International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 6

Number 1

March 2012

143

1 INTRODUCTION

Although the situation has improved somewhat re-

cently, a series of collisions have occurred in some

Japanese sea routes between hydrofoil-type super

high-speed vessels (hereafter “HF vessels”; Fig. 1)

and large marine life and continue to concern

transport officials and other relevant peoples to this

issue. These collisions are often the target of marine

accident inquiries that examine the responsible fac-

tors, and it would be accurate to state that in most

instances, the collisions involve cetaceans (Fig. 2).

Thus, such collisions not only negatively impact safe

navigation, but also represent a risk to the survival

of cetaceans.

Figure 1. Hydrofoil type of high-speed vessel, which are used

for important high-speed sea routes linking remote islands with

the Japanese mainland. (Photograph by H. Kato)

Figure 2. Sperm whale, a whale species with a high collision

risk with hydrofoil-type super high-speed vessels. Their popu-

lation in the waters around Japan has increased in recent years.

(Photograph by H. Kato)

Towards Safer Navigation of Hydrofoils:

Avoiding Sudden Collisions with Cetaceans

H. Kato, H. Yamada, K. Shakata, A. Odagawa, R. Kagami & Y. Yonehara

Tokyo University of Marin Science and Technology (TUMSAT), Tokyo, Japan

M. Terada & K. Sakuma

KHI JPS Co., Ltd., Kobe, Japan

H. Mori & I. Tanaka

Kawasaki Heavy Industries Ltd., Kobe, Japan

H. Sugioka & M. Kyo

Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokohama, Japan

ABSTRACT: Recently, sudden collisions between large cetaceans and high-speed hydrofoils have become

problematic to Japanese sea transport in some localities. We therefore initiated a project to investigate ap-

proaches for minimizing risk to both ships and cetaceans. Under the present project, the following three sub-

projects are underway: clarifying which whale species are found near sea routes and determining their season-

al variations; identifying whale species that have a high collision risk; and determining the unique acoustic

characteristics of high-collision-risk cetaceans for the improvement of underwater speakers (UWS). By con-

ducting acoustic surveys using novel methods, including an anatomical approach based on characteristics of

the inner ear, the aim of this project is to accurately estimate the audible range of species with a high collision

risk and improve the sounds generated by the UWS. Thus far, we have identified the cetacean species at high-

risk in two major sea routes. In the next phase of the study we plan to develop an imaging system that recog-

nizes a cetacean's unique blow using an infrared camera, in an attempt to warn of the approach of high-

collision-risk whale species at an early stage by sounding an alarm.

144

Beginning around the year 2000 in Europe, the

Agreement on the Conservation of Cetaceans in the

Black Sea Mediterranean Sea and Contiguous Atlan-

tic Area (ACCOBAMS), which is based on the Bonn

Convention on the Conservation of Migratory Spe-

cies of Wild Animals (UNEP/CMS), was formed in

response to increased concerns about collisions be-

tween large cetaceans and ships. In tandem, discus-

sions were also initiated at the International Whaling

Commission (IWC), which is the main organization

for the management of cetacean stocks and whaling

issues. In 2008, at the 60th IWC Annual Meeting

held in Santiago, Chile, cooperation with the Inter-

national Maritime Organization (IMO) was strength-

ened, as proposed by the Netherlands, and this coop-

eration was also promoted at the 61st IWC Annual

Meeting held in June 2009 in Madeira, Portugal.

Under this cooperative effort, both international or-

ganizations organized the Joint IWC-ACCOBAMS

Workshop on Reducing Risk of Collisions between

Vessels and Cetaceans (Anon, 2010).

Against this background, this paper outlines our

research project aimed at reducing risks to both

ships and cetaceans against sudden collisions, par-

ticularly for large cetaceans, and discusses future di-

rections in this field. The main sections of this paper

have been taken from selected sections presented in

a previous paper by Kato (2009).

2 WHY IS OUR RESEARCH PROJECT

NECESSARY?

The IWC, ACCOBAMS, and IMO regard collisions

between large cetaceans and super high-speed ves-

sels as one of significant threats to the survival of

cetaceans. Their main strategies for deterring such

collisions are clear and simple, and involve requiring

HF vessels to settle on the surface and reduce speed

whenever whales appear, and establishing protection

areas for whales. However, as these approaches will

not always prevent collisions, additional research

projects to identify more effective strategies are nec-

essary.

Japan, which is completely surrounded by sea,

has a population of approximately 130 million peo-

ple. The Japanese population is predominantly con-

centrated in urban areas, whereas in rural and moun-

tainous areas, extreme depopulation is occurring.

The numerous islands surrounding Japan are no ex-

ception; the depopulation of the once well-

developed islands will devastate them, leading to

environmental damage and disturbances to the coast-

line, which will eventually penetrate the offshore ar-

eas. HF vessel services help limit the depopulation

of the islands, as they drastically shorten the travel

time between them and the mainland, making fre-

quent travel more feasible. However, increases in the

number and frequency of HF vessels on sea routes

poses increased risk for collisions between vessels

and cetaceans. . The main goal of our research pro-

ject is to identify effective approaches for limiting

the risks associated with collisions between large ce-

taceans and HF vessels.

3 OUTLINE AND PROGRESS OF THE

RESEARCH PROJECT

In April 2006, the Maritime Bureau of the Ministry

of Land, Infrastructure, Transport and Tourism es-

tablished a committee for considering safety

measures for HF vessels. The Laboratory for Ceta-

cean Biology at Tokyo University of Marine Science

and Technology, based on the working group estab-

lished by the above-mentioned committee, began

conducting research on collision avoidance by seek-

ing the cooperation of Kawasaki Shipbuilding Cor-

poration, a maker of Jetfoils (JF) which are the main

type of hydrofoil-type HF vessels, KHI JPS Co.,

Ltd., which is in charge of HF vessel maintenance,

and several additional companies, such as Sado

Kisen Co., Ltd., and Tokai Kisen Co., Ltd., which

operate JF services.

A number of HF vessels are equipped with un-

derwater speakers (UWS) that emit sound waves

with the aim of repelling cetaceans. However,

whales (86 species in total; 14 species within the

suborder Mysticeti and 72 species within the subor-

der Odontoceti, as recognized by the Scientific

Committee of the IWC in 2010) differ markedly in

their acoustic characteristics depending on the spe-

cies, particularly between baleen whales, which are

highly adapted to the ocean, and toothed whales,

which have retained numerous traits from their ter-

restrial mammal ancestors (Fig. 3).

Figure. 3 Differences in the sonar frequency bands of cetacean

species grouped at the sub-order level of taxon. Cited literature

for sonar frequencies: Mysticeti (baleen whales), Au, 2000;

Odontoceti (toothed whales), Backus and Schevill, 1966.

145

Due to the large variations in sonar frequency

bands among cetaceans, questions remain concern-

ing the efficacy of the currently used UWS. It is also

not clear what type of sound each whale species can

hear, particularly by large cetacean species, which

are difficult to keep in captivity. However, working

on the assumption that cetaceans are capable of

hearing calls of their fellow whales, we propose

identifying the hearing range of high-collision-risk

cetacean species using a novel method.

To this end, the following two sub-projects have

been established:

1 Clarify which whale species are found near ship-

ping routes and determine their seasonal varia-

tions to identify whale species that have a high

collision risk, and then reflect their unique acous-

tic characteristics in UWS. To achieve this goal,

we have initiated the following sub-projects.

− Analysis of visual data typically collected by

ship crews in service

− Visual surveys to determine whale species by

whale specialists

− Improvement in the accuracy of typical visual

data collection by visual training of ship crews

to identify whale species

− Improvement in the identification accuracy of

cetacean species and detection ability through

the introduction of high-definition video cam-

eras. Identify whale species with a high colli-

sion risk based on surveys of whale body size

and the above research results, and then modify

the sounds generated by UWS for each route

and season

2 Conduct acoustic surveys using novel approach-

es, with the aim of estimating the audible range of

whale species with a high collision risk.

− Estimations using an anatomical approach of

the inner ear

− Estimations from correlations with vocal char-

acteristics

− Further improvement of the sounds generated

by UWS based on the above findings

With regards to sub-project (1), significant pro-

gress has been made, and the results have been com-

piled in two Master’s theses submitted to Graduate

School, Tokyo University of Marine Science and

Technology (Odagawa, 2007; Shakata, 2008).

In addition to the analyses presented in these two

theses, we collected further survey data until 2010.

Through analyses of visual data typically collected

and data from specialized cetacean sightings on the

major HF vessel sea routes from Tokyo to Okada on

Izu-Ohsima Island and from Niigata to Ryotsu on

Sado Island (Fig. 4), we were able to identify the

high-risk species and their peak season for predict-

ing the most probable months for collisions (Table

1).

Table 1. High-risk cetacean species involved in collisions with

HF vessels and their peak season associated with selected sea

routes.

__________________________________________________

Sea route Critical species Season

__________________________________________________

Tokyo – Okada

Sperm whale Year round with

(Izu-Ohshima Island)

(Physeter peak in Oct.-Dec

Macrocephalus)

Baird’s beaked whale May-Aug.

(Berardius bairdii)

Niigata – R

yotsu Minke whale Year round with

(Sado Island)

(Balaenoptera peak in Apr.-May

acutorostrata)

__________________________________________________

Table 2. Estimated vocal frequencies for sperm and Bryde’s

whales based on vocalizations collected from field surveys us-

ing a hydrophone (from Yamada et al., 2011).

__________________________________________________

Survey location Species Vocal

frequency (kHz)

__________________________________________________

Tosa Bay Bryde's whale 0.15-0.40

(Balaenoptera edeni),

Mysticeti (baleen whales)

Bonin Island Sperm whale 1.90-4.80

(Physeter macrocephalus)

Odontoceti (toothed whales)

__________________________________________________

With respect to sub-project (2), we have been

conducting field surveys for the collection of natural

vocalizations of several large cetaceans. The results

of this work are described in the report by Yamada

et al. (2011), submitted to the same volume as the

separate dedicated paper.

Figure 4. Map showing the two major HF vessel sea routes for

Tokyo - Izu Ohshima Island (bottom right) and Niigata - Sado

Island (top right).

146

Due to logistical limitations to access large ceta-

ceans, we prioritized two field sites to collect vocali-

zations from Bryde’s whales (Balaenoptera edeni)

and sperm whales, which were located in the neritic

waters off Kochi (Tosa Bay; approx. 33N–133E)

and in the waters off the southern coast of Chichi-

jima Island (Bonin Islands; 27N-142.2E), respective-

ly, which are promising locations to access these ce-

tacean species. As reported in Yamada et al. (2011),

the observed ranges of vocal frequencies were 1.90-

4.80 kHz and 0.15-0.40 kHz for sperm and Bryde’s

whales, respectively (Table 2). As both upper values

for the vocal frequencies of the two species are

higher than the reported values presented in Fig. 1,

this finding may allow the signals emitted by UWS

to be modified for increased efficacy.

Although vocal frequencies provide indirect evi-

dence of the audible (frequency) range, more direct

measurements clearly represent a more suitable ap-

proach in the context of UWS. Yamada et al. (2011)

also reported the predicted audible range for several

large cetaceans determined using an anatomical ap-

proach of the inner ear: 0.12-15.00 kHz and 0.11-

31.10 kHz for the common minke and Baird’s

beaked whale, respectively (Table 3). Due to differ-

ences in the species examined, the values estimated

using this approach cannot be directly compared to

those of the vocal frequency estimated in the field

surveys. However, as similarities in vocal character-

istics are generally expected among related taxon

groups (Fig. 1), comparisons among Balaenoptera

species (common minke whale - Bryde’s whales)

would appear to be valid.

Table 3. Predicted audible ranges for the common minke and

Baird’s beaked whales based on anatomical approaches using

the inner ear (from Yamada et al., 2011).

__________________________________________________

Sampling location Species Predicted

frequency (kHz)

__________________________________________________

Off Ishinomaki, Common minke whale 0.12 - 15.93

Miyagi, Japan

(Balaenoptera acutorostrata)

(Pacific coast) Mysticeti (baleen whales)

Off Wadaura Baird's beaked whale 0.27 - 33.09

Chiba, Japan

(Berardius bairdii),

(Pacific coast) Odontoceti (toothed whales)

__________________________________________________

From the reported literature, it was confirmed that

the audible range is wider than that of the vocal fre-

quency range, indicating that cetaceans can hear

sounds of higher frequency than of their own vocali-

zations, at least among Balaenoptera cetaceans and

also likely among Mysticeti cetaceans. Although the

obtained evidence is not strong enough to reach a

firm conclusion, this nature of cetaceans (i.e, audible

range > vocal frequency range) is likely also true

among Odontoceti species, as determined from the

comparison between the vocal frequency of sperm

whales and the audible range of Baird’s beaked

whale. As a further step for reducing risk of colli-

sions between HF and cetaceans, this rationale can

be implied for the improvement of UWS.

4 SHORT-TERM PROPOSAL FOR IMPROVE-

MENT OF UWS

To minimize risks for both HF vessels and ceta-

ceans, we are presently preparing interim proposals

for improving specifications of UWS by taking into

account the results of the present project; these im-

provements are ongoing and are halfway complete.

First, it is necessary to adjust the sounds generat-

ed by UWS using appropriate acoustic specifications

of the high-risk cetacean species for which sudden

collisions are to be avoided. We have already identi-

fied the critical cetacean species to be sperm whales

and Bride’s whales in the Tokyo-Izu-Ohshima sea

route, and common minke whales in the Niigata-

Ryotsu sea route. For the seas routes in other locali-

ties, identification of the critical species through ce-

tacean sighting surveys is an essential first step.

For the improvement of UWS, it is of critical im-

portance to identify the most effective sound fre-

quency to repel the critical cetaceans. In this regard,

Yamada et al. (2011) suggested that existing UWS

(operating at 6-20 kHz) should be modified to pro-

duce frequencies less than 15 kHz for common min-

ke whales, less than 0.4 kHz for Bryde’s whales, and

less than 4.8 kHz for middle to large-toothed whales,

such as sperm whales. However, it is unknown

whether such modification is technically feasible, or

if installation of the necessary hardware is realistic.

Therefore, more investigations are needed to better

estimate the audible range for critical cetacean spe-

cies, and to determine the required technical and

mechanical improvements of UWS. Particularly, an

increased number of anatomical inner ear samples is

expected to help clarify the audible range and effec-

tive frequency for deterring high-collision-risk ceta-

cean species.

5 FUTURE CHALLENGES AND POTENTIAL

APPLICATIONS

In the course of our investigations and research for

the improvement of UWS, specific challenges for

future research have been identified. We previously

attempted to introduce high-definition cameras to

improve the accuracy of identifying whale species,

but a new technique for obtaining high-quality im-

ages has emerged that might contribute to the early

detection of whales, as well as allow the more accu-

rate identification of cetacean species.

147

In a potential application utilizing this imaging

technique, we are considering constructing a system

that recognizes a whale's unique blow in an image to

warn of the approach of high-collision-risk cetacean

species at an early stage by sounding an alarm by

UWS. We have already initiated the implementation

of such a system, as outlined in a pilot study by

Yonehara et al. (2011). Although some collisions are

inevitable, considering the user friendliness of cur-

rent HF vessels and the high ability of crew mem-

bers to steer and maneuver ships, we believe that if

an approaching cetacean is detected in advance, the

frequency of collisions with large cetaceans can be

drastically reduced.

The positions of the HF vessel manufacturers and

operating companies regarding this issue have been

very positive, and further efforts are being made in

the pursuit of greater safety for both passengers and

cetaceans.

ACKNOWLEDGEMENTS

Our sincerely thanks are due to cooperation with the

managers, officers, and ship crew of the HF vessel

operating companies, Sado Kisen Co., Ltd. and To-

kai Kisen Co., Ltd. We also thank the many officers

of the Maritime Bureau of the Ministry of Land, In-

frastructure, Transport and Tourism for their initial

guidance.

REFERENCES

Anonymous. 2010. Report of the joint IWC-ACCOBAMS

workshop on reducing risk of collisions between vessels

and cetaceans. Report of the joint IWC-ACCOBAMS work-

shop on ship strikes :1-42.

Au, W.W.L. 2000. Hearing in whales and dolphins; An over-

view. In W. W. L. Au, A. N. Popper & R. R. Fay (eds.)

Hearing by whales and dolphins: 1-42. New York: Spring-

er.

Backus, R. and W.E. Schevill. 1966. "Physeter clicks," in

Whales, Porpoises and Dolphins. In K. S. Norris (ed.)

Whales, dolphins, and porpoises. : 510-528. California:

Berkeley.

Kato, H. 2009. Towards Avoiding Collisions between Super

High-speed Vessels and Whales. The Ship & Ocean News-

letter.217:4－5.

Odagawa, A. 2007. Fundamental research of collision avoid-

ance between cetaceans and super high-speed vessels. Mas-

ter Thesis, Tokyo University of Marine Science and Tech-

nology :1-105.

Shakata, K. 2009. Fundamental research of collision avoidance

between cetaceans and super high speed vessels - Analysis

for the occurrence of cetaceans on the sea routes and in-

crease in precision of cetacean identification by the intro-

duction of video camera research-. Master thesis, Tokyo

University of Marine Science and Technology :1-90.

Yamada, H., L. Kagami, Y. Yonehara, H. Matsunaga, M. Te-

rada, K. Okanoya, T. Kawamoto & H. Kato. 2011. Estimat-

ed audible range of large cetacean for improvement of the

Under Water Speaker. The TransNav2011 monographs.

Yonehara, Y., L. Kagami, H. Yamada, H. Kato, M. Terada &

S. Okada. 2011. Feasibility study for infrared detecting of

large cetaceans to avoid sudden collision. The Trans-

Nav2011 monographs.