207
1 INTRODUCTION
Laist et al. (2001) suggested that risk of vessels
collidingandcausinglethalorsevereinjuriesonlarge
cetaceanswouldincreaseatvesselspeedof14knor
faster.Toreducesuchrisks,theUnderwaterSpeaker
(UWS) has been installed to a high speed vessel,
Hydrofoil,whose maximum speed reaches at 45 kn.
TheUWSgeneratesasoundofacetaceanrepellantto
scareoffcetaceans,anddecreaseariskofhydrofoils
collidingwithwhales.However,unfortunately,itdid
not prevent the collisions complet
ely, because the
noise level of the sound currently installed on the
hydrofoilswastoosmalltotriggerarepellantreaction
againsthydrofoilsbycetaceans(Y
amadaetal.2012).
Thus, the new sound was devised by Yamada et al.
(2015). The characteristic of the new sound source
would be using a potential repelling sound for
cetaceans and synthesizing audible frequency for
whalewithcollisionrisk(Patentappliedfor,JP2014‐
171411).Inthi
sresearchproject,theimprovementof
this new sound was investigated through following
tworesearches:
1.1 PlaybackExperimentoftheNewSoundonHumpback
Whale(Megapteranovaeangliae)inOkinawa,Japan
The effectiveness of the new sound triggering
physiological and behavioral changes of Cetacean
was investigated with a pla
yback experiment on
humpback whale in Okinawa, Japan. Humpback
whale was preferred as a subject species for this
experiment due to its frequent surface intervals and
easy indication of surfacing behavior. Also,
humpbackwhaleislistedasacetaceanofhighestrisk
of collision with hydrofoils. The experiment was
Repellence Effect of the New Sound for Underwater
Speaker of Hydrofoil
T.Nakashima,N.Kobayashi,H.Yamada,T.Katsumata,R.Yoshida,&H.Kato
TokyoUniversityofMarineScienceandTechnology,Tokyo,Japan
H.Okabe&I.Kawazu
OkinawaChurashimaFoundation,Okinawa,Japan
Y.Yanase,M.Omine,&M.Terada
KHIJPSCo.,Ltd.,Kobe,Japan
H.Sugioka&M.Kyo
J
apanAgencyforMarine‐EarthScienceandTechnology(JAMSTEC),Yokohama,Japan
ABSTRACT:Inordertopreventhydrofoilcollidingwithcetaceans,theunderwaterspeaker(UWS) hasbeen
installedtorepelcetaceans.Yamadaetal.(2012)analyzedanddevisedtheUWSsoundasitfitsthecetaceansʹ
acousticpropertiestopreventthecollisionfurthermore.ThenewUWSsoundwasdevisedandsynthesizedby
Ya
madaetal.(2015) with expectation of avoiding collision with large cetaceans(Patentapplied for, JP2014‐
171411). In this research project, the new UWS sound was investigated by the playback experiment on
humpback whale (Megaptera novaeangliae) and by sighting survey in the act
ual hydrofoil shipping service
route.Asaresult,aphysiologicalandbehavioralchangeofthehumpbackwhalewasobservedintheplayback
experimentofthenewUWSsound,andthechanceofhydrofoilencounteringcetaceansofthenewUWSsound
wassmallerthanthatofthepreviousUWSsound.Therefore,theimprovementofthenewUWSsoundwas
confirmed.Lastly,wewishthi
sresearchprojectwouldcontributetowardthesafercruiseofhydrofoilinthe
future.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 9
Number 2
June 2015
DOI:10.12716/1001.09.02.07
208
analyzed both qualitatively and quantitatively to
confirmthenewsoundtriggeringthereactions.
1.2 SightingSurveyfromanOperatingHydrofoilwith
theNewSoundinNiigata,Japan
Itisalsoimportanttounderstandtheimprovementof
repellanteffectofthenewUWSsoundinactualusage
condition. The new sound
was installed to the
operating Hydrofoil, and the effectiveness of this
soundwasinvestigatedthroughthissightingsurvey.
Theprobabilityofsightingoftheprevioussoundand
new sound was calculated from the sighting record
andcomparedbetweenthetwosounds.
2 METHOD
2.1 PlaybackExperimentoftheNewSound
on
HumpbackWhale(Megapteranovaeangliae)in
Okinawa,Japan
Inordertoinvestigateandexaminetheeffectiveness
ofthenewUWSsound,theplaybackexperimentwas
conductedatoffthecoastofMotobutown,Okinawa,
Japan (Fig 1). The Furuno Electric Company’s UWS
(FC‐510K)wasausedinthisexperiment.
Figure1. Map of Okinawa, Japan. Black dot indicates
MotobuTown.
Before operating the experiment, any surfacing
behavior,includingsurfacingintervaltimeandbreath
count,ofthetargethumpbackwhalewasmonitored
and recorded as the research ship follow after the
whale with enough distance for at least one hour.
These behavioral data was recorded every time the
whalesurfacethroughoutthis
experiment.Then, the
research ship moved to the next expected surfacing
areaofthewhaleandceasedtheenginetooperatethe
experiment.
TheUWSwasputtwometersundersurface,and
thesound was generated as the whale surfaces. The
loudness of the sound was controlled based on
distance
tothewhalewithaudiopoweramplifier.The
voltage gain of‐35 dB for those surfaced near the
researchship(300metersorless),and‐18dBforthose
at further distance (300 meters or more) and those
appearedtobenoreactionagainstthe‐35dBsound.
Thesoundwasstopped
whenthewhaledivedownor
anintensivereactionwasobserved.Thebehaviorwas
continuously monitored after the playback
experiment for at least another one hour until its
behaviorwasappearedtobebacktonormal.Allthe
experimentalprocedureswererecordedonvideofor
furtheranalysis.
The effectiveness of
the new UWS was analyzed
basedonanychangeinrecordedbehavioraldata;any
significant difference in behavior from before and
aftergeneratingsoundwasconsideredasthereaction
againstthesound.
2.2 SightingSurveyfromanOperatingHydrofoilwith
theNewSoundinNiigata,Japan
The repellant effect of the
new UWS sound was
investigated through the sighting survey from May
12th, 2014 to June 10th, 2014 in Niigata, Japan. This
surveywasconductedwithasupportofSadoSteam
ShipCo,Ltd,whoownsthreehydrofoilsforshipping
servicebetweenNiigatacityandSadoIsland(Fig2).
Figure2.MapofNiigata,Japan.(A)isRyotsuPortofSado
Island, and (B) is Niigata port. The hydrofoil shipping
servicerouteisindicatedasblackline.
Thepurposeofthissurveywastoinvestigatethe
repellenteffectofthenewUWSsoundundernormal
hydrofoiloperatingservicecondition.ThenewUWS
sound was installed to one of their hydrofoils, and
cetaceansightingrecordswerecollectedfromall the
three hydrofoils, one with the new UWS sound and
two with the previous UWS sound, under normal
operating service condition. The sighting records
werecollectedfromthecockpitofhydrofoil.
From the sighting record, the probability of
sighting,whichequalstothetotalnumberofcetacean
sightingrecordsdividedbytotalnumberofshipping
services of hydrofoil during the
survey period, was
calculated for both the new and previous UWS
sounds. This probability indicates a chance of
hydrofoil encountering cetaceans in one shipping
service basis, thus, smaller probability means less
chance of encountering cetaceans and so that less
chanceofcollisionwithcetaceans.
209
3 RESULT
3.1 PlaybackExperimentoftheNewSoundonHumpback
Whale(Megapteranovaeangliae)inOkinawa,Japan
Total of three trials of playback experiment were
conducted. In each trial, the route and speed of
researchshipwas recorded. The direction, speed, or
both had changed after generating the new UWS
sound,whichimplies that the target whale also had
changeditsdirectionandswimmingspeedsincethe
research ship follow after the whale throughout the
experiment(Fig3).
In the first trial, the whale quickly changed its
direction,movingawayfromtheship,withincreased
swimming speed after the new
UWS sound was
generated. The distance became even further in one
surface period, and thus, the voltage gain was
increasedfrom‐35dBto‐18dBinthissurfaceperiod.
The result of the second trial was distinctive from
othertwotrialsbecausethetargetwhalewaslostafter
generating the new UWS
sound. A change of
directionandanincreaseofspeedwerealsoobserved
inthethirdtrial.
Thephysiologicalandbehavioralchangewasalso
confirmed by the results of surface period and
breathes count record (Fig 4). In the first trial, the
surfaceperiodandbreathcounthadincreasedas
the
whale swim away from the ship. The new UWS
sound caused a physiological change in whale’s
behavior. For the second and third trials, either
surfacing interval time or breath count increased
relatively as well at the point when the new UWS
soundwasgenerated.
3.2 SightingSurveyfromanOperating
Hydrofoilwith
theNewSoundinNiigata,Japan
Inthissurvey,thenewUWS soundwasinstalledto
the operating hydrofoil, and the cetacean sighting
recordwascollectedundernormal operatingservice
condition.Thesightingrecordwascollectedfromone
hydrofoil with the new UWS sound and two
hydrofoilswith
thepreviousUWSsound.Inorderto
compare the sighting records based on the type of
installed sound, the probability of sighting, which
equalsthenumberofsightingrecorddividedbytotal
numberofhydrofoilservice,wascalculated.
For the previous UWS sound, during the survey
period,totalofsixsighting
recordwascollectedoutof
343 services, while only one sighting record was
collectedoutof185servicesforthenewUWSsound
(Fig5).
A.PlaybackExperiment:Trial1(February28th,2014)
B.PlaybackExperiment:Trial2(March11th,2014)
C.PlaybackExperiment:Trial3(March16th,2014)
Figure3. Route and speed of research ship during the
playbackexperiment.The white flagisthe startpoint and
theblackflagistheendpointofeachtrial.Theredtriangle
pointsouttheredcircle,whichistheplacewhere
thenew
UWSsoundwasgenerated.Thecoloroftherouteindicates
the speed of the research ship following after the target
whale. The color changes from blue to red as its speed
increases.
400m0
2km
0
210
A.PlaybackExperiment:Trial1(February28th,2014)
B.PlaybackExperiment:Trial2(March11th,2014)
C.PlaybackExperiment:Trial3(March16th,2014)
Figure4.Thesurfaceperiod(upperrow)andbreathcount(lowerrow)ofthetargetwhaleduringplaybackexperiment.For
thesurfaceperiod,onefilledsquareisoneminuteofsurfaceperiod,andoneblanksquareisoneminuteofdivingperiod.
The
flukemarkisshownabovethesurfaceperiodifthewhaledidflukeupdives.Forthebreathcount,onefilledsquareis
onebreathcount.RedtriangleindicatesthepointwhenthenewUWSsoundwasgenerated,withvoltagegainofnumber
shownabove the triangle (for example, G35
as‐35dB). Each letter on surface period indicates behaviors as follows: BR:
Breach(Jump),HS:HeadSlap,TS:TailSlap,PS:PecSlap,andPDS:PeduncleSlap.
Figure5. Number of Sighting Cetacean and Number of
Hydrofoil Service for hydrofoil with the previous UWS
sound and hydrofoil with the new UWS sound during
surveyperiod.
The probability of sighting was calculated from
these data. The probability of sighting cetaceans in
one hydrofoil service for the previous UWS sound
was1.7%,butontheotherhand,thatofthenewUWS
soundwas0.54%,whichwaslessthanathirdofthe
previousUWSsound(Fig6).
Figure6.ProbabilityofSightingCetaceanofhydrofoilwith
thepreviousUWSsoundandhydrofoilwiththenewUWS
soundduringsurveyperiod.
4 DISCUSSION
ThroughthisresearchprojectonthenewUWSsound,
its effectiveness of repelling cetaceans was
investigated. From the playback experiment,
physiological changes, such as increase of surface
period and breath count, were observed after
generating the new UWS sound. This result
supported the hypothesis of these physiological and
behavioral
changes were due to development of an
uncomfortablenessandnervousnessbythenewUWS
sound.Thus,therepellingreactions,suchaschanging
swimmingdirectionandincreasingswimmingspeed,
were observed as a result of this experiment.
Therefore,thenewUWSsoundconceivablytriggered
the repellence reaction of whales and led
them to
swimawayfromtheresearchship.
Based on the result of sighting survey, the
probability of sighting cetaceans, or chance of
hydrofoil encountering cetaceans, became relatively
smallerforthenewUWSsound.Thisresultverified
that the new UWS sound obtained more repellent
effect than the previous UWS sound.
The Fisher’s
exact test was performed to analyze the significant
difference in the two probabilities (Table 1).
Although,therewasnosignificantdifferencebetween
theeffectivenessofthepreviousandnewUWSsound
under normal operating service condition (P‐value:
0.2314),thisresearchprojectasawholesupportedthe
effectiveness
oftheUWSsounddevisedbyYamadaet
al.(2015).TherepellenteffectofthenewUWSsound
was verified in the playback experiment, and the
tendency of decreasing the chance of hydrofoil
encountering cetaceans was observed from the
sighting survey. However, both the playback
experimentandthesightingsurveyneed
moretrials;
moresamplesareneededforfurtherresearch.
211
Table 1. Fisher’s exact test on the probability of sighting
whaleforthepreviousandnewUWSsound.
_______________________________________________
Sighting NoSightingTotal
_______________________________________________
NewUWSSound1184 185
PreviousUWSSound 6337 343
_______________________________________________
Total7521 528
_______________________________________________
P‐value: 0.2314
_______________________________________________
5 CONCLUSION
TheUnderwaterSpeaker(UWS)hasbeeninstalledto
thehighspeedvessel,hydrofoil.TheUWSgenerates
therepellencesoundfor cetaceanstodecrease a risk
of ship strike to cetaceans. The previous sound was
devised by (Yamada et al. 2015). In this research
project,which isconsistof
playbackexperiment and
sighting survey, of devised new UWS sound was
investigatedandexamined.Asaresult,physiological
and behavioral changes were observed in the target
whale;itchangeditsswimmingdirectionandspeed,
andswamawayfromtheresearchship.Furthermore,
therewasatendencyofdecreasedchanceof
sighting
cetacean for hydrofoil with the new UWS sound.
Therefore,therepellenteffectofthenewUWSsound
wasverified.
ACKNOWLEDGEMENT
WearegratefultoallthestaffofSadoSteamShipCo,
Ltd.forkindsupportandassistanceofconductinga
sightingsurvey.
REFERENCES
Laist,D.W.,Knowlton,A.R.,Mead,J.G.,Collet,A.S.and
Podesta, M. (2001), COLLISIONS BETWEEN SHIPS
AND WHALES. Marine Mammal Science, 17: 35–75.
doi:10.1111/j.1748‐7692.2001.tb00980.x
Yamada,H.,Kagami,L.,Yonehara,Y.,Matsunaga,H.,Kato,
H., Terada, M., Takahashi, R., Okanoya, K., &
Kawamoto, T.: Estimation on Audibility
of Large
CetaceansforImprovementoftheUnderWaterSpeaker.
TransNav, the International Journal on Marine
NavigationandSafetyofSeaTransportation,Vol.6,No.
4,pp.589‐593,2012
Yamada, H., Kobayashi, N., Nakashima, T., & Kato, H.
(2015), Development of the Effective Underwater
SpeakerSoundModulatedbyAudible
SoundFrequency
Range of Large Cetaceans for Avoidance with Ship
Collision.2015
