# Consultancy Report

Clients: 

### ETSU, Harwell, for DTI Nuclear Electric plc



### EXPERIMENTS ON THE USE OF SOUND 

### AS A 

### FISH 

### DETERRENT
A W H Turnpenny, K P Thatcher



### R Wood and P H Loeffelman*



## * Energy Engineering Services Company 3750A Hacienda Boulevard, Ft. Lauderdale, Florida 33314, USA

For the attention of: Dr 

### M Davies, ETSU Mr C J L Taylor, Nuclear Hectric plc FCRO40193 

### April 

### 1993a Obiectives The 

### aim of the project was to assess 

### the effectiveness of underwater sound signals for repelling fish from areas of water, �orpotential applicationto fish exclusionatpower station or other water intakes. Sound systems offer potential advantages over physical screening systems, of low capital and runningcosts, no hydraulichead loss and, elsewhere,havebeen shown to be highly effective, with diversion efficiencies of 

### 80-100%. Two candidate systems were selected for 

### trial: 

### an empirical signal development process developed by Fawley 

### arl Ltd for Nuclear Electricplc and a novel signal developmentprocess developed by Loeffelman and co-workers in the USA. Background 

### Many of Britain’slarge nuclear or fossil-fuelled power stations 

### are sited 

### on the coast or 

### on estuaries. Fish catch at these stationsmay include species ofeconomic andorconservation importance: cod 

### (Gadus morhua), bass (Dicentrarchuslabrax), salmon (Salmosalar), 

### sea trout (Salmo trutta) and Twaite shad (Allosa fallax). Substantialquantities of other species, notably whiting (Merlangius merlangus), sprat (Spratm spratw) and herring (Clupea harengus) 

### are also captured, potentially causing operational difficulties. Any future tidal power barrages 

### in Britain would also be sited on estuaries and would, potentially, have an impact upon the same range of species. Passage of fish through hydroelectric turbines or their 

### entry into the cooling water systems of power stations leads to increased mortality rates 

### in fish stocks. 

### This may 

### place an additional pressure on fish populations, some of which are already under pressure from exploitationby fisheries and through habitatloss, and their exclusion is thereforedesirable. Nuclear Electric plc wish to improve this aspect of the environmentalperformance of their power stations wherever practical and cost-effective solutions 

### can be devised. The Department of Trade and Industry are funding generic research into fish diversion methods for thebenefit ofpossiblefuturetidalbarrage developmentson 

### Britain’s estuaries. For 

### tidal barrage application, fish diversion methods form only part of 

### an integrated arrangementof diversion systems and fish passes which would be required to encourage fish to cross 

### a barrage

### line, other than via the turbines. Physical screening methods do not present 

### a viable option

### for fishprotection at largepower plants owingto the very high water flowsinvolved and the high capitalcosts 

### incurred. Most behavioralfish deterrent systems, based on light, sound, electrical or hydraulic stimuli, have metwith limited or no success. Themost successfulsystemtestedto dateon aBritishpower station is a bubble 

### curtain which 

### was recently 

### installed and tested at Nuclear Electric’s Heysham 2 Power Station. This gave a predicted 

### annual catch reductionof around40% for fish and 60% for shrimps. 

### &ly trials with acoustic systems either failed 

### to produce 

### a response 

### in fish, 

### or proved unreliable for long term application. More recent trials conducted in the UK at Nuclear Electricplc’s Oldbury on Severnpower station produced somepositive results, yielding 

### an estimated 39% reductionin bass catch. In this work signals were developedby an empirical

### Es-2 method. Fish were subjected to a series of underwater sounds in a 

### tank and a signal that appeared to disturb the fish was then used for field trials. The Loeffelman signal development process 

### is based on signal synthesis using information gained from the spectralanalysis of recorded fish sounds. The method assumes that fish will be sensitiveto soundshaving similarfrequencyand temporalcharacteristicsto thosethatthey 

### emit, 

### so that deterrent signals 

### can be targeted to particular fish species. 

### In both systems 

### the chosen signalisplayed back through a durableunderwater sound system.

For the Loeffelman method, groups of fish were placed within an acoustically isolated chamber, and their sounds recorded using a sensitivehydrophone coupled to a digital audio taprecorder. All sounds that could not be attributed to background noise or mechanical sources and werebelieved to be fish communication sounds, 

### were then analyzed for spectral composition and temporal patterning. Potentiai deterrent signals were then developed from characteristics of these fish calls. For 

### the empirical method, 16 different signals were composed, comprising eitherpure sine wave tones or mixed tones, delivered as constant, pulsed, swept frequency or swept amplitude (crescendo) forms. These were recorded as a series on tapfor playback during experiments. First, a screening trial was carried out 

### in which the tape was played to a group 

### of fish. From this, fish responses were scored and one or more candidatedeterrent signals were chosen for more comprehensive testing. The signal, derived by either method, was tested on fish under laboratory conditions. Initial attempts to duplicate a floating cage experimental arena, as used by Loeffelman for initial trials of deterrent signals, failed owing to low water clarity and siltation problems. Further experiments were carried out in test pools at 

### the Fawley laboratory and at a salmon 

### farm in south west Scotland. 

### A Model 

### 220 Argotec electromagnetictransducer, capableofproducing 180dB re lpPa 

### @Im, was employed as the underwater sound sourcefor the trials. Fish 

### used for the experiments were: adult Atlantic salmon, adult andjuvenilebrown trout, adult cod, adult whiting, adult andjuvenile bass, and adult eels. 

### In addition recordings 

### were made of sounds produced by herring, although none were available for experimental testing 

### of deterrent signals. For each 

### trial, a group of fish was placed within the 

### tank and their distribution observed during control periods with no signal applied, and during experimental periods 

### with the candidate signal played through the sound system. Sound levels were monitored and modifications made to take account of the acoustic environment. ~

To test for habituation, trials were repeated 10 times, with intervening control and rest periods, over a period of 1-2 days. The data were then examined for any deterioration 

### in response to sound through the 

### trial series.

### Es-3 Results Signals were developed by the Loeffelman method for 

### salmon, adult brown trout, whiting and cod; no sound was detected fromjuvenile trout, althoughit did provepossible to apply theadult-derived signalto thejuveniles. 

### No soundswereproducedby eitherbass or eels and 

### so no deterrent signalcouldbe developedusing this technique for either species. Significant positiveavoidanceresponses wereobservedwith 

### all the speciestested. No habituationto the signals was observed in response to 

### any of the signals. In brown trout, there 

### was evidence of a learntresponse, in which the fish remained away from the sound source

### after the 

### initial few 

### trials. Of the 

### sixteen Nuclear Electric signals 

### tested, four were identified 

### as useful signals for furthertrials. Ofthese, onlythe 

### two signals comprisinga sweepoffrequencies

### from 

### 100-500 Hz were observed to produce significantavoidance responses. 

### However, dl 

### species tested, 

### with the exception of 

### eel, were shown to respond to one

### or both of the swept signals. 

### No significanthabituation was observed to either Signal. Discussion Both series of trials met 

### the objectives of 

### this stage of the project. 

### In the 

### case of the 

### empirical method, these were to 

### consolidate the findings of the earlier preliminary trials conducted 

### on behalf of NuclearElectric plc, and to expand 

### the range of species tested. The earlier success with bass at Oldbury on Severn Power Station, achieved using the 

### 100 to 

### 500Hz swept signal, was repeated, and the signal was found 

### to offer 

### an effective, broad spectrumdeterrent, capableof repelling a'rangeof species. Of the speciestested, only 

### eels failed to show 

### any useful response to this signal. 

### The objectivein the case of the Loeffelmanmethod 

### was see if the method already tested on North American fish species would work on UK estuarine fish species. Good results were obtainedwith the speciestested. Unfortunately, 

### in 

### thesetrials themethod was 

### limitedby the failure to detect sounds 

### in 

### two out of the seven species 

### tested, so that no signal could be developed for 

### these 

### two species. 

### Comparison of the 

### two methods, setting aside the problem 

### in the Loeffehan method associated with lack 

### of vocalization, showed that 

### there was little to choose between the effectiveness 

### of the signals developed on a given species. 

### The 

### Loeffelmanmethod yielded stronger reactions with brown trout, whilst the empirid method resulted in stronger responses 

### in salmon, cod and whiting. Sincethe 

### scope for response was constrainedby the walls of the experimentalpools, itisnotpossibleto 

### statewhetherone

### or othermethod would move aparticular species further away from the sound source, 

### in a free-field situation. 

### The sound fieldwithinthepools was variable, dependingupon thewater depthandthe sound frequencybeing used. This makes 

### a directassessmentof the threshold sound levelrequired 

### to repel fish difficult 

### from the results of the present study. However, sound levels throughout the pools were maintained at 

### >30 to 4OdB 

### re 1pPa above ambient, 

### in the frequency range 

### 100to 

### 300Hz, and it would be wise to achieve at least 

### this differential

### in any field trials.

### Es-4 In contrast to the findings of someprevious investigations, no habituation to the test signals was detected, based on either signal development method, over a 

### 1

### to 2 day trial period. This absence of habituation 

### is ascribed to the continually-changing nature of the successful sound signals, 

### in terms of either frequency or amplitude. The experimentsrevealed some evidence that fish can 

### learn to stay away from the sound source after 

### an initial exposure to the signal. Conclusions 

### 1. Both the Loeffelman signal development process and the empirical screening method were successful 

### inproducing signals which could be shown to have a statistically significant deterrent effect 

### in laboratory trials. 2. The empirical system yielded one signal 

### in particular, based on a sweep of frequencies, which was shown ,tobe effectivewith all species tested, except the eel. None of the signals tested was found to be effective against eels. 

### 3. A limitation of the Loeffelman approach was that two out of seven species did not produce sound under the test conditions, and 

### so no deterrent signal could be developed. 4. 

### No evidenceof habituationwas detectedin the trials. There was someindicationthat brown trout learnt to stay away from the sound source. 

### 5. Based 

### on the effectiveness 

### of the signals in these laboratory 

### trials, a properly developed and sited acoustic fish deterrent system is expected to significantly reduce fish impingement at water 

### intakes. Recommendations 

### 1. For non-selective deterrence of a wide range of fish species and life stages, the swept-frequency signal approach developed under the Nuclear Electric plc contract is recommended. Where the signal must be applied to one or more selected speciedlifestages, 

### the Loeffelman signal development process should be tried. 

### 2. In view of the successfulcompletion of the laboratory trials, it is recommended that fieldtrials should be undertaken 

### on an estuarine

### power station where conditionswould 

### also be representitive of a potential tidal barrage power generating site. Nuclear Electric plc’s 

### Rinkley Point 

### B power station meets 

### the requirements for such a 

### trial. 

### An initialplanning survey would need to be undertaken over the summer months; the autudwinter period, when fish catch on the stations cooling water intake screens 

### is highest, would be optimal for the trials.



### A W H Turnpenny for: FAWLEY aquatic research laborabri% Ltd Marine and Freshwater Biology Unit Fawley, Southampton 

### SO4 1TW1. Introduction 

### 1.1. The need for fish deterrents 

### 1.2. Underwater sound: elementary concepts and definitions 

### 1.3. Sound production and hearing in fish 

### 1.3.1. General 1.3.2. Soundproduction mechanisms 

### 1.3.3. Hearing 

### in 

### fish

2. Materials and methods 

### 2.1. Sources of experimentalfish 2.2. Recording and analysis of fish sounds 

### 2.3. Signal development 

### 2.3.1. The Loeffelman approach 

### 2.3.2. The empirical method 

### 2.4. Fish response 

### trials 2.4.1.The sound generating system 

### 2.4.2. Observation

### of fish behaviour 3. Results 

### 3.1. Atlantic salmon 

### (Salmo

### sdar) 3.1.1. Loeffelman method 3.1.2. Empirical method 

### 8 8 9 

### 9 

### 9 9 

### 10 10 

### 10 16 16 

### 16
17

### 3.2. Brown trout 

### (Salmotrutta) 17 3.2.1. Loeffelman method 17 

### 3.2.2. Empirical method 18 

### 3.3. 

### whiting (Merlongiwmerlangw) 

### 18 3.3.1. Loeffelman method 

### 18 3.3.2. Empirical method 

### 19 3.4. 

### Cod (Gadus

### morhua) 19 3.4.1. Loeffelman method 

### 19 3.4.2. Empirical method 

### 19 3.5. Bass 

### (Dicentrachuslabrax) 20 3.5.1. Loeffelman method 

### 20 3.5.2. Empirical method 

### 20 3.6. Eel 

### (Anguillaanguilla) 20 3.6.1. Loeffelman method 

### 20 3.6.2. Empirical method 

### 20 3.7. Herring 

### (Clupeaharengus) 

### 21 3.7.1. Loeffelman method 

### 21 3.7.2. Empirical method 

### 21

4. Discussion 

### 21 

### 4.1 Limitationsof experiments 

### 21 4.1.1. Acoustic conditions 

### 21 4.1.2. Confinement of fish 

### 22 4.1.3. Use 

### of farm-raised 

### fish 224.2Performance

### of methods 

### 23 4.2.1. Empirical method 

### 23 4.2.2. Loeffelman method 24 

### 4.2.3. Comparison of the Loeffelman method versus the empirical 

### method 24



### 5. Conclusions 25

6. Recommendations 26

References 

### 28

Tables
Figures
Appendix1



### I. INTRODUCTION This report describes a seriesofexperimental studiesintothepotential use

### of acoustic 

### stimuli to deter fish 

### fromwater intakes at thermal and hydroelectricpower stations. 

### It combines the results of

### two parallel projects, fundedindependentty by NuclearElectric plc and 

### ETSU 

### (on behalf of the Department of Trade and 

### Industry: DTI) respectively. The Nuclear Electric elementofthe study looked at 

### anempirical.

### signaldevelopmentprocess used with some success in earlier trials at Oldbury-on-Seven power station (Thatcher and Irving, 1992). Theaim was to enlarge therange 

### of

### candidate signals

### fortesting, and to apply these in more rigorous laboratory trials and to 

### a wider range of estuarine and marine fish species than was possible in the initial preliminary studies. The 

### trials were 

### also required to investigate the degree to which 

### fish might become habituated to the sound signals, consequently reducing 

### their effectiveness. The DTI-funded part of the study 

### was to apply the novel signal development process developed in

### North America 

### by Loeffelman and co-workers (Loeffelman et

### al., 1991; 1993; Klinect etal., 

### 1992), to examplesofBritish estuarine fishin laboratory trials, and to compare the results with the findings 

### of the Nuclear Electric study. To simplify comparison, both funding bodies agreed that the results should be combined in a single report. The species of fish which were of interest in this study were the Atlantic 

### salmon (&lmu salar), seatrout 

### (Slmutrutta),the shads 

### (Absa fillax,

### A 

### alma),the 

### European eel 

### (Anguilla anguilla), bass 

### (Dicentrarchuslabrad, herring 

### (CrUpea 

### harengus), whiting (Merlangiks 

### mrlangus)and cod (Gadus 

### mrhua).

### All ofthese species

### areconsideredtobe 

### ofconservation and/or commercial importance in 

### Britain today and are potentially vulnerable 

### to capture by nuclear, fossil-fuelled and tidal generating stations. 

### 1.1 The 

### Need �orFish Deterrents Earlier 

### studiescommissionedby ETSU, 

### on behalf of 

### the DTI, into the risk 

### ofdamage to fish passing through 

### tidalpower turbiies (Solomon, 1988; Turnpenny etal., 

### 1992)identified the 

### need for developing methods 

### of repelling 

### or guiding 

### fish 

### away from turbine intakes. The 

### need arises 

### since diadromous species would need to cross the 

### tidal barrage 

### to enter the 

### river or 

### sea, depending on the 

### direction of

### migration, in order to compIetethe life cycle: 

### in doing 

### so,somewould 

### be atrisk of

### passing throughthe turbines andbeing damagedby blade contact ’ or hydraulic conditions. In view 

### of the large flows of water involved, and the high debris loads carried by estuarine waters, physical sereedng methods are deemed to 

### be 

### both impractical and

### uneconomical: impractical owing to the 

### high maintenancerequirements, 

### and uneconomicbecause

### ofthehigh capitalcost

### ofinstallation, coupled

### withgeneratinghead

### loss. Solomon (1988) estimated the cosfs 

### of installing travelling meens to be of the order 

### E28 million per unit for a barrage on the Severn estuar)r, with 

### an ovedfigure 

### for the barrage 

### of f5,600 million. Any type 

### of fish 

### diversion method would, of course, fcmn part of 

### an integrated system of diversion facilitiesand fishpasses, designed to promote the passage 

### of fish 

### via routes other 

### than the turbines.2 Steam-electric 

### power stations, whether nuclear or conventional, require large volumes of water for condenser cooling. Those sited on the open coast or on estuaries commonly use once-through rather than tower-assisted cooling systems. The cooling water requirement is typically ofthe order 5Om3s-'for a 

### 1300MWenuclear station, or 40m3s1 for a similarly-sized conventional 

### thermal station. Fish and other organisms become entrained in the 

### cooling water flows 

### of both types of power stations, and whilst 

### the quantities 

### are not sufficiently largeto have caused any discernibleimpacton fish stocks (Turnpennyand Coughlan, 19921, Nuclear Electric plc are seeking 

### to reduce these catches where practicable by a means that is robust, inexpensive, easy to deploy, and that is effective. This objectiveis driven by 

### an 

### aim to improve the environmental performance 

### of their power stations, and not by current regulatory requirements. A number of behaviourally-based 

### frsh protection systems have been 

### used at water intakes, though with varying success. Behavioural systems have thepotentialadvantage

### of excluding fish without the need for physical screening structures, which are both costly to install and maintain, and prone to blockage. They rely upon generating, in frontof the intake, stimuli which fish 

### can detect and avoid or, in some cases, stimuli which attract fish away from 

### the intake. By appropriatedesign of the stimulus field, it may be possible to guide 

### fish to safe havens or fish passes. Such systems may be based on electric fields, air bubble curtains, strobe lights, moving lights, mercury vapour lights, underwater sound generators or turbulencegenerators (e.g. louvre screens). 

### In the case oflouvre screens, there 

### is aphysical screening structure which creates 

### an impediment to water flow, though the gaps 

### are much larger and provide lower head loss 

### than a conventional passive screening system. The principles of operation and typical applications of these behavioural methods 

### are described 

### in a number of reviews (e.g. Turnpenny, 1988; Turnpenny 

### et aZ., 1992; Solomon, 1988; Solomon, 1992). Unfortunately, whilst good results have been obtained with 

### some of these systems 

### in specific applications,

### in general the track record ofbehavioural systems has been poor, either in terms of unpredictable performance, or poor reliability. To date, the best results on a British power station were obtained in a recent trial of a bubble curtain at Nuclear Electricplc's Heysham 2 Power Station. Thepotential 

### annual reduction 

### in fish and shrimp catch with this system were estimated to be 

### 40%and 

### 60%respectively. Acoustic deterrent methods have been tried for many years but, 

### until recently, with limited success. Sound generating systems of various kinds have been used, including pneumatic poppers, and 

### a variety of other mechanical devices capable of producing high underwater sound levels (Patrick 

### et aZ.,1988). These have met with some limited 

### success 

### as fish deterrents, though results have b&n species-specific, owing to the different sound characteristics needed to deter different species. Mechanical sound generators 

### can be tuned to alter the sound characteristics but offer little flexibilityonce in place. The reliability of some systems has 

### also precluded their use for continuous service applications. 

### In the UK there has been some experience with acoustic deterrents. Early trials using 

### low frequency sound 

### (50Hz)were undertaken by the Central Electricity Generating Board at Oldbury-on-Severn power station 

### in the 1960s 

### (Ray 

### et ul., 1976) to deter salmon 

### (Salmo 

### sulur) smolts. These 

### trials did not successfully deter fish, probably since 

### the sound signal 

### used and the 

### level at which it could be generated using the equipment available (underwater3 loudspeakers) were inappropriate. 

### No attempt was made to test the 

### efficacy of the signal on captive salmon smolts before it was applied 

### in the field. More recent 

### UK trials were carried out in 1992 at Nuclear Electric’s Oldbury-on-Severn Power Station Vhatcher and 

### Turnpenny, 

### 1992;Thatcher and Irving, 1992). 

### In these 

### trials, specimensofbass 

### (Dicmrurchuslabrax)and

### whiting(Merlangius

### merlangus)were subjected to a selection of acoustic signals 

### in a laboratory 

### tank. A signal which appedto disturb thebehaviour of the fish 

### was then generated 

### via 

### an underwater loudspeaker system placed in front of the cooling water intakes 

### of the power 

### station. This resulted 

### in a minor 

### (1 1%) but non-significant 

### (p>0.05) reduction 

### in the catch of all fish species but a significant 

### @<0.02)reduction (39%)

### in bass catch. 

### The signal used was a sine wave, continuously varying 

### in frequency from 100to 

### 500

### Hz,played at sound pressure levels of around 

### 58 dB above background noise level. The placement of the loudspeakers immediately 

### in front 

### of the intakes was probably 

### far from optimal, since water velocities 

### in the 

### area 

### (up to 

### 65 

### cm s-l) were 

### well above the swimming capabilities 

### of many 

### of the fish present; thus 

### many fish would not have been able to escape by the time they encountered the signal. An alternative signaldevelopment has been 

### studiedin the USA, and patentedby Loeffelman (US Patent 

### No. 4,955,005; UK Patent No. 2 223 

### 386 A), in which recordii1gs 

### are made of fish communication sounds. The sounds produced are examined by spectral analysis and time 

### series amlysis to determine the 

### main characteristics of the fish calls. New signals are then developed electronically, based on key features of the fish sounds, and are played through 

### an underwater sound system 

### in front of the water intake. The sound pressure levels 

### used are designed 

### so as to be high enough to avoid masking by background noise. 

### Thebasis 

### of this method is that the fish sounds indicate the sensitiveportion of the hearing range for particular fish, and the temporal patterning to which fish are most responsive. By listening to specimens ofthe population at the application site, the signals 

### canbe customized to their particular characteristics. Combined with a sound system using military-grade underwater loudspeakers,

### in North American trials the system 

### has been shown to offer 

### acombination of high fish diversion efficiency, for example 80-100%for salmonid 

### fish, with a durability 

### of hardware appropriate to continuous service in hostile underwater conditions (Loeffelman

### et 

### al., 1991; 1993; Klinect

### et

### al., 1992). The 

### aim ofthe presentproject was to assess whether selected British estuarine 

### fish species could be repelled using 

### an underwater sound system. 1.2 Underwater Sound: Elementary Concepts and Definitions


### Tounderstand the experimental

### trials, somebasic understandmg ofthephysics ofunderwater sound 

### will be helpful. Both Tavolga (1971) and Hawkins (1986) give succinct introductions

I to this subject, insofar as it is relevant

### to fish hearing and sound production. The following brief summary covers the 

### key points that will be encountered later in the 

### text. Any object moving or vibrating 

### in water will produce underwater sound. This sound 

### is characterizedby minute 

### (of the order nanometres) 

### to-and-fro displacements 

### ofparticles, and oscillatory changes in pressure above and below hydrostatic pressure. Sound 

### can thus be measured in terms of the

### partick velocity, 

### Le. the vibrational velocity 

### of the moving particles, and the 

### soundpressure @). Particle velocity is measured in metres 

### per second and sound pressure in pascals (Pa). More commonly, owing to the vast range of levels encountered

### in nature, soundpressure 

### is expressed 

### on the logarithmic decibel scale, relative4 to a reference quantity: soundpressure level (SPL) = 

### 20 

### loglo p/predB Here, 

### pref is a reference pressure, normally taken as 1 pPa for water, with SPL being expressed 

### as d33 re 

### 1 pPa. A ten-fold increase 

### in SPL is equal to 20 

### dB, a hundredfold is 40 dB, and 

### so 

### on. Table 1.1 gives typical SPLs for 

### various sources 

### in air and water to give the reader some feel for the 

### levels involved. It shouldbe pointed out that, since underwater acoustics are based 

### on a 1pPareference level as opposed to 20pPa in 

### air, a given level of sound expressed in the 

### units that would be 

### used underwater is thus 26dB higher than the identical level expressed in the units that would be 

### used in 

### air. Sound, measured 

### as either SPL or particle velocity, diminishes 

### with distance from source. 

### Far away from the source, either quantity declines 

### as the inverse of the distance from that source, 

### Le. by a factor of 2, or 

### 6 

### dB, for a doubling of distance. Here, SPL and particle velocity are directly proportional to one another. Closer to the source, a different relationshipexists. In the simple situationof a pulsating sphere (a monopole source) in open water, the sound waves emanating close to the source willbe spherical; particle velocity is much higher for a given soundpressure, and declines 

### with theinverse squareof the distance. With increasing distance away from the source, the waves become planar and the 

### linear relationship then applies. For the pulsating sphere model, the limit of the inverse-square relationshipis reached at distance

### of X/27r, where 

### X is the wavelength. Thevolume enclosed within this boundary is known 

### as the 

## near-field and that beyond it thefar-field. Table 1.2 gives examples of wavelengths at different sound frequencies 

### in water, and their associated near-field distances. It should be noted that these relationships apply to idealized, free acoustic field conditions, such as in deep, open water and close to reflecting surfaces they become more unpredictable. 

### Air /water interfaces, and the walls of experimental tanks, are examples of reflecting surfaces. The propagation of sound waves in water is dependent 

### upon the depth of water relative to thewavelength. Ifthe water depth is less 

### M4,then the wave amplitudewill attenuaterapidly with distance from source. On the other hand, 

### in deep water, low frequency sound will propagate successfully over hundreds of miles. Table 1.2 shows the water depths required to propagate fully different frequencies. 

### 1.3. Sound Production and 

### Hearing in Fish 

### 1.3.1 General Sound production is 

### a very common phenomenon 

### in fish, 

### with over 

### 50 families known to contain sound-producingspecies (Myrberg, 1981). Many ofthe soundsproduced areknown to have a communicatory function with other fish of the Same or different species, related for exampleto agonistic (e.g. territorial)or reproductive behaviour or warning ofperceived danger. Other sounds are incidental, �or example the hydrodynamic and muscularcontraction sounds caused by fish swimming or turning, mechanical sounds of grinding teeth, or sounds associated with release ofgas from the swimbladder, although someof these sounds may have a biological signifimce. There is evidence, for example, that predators 

### can be attracted by the swimming sounds of prey fish schools (Moulton, 1960). Temporal5 patterns of sound delivery, as well as frequency range and amplitude, 

### is 

### an important determinant of how sounds 

### are interpreted by the receiving 

### fish. For example, 

### in the 

### male haddock 

### (Melanogrammus 

### aeglefinus),which emits repeatable patterns of sound pulses at different stages during its courtship behaviour, it has been demonstratedthat these sounds, played back to a maturing female, will elicitreciprocal courtshipbehaviour. Other species also distinguish courtship 

### calls from those 

### of other species, simply from the interpulse intervals (Hawkins, 

### 1986). There existvery extensivereviews of hearing and soundproduction in fishes. Good general reviews are given by Marshall (1962), Tavolga (1971) and Hawkins (1986), whileFish and Mowbray (1970) review sound production (or lack of it) in families of fishes from the western North Atfantic. For 

### the present purpose, it willbe sufficient to 

### state some of the generalizations apparent from 

### these reviews, and to draw upon some 

### of the more specific information relevant to the species featured in the present investigations. Table 

### 1.3 summarizes available published information about sound production 

### and sonic mechanisms found 

### for these species. 1.3.2 Sound ProductionMechanisms Marshall (1962) distinguishesfive kinds of soundproduction 

### in fishes, including swimming sounds, gas-bubble sounds, stridulation, vibration of the swimbladder and sounds produced by quickmovements of the head. Whilstlater authors (e.g. Tavolga, 1971)have elaborated 

### on this classification, 

### the additionalclasses 

### of sound production are merely subdivisionsof Marshall’s categories. The following information is taken from Marshall. Swimminr Sounds Studies 

### of swimming 

### sounds have been made largely 

### in relation to schools of fish 

### in open water. When idling, 

### no swimming noise is detectable, but during active periods of swimming(’streaming’), noiseisgenerated,especiallyduringveeringorturning manoeuvres. In anchovy schools 

### (Anchoviellasp.), the greatest 

### sound intensity 

### was emitted at below 

### 500 

### Hz, and up to 1,600 

### Hi, when streaming, and at below 

### 8OOHz when veering, with a 

### maximum of 2,OOO 

### Hz. The origins of the sounds may be 

### various: movement 

### of water over the body surface, breaking 

### of the water surface, tailbeat movements, muscular contractions and friction between moving body parts.

+ Gas Bubble Sounds Fish with ducted swimbladders (phystostomes), for example the clupeid fishes (herrings, shads) and 

### eels (Angfidae), may produce sound when gas 

### is released into the water. The sound has been described 

### as a mouse-like squeak. 

### This normally occurs as fish 

### rise in the water mlurnn and have torelease excesspressure, but 

### can occur 

### as 

### aresult of alarming fish, especially when 

### in captivity.6 Stridulation Stridulatory sounds are produced by the friction of neighbouring skeletal parts, commonly the upper and lower pharyngeal teeth, though other spines or bones may be involved. The sounds produced are described as ’rasping, scraping, scratching or whining in character’. The swimbladder 

### (if present) 

### appears to contribute a resonant quality to sounds of this type. 

### The frequency range 

### of stridulatorysounds is relatively wide, 50 to 4,800 

### Hz,with most of 

### the energy concentrated 

### in the upper frequencies. Vibration of the Swimbladder

### Wall Swimbladder sounds are typically low-pitched, drum liesounds, resonant in quality. They may be heard as thumping or knocking sounds, delivered 

### in short bursts. 

### The frequency range is commonly 

### 50 to 1,400Hz, but with most of the energy concentrated 

### at the low end 

### of this range. Muscles attached to the internal or external wall of the swimbladder are responsible for generating the vibration, 

### in most cases acting against a spring mechanisms provided by the elasticity of the bladder walls, body wall musculatureorconnectivetissues. Sounds Produced bv Ouick Head Movement In various species, notably blennies, thumping sounds are made by sudden downward or sideways movements 

### of thehead. These sounds arereported to play 

### an importantpart 

### in the pre-spawning behaviour 

### of certain species. 1.3.3 Hearing in Fishes The sensitivity of fish to sounds is normally described in the form of an audiogram, which relates the detectable sound level threshold 

### (in terms of SPLor particle velocity) to different frequencies. An example is shown 

### in Figure 1.1, which gives 

### the audiograms for four separate species of fish. It 

### is perhaps unsurprising that the sensitive frequency range is in general below 1,OOO 

### Hz, correlating in broad 

### terms with sound spectra emitted by fish (Section 1.3.2). Figure 

### 1.1demonstrates clearly that marked differences

### inhearing sensitivityoccur amongst different 

### species, and that the centre and bandwidth of optimum sensitivity also varies. Acoustic deterrent signals must be designed to take account of these characteristics. Few species are sensitive to sounds at frequencies above 

### 2 or 

### 3 kHz. If 

### the fish do not 

### hear the signal, 

### the deterrent will not stimulate the fish to change its swimming behaviour. Sound sytems designed 

### to produce signals targeted at the fish’s optimum sensitivity will be more effectiveat achieving this. Because lower SPLs 

### arenecessary to stimulatethe fish when the sound frequencies are correctly targeted, smaller, lower cost underwater 

### speakers can be used, resulting 

### in more economical guidance system installations. The usual method of determining fish audiograms 

### is by conditioning the fish to respond to loud sound 

### stimuli, at a particular frequency, 

### and then to lower the sound level progressively, untiltheresponse ceases. Unfortunately, sincethis method islabour-intensive, relatively few fish species have been investigated by 

### this means.* 7 Differences 

### in sensitivityamongst different species are related 

### to the anatomy 

### of the hearing mechanisms (Hawkins, 1986). Sound in 

### al�species is detected by the otolith organs 

### of the inner 

### ears, which arepaired structures embedded in the 

### cranium on either side of 

### the midbrain. The lateral line organs are 

### also sensitive to low frequency sound (20 to 

### 500

### Hz), but only 

### in the 

### near field 

### (see Section 1.21, since they aredetectors

### ofparticlemotion rather than sound pressure. 

### An important factor determining overall hearing sensitivityis the presence of a swimbladder and the proximity 

### of it to the inner 

### ear. in the flatfishes (plaice, 

### Pleurunectesplatessa; dab, 

### Lirnanda limanda),for example, which are quite insensitive to sound, there is 

### no swimbladder. The swimbladder, 

### in those species possessing one, acts 

### as a pressure transducer, converting sound pressure to particle 

### velocity. 

### Thus species without a swimbladder, 

### or in which the swimbladderhas 

### no close connection with the inner 

### ear, are insensitive to sound pressure and rely upon detection of particle displacement. An important feature of hearing ability is 

### the 

### need to distinguish sounds that are of interest to 

### the fish from background noise. Auditory masking occurs when a tone is surrounded by background noise of the same or close frequencies. In sensitive species such 

### as the cod, this may make hearing difficult in noisy environments and, indeed, the cod requires a sound’to be of the order of 

### 20 

### dB above background noise level to detect, it (Hawkins, 1986). Frequency-selectiveauditory filtersareknown to bepresent in a number of species and assist in auditory discrimhation. It has 

### also been shown that this mechanism can be 

### used to discriminate between frequencies, with the goldfish 

### (Carassius auratus), for example, able to distinguishtones differingin frequency by only 

### 3-5%. Auditory masking is 

### an important factor when considering the feasibility of, and sound levels required for, acoustic fish deterrence. Loeffelman 

### etaZ. (1993) demonstrated the influence

### of masking in field 

### trials at a fish ladder 

### in Michigan, USA. When the signal was only 

### a few dB greater 

### than the ambient sound pressure levels in a concrete pool in the ladder, up-migrating adult steelhead trout (Oncurhynchus 

### mykiss) were not deterred. By placing the signal in a quieter pool and increasing the sound level over ambient (133dB re $Pa) to 158 dB re 

### lpPa, 73% of fish were stopped from moving up the ladder. Sound levels 

### in most natural waters ranges 

### from 80 to 100dbre lpPa for all frequencies. Advanced sound systems arecapable 

### of producing SPLs sufficiently greater than these ambientlevels. 

### A speakerweighing 25kg, forinstance, is capable of producing 170dBre 1pPa 

### @lm. Itis 

### also importantto evaluatethe influence 

### of site conditions 

### on the signaldesigned 

### for the fish’s hearing ability. Bottom substrate, bathymetry and other physical factors will cause frequencies to propagate with less sound pressure and over shorter 

### distances than 

### in a free field (Le. open water). In some cases 

### a signal may fail to propagate at 

### all owing to lack of depth, 

### or wave cancellation due to reflecting surfaces. 

### By knowing the fish’s sensitive hearing range, the signalfrequencies may be adjustedto siteconditions forgood propagation, without fatling outside this range. In view of the importantrole of the swimbladder

### in the hearing process, it mightbe guessed that swimbladder size 

### - and hence resonant frequency 

### - would have a significant influence 

### on the audiogram, with the expectation that small fish would have 

### mdum sensitivity at a higher frequency than larger fish of the same species. This argument might be applied equally well to sound production. According to Hawkins (1986), experimental 

### studies have

### 8 shown that the resonant frequency of the swimbladder is generally well above the hearing range of the fish and therefore that it is detuned to provide moderate amplification over 

### a wide frequency range. This would serve to facilitatecommunicationover a wider range of fish sizes 

### than would a tuned swimbladder. The finding has potentially important implications for fish deterrence and suggests that 

### an acoustic deterrent signal would not be too dependent

### on the sizes of fish to be deterred. Nevertheless, soundproductiondoes seem to be (inversely)related 

### to size. Loeffelmanet aZ. (1993) have shown that 

### in Pacific salmon 

### (Oncorhynchus spp.), smolt sounds wereapproximately700Hzhigher than adultsounds. A. Turnpennyrecently observed 25mm chinook salmon (0. 

### ts~tsch) producing sounds at a sound system installation using the Loeffelman method 

### in North America: these fish produced sounds at predominantfrequenciesaround 

### 1.5kHz higher than adults. Fish (1954) 

### also gives sound 

### spectra for eels 

### (AnguiZZu 

### rostrutu) of 

### 545 and 700mm length respectively, showingthat the larger specimenproduced sounds 

### 100to 

### 400Hzlower than the smaller one, Given these directobservationslinking the frequency 

### of sound production to fish 

### size, it is clear that, if the Loeffelman hypothesis is 

### correct, that fish hearing capability corresponds with sound production 

### spectra, then the development of deterrent signals should take account of fish 

### size and life stage.

2 MATERIALS 

### AND METFtODS 2.1 Sources of Experimental Fish Fish for the experimentswere obtained as follows: 

### Atlantic 

### salmon (adults, 

### 40 

## - 60 

### cm length): Otter Ferry Salmon Ltd, Argyll, Scotland; 

### Brown 

### trout (juveniles, 10

### - 12

### cm and adults, 30 

### - 40 

### cm length): Itchen Valley Trout Farm, Alresford, Hampshire; 

### Cod (juveniles, 

### 30 

### - 40 cm length): MAFF Fisheries 

### Laboratory, Lowestoft, Suffolk; rodand-line caught, by anglers at Lowestsoft; 

### Whiting (adult, 

### 30 

## - 40 cm length): as for cod. 

### Bass (juveniles, 7 

### - 20 cm): seine-netted, 

### R. Itchen 

### Estuary by MAFF/NRA; (adults, 30 

## ­ 40 cm): from stock held at 

### MAW, Lowestoft.

1 

### Eels (adults, 40 

### -80 cm length): fixed engine fishery, Stolford Flats, Somerset (Mr �3 Sellick); also, from stock held at MAFF, Lowestoft. 

### Herring (adults 20-30cm length): from stock held by the Sottish Marine Biological Association, Dunstafhage, Oban, Argyll, Scotland. Attempts were made, in collaboration with the National Rivers Authority (Severn Trent Region), to collectTwaite shad for the study but these were unsuccessful.9 2.2 Recording.and Analysis 

### of Fish Sounds This applied to the Loeffelman method only and the equipment and methodology was as described by Loeffelman et al. (1993). Groups 

### of fish were placed 

### in 

### an acoustically-isolated recording chamber (Flexwrap Corporation), of approximate size 120 Q x 25 (W) x 

### 120 (D) cm. 

### This was normally operatedindoorsto avoid interferencefromlow frequencywind noise. Soundproduction was detected by a miniatureBruel and Kjaer (�3 &K) Model 8103 hydrophoneplaced within the recording chamber. This was coupled to a B & 

### K Model 2635 charge amplifier and Rockland System 90 spectrum analyzer. An Aiwa 

### HD-S1 digital @AT) 

### tape recorder was used to make audio recordings of each sampling session, which was normally of 45 minutes duration. The overall layout of 

### the recording equipment is shown 

### in Figure 2.1. Observers listened in continuously throughout the recording session and recorded the times of any sounds produced. Any fish behaviour or outside interferenceswhich might have produced sound artefacts was noted; for example, fish bumping into the hydrophone, the fall 

### of condensationdropletsintothe water, or fish breaking the 

### surfaceofthe water. A continuous visual record was 

### also made

### by means 

### ofatelevisioncamera 

### andrecorder (PanasonicM7000 camcorder) placed in front of the recording chamber. Recorded sounds and video records could be synchronised by means of timebases on both media. Analysis of the sounds was carried out 

### on recorded signals. For 

### each sound which was clearly not 

### caused by 

### an artefact, the sound spectrum was printed out, together with the amplitude-time trace. Only where several sounds having similar characteristics were obtained, and for which no extraneous cause could be found, were they deemed to be valid fish calls. 

### 2.3 Signal Development 2.3.1 The Loeffelman Approach Signals were synthesized

### on an IBM@ 

### XT PC fitted with a Roland SCC-1

### GS Sound Card. Information obtained from analyses of fish calls (amplitude, frequency content, waveform, callduration, call interval) was used to formulatethe test signal. The signal was then tested by playing it back to the fish using 

### an underwater sound system in a test tank 

### (see Section 2.4). 

### In somecases, the signal was subsequently modified during theplayback phase, when environmental conditions did not 

### allow adequate propagation 

### of key frequencies. 

### In such cases, the frequency range was shifted up or down 

### by the 

### minimum amount required to * ensure propagation.

2.3.2 The EmDiriCat Method 

### Thealternativeapproach 

### used a standard series of sound signalswhich could beplayed back to each test species, with no customization, other 

### thanto determineempirically which signal worked best 

### (if at all). The standard signalsetcomprised 16discretesoundpatterns, differing 

### in frequency, amplitudeor temporal patterning. 

### Their descriptions aregiven in Figure 2.2, 

### with examples of time series. The signals 

### used were an extension of those 

### used 

### in earlier

### 10 work carried out on behalf of Nuclear Electric during 1991-2. 

### One of these (Signal 

### No. 7) was tested and found to reduce significantly bass impingement at Oldbury-on-Severn Power Station (Thatcher and Turnpenny, 1992; Thatcher and Irving, 1992). A number of different signal classes 

### can be distinguished, 

### as follows: Group 

### 1 Signals 

### 1 to 3: pure tones, fixed frequencyand amplitude; Group 2 Signals 4 to 6: pure tones, fixed frequency, delivered in discrete, repetitive bursts; Group 3 Signals 7 & 8: continuously-varied frequency, fixed amplitude; Group 

### 4 Signals 9 & 10 fixed frequencies, continuously-varied amplitude; 

### Group 5 Signals 

### 11 to 14 continuously varying frequencies and amplitude; Group 

### 6 Signals 

### 15 & 16 broad frequency band signals.



### No modification of this signal series was made during the trials. 2.4 Fish Response Trials 2.4.1 The Sound GeneratinP System The sound generating system is shown schematically 

### in Figure 

### 2.3. Signals were composed as described 

### in Section 

### 2.3, and eitherplayed directlyby the signalgenerator or sound card, or firstrecorded onto magnetic tape and played back viathe sound system from this source. The Kemo filter was used primarily in this set-up to provide additional signal amplification (up to 10 x) when necessary, rather than as a bandpass filter. Amplification was provided by a 

### Ross Power Amplifier, capable of producing about 1000

### W RMS power output. The underwater transducer (loudspeaker) used to generate the sound 

### in the water was 

### an Argotec Model 

### 220. This is the largest of the transducers used by Loeffelman and co-workers in north-American sound experiments (Loeffelman 

### et 

### al., 1991, 1992, 1993; 

### Beet 

### et 

### al., 1992). The unit is capable of producing sound levels of up to 180

### d3re lpPa @ 

### lm, over a frequency range from 50 to 1OOOHz.

2.4.2 Observation of Fish Behaviour The effectivenessof the signals for repelling fish was determined 

### in behavioural trials. 

### The initial intention was to 

### use an underwater observation chamber, of the kind described by Klinect 

### et

### al. (1992). A polyethylene-coveredchamber was constructed with dimensionsof 9mC) x 1.2m(W)

### x 0.3m@) and suspended in a 

### sea water dock adjacent to the Fawley laboratories. Underwater television cameras 

### were used 

### to observe fish movements. This* 

### 11 approach was, unfortunately, made unworkable 

### by problems of visibility, which Klinect 

### et u2. had not experiencedintheir solely freshwater experiments. Theproblems atFawley were caused by poor water clarity, but also deposition of fine sediments onto the outer surfaces of the observationchamber. Thus it was not possible to make any reliable observations of fishbehaviour by this method. At first, the idea 

### of conducting the behaviourd experiments in 

### tanks or pools was 

### rejected, on accountof the complex acoustics ofmost small containments (Hawkins, 1986). However, following the lack of success of the open water trials itbecame 

### necessary to use other means and, inrecentexperiments inNorway, Knudsen 

### et ul. (1992) successfully demonstratedfish aversion to low frequency sound (10-150Hz), using 

### a 4m 

### x 5m 

### x 2.5m@) concrete pool. 

### A pool was tried and gave good results, 

### so was finally adopted for 

### all the behavioural trih. Salmon Farm Trials Thepool experiments were firstdevelopedatan onshore salmon farm

### in south west Scotland (Otter Ferry Salmon 

### Ltd,Argyll). Owing to the difficulties of transporting large numbers of adult salmon to theFawley laboratory and keeping them there, it was decided to carry out all the salmon work at the fish farm. For this purpose, a circular, below-ground concrete pool 

### of 15m diameter and 2m 

### depth was made available. Water was provided from a pumped supply of 

### sea water abstracted fromthe adjacentLochFyne. Water 

### claritywas good and, 

### since the pool was coated with 

### a pale-colouredpaint 

### and had been cleaned prior to the trials, any fish within the pool could be seen clearly from above. Before the start of the experiments, the pool was stocked with 200 farm-raised Atlantic salmon, 

### of nominal 600g weight. 

### The Model 

### 220 transducerwas placed 

### on the floor of the pool, against the side wall. The rest of the sound system and instrumentation was located in a trailer, adjacent to the pool. The experimental method was based upon the observation that the salmon stocked into the pool aligned themselves with the circular current, which was generated by the tangential inflow of water at the side wall and the exit of water via a central 

### drain (Figure2.4). Left undisturbed, the majority of fish adopted stablepositions on the streamlines. When disturbed by an outside stimulus, for example

### an object

### thrown into 

### the water, the stablepattern would break down, with the fishchanging orientationand moving away from the stimulus source. Sincethe floor of the

### pool was divided up into sectors, visible asjoints 

### in the concrete 

### floor sections, it was possible for observers standing around the edge 

### of the 

### pool to count the numbers of fish 

### in each sector. This was repeated at intervals over time, comparing the numbers of fish present 

### in the sector containing the underwater speaker, and 

### in the 

### two adjacent to it (Sl, 52 and 

### 53 in Figure 2.4), forperiods 

### with sound on ('test') and sound off ('control'). Thus, 

### apositive response was shown 

### by a significantlyreduced number of fish present in these 

### threesectors 

### inthe test 

### versus controlperiods. More detailedvisual records were, at the 

### same time, 

### made by a camcorder (Panasonic 

### M7000) mounted on a tripod to 

### view fish 

### in a small 

### area (about 

### 5m x 3m of pool floor) close to the sound source.* 12 The detailed protocol used was as follows: i) All aerators were removed and 

### the water supply to the pond 

### was cut off to eliminate these sources of noise. The inertia of 

### the water mass would keep the water moving around the 

### tank for at least 1 hour after this, 

### so that the fish would retain their orientation 

### on the streamlines. ii) Three observers took up position at the edgeof the

### pool to monitor sectors S 1,S2 

### and 

### S3. This 

### was done cgefully to avoid disturbing thefish. A fourth person took charge of the sound system and called out times to the three observers. iii) At 30 second intervals over a five minute period, the number of fish in each of the sectors S1 to S3 was counted, with sound off (control). iv) Flow was restored and, after a five minute rest period, was cut off again. v) Step (iii) 

### was repeated but with sound 

### on (test). 

### vi) Steps (iii) to (v) were repeated ten times to complete the experimental series. vii) Flow and aeration were restored. Thetrials were, in fact, conducted 

### in two 

### runs of five control-testpairs, on consecutivedays (8th and 9th December, 1992). The transducer was moved about one-third 

### of the way around the edge 

### ofthe pool for the second day's trials to avoid bias in the results associated with transducer position. The data from the trials were analyzed to determine the 

### mean and standard deviation of the number 

### of counts 

### per observation sector for successive test and control periods. A test for significantdifference between test and control counts was made using the Student t-test for equal sample sizes (Clarke, 1969). The possibility of the fish becoming habituated to the signals was examinedby plotting thepercentagereduction (positiveornegative) in fish count in the observation area 

### as a whole (S1 to S3 inclusive) 

### versus the number of test exposures. 

### A linear regression line was then plotted through the resulting time-series, the goodness of fit being shown by the correlation coefficient 

### .r (Clarke, 1969). A positive slope to the regression line, or 

### a value of the x-coefficient which was not significantly different from zero, was deemed to be evidence 

### of no significant habituation. Additional analysis 

### was performed 

### on video tape images, to show changes 

### in fish behaviour between test and control 

### periods. Thevideo tapes wereplayed back through a video cassette recorder in freeze-frame mode. Clear acetate sheets were fixed over the video screen, and the positions and alignments of fish marked onto the sheet with permanent marker pens. Observations were repeated at'15 second intervals over one test and one control period, recording the data 

### on separate acetate sheets for each. The sheets were then removed and fish alignment angles measured by protractor.

### 13

' Laboratory 

### Trials at Fawlev As the method 

### of assessing 

### fish responses to sound that was 

### used at the 

### fish farm worked well, a similar approach was adopted 

### for laboratory trials at Fawley. 

### A suitable belowground pool was not available, so 

### an above-ground swimmingpool was purchased and set up within the laboratory buildings Figure 

### 2.5). This was smaller 

### than that used at the fish farm, being 

### 5m diameter and 1.2 m deep. A circular flow was generated by means 

### of a submersible pump 

### (4.2 1 

### s" flow rate) placed at the 

### centre of the pool, with the outlet arranged to discharge at the edge of the pool, tangential to the wall. Water would continue to circulate for at least one hour after the pump was turned off. As in the fish farm trials, 

### an Argotec Model 220 transducer was placed on the floor of the pool againstthe side wall. Observation of fish behaviour was carried out remotely in the laboratory trials. A monochrometelevision camera (Sony CCD, ModelAVC DS-CE), fitted with a4.5mm focal length, wide-angle lens, was fixed to 

### an overhead beam above the pool and the area 

### of view covered about 

### 90%of the entire pool area. A pair of 

### 500W halogen floodlights mounted above and to either side of the pool provided even illumination. Since water turbidity at Fawley is high, before entering the pool the raw water was passed firstthrough a sand filter and then through a cartridgefilter 

### (56ympore size), to improveclarity. Using this method, fish could be seen clearly on a remote television screen. The results video-recorded for subsequent analysis. A timer function on the videorecorder imprinted the time (to 1/1OOth second) onto the video image. A minimum of 10 and maximum of 40 fish were introduced into the pool the day before experimentationbegan. The experimental protocol was similarto that used on the fish farm but adapted to the remote observation and recording methodology. An identical experimental sequence was used, with fish counts being made every 30 seconds over five minutetest and control periods with no water flow or aeration, separated by five minuterest periods during which water flowwas restored. Again, ten pairs of test and control sequences were run in each experimental series. The

### main difference was the method of scoring fish numbers. The intention was, having mapped the sound field in the tank, to score fish numbers 

### in relation to SPL isopleths, with the 

### aim of determining the threshold 

### SPL for avoidance 

### of each signal type. Sound was mapped at the start of the trials, 

### as shown in Figure 

### 2.6, showing a clear SPL gradient across the tank and, initially, counts of fish between each 

### of these isopleths were made. It subsequentlybecame apparent that, although the experimental system had remained identical throughout the experiments in all other respects, changes 

### in water level 

### of only 

### a few centimetres markedly altered the distribution of 

### SPLs within the 

### tank. As SPLs had not been mapped individually for each 

### trial, 

### no reliance could be placed upon the relationshipbetween SPL and fish distribution. Instead, fish positions were counted in relation to the map shown 

### in Figure 2.7. The curved lines shown are based 

### on concentric circles drawn around the transducer centre at radial increments of 

### 0.83m. Counts were made by placing 

### an acetate overlay of this map 

### on the television monitor scrcen and replaying, 

### in freeze-frame mode, 

### the video tapes of the experiments. The number 

### of fish within each zone was counted and recorded at 30 second intervals. Thus, the records represent fish distance from the sound source rather than distribution in relation to sound level. Analysis of the data

### was broadly similarto that in the fish farm trials. However, rather than14 lookingjust at 

### an overall reduction of fish numbers within the vicinity 

### ofthe transducer, the mapping procedure allowed the fishes’ distance away from the transducer to be determined for both test and control conditions, even though this distance was bounded 

### by the wall of the 

### tank. The average displacement from the transducer for test ad control states was therefore used as the measure of response. To calculate this, it was first necessary to correct the frequency counts obtained from the video 

### tape analyses for the differences 

### in area of each 

### ofthe 

### six map zones. 

### This was done by dividing the raw count figures by the correction factors shown in Figure 2.7. The average distance away (m) from the transducer for an experimental

### run was calculated 

### as:

6 

### X <:Di 

### AverageDistance= i= 6
where is the average fish count for the zone i, and Di is the distance 

### (m) from the transducer to the middle of zone 

### i. Since the fish distances could not be normally distributed, owing to the boundary imposed by the 

### tank wall, a test of significancefor differencesbetween control and test distributions was carried out using the non-parametric Kolmogorov-Smirnov test, following the procedure for large sample sizes (>

### 40) described 

### by Campbell (1974). Thus, the differencein average distancefrom the sound sourcebetween test and control pairs gives a measure of response, and the Kolmogorov-Smirnoff test ascribes the significance level to any differences in distribution pattern. The test for habituation closely resembles that used in the fish farm trials. For each testcontrol trial pair, the difference in the average distance from the sound source was plotted against the number of exposures. A linear regression line was fitted to the points to reveal any trend, and a negative slope, coupled with 

### an x-coefficient which differed significantly from zero, 

### was deemed to be evidence of habituation, or 

### vice 

### versa. A limitation of this approach is that it does not allow for the possibility that fish may learn to stay away from the sound source, remaining away in control as well as experimentalperiods. This would have the effect of reducing the difference 

### seen between control and experimental periods. Tocater for this, where 

### the habituation test was positive, control and experimentaldistances were both plotted to reveal possible learning trends, applying a regression line to test for significance. SubiectiveScorin? ofFish Behaviour Certain aspects of the fish behaviour 

### seen by the observers could not readily be quantified, forexample the speed 

### at which fish moved away from the sound source when the signal was applied. A true impression can only be gained from viewing the Video tape records of the experiments. In an attemptto convey some

### of these aspects of behaviour, a subjective scoring system was15 adopted to record the observers’ impressions of the strength 

### ofresponse to the 

### sound signal. Five categories were defined: Category 1: Extreme startle reaction away from the sound source, some fish leaping out of the water. Category 2: Clear startle reaction away from the sound source, but 

### no fish leaping out of the water. Category 3: Steady swimming away from the sound source but 

### no obvious startle reaction. Category 

### 4: Slight response to the sound signal but not a sustained movement 

### of fish away from the sound source. Category 

### 5: No response seen.

Differences in Procedure with the Fixed Signal Approach In the work carried out for Nuclear Electric, a signal selection procedure was applied prior to the applicationof the protocol described above. A tape recording of the sixteen candidate signals, each lasting for one minute with a one minute resting intervalbetween, was played to the fish 

### via the underwater sound system 

### in the test pool. From these, the signal which evoked the most obvious behavioural response, based 

### on the subjective scoring system described above, 

### was selected for the full test protocol. In some cases, where good

. responses were generated by two or more signals, more than one was tested using the full protocol. Sound Mapping Sound mapping was carried out by generating sine wave signals of constant amplitude arid frequency through the transducer. Sound pressure levels were measured at differentpoints in thepool and at lo%,

### 50% and 

### 90% depth. This was repeated for frequencies of 

### 100, 200 and 

### 300Hz (210 and 275 

### Hz at Otter Ferry) 

# . Values at mid-depth 

### (50%)only are shown 

### in the present report. SPLs at 10 and 

### 90,%were within lOdB of mid-depth values. The equipment was the same as that used for listening to fish sounds (Section 2.2). The hydrophonewas attachedto a long boom to allow access 

### to different areas of the

### pool. SPLs were read from the display of the Rockland spectrum analyzer, which had been set up with the calibration parameters of 

### the hydrophone. *

The results are presented, in summary form only, in Figure 2.6, for both the Otter Ferry and Fawley test 

### pools.16 3. RESULTS To 

### aid comparison between the two signaldevelopmentmethodologies, the results are shown species by species. .Most but not all species were tested by both methods, therefore the comparison has not been possible 

### in all cases. Table 3.1 summarises category scores for 

### all species tested, against each of the 15 signals 

### in the empirical series. 3.1 Atlantic Salmon 

### (Salmo

### salur) Experiments 

### on Atlantic salmon (carried out at Otter Ferry salmon farm) were not included 

### in the Nuclear Electric project brief and therefore centred primarily 

### on the Loeffelman method. Preliminary screening observations only were made using the Nuclear Electric signal series, since availabletime did not allow 

### the full test protocol. 3.1.1 Loeffelman Method Sound Production and Sound Signal Development Large numbers of sounds were recorded from salmon. Many 

### ofthese were associated with quick head movements, of the kind described by Marshall (1962). Figure 3.1 shows 

### a typical example of the sound spectrum and wave-train time series associated with one 

### of these sounds. A 

### low frequency peak at 

### < lOHz represents the head movement. Most of the sound energy was concentrated below 300Hz, with a signal duration of 1.5 to 2s. The sound signal used in the trials was a two frequency sine wave tone at 210 and 275Hz, delivered as a repeated 2 second crescendo at 

### maximum power output. Behavioural Response Recorded counts 

### from the experiments are given in Table Al.l (Appendix). A 

### summary of the data obtained by the counting method is given 

### in Figure 

### 3.2. 

### Mean counts per sector for the observation area were approximately twice as high with sound offas with sound 

### on, yielding a highly significantdifference on both test dates (Figure3.2a). Overallcounts were lower 

### on the second 

### day of the trials (9th December): 

### this was attributed to bright sunlight 

### on that 

### day, which encouraged 

### fish to 

### remain in shadow, 

### on the side of the pool away from the transducer; the previous day was overcast and fish were uniformly distributed around the pool. 

### An effective response was obtained throughout the trials, with 

### no evidence of habituation (Figure 3.28). The subjectiveresponse was classified 

### as Category 

### 3, with most fish swimming steadily away from the transducer but some fish, presumably enteringpoints of high soundpressure, reacting more violently and, 

### on occasions,jumping out of thewater. A fact which the results 

### in Figure 3.2 obscure is that, although some fish were recorded 

### in the observation area around the transducer when the 

### signal was applied, they were 

### not holding station 

### on the streamlines as were the majority of fish countedin the controlperiods. They were swimming past in a disorientated fashion, apparently looking for a means of escape which was not available to them within the confines of the pool. Figure 3.3, which17 compares 

### the alignment 

### of fish relative to strmline direction for test 

### and control periods, gives some indication 

### of the chaotic orientation 

### of the fish when the 

### sound 

### was on. 3.1.2 Empirical h�ethod Results for the initial screening process only are available for Atlantic 

### salmon and are shown 

### in Table 3.1. Strong reactions (Category

### 2: moderate startle) were shown with signals

### 7, 12, 14and 

### 15. 3.2 Brown Trout (Sulmo trutla) 3.2.1 toeffelman Method Sound Production and Sound Signal Development Though sound production 

### in brown trout was less prolific than in salmon, a number of sounds were successfully recorded and analyzed, a typical sound spectrum and time series for a 30cm trout being shown in Figure 3.4. The sounds were heard 

### as dull thumps 

### or clicks, with energy principallybelow 

### 400H2,indicatingthe swimbladder

### as the likely origin. Pulses were brief, 

### of the order 150ms. The original signal developed comprised 200 

### and 

### 3mHz sine waves, delivered as a 

### 2s crescendo at maximum power output. Since it was found that the signal, in this form, propagated poorly 

### in the test pool 

### (see below), the signal was modified subsequently to 

### 200 plus 300Hz. Despite 

### many hours of listening to and recording juvenile trout (1Ocm nominal length), in group sizes of up to 40, no calls were heard. The greater success with the adult trout may have been related to the time of year when the recordings were made 

### - November 

### - the spawning time for this species. Behavioural Response Figure 

### 3.5 shows results obtained with the original 200/300Hz signal. The results indicate no significant response. 

### The observers also reported this as a Category 

### 5 response (no visible reaction), and repeated the experimentthree times with 

### no more success. It was then that the sound level 

### was monitored, showing that the signal would not propagate properly, perhaps owing to destructive interference. The 100/300Hzsignalwas then tested and found to propagate well. The response of the adult brown trout to the 200/300Hz signal 

### is shown in Figure 3.6. A Category 2 response ws observed (startle reaction), 

### With a highly significant 

### (p<O.OOI) redistribution of 

### fish away from the sound source. Thehabituation test shown 

### in Figure 3.6b appears to show a 

### marked reduction through the 

### trial series, 

### the regression line indicating a significant (p

### <0.05) degree ofhabituation. However, further inspection of the data show that the declining differencesbetween control and test distancesfrom the signal source were not the result of the fish moving progressively closer to the transducer but because during the control periods, the fish remained progressively further away. 

### This suggests that the

### 18 fish were leanzing to stay away 

### from the aversive stimulus. 

### As no sound signalhad been obtained for thejuvenile trout, the adult trout 100/300Hz signal was 

### also tested on the juvenile trout. The response was classified as Category 3, with occasional startlereactions by individuals, but never by the whole group. The movement of fish away from the sound source was highly significant 

### @<0.001), and whilst the level of response was somewhat erratic through the experimental series (Figure3.3, there was 

### no indication 

### of significanthabituation. 3.2.2 Empirical Method Adult brown trout showed some, though little, reaction to the empirical series (Table 3.1). Signals 

### 8 and 

### 11 were selected for full trials and the results are shown 

### in Figures 3.8 and 3.9. Both were Classified as Category 

### 4 responses (slight). Statistidanalysis showed 

### no significantresponse to Signal 

### 11, and a small but significant (p

### <0.05) response to Signal 8. Although a slightdownward trend is 

### seen in the habituationregression line (Figure3.8b), it is not statistically significant. Figure3.10shows the results forjuvenile trout. Signal

### 7was selected 

### as the most promising (Table 3.1). In the 

### full trials, the response was classified as Category 

### 3 (steady movement away). Startle reactions were occasionally seen for the odd fish, but never for the whole group. A small but highly significant 

### @<0.001) redistribution 

### of fish away from the transducer was seen. A downward trend in the habituation regression is evident (Figure 3.lob) but this 

### was non-significant. 3.3 Whiting (Merlangiurmerlannus) 3.3.1 Loeffelman Method Sound Production and Sound Signal Development Few 

### sounds were recorded from whiting. A sample spectrum and time series are shown 

### in Figure 

### 3.11. Sound energy was concentrated at frequenciesbelow 

### 500Hz,with a protracted 'bump' lasting over 

### Is. Two sound signals were composed and tested for whiting. One was a dual frequency 360/390Hz signal; the other, 

### 410/480Hz. Both were delivered as a repeated 2s crescendo.

Behavioural Response Results for the 

### 410/480Hz signal 

### are shown in Figure3.13. A highly significant (p

### <0.001) positive response was obtained, with fish moving away from the sound source. There did, however, appear to be a degree of habituation with 

### this signal (Figure 3.12), although 

### this proved not to be statistically significant. Using the second signal, comprising the 360/390& mix, good results were 

### also obtained (Figure 3.13), though with 

### no evidence of habituation.19 Both signals gave 

### a response classified as category 

### 3, with the fish showing a steady movement away from the transducer but 

### no startle reaction. 

### 3.3.2 Empirical 

### Method In screening trials, whiting reacted most strongly 

### to Signal7 vable 3.l),and this signal was selected for the 

### full trials. Results of 

### a full trial are shown 

### in Figure 3.14. 

### The signal evoked a dramatic response (Category l), 

### with fish leaping out of the water when the signal was applied. A highly significat(p 

### <0.001) shift of fish away from thetransducer was observed, with no evidence of habituation. This 

### trial was repeated in full and yielded similar results (Figure 3.15). 3.4 

### Cod lGadm 

### morhual 3.4.1 Loeffelman Method Sound Production and Sound Signal Development Cod were prolificin their sound production. Figure 3.16 shows an example 

### ofa cod sound, which contained, predominantly, frequencies below 200Hz. The sound duration was of the order 

### of 

### 1-2 

### seconds in most cases. The test signal was composed of frequencies 140 

### and 

### 170Hz, delivered as a 2 second crescendo. Behavioural Response The response was classified as Category 3, showing steady movement away from the sound source. The observers described it as "thebest example of this type of response". Curiously, the results 

### of the statistical analysis show a less obvious, though statistically significant (p <0.05), redistribution of fish away from the sound source (Figure

### 3.17). The reason'for this apparently limited effect is that the fish remained mobile throughout the experiment, first moving away from the transducer, then making exploratory movements back towards it, before turning away again. 3.4.2 Empirical Method


### Inpreliminary screening, cod showed Category 

### 2 reactions to Signals 7 and 14 (Table 

### 3.1), 

### and both 

### these signals were fully tested. Results are shown 

### in Figures 3.18 to 

### 3.20. Cod responded obviously to Signal7, giving a

### clear startlereaction (Category2). Significant movement of fish away from the sound source (p <0.05 

### to 0.01) is shown by Figures 3.18 and 3.19. 

### No significanthabituation occurred.20 Signal 14 failed to evoke a useful response when tested 

### in full (Figure 3.20), with only a minor (Category 4) reaction 

### seen. 3.5 Bass 

### Dicentrarchus labrax) 

### 3.5.1 Loeffelman Method Many hours were devoted to listening for bass sounds fromjuvenile and adult fish, under a widerange ofconditions(highllow salinity,highllowdissolvedoxygen, varying temperature) but nonewere detected. Unfortunately,it was 

### not thereforepossible to apply theLoeffelman method to 

### this species. 3.5.2 Empirical Method Signals 7 and 8 both showed a Category 2 reaction in the screening trials (Table 

### 3.1), and both were tested in 

### full (Figures 3.21, 3.22). Both were classified similarly in the full trials, though it was noted that the more obvious agitation lasted only for about 1minute, In statistical terms, both signals proved to have a significanteffect (p 

### <0.05

- 0.01). There was no significantfall-off in response over the trial series. 3.6 Eel 

### (Anguilla 

### anguilla) 3.6.1 Loeffelman Method 

### As for bass, many hours were spent listening to eels, under a similarly wide range of condition, but with 

### no positively attributable sounds. Again, it was not, therefore, possible to apply the Loeffelman method. 3.6.2 Empirical Method Eels showed Category 

### 2 responses for Signals 1

### and 

### 7in screening trials, and both were used 

### in full trials. Reactions ofthe eels to either signal were minimal (Category 

### 4) in the more protracted trials. As the transducer 

### was the only source of cover 

### in the pool, all the eels, 

### on being placed 

### in the pool, dived for cover under the Model 

### 220. They continued to remain within Zone 

### 1, even when the sound was turned 

### on, thus there was 

### no 

### need to apply the statistical analysis used for other species. The slight reaction which was seen was in those eels which were in direct contact with, or 

### very close 

### to the transducer. These showed some signs ofbeing startled when the sound was turned 

### on, but moved only a very short distance away.21 3.7 Herring 

### (Clupea

### harengzis) 3.7.1 Loeffelrnan Method 

### An opportunity to listen to herring sounds was provided 

### by the Dunstaffnage Marine Laboratory at Oban, where numbers of herring are held for experimental work. It was not possible to conduct behavioural 

### trials since neither the time nor facilities were available to do so. 

### A number 

### of herring sounds were recorded, and a typical signal is shown in Figure 

### 3.23. This showed the frequency content to 

### be concentrated in the sub-200% range, with a sound duration of about 250ms.

4 DISCUSSION Since this Report encompasses two studies which began as separateprojects, it is necessary to consider separately how each 

### has matched up to its own objectives. Equally, since they both had the same overall objective 

### of demonstrating the feasibility of moving fish using sound, it is desirable to compare in the same terms how each method performed. However, as both methods were tested in a comparable manner, before discussing either method in detail, it will be helpful to discuss any methodological limitations which are common to both studies. 4.1 Limitations of the Experiments 4.1,l Acoustic Conditions The unpredictable acoustic conditions of small water bodies, such as pools and tanks, considerablyrestrict the interpretationof fish responses to sound. The unpredictabilityarises from the occurrence

### ofreflections, from all the 

### tankboundaries, including 

### thewater surface, and from thepossible constructiveand destructiveinterferenceof reflected waves. This was evident from the failure of some signals to propagate well 

### in the present trials. Depth is 

### also 

### an important consideration, since long wavelengths will not propagate 

### in shallow water. Table 1.2 gives minimum propagation depths for different frequencies, showing that in the Otter Ferry trials, where water depth was 

### 2m, the lowest frequency that would propagate well is 

### 200H2,while for the 1.2m Fawley 

### pool, frequencies below 

### 350Hz would be strongly attenuated. Depth is 

### also important with regard to transducer function: 

### in shallow water, low 

### frequency transducers tend to cavitate or de-gas the water at high amplitudes. 

### In the trials, the Model 220 transducer was driven to the 

### maximum output 

### level that could be achieved without distortion. With a lOOHz signal, this yielded a 

### maximum output level of 138

### dB re 1pPa 

### @lm in the Fawley test pool, 

### and a slightly higher 

### level of 142dB re 1pPa @lm in the Otter Ferry pool. Levels of 180dB re ZpPa 

### elmat this frequency could be expected in open water conditions with a depth of 

### 4m or more.

### 22 The fact that good directional responses were found for most species, despite these limitations, indicates that even better responses could be expected under deep, open water conditions but that, nevertheless, sound should work as a deterrent 

### in less-than-ideal circumstances. It is interesting to note that the Empirical Series Signal 7 produced only a moderate response with bass in the present laboratory 

### trials, whdst when fitted to a power station in far 

### from ideal conditions, a 39%reduction in bass catch was achieved (Thatcher and Irving, 1992). In view of the changeable acoustic field within 

### the test pools, it would be unwise to overinterpret the findings on how fish redistributed themselves in relation to the sound pressure 

### level distributions. The chief point is that the fish, where significant responses were demonstrated, moved away from the sound source. The most important factor, in acoustic terms, was that the sound levels throughout the 

### tank were maintained at a high level relative to the ambient background noise level, which was in the range 

### 65 to 70dB re 1pPa at all times, both at Fawley and Otter Ferry. This represents a differential between test and control SPL of at least 

### 30 to 40dB re lpPa in all trials, for frequencies of 100 to 

### 300Hz. Whilst lower SPLs might prove effective, it would be wise in any future field trials to 

### aim to exceed, in the proposed fish exclusion zone, both the minimum absolute and differential (relative to background) sound levels used in the present trials. 4.1.2 Confinement of Fish An obvious limitation of the present trials was that sound levels were high throughout both the experimentalpools, albeit with some gradation, and the fish had no means of escaping from the sound field altogether. As a consequence, fish trying to flee the sound field had two choices: either move as far away as possible from the source, or search for a way out. Most fish tended to do both to a greater or lesser extent. The confused result for cod with the Loeffelman signal, for example, was not because the fish did not react to the sound but because the main behaviour was to search the tank. 

### In open water, where the system can be placed so as to offer the fish a free choice of movement, a more fruitful response might be expected. The high diversion efficiencies reported 

### by Loeffelman et 

### al. (1991;1993) would tend to confirm this. Whilst the full details of the observations 

### on fish behaviour have been presented in this Report and attempts have been made 

### to apply quantitativemeasures to the responses, again it would be unwise to over-interpret the significance of variations 

### in response seen with different signals 

### used on the same fish species. 

### Any form of positive result, 

### Le., significant movement of fish away from the sound source, indicates that the fish have the capacity to react appropriately to that signal: a more impressivehigh-speed reaction will not necessarily imply a more effectivedeterrence in the field, where a more considered responseby the fish might actually be more effective. 4.1.3 Use of Farm-RaisedFish The 

### salmon and trout used in this study were farm-raised; all other species were taken from the wild.23 Somedifferences 

### are to be expected with farm-&sed fish. At the salmon farm 

### in Scotland, for example, the fish were grown on in ponds suppliedby 

### apulsed aeration system, resulting 

### in their continuousexposure to high 

### level, low frequency noise (no measurementwas made of this). Knudsen 

### et al. (1992) compared the behaviour of wild and hatchery-raised Atlantic salmon and found differences in their escape responses when confronted with high sound levels. They 

### used a tank with a sloping bottom and found that, whereas hatchery-raised fish would make for the most distant part of the pool. when escaping, wild fish would make for the deepest part. This may not be important

### per se, but illustrates that behaviour cannot be assumed to be the 

### Same for farmed and wild fish. 4.2 Performance of the Methods 4.2.1 The Empirical Method The objectives of this part 

### of the work were to consolidate the preliminary laboratory findings presented by Thatcher and Turnpenny 

### (1992) and Thatcher and Irving 

### (1992) by developing a more objective test method which also assessed habituation, and to extend the approach by testing a wider variety of signals 

### on 

### a range of estuarine species. These objectiveswere 

### met, with the developmentof a repeatable test methodology,which was 

### then applied to a variety of species with a broader range of candidate signals. Themost obvious finding fromthe empirical trials was that, ofthe sixteen signals under test, few generated any significantreaction. Some assessment of the success obtained with the various signalscan be madeby totalling theResponseCategory scores given

### inTable 

### 3.1 for the screening trials. Here, the lower the number, the more effective was the signal over a range of species. This information is more easily absorbed when the scale is reversed by subtracting the totals from the maximum available score of 35, as shown 

### in Figure 

### 4.1. In this scheme, signals which produced no response at all, with any of the species tested, yield an overall zero value. 

### On this basis, 

### all signals but numbers 3,4 and 10 evoked some response 

### in fish. Other signals produced varying degrees 

### of response, but outstanding amongstthem all were the Group 3 Signals, numbers 7 and 8. When subjected to the full test protocol, only these two signals produced a statistically-verifiable deterrence response Figure

### 4.1). The success ofthese signals over the others may be owing 

### to the combination of high signal amplitude and the frequency sweep: 

### a swept frequency band offers nonspecific frequency targeting, while maintaining maximum amplitude across the whole frequency band. All other signals in the series either had reduced amplitude during part of thedelivery

### cycle(crescendoorpulsed signals), reducedfrequencycoverage(fixed frequency signals) or reduced amplitudesince the signal was spread over a range of frequencies at the same time (e.g. broad band signals). If a single signal were required for multi-species deterrence, Signal 7 would clearly be the one to choose: it had the largest Fish Response Score (Figure 

### 4.

### I) and yielded a Category 3 or better response from all of the species on which it was tested (Table 

### 3.1). In 

### no trial was there any evidence

### of fish becoming habituated to the signal.

### 24 The onefailurewith the empirical method was the European eel. The lack of any significant deterrence effect may have been a result of using inappropriate signal frequencies. 

### In the absence of any published information 

### on hearing or sound production 

### in this species, the question cannotbe resolved. A second possibility 

### is that, since eels taken from low salinity or fresh waters are benthic in habit and their swimbladders are not fuily inflated, they may not be sensitiveto sound pressure. This would limit 

### any sound detection to 

### the near-field of the transducer, perhaps explaining the slightresponse observed for eels in close contactwith 

### the transducer. There is 

### no doubt that 

### the cover provided by the transducer provided stronger attractive influence 

### on eels that the aversive stimulus of the sound. 4.2.2 The Loeffelman Method The main objective with these trials was to confirm that the method, 

### as developed by Loeffelman and co-workers, would work with estuarine species of interest within the 

### UK. Of seven species investigated in the trials (Atlantic 

### salmon, brown trout, cod, whiting, eel, bass, herring) only fourcould be fully tested using the Loeffelman method, since no relevant sounds were detected for bass and eel, despite protracted 'listening'. For four species, sounds were successfullyrecorded 

### and analyzed and, in all cases, effectivedeterrent signals were developed and statisticallyproven. In herring 

### dso, sounds were recorded that would have enabled signal development, but there was no opportunity to conduct behavioural trials on this species. No habituation to the test signal was detected in 

### any of the species tested. 

### In brown trout, there was evidence that fish learnt to stay away from the sound source. 4.2.3 Comparison of the Loeffelman 

### versus the EmDiricai Method 

### For those species which do not readily (if at all) produce sound, the Loeffelman method is clearly not applicable and this must be recognised 

### as a potential limitation of the method. Most species in the present study did produce sound, with only bass and eelremaining silent. If their close American relatives (Table 1.3) are 

### any indication, these species may be sound producers, given the right conditions. According to Loeffelman (pers. comm.), fish tend to 

### be more vocal at warmer temperatures, whereas thepresent studies were conductedin wintertime. It would be worth making further attempts 

### with these species during the summer months. There may 

### also be differences between males and females of 

### the same species, and some life stages may be more talkative than others, 

### as found in thepresent study 

### with brown trout. With regard to the relative efficacy of the signalsproduced by 

### the two methods, the results must be treated 

### with caution, owing to the limitations stated above. 

### A comparison can only be made for those species which could be tested by both methods, 

### Le., the salmonid and gadid species. Both produced 

### statistically-signifTcant 

### (p=0.05 orbetter) movement of these away 

### from the sound source. A summary of the responses obtained by each method is shown in Table 4.1. For salmon, the Empirical Series signal produced a stronger response (Category

### 2 

### versus 3) 

### thanthe Loeffelman signal, though forbrown trout adults andjuveniles more marked reactions were obtained using the Loeffelman method. Cod and whiting25 reacted more strongly to the Empirical Series signals. Overall, the Empirical Series scored more successes, chiefly because more species could be tested. The principal differencebetween the two methoiis is the degree of customization: the signal 

### (No. 

### 7)selected as being most effective from the Empirical Series offers, potentially, a broad-spectrum deterrent which might be expected to work for a range of fish species 

### in 

### an indiscriminate way. This range might 

### need to be shiftedup or down to cater for fish with higher or lower frequency hearing optima. The Loeffelman method, 

### on the other hand, is sharply focused 

### on individual species. The degree of discrimination was obvious during the trials, when signalsdeveloped forone species were tried out on others, invariably producing negligibleeffect. As much may beinferredfromthe Empirical Seriesscreeningtrials, where a number of signalswhich were generally similarto those derived 

### by theLoeffelman method, typically comprisingone or more tones applied as acrescendo (e.g. Signals

### 9 and 10)evoked virtually no response in any of the fish tested (Table

### 3.1). The Loeffelman method may be 

### used for multiple species and lifestages

### by combining signals designed for individual species into 

### a signal train or, in some cases, by electronically mixing the signals into one signal. Trials currently being undertaken by Loeffelman and co-workers on the Sacramento River in northern California are 

### taking advantage of the selectivepotential of the method, where a high frequency signal (about 

### 1.5kHz) is being used to deter down-migrating juvenile chinook salmon: this frequency 

### is believed to be well above the hearing range of adults returning up-river and therefore should disturb their migarations. The results from this trial are not yet available. The method could also be used to guide species during sequentially timed migrations by having different signals running at different times of the year. The sound system offers this flexibility. Habituation of fish to the sound signals was not found with either method in the present study. Habituation to sound has been found to occur in Atlantic salmon (Knudsen 

### et al., 1992),presumably 

### as a result 

### ofthe differentnature 

### ofthe sound signals used in their study. These authors 

### used 

### a sound which was constant in both frequency and amplitude, whereas either or both were continuously varied in the successfulgignals used in the present study. The replicate experiments in the present study were carried out over a period of a day or more and the absence ofhabituation on this timescale should ensure that a sound system will remain effective for 

### any population migrating past a water intake. The findings for brown 

### trout may 

### also indicate that a more residentpopulation may quickly 

### learn to stay away from the sound field. This would therefore meet the requirements for fish protection at coastal and estuarine thermal or hydroelectric plants, as well as other types of water intake.



### 5. CONCLUSIONS 5.1 Both the Loeffelman signal developmentprocess and the empirical screening method were successful

### in producing signals which could be shown to have a statistically-significant 

### (p<0.05) and, in most cases highly significant (p<O.OOl) deterrent effect in laboratory trials. 5.2 The empirical approach yielded one signal, based on a constant amplitude, swept frequencyrange, which was shown to be effectivewith all the fish species tested, apart from eel. Neither method was successful with eels,5.3 A limitationexperienced with the Loeffelman approach was that two out of the seven speciestested did not produce sounds in the trials, and thereforeno signalcouldbe developed for them. This risk may be reduced by developing better protocols 

### to ensure that sound production from a particular lifestageis encouraged. This limitation has not been apparent in previous North American work by Loeffelman and co-workers. 5.4 No evidence of habituation was detected in the trials. 

### In one species (brown trout), the fish quickly learnt to remain away from the sound source, a featurewhich would enhance the protection of populations resident near water intakes. 

### 5.5 Based on the effectiveness of the signals 

### in these laboratory trials, a properly designed and installed sound system should should be capable 

### of guiding fishpast water intakes. For tidal barrage applications, this would need to be be designed as part of a complementary system of acoustic deterrents and fish passes that would encourage fish to pass via routes other than the turbines.

6. RECOMMEXDATIONS 

### 6.1 Signal Development Method 

### 6.1.1 For broad 

### spectrum applications, where it is desired to deter the widest range of fish species and life stages possible, the swept frequency signal developed under the Nuclear Electric plc contract 

### is most appropriate. In the present trials, this type of signal produced a sound field which 

### was repulsive to all species tested, apart from eels. However, the 100 to 

### 500Hz sweep used might not be appropriate to 

### all species: there is scope for definingthe optimum range for the particular suite of species and life stages using the Loeffelman method. 

### 6.1.2 For applications where it is neccessary to deter selectively particular life stages 

### or species, the Loeffelman method potentially offers a higher degree of targeting, provided that the overlap 

### in auditory spectra is small. This approach is currently being tested in North American trials, where it necessary to deter downstream-migrating juvenilefish while, at the same time, not deterring upstream adult migrants of the same species. Multiple signals can be compiled into a single signal 

### trainbut, for non-specific deterrence, it would be easier in practise to use a swept signal for this purpose. 

### 6.1.3 To make thebest use of the heffelman method, furtherinvestigation of factors and conditions which lead fish to vocalize is required. These may relate to environmental conditions such as temperature, salinity and daylength,

### or the physiologidanatomical state of the fish, which may be related to lifestage, sex or season.

6.2 Field trials 

### 6.2.1 The results of these laboratory trials have met the chief objective of.showingthat 

### a selection of British estuarine species which are of conservation or fisheries interest can bemoved 

### in a predictable 

### way using approPriate underwater 

### sound signals. It 

### is therefore recommended that 

### the programme should

### be 

### taken on to the next phase 

### of proposed testing 

### on

### an estuarineormastally sited 

### nuclear power 

### station. 

### NuclearElectric plc's 

### Hinkley Point B Power 

### Station is the preferred option, 

### for the following 

### reasons: i) NuclearElectric plc have 

### in excess 

### of 12

### years data on seasunal catch rates 

### of fish, which would aid in statisticalplanning of the 

### trial. ii) The cooling water 

### intakes are located offshore 

### in high tidal-velocity, turbid waters; no other 

### type of behavioural 

### fish deterrent system would be feasible under these conditionsand 

### so the system 

### would be 

### highly relevant 

### to this 

### type 

### of site 

### and a severe test 

### ofthe system's durability; the conditionsare 

### also typical of those 

### at potentialtidal barrage sites 

### in the UK. iii) There is tunnel access to the offshoreintalce structure at the site, and an electricalpower supply, adequate for the needs of the acoustic deterrent systemhardware.

Theautumn-winter

### period is 

### oneofseasonally-highfish catch, and wouldbe optimal forthe trial. 6.2.2 Before conducting such a 

### trial, it will be 

### necessary to 

### carry out a 

### full planning survey at the test site to assess the flow geometry and acoustic conditions. Only then will it be possible to specify the number and size ofthe underwater transducer units 

### and associated driving systemrequired. The sound systemwill need to generate sound levels 

### >40dB above ambient levels. It isrecommendedthat theplanning survey shouldbe carried outinthe summer

### months, with a view to system inscallationIater in 1993for testing in the same year. 

### 6.2.3 Sinceabroad spectrumdeterrent, effectiveagainsta widerange 

### of species, isrequired for this site, it is recommended that the Empirical Series 

### 7 signal be adopted for this 

### trial.28



### REFERENCES Campbell, 

### R 'C, 1974. Statistics for Biologists. Cambridge,University Press, 385 pp. Clarke, 

### G M, 1969. Statistics and Experimental Design. London, Arnold, 161pp. Day, 

### F, 1884. The Fishes of Great 

### Britain and Ireland (Volume

### ZI). London, Williams and Norgate, p.234-236. Fish, 

### M P, 1954. The character and significanceof sound production among fishes of the western North Atlantic. Bingham Oceanographic Collection, Bulletin 14 (3), pp3­ 109. Fish, M P and Mowbray, W H, 1970. Sounds ofwestern North Atlantic Fishes: a Reference File of Biological Underwater Sounds. London, John Hopkins, 207 pp. Hawkins 

### A D, 1986. Underwater sound and fish behaviour. 

### In: The Behaviour of Teleost Fishes, (Ed. Pitcher, T J), London Croom Helm, pp 114-151. Klinect D, Loeffelman P H and Van Hassel J H, 1992. A 

### new signal developmentprocess and sound system for diverting fish from water intakes. Proc. Amer. Power Conference, Illinois Institute of Technology, April 13-15, 1992, Chicago, Illinois. Knudsen, F R, Enger, P S and Sand, 0, 1992. Awareness reactions and avoidance responses to sound injuvenile Atlantic salmon. J. Fish Bid,40 (4), pp523-534. Loeffelman 

### P H, Van Hassel J 

### H, Klinect D A, 1991. Using sound to divert fish from turbine intakes. 

### Hydro Review, October, 1991pp 30-43. Loeffelman P H, Klinect D A and Van Hassel J H, 1993. A behavioural guidance system for fish using acoustics customized to target fish hearing. 

### Can. J. 

### Fish.Aquat. Sci. 

### , (in press). Marshall, 

### N B, 1962. The biology of sound-producing fishes. 

### Symp. Zool. 

### SOC. London, 7, pp 45-60. Moulton, 

### J M, 1960. Swimming sounds and the schooling 

### of fishes. 

### Biol. Bull. 

### Woods 

### Hole, 119, p210. Patrick P H, McKinley R S,Christie A E and HolsappleJ G, 1988. Fish protection: sonic deterrents. 

### In: 'Proceedings: Fish Protection at steams and Hydro electric Power P�ants', pp 4.1-4.12. Electrical Power Research Institute. 

### EPRI CS/EA/AP-5663- SR.29 

### Ray S S, 

### Snipes R L and Tomijanovich 

### P A, 1976. A state-of-the-art report on intake 

### technologies. Rept. to Office of Res. and Dev., 

### US 

### Envir. Protect. Agency, Washington 

### DC. EPA-60. 0/7-76-02 

### 0. Solomon D J, 1988. Fish passage through tidal energy barrages. Energy Technology Support Unit, Harwell. Contractors Report Number ETSU 

### TID 4056, 76 pp. Solomon 

### D J, 1992. Diversion and entrapment of fish at water intakes and outfalls. National Rivers Authority, R&D Report No. 1, 

### NRA, Bristol BS12 2UD. Tavolga, 

### W N, 1971. Soundproduction and detection. 

### In: Fish Physiology 

### (eds. Hoar, WS and Randall, 

### D 

### J), London, Academic, pp.135-263. Thatcher K P and Turnpenny A W 

### H, 1992. Acoustic fish deterrent system: preliminary observations, 1991. Report to National Power plc and Nuclear Electric pfc. FAWLEY arl Report No. FCR 008/92. FAWLEY arl Ltd, Southampton SO4 1W, 

### ZIX. Thatcher

### K P and Irving P, 1992. Fish deterrenttrials at Oldbury Power Station,November 1991 to January 1992. Report to National. Power plc and Nuclear Electric plc, FAWLEY arlReportNo. FCR009/92. Fawley 

### arlLtd, SouthamptonSO4 lTW, UK. Turnpenny A W 

### H, 1988. The behaviourial basis 

### of fish exclusion from coastal power 

### station cooling water intakes. 

### CEGB Research Report 

### No. RD/L/3301/R88.
Turnpenny A W H and Coughlan, J., 1992. Power generation on the British coast: thirty 

### years of marine biologicalresearch. Hydroexol. Appl. 

### (4) 1,pp 1-11. Turnpenny A W H, Davis M H, Fleming J M and Davies J K, 1992. Experimental studies relating to thepassage of fish and shrimpsthroughtidalpower turbines. Unpublished report to National Power plc and AEA Technology, Harwell.

# Figure 1 .I. 

# Audiograms 

# of Teleost 

# Fish

140

100

80

60

50 100 200 500 1,000 2,000 5,000 10,000 

## Frequency 

# (Hz)

Adapted 

# from Hawkins, 1986

# Figure 2.1 

# Equipment Used

# for 

# the 

# Recording

. 

# and Analysis of 

# the Fish 

# Sounds

(a)Fish 

### Recording Apparatus 

### (from 

### Klinect et 

### al, 1991)

Charge Amplifier



### B&K Model 8103 Transducer 

### fn OX7520 

### i Rockland 

### 1 Digital Spectrum Oscilloscope Analyser

Loudspeaker

AlWA HD-SI DAT Recorder 

### (b)

### Block 

### Diagram of 

### fnstrumentation

# Figure 2.2 Description

## of 

# Signals in

# the

# Empirical 

# Series 

# used for 

# the

# Nuclear Electric Trials

(a) 

### Example of pure sine 

### wave @ 

## i63 Hz

. 

### pool

,. . . . . . . . . , -19.7 rSiC 1:-13 .ZE-3 58.5 m 

### Example 

### of 

### 163Hz crescendo

..... ....

-394. rSEC 

### (e) Definitions 

### of a31 

### 16 signals 1. Sine wave, 163Hz 2. Sine wave, 217Hz 3. Sinewave, 294Hz 4. Sine wave, 163Hz, 10 cycle burst 5. Sine wave, 217Hz, 10 cycle burst 6. Siewave, 294'&, 10 cycle burst 7. Sine wave, sawtooth sweep from 100 to 500Hz, 4.5Hz sweep rate

. 8. sine wave, Sawtooh sweep from 100 to 500% , 2.5% sweep rate 9. Sine wave, 163Hz, 1s crescendo 1.1714 SIC 10. Sinewave, &xed 163,217and 294Hz, 1s crescendo 11. Sine wave, 163-197Wz sweep crescendo 12. Sinewave, 217-253'Hz sweep crescendo 13. Sine wave, 294-340Hz sweep crescendo 14. Sine wave, 163, 217 and 294 Hz sweep

. crescendo 15. Sine wave, multi-frequency 139 to 463Hz, 500mspulses 16. Sinewave, multi-frequency139 to463Hz, 1s crescendo....................

\ /

.................. , I

# Figure2.4. 

# The 

# Otter Ferry Test-

# Pool 

# Used

# for Atlantic 

# SalmonTrials

s3

9 Observation 

### a Observation Point 3 \



# 15m

/

Obsewafion Point Point i Point 2

Groundlevel

# Figure 2.5.The 

# Fawley 

# sound 

# Pool

. 

# (a) 

# Plan View

\



## 5rn Submersible 

# ' D
Light2

\ I' Tangential discharge 

# (b) 

# Section 

# n Overhead TVCamera

# Figure 2.6. 

# Isopleths 

# of Sound 

# Pressure 

# Level easiared 

# at 50% 

## Depth in 

## the 

## Fawfev Sound 

# Pool (a) 

## Signal

# - 300 

# Hz Sine 

## Wave



## (b) Signal 

# - 100 

## Hz 

# SineWave

## Fiaure

## 2.6. Isopleths 

## of Sound 

## Pressure Level Measured at 50% 

## Depth 

## in the Otter Ferrv Sound poof 

## (e) Signal

# - 210 

## Hz 

# SineWave

level =6570dBRMS

Backgroundsoundlevel = 6570dB RMS

# Figure2.7. 

# Concentric 

# Zones Used

# for 

# Scorinq 

# of Fish Distribution inthe 

# Fawlev

# Sound 

# Pool

J



# Area adjustments Area 2 = 

## 1,21 

## (Area 1) 

## Area 

# 3 = 

## 1.27(Area 1) Area 4 = 

# 1.69(Area 1) Area 

## 5 = 

## 1.64(Area 

## 1) Area 

## 6 = 

# 1,03(Area 1)

# Figure3.1 

# (a) 

# Spectrum and (b) 

# Time Series 

# for Atlantic 

# Salmon Sounds, Fish Size 

# - 600g

i i i i i i i i i 110.00

d0R

: : : : : 3 

### ......

....

30

. _,__I_.._.... 0.00 Frequency/Hz 1000.0

### Figure 

## 3.2 Summary 

### of 

### Resultsfor

## Atlantic Salmon Deterrence Signal: 210Hz and 

### 275Hz,

### 2 second 

### crescendo 

### (Responsecategory 3) Tbe experimentwas performedin a 15m diameterx 2m deeppool. Observationswere madeofthe numbersoffish presentwithin adefinedarea (45 sq. m) closeto#e Model 220 transducer. Countswere made every30soverten Sminutetestperiods, alternatingwith controlandrest periods. 

## Fish

# Countswith 

## and without 

## Sound

m Otter Ferry, 8-95ecember,l992 

# 3 70



### Mean 

### counts and significanceof 

### differences: {seeAppendixt, TableAI.I for full&ta) 8thDecember9thDecember SoundOR 15.2(3.6) 13.0 (7.3) Sound on: 7.0 (2.3) 7.7 (4.3) p<O.OOI p<O.OOI 

## Habituation

8thDecember

- -so

# Figure 

# 3.3 

# Fish Orientation 

# Relative 

# to Streamlines, 

# with and 

# without 

# sound Atlantic Salmon,Otter

### Feny,9th December 1992

25 

# Sound Off

-90 -80 -70 -60 -33 -40 -30 -20 -10 0 10 20 30 40 53 50 7u 80 90 -85 -75 4s -55 -45 -3s -25 -15 -5 5 15 25 35 45 55 65 IS 85 Anglefromflow 

# Sound On

-90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 -85 -75 -65 -55 -45 -35 -25 -15 -5 5 I5 25 35 45 55 65 75 115 Anglehm flow

# Figure 

# 3.4.(a) Spectrum 

# and (b) 

# Time 

# Series 

# forBrown Trout Sounds, 

# Fish Size



# - 

# 30cm

dBR

30 0.00 Frequency///Hz 1000.0



## RelativeAmplitude

0 Timeims

### Figure3.5 

### Distributionof 

### Fish in the Fawley

### Pool,with and withoutSound Signals Species: BrownTrout (adult) 

### Salmo trutta (Response Category5) Signal Description: 

### 200 & 300 

### Hz, 

### 2 second crescendo 

## (a)Adjusted Distribution of 

## Fish 901

1 2 3 4 5 6 Zone Number Sound Off USound On

Kolmosrorov-Smimoff TwoSample Testfor Significant DifferenceinFish Distribution MeanDistance of fish

### From Sound Source (metres) Sound Off: 1.49 Sound On: 1.58

5.00 13.26 32.95 196.15 193.62 0.95 

### I 0.93 

### I 0.02 6.00 11-06 15.33 207.21 208.95 1.00

### I 1.00

## I 0.00 Sum 207.21 208.95 

### Max Difference 0.03 Siginficance Level: Not Significant 

## (b) HabituationTest Differencein Distancefrom TransducerinTest andControl Periods 1.5

-1.5 1 ' 1 2 3 4 5 6 7 8 9 ie Number of Exposures r-squared =0.34 No1Significant

### Figure 3.6 

### Distribution of 

### Fish in 

### the Fawtey Pool,

### with 

### andwithout 

### Sound Signals Species: 

## Brown Trout 

### (adult) 

### Saimo

## frutta (Response Category2) 

### SignalDescription: 100 & 

### 300 

### Hz,2 second crescendo 

## (a)

## Adjusted Distributionof 

## Fish 601

1 2 3 4 5 6 Zone Number Sound Off L1Sound On
KolmogorovSmimoffTwo-Sampie Testfor SignificantDifferencein Fish Distribution Mean Distanceof Fish From Sound Source(metres) Sound Off: 2.23 Sound On: 2.79

5.00 28.59 46.56 181.71 158.14 0.90

## I 0.83

## 1 0.07 6.00 21-05 33.37 202.76 191.50 1.00

## 1 1 

## .ooI 0.00 Sum 202.76 I91-50 Max Difference 0.20 SiginficanceLevel: p<0.001

# (b) HabituationTest Difference in Di&n& from Transducer inTestand Control Periods 3,

-3 I ' 

### I 1 2 3 4 5 6 7 8 9 10 Number of i3posures r-squared = 0.70 p~O.aOl:

# Figure 

# 3.6 (continued) (c) 

## Testing

# for aLemtResponse

1 2 3 4 

### 5 6 7 

### 8 9 

### 10 

# Number ofExposures 

## Sound On Control

Testfor effect 

### shown in

### figure 3.6(b)being a 

### learnt response. 

### R Squared 

### 0.59 Significantat 

### p 0.01

### Figure3.7 

### Distributionof Fish 

### inthe Fawley

### Pool, with andwithout Sound Signals 

### Species: BrownTrout 

### (juvenile) 

### Saimo frutta 

### (ResponseCategory3) Signal 

### Description: 100 & 

### 300 

### Hz, 2

### second crescendo 

## (a) Adjusted 

## Distributionof Fish 300 250 

### 5 200 C 

# g 150 Q & loo 50

0 6 Sound Off USoundOn

KolmogorovSmimoff TwoSampie Test for Significant Differencein Fish Distribution Mean Distance of Fish FromSoundSource (metres) Sound Off: 3.61 Sound On: 3.92

SiginficanceLevel: p<o.001 

## (b) Habituation 

## Test Differencein Distancefrom Transducerin Testand ControlPeriods 8

- 6 ' 1 2 3 4 5 6 7 8 9 Numberof Exposures 10 r-squared =0.01 Nol Significant

### Figure 3.8 Distribution

### of 

### Fish inthe 

### Fawley Pool, with and without Sound 

### Signals Species: 

### BrownTrout 

### (adult) Salmo

## truth (Response Category4) Signal Description: 

### NE Signal #8 

## (a) Adjusted Distribution of 

## Fish 80 70 50 x 

### Em 340 230 U 20 10 0 1 2 3 4 5 6 Zone Number Sound Off USound On

Kotmosorov-Smirnoff Two-SampleTest for Significant Difference inFish Distribution Mean Distanceof Fish From Sound Source (metres) Sound Off: I.74 Sound 

### On: 2.18

5.00

## I 16.44 28.78 207.71 187.32 0.96

## I 0.93 0.03 6.00

## I 7.95 13.39 215.66 200.71 1.00

## 1 1.00

## 1 0.00 Sum 

### I 215.66 200.71 Max Difference 0.16 Siginficance Level: pe0.05

## (b) 

## HabituationTest Difference inDistancefromTransducerinTest andControl Periods 2

-2 I ' 1 2 3 4 5 6 7 8 9 10 Numberof Exposures r-squared 

### =0.38 NotSignificant

### Figure3.9 

### Distributionof 

### FisR 

### in the 

### Fawley Pool, 

### with 

### and without 

### Sound Signals 

### Species: 

### BrownTrout (adult) 

### Saimofrutta (Response Category

### 4) 

### NE Signal #I 

### 1 

### Signaf Description: 

## (a) 

## Adjusted Distribution 

## of 

## Fish 501

I 2 3 4 5 6 Zone Number Sound Off 0 Sound On

KolmonorovSmimoffTwoSample lestfor Significant Differencein FishDistribution Mean Distanceof Fish From Sound Source (metres) Sound Oft 2.10 SoundOn: 2.22

Siginficance Level: Not Significant 

# (6)Habituation 

## Test Differencein Distance from Transducerin Testand Control Periods 15

-1.5 I ' 1 2 3 4 3 6 7 8 9 10 Numberof Exposures r-squared=0.02 Not Significant

### Figure 3.10 

### Distributionof 

### Fish inthe 

### Fawby

### Pool, with

### and without 

### Sound Signals Species: 

### BrownTrout 

### (juvenile) Salmo

### frutta (Response Category3) Signal 

### Description: 

### NE Signal #7 

## (a) 

## Adjusted Distributionof 

## Fish

n

0 I 2

- 3 4 5 6 ZoneNumber SoundOff Sound On
Kolmogorov-Smirnoff Two-Sample Test for Significant Difference in Fish Distribution Mean Distanceof Fish From Sound Source(metres) Sound Off: 2.96 Sound On: 3.22

Siginficance Level: p<o.O01

## (b) 

## HabituationTest Differencein Distancefrom Transducer inTestand Control Periods 3

-3 1 2 3 4 5 6 7 8 9 10 Numberof Exposures r-squared= 0.14 Mot Significant

# Figure 3.1 1 

# (a) 

# Spectrum 

# and (b) 

# Time Series 

# for 

# Whiting Sounds, 

# Fish Size



# - 

# 30cm

dBR

30



## (b)

Relative

### Arnplitt

Time/s 1.5I 

### Figure3.12 

### Distributionof 

### Fish inthe 

### Fawley Pool, with 

### and without 

### Sound Signals Species: 

### Whiting 

### (adult) 

### Merlangius

### merlangus (Response Category 3) Signal 

### Description: 41 

### 0 & 480

### Hz,2 second crescendo 

## (a) Adjusted Distribution

## of Fish I 90r 80 70 8 60 @= 540 

### ti= 20 IO

0 1 2 3 4 5 6 Zone Number Sound Off Sound On
Kolmogorov-SmimoffTwoSample Testfor SignificantDifferencein Fish Distribution Mean Distanceof Fish From Sound Source (metres) Sound Off: 3.1 1 Sound On: 3.59

Siginficance Level: p<o.o01

c

### Figure 3.13 

### Distribution of 

### Fish 

### in the Fawley Pool, 

### with and without Sound Signals Species: Wbiting 

### (adult) Merlangius metfangus (Response Category3) 

### Signal Description: 360 & 390 

### Hz,2 

### second crescendo 

## (a) Adjusted Distribution 

## of Fish 100 90 80 ). 70 Em s50 z40 E30 20 10 0 Zone Number Sound Off 

## aSound On Kdrnogorov-SmirnoffTwoSample Test 

### forSignificant Diffemnce in Fish Distribution Mean Distance of Fish From SoundSource (metres) SoundOR 3.26 Sound On: 3.60

Siginficance Level: p<O.OI

2

h E wl­ 

### 8 C 

## 9 O ­ 

### ii m 

### = - a -1 

### a

-2 8

### Figure 3.14 Distributionof 

### Fish inthe Fawley

### Pool,with and withoutSound Signals Species: Whiting (adult) 

### Meriangius

### mertangus (Response Category 1) 

### Signal Description: 

### NE signal

### #7 

## (a)

## Adjusted 

## Distribution of 

## Fish

n
IO

0 1 2 3 4 5 6 Zone Number Sound Off 

## aSoundOn Kolmogorov-SmirnoffTwo-SampleTestfor SisnificantDifference in Fish Distribution Mean Distanceof Fish from Sound Source (metres) SoundOR 2.83 SoundOn: 3.36

5.00 44.48 7037 155.15 133.66 0.91

## 1 0.81 

## 1 0.10 6.00 15.04 31.23 170.19 164.89 1

### .oo

## I 1.00

## I 0.00 Sum 170.19 164.89 MaxDifference 0.27 Siginficance Level: p<O.ool 

## (b) 

## Habituation Test Differencein Distancefrom Transducer inTestand Control Periods 2,

h E VI 0) -0

c 8 0 rn

1 2 3 4 5 6 7 8 9 10 Numberof Exposures r-squared =0.01 NotSignificant

### Figure 3.15 

### Distribution of 

### Fish in 

### the Fawley 

### Pool,with 

### and 

### without Sound Signals 

### Species: Whiting 

### (adult) 

### Mefiangius rnerlangus 

### (ResponseCategory 1) 

### Signal 

### Description: 

## NESignal #7 

## (a) Adjusted 

## Distribution

# of Fish 60 50 2;a c 

## $ 30 Q) 1;: 20 10

0 6 ZoneNumber Sound Off tII Sound On
Kolrnogorov-Smirnoff TwoSampieTest for SignificantDifference in Fish Distribution Mean Distance

### of Fish From Sound Source(metres) Sound Off: 3.18 Sound On: 3.98

Siginficance

### tevei: p<O.OOI 

## (b) 

# Habituation Test DifferenceinDistance from Transducerin Testand Control Periods 3

- 2 E W $ I c: B o 9 n 8 

## -' Q) Q -2

-3 1 2 3 4 5 6 7 8 9 10 Numberof Exposures r-squared = 0.23 MotSignificant

# Figure 3.16.(a) 

# Spectrum and 

# (b)Time 

# Series 

# for Cod

# Sounds, Fish

# Size


# - 45cm

dBR

30



### Relatlve 

# li.

-

0 Timefs I .5

### Fiaure 

### 3.1 7 

### Distribution

### of Fish 

### in the 

### Fawley

### Pool,with and 

### without Sound 

### Signals Species: 

### Cod (adu!t) 

### Gadus

## morhua (Response Category3) 

### Signal 

### Description: 140 & 

### 170

## Hz,2 

### second crescendo 

## (a)Adjusted Distribution of 

## Fish 

# r I

1 2 3 4 5 6 Zone Number Sound Off L_1 Sound On
Kolmogorou-SmirnoffTwoSample 'Testfor SignificantDifference inFish Distribution Mean Disbnceof Fish From Sound Source(metres) Sound OR 3.02 Sound On: 3.41

SiginficanceLevel: p4.05 

## (b) Habituation

## Test Difference in Distance from TransducerinTestand Control Periods 1.5

n l E v Q) 0.5 0 c ...... 

# -

................. ....... ....... Eo

.......................... v) 

### B 4.5 Q) n

1 2 3 4 5 6 7 8 9 10 Number of Exposures r-squared=0.22 Not Significant

### Figure3.18 

### Distributionof 

### Fish inthe Fawley 

### Pool, with and without 

### Sound 

### Signals Species: 

### Cod 

### (adult) Gadus

### morhua (Response 

### Categmy 2) 

### Signal Description: NE Signal

### #7 

## (a) Adjusted Distribution 

## of 

## Fish 50 

# r

1 2 3 4 5 6 Zone Number Sound Off 0 Sound On

Kofmogorov-SmirnoffTwo-Sample Test for SignificantDifferencein Fish Distribution Mean Distanceof Fish From Sound Source (metres) SoundOR 3.16 Sound On: 3.74

Siginficance Level: p<0.05

## (b) Habituation Test Differencein Distancefrom Transducerin Testand ControlPeriods

-1.5 8 1 2 3 4 5 6 7 8 9 Lo Number of Exposures r-squared =0.18 NutSignificant

### Figure

### 3.19 Distribution

### of 

### Fish 

### in the Fawley 

### Pool, with and 

### without Sound Signals Species: 

### Cod (adult) 

### Gadus

### morhua (Response Category2) 

### Signal Description: NE Signal# 7 

## (a) Adjusted Distribution

## of Fish 50 40

z-i g30 a 20 lL 10 0

Sound Off Sound On
KolmogorovSmirnoffTwoSample Test for Significant Difference inFish Distribution Mean Distanceof Fish From Sound Source (metres) Sound Off: 2.84 SoundOn: 3.45

Siginftcance Level: p<o.o1

L5 

## (b) HabituationTest Difference in Distancefrom TransducerinTest and ControlPeriods

5 6 1 2 3 4 NumberofExposures 7 8 9 io r-squared = 0.1 1 Not Significant

### Figure 3.20 

### Distributionof 

### Fish inthe Fawley

### Pool, with and without

### Sound Signals 

### Species: Cod 

### (adult) Gadusmorhua 

### (Response Category4) 

### Signal 

### Description: NE 

### Signal #I4 

## (a)

## Adjusted Distribution 

## of Fish 50

2 3 4 5 6 Zone Number Sound Off 0 Sound On

KolmworovSmirnoffTwo-Sample Test for Significant Difference in Fish Distribution Mean Distance of Fish FromSound Source (metres) Sound Off: 3.41 Sound On: 3.64

5.00 23.71 30.00 57.70 54.25 0.61 

## I 0.57

## I 0.05 6.00 35.79 41.61 92.90 95.87 1.00

## I 1.00] 0.00 Sum 92.90 95.87 MaxDifference 0.1 1 Siginficance Level: Not Significant 

## (b) 

## HabituationTest Differencein Distance from Transducer in Testand Control Periods 1.5

v It\ , 

## \ 0.5 

# 1

.._....___ .... ­ 

### r \ \\ /

-1.5 1 ' 1 2 3 4 5 6 7 8 3 10 Number of Exposures r-squared=0.03 NotSignificant

### Figure 3.21 

### Distribution

### of Fish in

### the Fawley 

### Pool, with and without Sound Signak 

### Species: Bass 

### (adult&juvenile) (Response Category2) Signal Description: 

## (a) 

## Adjusted Distribution 

## of Fish

2 3 4 5 6 Zone Number Sound Off USoundOn
Kolmogorov-SmimoffTwo-SampIe Test forSignificant Difference inFish Distribution Mean Distance of Fish FromSound Source (metres) Sound Off: 3.49 Sound On: 3.89

Siginficance Level: p4.05 

# (b) Habituation 

## Test Differencem Distance from Transducerin Testand Control Periods l.5 1

-1.5 

# I
1 2 3 4 5 6 7 8 9 10 Number of Exposures r-squared = 0.05 Not Significant

### Figure 

### 3.22 Distributionof 

### Fish inthe Fawley Pool, 

### with and without Sound Signals 

### Species: Bass (adult &juvenile) 

### Dicentrarchus labra 

### (Response Category 2) 

### Signal Description: 

## NE Signal 

### #8 

## (a) Adjusted Distribution

## of Fish 601

10

0 4 2 3 4 5 6 Zone Number SoundOff 0 Sound On

Kolmoaorov-SmimoffTwoSample Testfor Significant Differencein Fish Distribution Mean Distanceof Fish From Sound Source (metres) Sound Off 3.37 Sound On: 4.16

Siginficance Level: p<O.OI

## (b) HabituationTest Differencein Distance &om Transducerin Testand ControlPeriods 2

h V E I Q 0 r: Bo v) 5. 

### d Q -1 n

-2 1 1 3 4 5 6 7 8 9 10 Number ofExposures r-squared=0.33 Not Significant

### ... ... ... ... 

# Figure 3.23. 

# (a) Spectrum 

# and (b) 

# Time 

# Series for 

# Herring Sounds, FishSize 

# - 20cm

11 0.00

d8R

...

0.00 Frequency/Hz 1ooc

0 Time/ms

## Figure4.1 

## Fish 

## Response Scores for Empirical Series Signals and 

## Signals Yielding Significant Deterrence

40

a, 

## 6 -30 0 

### m a, Group 3 v1 S 3 0 20 Q u) 

# 2 Group 5 Group 6 r # 10 

### ii

0 1 2 3 4 5 6 7 8 9 10111213141516 

### Signal Number



## Note: Numbers above bars indicatethe number of 

## full trials 

## in which significant (pgO.05) 

## deterrencewas achieved.Table 

### 1.1 Examples 

### of Sound Levels Produced by Various Sources 

### in 

### Air and Water (after Tavolga, 

### 1971)

Source of Sound

r Jet aircraft takeoff at 100 

### m Threshold for human aural discomfort New York subway 

### train at 10 

### m In Air Noisy

- business office

~ ~~ ~~ ~ Home hi-fi system Average converstaion at 

### 1 

### m Private business office Average residence Underwater dynamite explosion at 

### 100

### m 25 hp outboard motor at 

### 15 

### m Large chorus of marine catfish Noise of ships in a busy harbour Large chorus of snapping shrimps at 100 

### m Calm 

### sea (state 0) Squirrelfishhearing threshold 

### Hearing threshold of ostariophysinefishes Sound Pressure Level 

### dB re 

### 1 Pa 134 124 

### 94 84 74 

### 64 54 

### 44 134 124 94 84 74 64 

### 54 34Table 1. 

### 2 SoundWavelengths, Near-FieldDistances and Minimum Propagation Depths in Water 

### for Various Frequencies

Frequency Wavelength Near-Field 

### Radius Propagation 

# m) (m) (m) Depth 

### (m) 50 30 

### 4.8 7.5 

### 15 

# 1 2.4 

# 1 3.8 100 

# I

I 

### 200 7.5 1.2 1.9 0.60 

### 0.94 0.30 

### 0.47 400 3.7 800 1.9 

### 1600 

# I 0.94 

# I 0.15 

# 1 0.23

-

~~

3200 

### 0.47 0.08 0.12

Note: wavelengthsare baed on a sound velociqin waterof1XUlmetresper second; thismay increase io a maximum of 1540 metresper second in sea water,giving a wavelength of 15.4m @ 1OOHz.Table 1.3 SoundProduction and SonicMechanismsin Species of Interest in this Study (Source:Fish and Mowbray, 1970, except where otherwise stated).
Species Descriptionof Sound Production and SonicMechanism

Cod (Gadidae) Loud, low frquency grunts peaking at SOHz, durationea. 0.2 s, Gadus morhua repeated 3 or 4 times : recorded from captive fishduring threat displays, flightof displaced fish and spawningprelimbmies. Muscularvibrationof the mullti-lobed swimbladderis believed to be the source; passage of gas over sharp transverse septabetween the lobes may reinforcethe sound. Frequencyrange 20 to 200Hk. Wting (Gadidae) No specific data given. May be similarto cod. Merlangius merlangus Eel (Angdlidae) No specificdata given, but may be similar to A. rostrata. In this Anguilla anguilla species, protracted clucking soundswere heard, resembling the "putput" of an outboardmotor, spontanwuslow knocks and clicking during night-timeactivityand single dull thuds (25 to 1,200Hz)and rasps inducedby mild shock. Frequency range, 25 to 2,500Hz. Bass (Percichthyidae) No specificdata but may be similartoMorone saxatilis of the same Dicentrarchuslabrax family. Low pitched thumps, single or in bursts of 3 or 4, when startled or electroshocked. Soundis generatedby the swimbladder, which has no special musculaturebut is probably vibratedby the generalbody musculature. Sound is always coincidentwith suddenly increased fish activity. Frequency range not specified. Hening (Clupeidae) Hydrodynamicand swimming noise when Swimmingfast in large Clupeaharengus shoals, especially during veering; shrill mouse-like noises due to swimbladderventing when fish taken out of water; low knocks and thumps stimulatedby handling and electroshock. Frequency range 20 to 300Hz. Twaite shad (Clupeidae) No specificdata. Data for otherAlosa spp. reveal no evidenceof Aha fallax soundproduction in captive fish. In thewild, water noise at the surfacewas heard during frenzied swimming activity. Accordiig to Day (1884), shads are "reputed to take pleasure from music", though there is no evidencethat they make it! Atlantic salmon (Salmonidae) No data given for salmonids. Loeffelmanet al. (1993) recorded Salmo salar soundsfrom Pacific salmon (Oncorhynchus spp.). Frequencies were predominantlybelow 400 to 600Hz, in pulses of 10to 30 ms duration. Brown Trout (Salmonidae) Loeffelman(unpublished)recorded 'softthump' sounds fromadult Salmotrutta brown trout of 60cmlength. Thepredominantfrequenciesproduced were in the 75 to 400Hzrange,Table 3.1 Response CategoriesofDifferentSpecies to the Empirical Signal Series in ScreeningTrials. (See Section2.4.2)

Response Category Summary: 1 = extreme startle; 2 = moderatestartle; 3 = steady swimming away; 4 = slightreaction; 5 = no Visible reaction.Table 

### 4.1 ComparisOn

### of the &&an 

### Fish Distances from 

### the 

### Sound Source (Test minus 

### Control)and Response Categoriesusing 

### SignalsDeve3opedby theLoeffelman and Empirical Methods.

species 

# I Loeffehnan

### Method 

### Mean Distance Respnse Cm) category Atlantic not applicabk 

### 3 salmon Brown trout, 

### Q.56 2 

### adult Brown trout, 

### 0.31 3

juvenile 

### whiting 0.48 3

Cod 0.39 3

Bass not testable not 

### testable

1 

### Ed not testable not testable Empirical Method MeanDistance 

### (m) not applicable

0.44 

### i 0.26 

# I 0.80.


### 0.61
0.40

1 not applical>le Response Category 

### 2

4

3


### 1 

# I 2

2

I 4



### Response Category 

### Summary: 1 

### = extreme startle; 

### 2 = 

### rn0derai.e startle; 3 = 

### steady swimming

### away; 4 

### = slight

### reaction; 

### 5 =no visible 

### reaction. Respmses 

### shamarethe best results recorded 

### in fufl-lengthtrials.

### APPENDIX

Raw Count Data from Otter Ferry Salmon Trials, December I992

### %cD 

### g o zc w ­ *-) n. 

### 0 3

3

### rn x U