 atthe 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 ofdegradation after two years in the water. The antifouling treatments on the surface net were eective: both the Flexabar Antifouling and Seagrove Soft Copperpanels 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. D.T. Michaud, E.P. Taft / Environmental Science & Policy 3 (2000) S499±S512 S502barrier 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 assessalternative 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  ̄owperiods (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, andNSP, 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 KingsfordProject 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 phaseof 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 S503Project. 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 usefulfor 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 testswere 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 includingsound 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 isreleased through two draft tube bays and the maximum discharge  ̄ow for Unit 1 is 44 m 3/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 addedto 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 associatedwith 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.

D.T. Michaud, E.P. Taft / Environmental Science & Policy 3 (2000) S499±S512 S504After 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 S505Acoustic signals were presented in the order listed above with a sound-on duration of 0.5 s for each signal and asound-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 m 3/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 serieswith 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 eectivenessFish 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-hperiods 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). Thefew 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 testsDuring cage tests, an avoidance or agitation response was elicited by most species to at least one behavioral stimuli, whereas no attraction responseswere observed to any of the stimuli that were evaluated. Most of the stronger responses to sound occurredwith 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 agitationwhen 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 lightsources 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-minexposures 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 D.T. Michaud, E.P. Taft / Environmental Science & Policy 3 (2000) S499±S512 S506total ®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 inJuly (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 whenstrobe 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 timeblocks 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 inJuly 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 S507periods 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. D.T. Michaud, E.P. Taft / Environmental Science & Policy 3 (2000) S499±S512 S508signi®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 timeperiods 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 testseries, which included the air bubble curtain, the number of ®sh collected was greatest for air bubble curtaintests and lowest for strobe light and air bubble combination tests. Overall, ®sh entrainment numbers for thesecond 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 S509collected 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 D.T. Michaud, E.P. Taft / Environmental Science & Policy 3 (2000) S499±S512 S510. 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 rearingponds. 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 hearingdetection 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  ̄ashrates 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 bassand 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 noneof 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 duringdevice 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 25 8 C in July, 17 to 19 8 C in September and 10 to

16 8 C 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 wouldhave been expected during what might have been considered optimal conditions for avoidance in Septemberand 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 riverineand 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 S511ley et al., 1996). Most of these studies, however, have demonstrated success with anadromous species, notriverine ®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 conductedwith 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 Rapidscould 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 extensivesampling conducted at White Rapids was able to eliminate the possibility that behavioral barrier eectiveness changed with seasonal dierences in biologicaland 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 thispaper. The authors also acknowledge the ®nancial support of EPRI and Northern States Power Company
for this work.

References

Electric Power Research Institute, 1992. Evaluation of Strobe Lights for Fish Diversion at the York Haven Hydroelectric Project.Prepared by Stone & Webster Environmental Services, EPRI TR101703. Electric Power Research Institute, 1994. Research Update on Fish Protection Technologies for Water Intakes. Prepared by Stone & Webster Engineering Corporation, EPRI TR-104122. Electric Power Research Institute, 1998. Evaluation of Fish Behavioral Barriers. Prepared by Alden Research Laboratory, Inc., EPRI TR-109483. Knudsen, F.R., Enger, P.S., Sand, O., 1994. Avoidance responses to low frequency sound in downstream migrating Atlantic salmon,

Salmo Salar L. Journal of Fish Biology 45, 227±233. McCauley, D.J., Montuori, L., Navarro, J.E., Blystra, A.R., 1996.Using strobe lights, air bubble curtains for cost-eective ®sh diversion. Hydro Review 15 (2), 42±51. Nestler, J.M., Ploskey, G.R., Pickens, J., Menezes, J., Schilt, C., 1992. Responses of Blueback herring to high-frequency sound and implications for reducing entrainment at hydropower dams. North American Journal of Fisheries Management 12, 667±683. Popper, A.N., Fay, R.R., 1973. Sound detection and processing by teleost ®shes: a critical review. Journal of the Acoustical Society of America 53, 1515±1529. RMC Environmental Services Inc, 1992. Final Report, Entrainment Studies at the White Rapids Hydroelectric Project, FERC ]2357, Volume I of IV, Summary of Hydroacoustic Studies and Details of Net System Studies. Prepared for Wisconsin Electric Power Company. Ross, Q.E., Dunning, D.J., Thorne, R., Menezes, J.K., Tiller, G.W., Watson, J.K., 1993. Response of alewives to high-frequency sound at a power plant intake on Lake Ontario. North American Journal of Fisheries Management 13, 291±303. D.T. Michaud, E.P. Taft / Environmental Science & Policy 3 (2000) S499±S512 S512