The role of the International Maritime Organization in reducing vessel threat to whales: Process, options, action and effectiveness

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The role of the International Maritime Organization in reducing vessel threat
to whales: Process, options, action and effectiveness
Gregory K. Silber
a,
n
, Angelia S.M. Vanderlaan
b,c
, Ana Tejedor Arceredillo
d
, Lindy Johnson
e
, Christopher
T. Taggart
b
, Moira W. Brown
f,g
, Shannon Bettridge
a
, Ricardo Sagarminaga
d,h
a
Office of Protected Resources, NOAA National Marine Fisheries Service, 1315 East West Highway Silver Spring, MD 20910, USA
b
Department of Oceanography, Dalhousie University, Halifax, NS, Canada B3H 4R2
c
Fisheries and Oceans Canada, St. Andrews Biological Station, 531 Brandy Cove Road, St. Andrews, NB, Canada E5B 2L9
d
KAI Marine Services, Nalo
´n, 16, La Berzosa, 28240 Hoyode Manzanares, Madrid, Spain
e
General Counsel for Office of International Law, National Oceanic and Atmospheric, Administration, 14th & Constitution, N.W., Washington, DC, 20230, USA
f
New England Aquarium, Boston, MA, 02110, USA
g
Canadian Whale Institute, Box 410, Wilson’s Beach, NB, Canada E5E 1Y2
h
ALNITAK Marine Environment Research Center, Nalo
´n, 16, La Berzosa, 28240 Hoyode Manzanares, Madrid, Spain
article info
Article history:
Received 24 June 2011
Received in revised form
6 February 2012
Accepted 11 March 2012
Available online 15 May 2012
Keywords:
International Maritime Organization
Whale
Vessel
Ship
Strike
Risk
abstract
Ocean-going vessels present a measurable threat of lethal collision with many marine species
worldwide, notably large whale species of which many are endangered. Various modifications to
conventional vessel operations have been recently used to reduce the threat. Some of the modifications
have been instituted by coastal states as a result of their adoption by the International Maritime
Organization (IMO) —a specialized agency of the United Nations that is the recognized authority for
international maritime shipping interests and their safety of navigation at sea. We describe the
processes through which coastal states can approach the IMO to seek review and adoption of
environmental conservation proposals involving international shipping. We also provide a description
of vessel navigation modifications in specific geographic areas where IMO-adopted measures to protect
large whales have been implemented —there are only 10 such cases and we describe each. We then
address the methods that can and have been used to assess the effectiveness of such measures. As
weighed against the goals of the modifications by estimating the ensuing reduced risk to whales,
actions taken are generally regarded as being successful in reducing the risk, but to varying degrees. We
conclude that the IMO can be a powerful entity in providing solutions to a range of marine
environmental and conservation problems. When used in concert with related efforts such as mariner
education, the IMO, and the range of navigational measures available to it, is an effective forum through
which coastal states can pursue large whale conservation objectives without unduly compromising the
activities of shipping interests.
Published by Elsevier Ltd.
1. Introduction
Worldwide, a number of marine species including sea turtles
[1,2], manatees [3,4], small whales [5], and all large whales [6,7]are
killed or injured by vessel strikes. As of 2007, there were 750
records of vessels striking large whales worldwide [8].Thisrepre-
sents a minimum count as an unknown number of vessel strikes go
undetected or unreported. When whale carcasses are recovered and
examined, the cause of death is often indeterminate [9,10], due, for
example, to advanced decomposition or no external evidence of a
vessel strike. For some endangered species, such as the North
Atlantic right whale (Eubaelana glacialis), vessel strikes are a mea-
surable impediment to the recovery of the species [11,12]. A high
proportion of dead right whales show signs attributable to vessel
strike including severe lacerations, broken bones, internal hemor-
rhaging and other lethal forms of blunt trauma [9,13].
Contents lists available at SciVerse ScienceDirect
journal homepage: www.elsevier.com/locate/marpol
Marine Policy
0308-597X/$ - see front matter Published by Elsevier Ltd.
http://dx.doi.org/10.1016/j.marpol.2012.03.008
Abbreviations: AIS, Automatic Identification System; AMVER, Automated
Mutual-Assistance Vessel Rescue System; ATBA, Area To Be Avoided; CD, Com-
pact Disc; DGMM, Direccio
´n General de la Marina Mercante (Directorate General
of the Merchant Marine); ECAREG, Eastern Canada Vessel Traffic Services Zone
Regulations; GT, Gross tonnage; IMO, International Maritime Organization;
INMARSAT, International Marine/Maritime Satellite; ICOADS, International Com-
prehensive Ocean-Atmosphere Data Set; IUCN, International Union for Conserva-
tion of Nature; MEPC, Marine Environment Protection Committee; MSC, Marine
Safety Committee; MSR, Mandatory Ship Reporting systems; NAV, Sub-Committee
on Safety of Navigation; NMFS, National Marine Fisheries Service; NOAA, National
Oceanographic and Atmospheric Administration; SOLAS, International Convention
for the Safety of Life at Sea; TSS, Traffic Separation Scheme; USA, United States of
America; USCG, United States Coast Guard; VOS, Voluntary Observing Ships
n
Corresponding author. Tel.: þ1 301 427 8485.
E-mail address: greg.silber@noaa.gov (G.K. Silber).
Marine Policy 36 (2012) 1221–1233

The occurrence and severity of vessel-strike threat to whale
populations in a number of regions around the world has made
strike threat an emerging conservation issue, particularly in those
places where extensive vessel traffic and whales co-occur. As mari-
time activities and associated vessel traffic increase, and as some
whale populations increase, the rate of lethal vessel-strikes is also
likely to increase. Various whale-conservation initiatives have been
designed to reduce the threat including vessel routing changes
[14–17] and mandatory [18–20] or recommended [14,15] vessel-
speed restrictions. Many of these changes were instituted by coastal
states following their consideration and subsequent adoption by
the International Maritime Organization (IMO).
As a specialized agency of the United Nations, the IMO is the
recognized authority for international maritime shipping interests
and the safety of navigation at sea. Thus, involvement by the
IMO is essential for ensuring internationally coherent solutions to
various maritime problems, including threats from vessel traffic to
highly mobile and trans-boundary animals such as whales, within
and beyond regions of national jurisdiction. In this paper we are
typically referring to regions within the Exclusive Economic Zone
of a given nation.
Not all research and resource management agencies and per-
sonnel engaged in marine conservation are well-versed in the
processes involved in approaching the IMO to secure the adoption
of marine conservation-oriented proposals relevant to shipping.
Each of us has been closely involved in developing proposals to the
IMO, and we have direct experience in implementing and analyz-
ing the adopted measures described herein. Thus, our first goal
here is to summarize the role and function of the IMO and its
process of receiving, reviewing, and adopting proposed changes
in vessel navigation that are related to conservation issues. Such
proposals are made by a Member State of the IMO, and if adopted,
the host nation subsequently implements the change domestically
(Sections 1.1, 1.2, below and Appendix A). Our second goal is to
detail the vessel strike problem through a description of specific
changes to navigation practices that were adopted by the IMO —
changes that were designed specifically to reduce lethal vessel
strikes to large whales. Worldwide there are only 10 such cases
(1.3,1.4,2,belowandTable 1). We do so to help ensure others are
appropriately informed and prepared prior to presenting a vessel
related conservational proposal to the IMO. We detail various
vessel-navigation modifications of the then existing practices that
were adopted by the IMO and subsequently implemented by the
host nation. In each case, the goal was to reduce the probability of
lethal vessel strikes to large whales without compromising naviga-
tional safety at sea. We also review the timelines and processes
related to securing an IMO adoption of a navigational modification.
Finally, we describe some methods that can be used to assess the
effectiveness of such modifications (3, below).
1.1. Role and function of the IMO
Based in London, UK, the IMO was established in 1948 as a
specialized United Nations agency, recognized by the International
Convention for the Safety of Life at Sea (SOLAS) [21],withrespon-
sibility for the safety and security of shipping and the prevention of
marine pollution. The IMO Secretariat is headed by the Secretary-
General who is appointed by the IMO Council with approval by the
Assembly. A principal task of the IMO and its 169 Member States
(nations) has been to develop a suite of comprehensive vessel-
operation conventions, protocols, codes, and recommendations that
address maritime safety, environmental protection, legal matters,
technical co-operation, and the efficiency of shipping. The IMO
has promoted the adoption of 40 conventions and protocols and
800 codes and recommendations. Codes and recommendations
provide guidance for framing national regulations and requirements.
Though they are not usually binding on the Member States, codes
are often implemented through national legislation or regulation.
Specialized IMO committees focus on technical work that is used to
review and advise other, or ‘parent’, committees on proposals, or the
development and adoption of new policy. Formal cooperation has
been established with 30 inter-governmental organizations and
almost 50 non-governmental international organizations. The latter
represent a range of maritime, environmental, and legal interests
and often have observer status and often participate in the work of
the various committees.
1.2. The process: Proposals to the IMO
To secure vessel-navigation regulations or policies, or modifica-
tions thereof, from the IMO, a Member State must develop and
submit a formal proposal. Only a government, or other affiliated
member, may submit a proposal that justifies the need for the
proposed action. A proposal must describe the problem, justify the
nature of the action proposed to solve the problem, and identify
potentially adverse effects such an action might have on maritime
interests and on the safety of navigation at sea. Documentation
should be provided for the region and problem of interest, the
Table 1
Table of text-referenced proposals submitted by Member States and the dates considered and approved/adopted by the Sub-Committee on Safety of Navigation (NAV), the
Marine Safety Committee (MSC), or Marine Environment Protection Committee (MEPC) and the date proposed actions were implemented by the Member State.
Text
reference
Proposals submitted/adopted by IMO Member
State
NAV MSC MEPC Implemented
2.1 Report to MSC-IMO: vessels striking right whales USA – – June 1997 Information 1997
2.2 Mandatory Ship Reporting (MSR): east coast USA July 1998 December
1998
– July 1999
2.3 Traffic Separation Scheme (TSS): Bay of Fundy CANADA April 2002 December
2002
– July 2003
2.4 Traffic Separation Scheme (TSS): Cabo de Gata SPAIN June 2005 May 2006 – December 2006
2.5 Traffic Separation Scheme (TSS) and Recommendatory Speed:
Strait of Gibraltar
SPAIN March
2006
December
2006
– July 2007
2.6 Traffic Separation Scheme (TSS): Boston USA July 2006 December
2006
– July 2007
2.7 Recommendatory Area To Be Avoided: Roseway Basin CANADA April 2007 October 2007 – May 2008
2.8 Traffic Separation Scheme (TSS): Boston USA March
2008
July 2008 – June 2009
2.9 Recommendatory Area To Be Avoided: Great South Channel USA March
2008
December
2008
– June 2009
2.10 Guidance document: Measures to reduce ship strikes with
cetaceans
USA August
2008
Information July
2009
G.K. Silber et al. / Marine Policy 36 (2012) 1221–12331222

associated nature of the vessel traffic (density, routes used, etc.),
the status of neighboring states regarding the region of interest and
the proposed action, and existing navigational rules, regulations
and (or) policies associated with the region. Proposals related to
environmental issues are typically reviewed and endorsed (or not)
by IMO committees that may include the Marine Environment
Protection Committee (MEPC), the Sub-Committee on Safety of
Navigation (NAV), and the Marine Safety Committee (MSC). The
latter two are engaged when proposals involve navigation and
marine safety.
In all cases, the solicitation of an IMO endorsement for a
proposed action must be founded on the soliciting Member State
having already endorsed the proposal. As most proposed actions
relating to navigation lie partly or wholly within territorial waters
or Exclusive Economic Zones [22], IMO endorsement is generally
preceded or followed by action involving rule making authorities
and regulatory instruments or policies such as declarations or
legislation. As in the actions taken and measures discussed below,
proposals emanating from the United States of America (USA)
require interagency clearance and are submitted to the IMO by
the US Coast Guard (USCG) on behalf of the USA government. In
Canada, responsibility lies with Transport Canada, and in Spain
with the Direccio
´n General de la Marina Mercante (DGMM).
1.3. The problem: Vessels striking large whales
To our knowledge, 10 specific actions have been endorsed by
the IMO to reduce the likelihood of vessels striking and killing or
injuring large whales, and with one exception, they are limited
to four whale species and three geographic regions: the North
Atlantic right whale (hereafter, right whale) along the eastern
seaboard of the USA and the Scotia-Fundy region of Canada, and
the fin (Balaenoptera physalus), sperm (Physeter macrocephalus),
and long-finned pilot (Globicephala melas) whales in the western
Mediterranean Sea. In each case, we provide a brief summary
of whale occurrence and distribution in these regions and the
magnitude of the threat they face from vessel strikes. The excep-
tion is a general, but relevant, international guidance document
that addresses vessel strikes to whales.
1.4. Northwest Atlantic
The right whale is a large baleen whale and is among the most
endangered of the large whales. It was severely exploited during
commercial whaling and is listed as ‘endangered’ by the Interna-
tional Union for the Conservation of Nature, (IUCN) [23], the USA
Endangered Species Act, and the Canadian Species at Risk Act.
Although estimates of abundance vary, most authors agree the
western North Atlantic population consists of 300–450 individuals.
Right whales inhabit the coastal shelf-waters of eastern North
America, although a few oceanic movements are documented.
Most individuals migrate annually between wintering, calving,
and nursery areas off the southeastern USA and summer feeding
habitats off New England in the USA and in the Bay of Fundy and
on the southwest Scotian Shelf in Canada. Five primary habitats
include the southern calving and nursery grounds off Florida and
Georgia, Cape Cod Bay, the Great South Channel east of Cape Cod,
the Bay of Fundy, and Roseway Basin [24]. Each of these habitats
is intersected by highly concentrated vessel traffic.
Vessel strikes account for 53% of all right whale deaths diag-
nosed from necropsies [13]. Probability estimates of deaths from
vessel strikes, based largely on Moore et al. [9] and Kraus et al.
[11], could be as high as 10 individuals in any given year [25].
Of the 50 documented right whale deaths occurring between
1986 and 2005, 19 were attributed to vessel strikes [11].An
average of two or more known North Atlantic right whale deaths
and serious injuries from vessel strikes occurred annually for the
last decade [10,26]. Based on existing records [7,27], and on a per-
capita basis, the right whale is two orders of magnitude more
likely to suffer a vessel strike than any other large whale species
[28]. Right whale vulnerability to vessel strikes is likely related to
their coastal distribution that exposes them to high-density vessel
traffic [29] and their apparent lack of avoidance of oncoming
vessels [30,31]. The endangered status of the right whale and
the magnitude of lethal vessel-strike risk led the governments of
the USA and Canada, in concert with various non-governmental
organizations, to seek ways to minimize the risk of vessel-strikes
to whales.
1.5. Mediterranean Sea
The Mediterranean Sea is one of the most heavily used
shipping regions in the world, with over 220,000 vessel ( 4100
gross tonnage, GT) transits each year. The number of transits is
expected to increase three- to four-fold in the next 20 years.
Vessel strikes in the region pose a measurable threat to fin and
sperm whales, and some smaller whale species [32]. Although
whale and dolphin population estimates for the entire Mediter-
ranean are unavailable, areas of high whale concentrations,
including fin, sperm, Cuvier’s beaked (Ziphius cavirostris), long-
finned pilot, and killer (Orcinus orca) whales are intersected by
major shipping lanes.
The IUCN has designated the sperm whale as ‘endangered’ in the
Mediterranean Sea [23] where it ranges throughout the western
and eastern basins, and in deep waters adjacent the continental
shelf. Sperm whale abundance data are unavailable, though quali-
tative estimates are in the hundreds and not the thousands [32].
This species is also vulnerable to vessel strikes in the Strait of
Gibraltar, the Pelagos Sanctuary, around the Balearic Islands, and off
southern Crete.
Fin whales have been designated by the IUCN as ‘vulnerable’ in
the Mediterranean Sea [23] where vessel strikes are considered the
primary threat to the species [33,34]. Fewer than 5000 fin whales
are believed to inhabit the Sea where they occur primarily in deep
offshore waters around Sardinia and Corsica and Balearic islands, in
the Gulf of Lion, and in the Alboran Sea. There are notably high
concentrations in the Strait of Gibraltar. Fin whale abundance has
decreased over the last decade in the Pelagos Sanctuary, an area
that includes waters around Sardinia and Corsica islands and the
coasts of Italy, Monaco, and France [35]. Although the reasons for
the decline are unclear, a Mediterranean-wide population decline
in fin whales cannot be discounted [32].
The status of Cuvier’s beaked whale is designated by the IUCN
as ‘data deficient’ [23] and it inhabits the western and eastern
basins of the Mediterranean and tends to be associated with deep
slope, submarine canyons, and escarpment habitats [32]. They also
inhabit the Alboran Sea, the Pelagos Sanctuary, and waters off the
south coast of Greece. Killer whales, long-finned pilot whales, and
Risso’s dolphins (Grampus griseus) also frequent waters associated
with high vessel traffic and are thus vulnerable to vessel strike.
The endangered and vulnerable status of the sperm and fin
whales and the general threat of vessel strike to these and the
other species listed above has prompted the government of Spain,
in collaboration with non-governmental organizations, to identify
means to reduce vessel-strike probability.
1.6. Options available to mitigate vessel strikes
There are a finite number of options available to mitigate vessel
strikes to large whales within the constraints of a safe and efficient
maritime commerce. These include, (a) educating maritime industries
about the vulnerability of whales to vessel strikes, (b) providing
G.K. Silber et al. / Marine Policy 36 (2012) 1221–1233 1223

whale location information to mariners to increase their awareness
and preparedness to avoid whales, (c) establishing time and (or) area-
specific vessel-speed restrictions to minimize the likelihood of
lethality of a strike should it occur, and (d) establishing time and
(or) area-specific modifications to vessel-traffic routing to minimize
theprobabilityofastrikeoccurring.
Thereislittleevidencethatextensivemarinereducation,(a),
or the provision of whale locations, (b), results in modified mariner
behavior with regard to reducing vessel strikes. Both types of infor-
mation require that mariners receive and heed the advisories
provided, choose to take voluntary actions (that may be inconsistent
amongst vessel operators), and perhaps engage in avoidance
maneuvers (that may not be feasible in all situations) [28,36].
Nonetheless, we suggest it is essential to foster and maintain
a constructive flow of information among the various conser-
vation agencies and vessel operators. Building mutual respect
and trust between vessel operators and those agencies and
organizations engaged in providing such information is crucial
to the execution of successful conservation initiatives while also
maintaining the safety of navigation at sea. Such relationships
may also help foster development of innovative approaches to
challenging conservation problems.
There is reliable evidence that vessel speed restrictions, (c), can
reduce the forces involved in [29] and the probability of death
resulting from [28] a vessel strike. Speed restrictions may limit
strike severity, but they may have concurrent negative time-
related economic consequences. There is also reliable evidence
that modified traffic routing, (d), reduces vessel strike probabilities
Fig. 1. Right whale Mandatory Ship Reporting systems (MSR) in waters off New England (a) and the southeast USA (b). Also shown is the original and modified Traffic
Separation Scheme (TSS) in the approach to Boston (a). The TSS was modified following adoption by the IMO, including a 12 degree shift of the northern leg and a
narrowing of both the north-south and east-west legs.
G.K. Silber et al. / Marine Policy 36 (2012) 1221–12331224

[17,25], though modifications may not be feasible in some regions
due to safe-navigation constraints. Nonetheless, eliminating or
reducing the extent of vessel and whale coincidence in time and
space is assured to reduce the likelihood of a vessel strike and thus
it is preferable, where possible, to vessel-speed restrictions. Given
the evidence that modified vessel operations can reduce vessel
strikes and (or) their severity, it is incumbent upon conservation
agencies to draw upon the IMO and its numerous navigation
instruments. The global reach of the IMO makes it an optimum
forum for considering proposals to minimize vessel strikes to
whales.
2. Proposals adopted by the IMO to mitigate vessel strikes
The IMO has been approached 10 times (Table 1) with
independent submissions by three nations seeking a reduction
of vessel strikes to whales in three geographic regions. Here we
summarize these submissions in chronological order of their
submission, the actions taken by the IMO, and the actions taken
by relevant Member states. To orient the reader – particularly
resource management personnel and policymakers – about the
suite of navigational instruments available to the IMO, we provide
a listing and a brief definition of each in Appendix A.
2.1. Information paper: Vessels striking right whales, USA (1997–1998)
The IMO was first approached about the problem of vessel
strikes to right whales in 1997. Recognizing the significance of
vessel strikes to the whales, the USA developed and submitted an
information paper [37] to the IMO-MEPC in June 1997 [38].
Developed collaboratively by the US Marine Mammal Commis-
sion, the National Oceanic and Atmospheric Administration
(NOAA) and the USCG, the paper identified and detailed the
threat of vessel strikes to right whales. The paper asked that the
IMO distribute the paper and called upon IMO member states to
inform their respective shipping interests about the issue and
provide relevant information on vessel strikes to NOAA’s National
Marine Fisheries Service (NMFS), the agency responsible for the
conservation right whales in the USA. The IMO acted accordingly
and this laid the groundwork for the possible and subsequent
reduction of vessel strikes under the auspices of the IMO.
2.2. Mandatory ship reporting (MSR): East coast, USA (1998–1999)
In June 1998 the USA followed the 1997 information paper
with a proposal to the IMO [39], prepared jointly by the USCG and
NOAA, seeking the establishment of two Mandatory Ship Report-
ing systems (MSR) (Appendix A) in regions of right whale
aggregations in USA waters. The systems were to provide infor-
mation (about whales and their vulnerability to vessel strike)
directly to individual vessels in near real-time when they entered
the defined regions [40–42]. The proposal had been endorsed by
President Clinton in April 1998 [40].
Under the proposed measure, all commercial vessels Z300 GT
would be required to report to shore-based stations when they
entered either of two regions off the east coast of the USA [39,40]
where and when right whales were known to occur: one off the
state of Massachusetts (Fig. 1(a)) operating year-round, and one off
the states of Georgia and Florida (Fig. 1(b)) operating annually from
15 November through 15 April. Each vessel-crew would be required
to report the vessel name, call sign, course, speed, location, destina-
tion, and route (waypoints). In return, the vessel would immediately
receive updated information concerning right whale locations, as
well as procedural guidance to help prevent a vessel strike. Mariners
would be advised to consult navigational publications such as the
US Coast Pilot, Sailing Directions (an international shipping guide),
and nautical charts for information on regulations and boundaries of
right whale critical habitat. Mariners would be further advised that
information placards, CDs, and other educational materials are
available from shipping agents, port authorities, relevant state
agencies, the USCG, and NMFS. Mariners would also be advised that
updated information on right whales locations would be available
through the broadcast media, including the USCG Broadcast to
Mariners, satellite-linked marine safety broadcasts, and NOAA
Weather Radio. The reporting system would affect no other aspect
of vessel operation and all two-way communication costs were to be
Fig. 2. Standardized (comparable scale) residual risk of lethal collision between a
vessel and a right whale associated with the original and amended (solid black
line) Bay of Fundy Traffic Separation Scheme (TSS). The original (solid black line)
TSS is also shown (b) with a hypothetical 10 knot speed restriction imposed over
the entire study area. Negative residuals indicate reduced risk. 100 m isobaths are
indicated. Modified from Vanderlaan et al. [16].
G.K. Silber et al. / Marine Policy 36 (2012) 1221–1233 1225

borne by the USCG and NMFS. The primary communication system
is via INMARSAT-C (satellite) for the majority of vessels, and thus
the information would be received in near real-time. In return, the
MSR systems would provide NMFS with data concerning number
and operations (e.g., courses, speeds etc.) of vessels transiting the
region [43]. The data would be used to assess and consider
additional or modified mitigation options (e.g., [44,45]).
The two MSR systems, reviewed by the NAV for recommenda-
tions to the MSC [41], were approved in July 1998, and adopted by
the MSC in December 1998 [46]. Following adoption by the IMO,
the systems became effective on 1 July 1999 and have remained
in effect as designed to the present. This was the first time an
IMO-endorsed measure was used to protect a particular marine
species [41]. Subsequently, the USCG issued a Final Rule in the
USA Federal Register codifying the systems by modifying the USA
Code of Federal Regulations [47] and the MSR areas were
incorporated into USA nautical charts by NOAA.
2.3. Traffic Separation Scheme (TSS): Bay of Fundy, Canada
(2002–2003)
A TSS (Appendix A) was established in the Bay of Fundy, to
organize traffic through fishing grounds and to enhance the safety
of vessels traveling to and from the entrance to the Bay and the
Port of Saint John, New Brunswick. The TSS was originally adopted
by the IMO in 1982 [48] and established in June 1983 (Fig. 2(a)).
However, the outbound lane of the TSS intersected a Right Whale
Conservation Area in the Grand Manan Basin that had been
created to identify an area in which summer/fall right whale
aggregations occur (2.7 below). Therefore, non-governmental
members of the North Atlantic Right Whale Recovery Implemen-
tation Team successfully petitioned Transport Canada to submit a
proposal to the IMO to amend the TSS with the goal of reducing
the probability of vessel strikes in the Basin [49,50]. The proposal
was considered by the IMO-NAV in July 2002 [51], approved and
forwarded by NAV to the IMO-MSC in July 2002, and adopted by
the MSC in December 2002 [52]. The TSS was modified on 1 July
2003. The amendment included a relocation of the northern
extent of the TSS by 3.9 nm to the east with a re-alignment
toward the Port of Saint John, and the establishment of an entry/
exit TSS junction north of the Basin for traffic navigating to and
from the Canada and USA ports to the west (Fig. 2(a)). The change
was published in Notices to Mariners and incorporated into
Canadian Hydrographic Services nautical charts.
2.4. Traffic Separation Scheme (TSS): Cabo de Gata, Spain
(2005–2006)
The Cabo de Gata (Cape Gata) region of the western Mediterra-
nean is situated in the Alboran Sea bordered by Spain, Algeria, and
Morocco. The coastal area is protected under Spanish law as a marine
reserve, a nature reserve, and site of European interest (Natural Park
of Cabo de Gata–Nijar). It is also a Special Area of Conservation for
Cetaceans in the Mediterranean Sea [32,53,54]. However, the area
was intersected by the Cabo de Gata TSS, established in 1998 [46],
that annually directed 35,000 vessel transits to and from the Strait
of Gibraltar and ports along the northern coast of the Mediterranean
(Fig. 3). The TSS also intersected rarely-used fishing grounds until
around 2001 when increased bottom trawling activities increased the
risk of vessel collisions. At the same time, maritime traffic authorities
became increasingly concerned with high traffic volume in relation
to the sensitive coastal and marine habitats designated as Sites of
Communitary Importance (European Union Habitat Directive) and in
relation to the numbers of cetacean species and loggerhead sea
turtles (Caretta caretta) that occur in the region.
In May 2005 the Spanish DGMM submitted a proposal to the
IMO that was designed to first reduce the risk of collision between
vessels using the TSS and the increased numbers of fishing vessels,
and second to enhance environmental protection. The proposal
sought a modification of the Cabo de Gata TSS such that it would
lie 20 nm seaward of the Cape (Fig. 3). The proposal was adopted by
the NAV [55],thenbytheMSCinthesameyear[56], and came into
effect on 1 December 2006 [57] along with a publication in Notices
to Mariners and incorporation into nautical charts [58].
2.5. Traffic Separation Scheme (TSS) & recommended speeds:
Strait of Gibraltar, Spain (2006–2008).
The 7-nm (13 km) wide Strait of Gibraltar provides the only direct
connection between the Mediterranean Sea and the Atlantic Ocean.
Fig. 3. The original and the modified Alboran Sea Traffic Separation Scheme (TSS). Vessel locations (derived from AIS studies) are shown in the revised TSS.
G.K. Silber et al. / Marine Policy 36 (2012) 1221–12331226

Approximately 110,000 voyages occur in the Strait each year
connecting numerous North African and Middle Eastern ports
with those in North, Central, and South America. This, along with
passenger and fast ferries that transport 4,000,000 passengers
per year, private yachts, whale-watching and fishing vessels, the
traffic volume makes this a region of major vessel-strike risk
to whales. Migrating and feeding aggregations of fin and sperm
whales occur in this area in relatively high numbers [59]. Sperm
whale foraging aggregations occur in the region in January
through May (Fig. 4) and early summer and winter fin whale
migration routes intersect commercial shipping and passenger
ferry routes, including the Gibraltar TSS and contiguous waters.
In March 2006, following the construction of the large indus-
trial port Tangier-Med, Morocco (Fig. 4), built to accommodate
transport of passengers and cargo to and from northern Africa,
Moroccan and Spanish maritime authorities proposed to the IMO
a re-configuration of traffic lanes in the Strait of Gibraltar [60]
(Fig. 4). However, this modification conferred with it an increased
risk of collision by intensifying traffic through key sperm whale
aggregation areas. Recognizing the threat to sperm whales, the
Spanish Ministry of the Environment made a request to the
Spanish Maritime Authority to include in the 2006 proposal a
vessel exclusion zone to limit traffic in areas of sperm whale
occurrence. Given the complexity and volume of shipping in this
TSS, and the fact that the attempt to include the exclusion zone
provision was made during the review process, the proposal to
modify the TSS was endorsed by the NAV, but the accompanying
proposal for an exclusion zone was rejected. The proposal to
reconfigure the TSS was therefore approved (without incorpora-
tion of the exclusion zone) by MSC in December 2006 [61],
as initially submitted to the NAV.
Seeking to reduce the new threat to sperm whales created by
the newly established TSS, the Spanish Maritime Authority sub-
sequently sought to establish a security area where vessels were
advised to limit maximum speed to 13 knots (this speed limit was
based on analysis by Laist et al. [7]), and to navigate with
particular caution. Following review by the IMO, 13-knot speed
recommendations were published by the IMO through the MEPC,
added to International Nautical Charts, and disseminated as a
Notice to Mariners (published on January 2007 by the Spanish
Navy Hydrographical Institute). In so doing, this measure became
the first vessel speed recommendation instituted in a TSS for the
purposes of cetacean conservation. Vessel monitoring studies are
underway to assess use of the TSS and compliance with the 13-
knot maximum speed advisories (see below for further discussion
of this).
The approach taken and outcomes of the Cabo de Gata TSS
(2.4, above) and Tangier-Med TSS scenarios provide an interesting
comparison as well as insight into the IMO. The Tangier-Med
proposal (and subsequent attempts to provide recommended
speed limits) suffered from a lack of intra- and inter-national
coordination and communication. This proposal was likely tech-
nically deficient, as well. The Tangier-Med situation also lacked
consideration of environmental issues (e.g., estimates of vessel
strike risks) sufficiently early in the process of establishing/
modifying shipping lanes. In contrast, the successfully endorsed
Cabo de Gata TSS proposal did not have these shortcomings.
In addition, in contrast to IMO adoption of specific routing
measures like a TSS reconfiguration, the IMO’s involvement in
matters regarding vessel speed, as in this case, is likely tentative
particularly in locations with significant trade routes and high
traffic volume.
2.6. Traffic Separation Scheme (TSS): Boston, USA (2006–2007)
A TSS in waters off New England, established in 1973 [62] to
manage traffic navigating to and from Boston, intersected an area
repeatedly inhabited by high concentrations of right whales (and
other large whale species) that migrate along the coast and in and
out of Cape Cod Bay. In April 2006, the USA submitted a proposal
[63] to the IMO to narrow and modify the location of the east-
west leg of the TSS where it joined the north-south leg (Fig. 1(a)),
thereby reducing the probability of vessel strikes by an estimated
58% and 81% in that area for right and other large whales,
respectively [44]. The proposal identified adverse effects to vessel
operators (increasing the voyage by about 3.8 nm) and provided
an analysis of benefit to right whales in terms of vessel strikes
based on a USCG Port Access Route Study that underwent inter-
agency clearance and public consultation [42,64]. The proposal
was approved by the NAV in July 2006, forwarded to the MSC, and
Fig. 4. Sperm whale sightings and security area as proposed to the IMO in the Strait of Gibraltar.
G.K. Silber et al. / Marine Policy 36 (2012) 1221–1233 1227

adopted by the IMO in December 2006. The amended TSS went
into effect on 1 July 2007 [57]. The amendment was added
to NOAA navigational charts and the USCG updated its list of
offshore traffic separation schemes and precautionary areas in the
USA Code of Federal Regulations.
2.7. Area to Be Avoided: Roseway Basin, Canada (2007–2008)
In addition to the Grand Manan Basin in the Bay of Fundy, right
whales also aggregate annually in the Scotian Shelf’s Roseway Basin
that is intersected by vessels transiting through Shelf waters and to
and from the approaches to New York City and other ports in the
USA (Fig. 5). The traffic posed a measurable risk of lethal vessel
strike to right whales [16,64]. In 2006, non-governmental members
of the North Atlantic Right Whale Recovery Implementation Team
once again successfully petitioned the regional and national Cana-
dian Marine Advisory councils (Transport Canada) to support a
proposal [65] to establish an Area To Be Avoided (ATBA) in the
Roseway Basin region. Transport Canada subsequently proposed
creation of the ATBA to the IMO in July 2007 [66] when it was
approved by the NAV, forwarded to the MSC, and adopted by the
IMO in October 2007; the ATBA was implemented in May 2008. The
ATBA is recommendatory for all vessels Z300 GT and is in effect
annually from 1 June to 31 December. The Canadian Hydrographic
Service incorporated the ATBA into nautical charts, the standard
notifications to mariners were issued, and Caution-to-Mariners
placards were distributed to a variety of shipping interests by the
non-governmental organization Canadian Whale Institute.
2.8. Traffic Separation Scheme (TSS): Boston, USA (2008–2009)
In March 2008 the USA submitted a proposal to the IMO for a
narrowing of the north-south leg of the previously modified
Boston TSS (2.6 above) to further separate vessels and right whale
aggregations near the TSS [45], and to make the leg consistent in
width with the previous narrowing of the east-west leg. The
proposed amendment was approved by the NAV in March 2008
[67] when it was forwarded to the MSC, adopted by the IMO in
July 2008 [68], and it went into effect in June 2009. As above,
Member States and shipping interests were notified and changes
were incorporated into navigational charts.
2.9. Area To Be Avoided: Great South Channel, USA (2008–2009)
In summer and autumn, right whale feeding aggregations are
persistent in the Gulf of Maine’s Great South Channel, an area that
includes the existing MSR area (2.2. above), the Boston TSS (2.6 and
2.8), and two heavily used but unspecified routes [43,45]with
generally NW-SE and NE-SW orientations (Fig. 6). Given the elevated
risk of lethal vessel strike in the region [69], the USA submitted a
proposal to the IMO in March 2008 seeking the establishment of an
ATBA in the Great South Channel [70]. The proposal would also
encourage increased use of the amended Boston TSS. The proposal
was approved by the NAV in March 2008, forwarded to the MSC,
adopted by the IMO in December 2008, and implemented in June
2009 [17]. The ATBA is recommendatory for all vessels Z300 GT and
is in effect annually from 1 April through 31 July. As in all cases
above, the ATBA was incorporated into nautical charts and standard
notifications to mariners were issued.
2.10. Guidance document: Measures to reduce ship strikes with
cetaceans, USA, Spain, France, Italy, and Monaco (2008–2009)
In August 2008 the USA provided the IMO with a draft guidance
document [68] that identified ways to minimize the risk of vessel
strikes of cetaceans globally. In October 2008, the MEPC agreed to
invite delegations to provide comments on the draft for eventual
approval by the MEPC [71]. In May 2009, Spain, in cooperation with
France,Italy,andMonaco,presented a supporting paper [72] with
a focus on the Mediterranean Sea. The Guidance Document was
approved in July 2009 and it was issued as an MEPC circular with an
invitation for member states to bring the circular to the attention of
all interested parties, including administrations, recognized organiza-
tions and shipping interests. The Document identifies general prin-
ciples for member states to monitor, assess, and mitigate vessel-strike
risk in their waters. These principles, while stressing that maritime
safety is paramount, include the scientific assessment of shipping and
the affected cetacean populations, science-based risk mitigation,
monitoring the effectiveness of any vessel strike reduction initiative,
and mariner education and outreach programs. Cooperation at an
Fig. 5. The Roseway Basin Area To Be Avoided (ATBA) (black polygon) in (a) and
(b) and vessel tracks through the region from 15 June to 31 October 2007 (a) and
from 1 June to 31 October 2008 (b) prior to and following implementation of the
ATBA, respectively. Modified from Vanderlaan and Taggart [17].
G.K. Silber et al. / Marine Policy 36 (2012) 1221–12331228

international level is also identified including coordination with
relevant international fora such as the International Whaling Com-
mission that is now addressing vessel strike reduction.
3. Assessing the effectiveness of measures to reduce vessel
strikes
A conservation initiative, no matter how well-intentioned, has
limited value unless it can be shown to have attained its objectives.
The relative effectiveness of a routing measure for instance should
be realistically weighed against the allocation of resources needed
for implementing and monitoring it and used in assessing the need
to improve or possibly abandon the measure. When it comes to the
reduction of lethal vessel strikes to whales, most studies to date
(as discussed in Sections 3.1–3.3, below) have focused on quantify-
ing vessel operations in response to the measure, determining
biological effectiveness (i.e., observed reductions in vessel strike
incidents), and risk reduction estimates. However, such assess-
ments may be confounded by variables that include shifts in
vessel-traffic density and patterns; seasonal, annual, and decadal
changes in whale abundance and distribution; inconsistent strike
detection ‘effort’ and reporting; and the availability of the neces-
sary whale, vessel and other relevant data. These limitations
notwithstanding, several data sources, technologies, and analytical
methods are available to assess risk reduction.
With regard to right whales in USA waters, Silber and Bettridge
[73] identified four issues related to assessing the effectiveness of
federal regulations that restricted vessel speed in certain loca-
tions [18]: (a) mariner education, (b) assessing economic impact
that may result from the regulation, (c) measuring the response
by mariners to the regulation, and (d) quantifying changes is
various whale-related variables and parameters. Of these, (a), (c),
and (d) are most relevant here.
Raising mariner awareness, (a), about the impact of vessel-
strike deaths on whale populations is worthy of considerable
attention because mariners cannot be expected to help reduce
strikes if they have no knowledge of the problem or the relevant
actions they could take. Given the opportunity, mariners may
help offer solutions, and their engagement helps build trust and
cooperation. Outreach programs also offer avenues for encour-
agement. There are a number of ways to educate mariners and
such approaches are identified elsewhere [e.g., 15,74].
3.1. Quantifying vessel navigation patterns
Quantifying vessel operations (e.g., routes and speeds), as a
measure of mariner adherence to required or voluntary conservation
measures, is essential to both designing vessel-related initiatives and
for subsequently evaluating their relative success. Various data
sources are available that can be used to characterize vessel speed,
traffic density etc. in time and space. Until recently, the most available
vessel-navigation data included the International Comprehensive
Ocean-Atmosphere Data Set (ICOADS, National Center for Atmo-
spheric Research, Boulder, Colorado USA) that includes data derived
from a fleet of Voluntary Observing Ships (VOS). The ‘fleet’ is repre-
sented by 4000 commercial vessels drawn from the world fleet
of 45,000 vessels [75–77]. These data are global in distribution and
provide information daily across a decades-long time series. However,
they represent 10% of the world fleet and the spatial resolution is
0.1 degree (approximately 6 nm). Similar national or regional data
include the Automated Mutual Assistance Vessel Rescue System
(AMVER) [78], the now disbanded Eastern Canada Vessel Traffic
Services Zone Regulations (ECAREG) [16], radar tracking [16],and
the MSR systems [43]. There are also globally distributed data that
can be derived from the long-range identification and tracking (LRIT)
of the world fleet as instituted by the IMO under the SOLAS
convention [79], though such data are not readily available outside
certain governmental regulatory agencies.
Recently, readily- and economically-obtained vessel Automatic
Identification System (AIS) information has been used to quantify
vessel operations. The AIS employs a VHF (161.9765 mHz and
162.025 mHz) ship-to-ship and ship-to-shore messaging system
that is required on all international vessels Z300 GT and cargo
vessels Z500 GT [80]. In the Vessel Traffic System areas of the
USA, AIS is also required on all self-propelled commercial vessels of
at least 65 feet and some passenger and towing vessels.
Transmitted AIS signals provide static (e.g., ship name, call
sign, hull specifications) and dynamic (e.g., vessel location, speed)
voyage-related information [81]. Initially designed to enhance
vessel safety, AIS is now being used to characterize vessel traffic
patterns [82], assess contributions of ocean-going vessels to
underwater noise [83], and quantify vessel-operator compliance
with mandatory [84] and recommendatory vessel strike reduction
measures [17]. Vessel track and speed analysis can be quite
precise given AIS signals are transmitted numerous time each
minute [84]. AIS receivers suffer from line-of-sight range-limita-
tions (ca. 45 km, depending on height of the receiver and certain
other, e.g., meteorological, conditions) [84] and thus require a
network of coastal towers for regional coverage. Development of
more advanced satellite-mediated AIS systems may be a reality in
the foreseeable future, but their status remains uncertain.
AIS technologies have been used specifically to assess mariner
response to the IMO-endorsed measures described in this paper.
For example, responses have been quantified with regard to the
ATBA in Roseway Basin in which vessel tracks exhibited clear
course changes to avoid the area (Fig. 5(a) and (b)), and in the
case of the USA Great South Channel ATBA, a shift toward use
of the TSS servicing Boston, as intended, has resulted from the
placement of the ATBA. Similarly, AIS-based studies indicate
clear differences in vessel traffic patterns before and after the
November 2006 shift of the Cabo de Gata TSS —full compliance
with the modified TSS has occurred (Fig. 3). In addition, surveys
indicate that several whale species are occurring primarily north
and south of these shipping lanes, suggesting that the re-positioning
of the Cabo de Gata TSS has lowered the risk of vessel strikes.
In contrast, AIS monitoring of the Gibraltar Strait TSS indicates that
mariners are not adhering to the 13 knot recommended vessel speed
limit. Low adherence levels are likely due to irregular (and limited
geographic range of) broadcasts about the advised speed limits and
because they were merely ‘noted’ by the IMO rather than being
endorsed as a specific measure. In addition, routing measures are
common and accepted actions for the IMO, but speed restrictions are
not —thus, the latter likely are not readily recognized by mariners. In
an analogous situation involving domestically-implemented vessel
speed limit requirements in USA waters (mandatory in this case) [18]
low initial compliance was observed in which over 60% of vessel
transits in the first 12 months exceeded the 10 knot limit [84].
On the whole, results of vessel monitoring studies help illustrate
both the potency of IMO involvement in establishing new vessel
operating practices when routing measures are involved, and the
difficulties inherent to invoking speed limits. Although a viable tool
for reducing vessel strikes [18,25], use of vessel speed restrictions
may encounter hurdles in part because they are rarely employed or
may be unfamiliar for some maritime communities, at least as far as
vessel-strike reduction purposes are concerned.
3.2. Assessing the biological effectiveness of vessel collision reduction
measures
Decreased vessel strikes events is the ultimate goal of vessel-
strike reduction measures and enumeration of a reduction in strikes
G.K. Silber et al. / Marine Policy 36 (2012) 1221–1233 1229

(e.g., documenting fewer whale deaths, or quantifying population
growth, the later being at least partly attributable to fewer mortal-
ities; item d in Section 3, above) is one direct measure of relative
success. However, quantifying such reductions may not be easily
accomplished because not all strikes are observed or reported. Pace
[85] used one biological metric in assessing the effectiveness of vessel
speed limits: time elapsed between subsequent known vessel strike
deaths or serious injuries, both before and after the enactment of a
specific measure (but, this has not been applied to the IMO-endorsed
measures discussed here). This approach helps avoid the pitfalls of
trying to assess trends in absolute numbers of whale-strike events
given they are rarely and incompletely observed or reported, but it is
also constrained by requiring a sufficiently long time series and
assumes the effort to detect whale deaths remains constant.
3.3. Risk reduction estimates
Risk reduction probability calculations have been used to
estimate strike rates and to assess the effectiveness of various
strike reduction measures. For example, based on strike-rate
analysis for large baleen whales, including right whales, on global
and regional bases, Vanderlaan et al. [25] reported a 3- to 4-fold
increase in the number of reported strikes worldwide from the
early 1970s to the early 2000s and estimated a 50% chance of 14
or more annual vessel-strike reports worldwide between 1999
and 2002. Noting that obtaining risk reduction probabilities rely
on the validity of several assumptions – including a vessel strike
can occur at any time or place along a vessel route, the probability
of a strike is small, and vessel strikes are independent events –
Vanderlaan et al. [25] concluded that where sufficient data are
available, a modeling tool they developed can be used to predict
the expected change in vessel strikes stemming from a given
conservation action in various geographic locations. Here, again,
long time series (i.e., years or decades) before and after the
implementation of a conservation initiative are needed to ade-
quately evaluate the action [25,73].
Estimates of risk reduction have also been applied to measures
adoptedbytheIMO.Forexample,theefficacyoftheRosewayBasin
ATBA was initially uncertain because it was based on recommenda-
tory actions. Indeed, adherence with its provisions was lowest in the
first two weeks and ranged from 57% to 87%, but some learning
about the ABTA may have been involved because in the course of the
first year compliance had stabilized at 71% [17]. The corresponding
risk reduction was estimated at 82% and, thus, Vanderlaan and
Taggart [17] concluded that an IMO-adopted ATBA, although recom-
mendatory, was an effective means to protect endangered whales.
In a comparison of the merits of vessel re-routing versus speed
restrictions in the Bay of Fundy, Vanderlaan et al. [16] reported a
62% risk reduction versus 52% risk reduction when using vessel
re-routing and speed restrictions, respectively (Fig. 2). Thus,
although there is still considerable risk of lethal vessel strikes
within the Bay, reductions in risk have been achieved with
minimal effects on maritime operations.
With regard to modification of the Boston TSS, Merrick [44]
provided estimates of vessel strike reduction of 58% for right whales
and an 81% reduction for other large whale species in the area (i.e.,
fin, humpback (Megaptera novaeanglia), and minke (B. acutorostrata)
whales) if the TSS was amended as proposed. However, post-
implementation analysis of this measure has not been conducted.
Canada’s proposal to the IMO to amend the Bay of Fundy TSS
provided an estimated 80% reduction in the relative probability of
a vessel encountering a right whale [16]. Further analyses (which
included a vessel speed term and an algorithm that ‘moved’ those
vessels transiting the original lanes into the amended lanes) indicated
an estimated average reduction in relative risk of a lethal vessel strike
of 90% relative to the TSS’s original configuration (Fig. 2(b)). In
considering the entire Bay of Fundy, amending the TSS reduced the
risk of a lethal vessel strike by approximately 62% [16], and resulted
in estimated decreases in risk of lethal strikes by 28% to minke, 27% to
fin, 17% to sei (B. borealis), and 9% to humpback whales.
4. Conclusions
Actions are being taken worldwide to reduce the threat of vessel
strikes of large whales, some via endorsement by the IMO. To date,
Fig. 6. North Atlantic right whale sighting locations January 1999–July 2005 and vessel traffic patterns June 2005–May 2009 in the area that later became the Great South
Channel Area To Be Avoided. Vessel data were derived from the Mandatory Ship Reporting system data. Right whale sighting information provided courtesy of NOAA’s
Northeast Fisheries Science Center’s aerial survey program.
G.K. Silber et al. / Marine Policy 36 (2012) 1221–12331230

the IMO has deliberated on a total of 10 actions to reduce the threat
of ship strikes to large whales in three regions. Although the
processes used by the IMO may be confusing to some, we found
that proposals that provided strong needs statements, were accom-
panied by relevant documentation, contained an assessment of
impact to maritime industries, and included robust risk reduction
analysis were likely to be successful. Only IMO members can
submit proposals. Consideration should be given prior to submis-
sion to monitoring of the measures, and to the necessary domestic
coastal state regulations, legislation, or other mechanisms that
might be instrumental in implementing the measures.
Specific actions described here for waters off Canada and the
USA and those in the Mediterranean share these features: sub-
stantial information existed on whale occurrence and distribu-
tion, thereby facilitating the establishment of specific routing
measures relative to whale occurrence; and vessel transit pat-
terns and volume were relatively easily obtained (and therefore,
compliance rates and impacts to industry could be assessed).
Analogous efforts in other locations (e.g., the open ocean) may
face difficulties if biological information and technological cap-
abilities for tracking vessels are limited.
The technology, data, and analytical tools exist for assessing
the relative effectiveness of IMO-endorsed measures. Vessel com-
pliance with IMO-endorsed measures, even for those that are
recommendatory, is generally high. The success of these measures
is likely enhanced by the existence of constructive links between
authorities implementing the measures and the affected maritime
shipping entities, bearing in mind that main concerns for these
entities, and that of the IMO, are safety and security at sea. The
relative success of IMO-adopted navigational measures speak to
the influence and international reach of the IMO, and make it a
powerful forum for coastal states to implement whale conserva-
tion measures and for addressing a range of marine environmen-
tal issues, especially where shipping has been identified as a
threat to the ocean environment.
Acknowledgements
We are deeply indebted to our coauthor, the late Lindy
Johnson, whose life and career were the definition of an unwaver-
ing commitment to marine conservation. Much of what is pre-
sented above would not have been possible without her guiding
hand. For their support in finding vessel-strike solutions we thank
G. Detweiler, E. LaRue, and M. Solosi at the USCG in the USA;
I. Martı
´n, S. Rodriguez, M. Nogueira, J. Pantoja and F. Ramos in
Spain; R. Tuner at Transport Canada; and M. Palomares at the
IMO. Research conducted in the Mediterranean was funded by
LIFE Nature Projects numbers LIFE02NAT/E8610 and LIFE07NAT/
E00732. Critical reviews by P. Openheimer, E. LaRue and anon-
ymous referees helped improve this manuscript.
Appendix A
A listing of vessel navigation definitions and instruments avai-
lable to International Maritime Organization (IMO) as reflected in
the annual IMO publication entitled: Ships’ Routeing.
Area To Be Avoided (ATBA): a routing measure comprising an
area where navigation is particularly hazardous or exceptionally
important to avoid casualties and should be avoided by all, or
certain classes, of vessels.
Deep-water route: a route which has been accurately surveyed
for clearance of sea bottom and submerged obstacles as indicated
on nautical charts.
Fairway: a lane or corridor in which no artificial island or
structure, temporary or permanent, will be permitted so that
vessels using ports will have unobstructed approaches.
Inshore traffic zone: a routing measure comprising a desig-
nated area between the landward boundary of a traffic separation
scheme and the adjacent coast.
Mandatory Ship Reporting System: systems used to provide,
gather, or exchange information through radio reports or other
means of communication. The information is used to provide data
for many purposes including, but not limited to, navigation safety,
environmental protection, vessel traffic services, search and res-
cue, weather forecasting, and prevention of marine pollution.
No anchoring area: a routing measure identifying an area where
anchoring is hazardous or could result in unacceptable damage to
the marine environment. Anchoring in a no anchoring area should
be avoided by all vessels or certain classes of vessels, except in case
of immediate danger to the vessel or persons on board.
Particularly Sensitive Sea Area (PSSA): an area that needs
special protection because of its significance for recognized
ecological, socio-economic, or scientific reasons and which may
be vulnerable to damage by international maritime activities. The
criteria for the identification of a PSSA and the criteria for the
designation of Special Areas are not mutually exclusive. In many
cases a Particularly Sensitive Sea Area may be identified within a
Special Area and vice versa.
Precautionary area: a routing measure comprising an area
within defined limits where vessels must navigate with particular
caution and within which the direction of traffic flow may be
recommended.
Recommended route: a route of undefined width, for the con-
venience of vessels in transit, which is often marked by centerline
buoys.
Recommended track: a route which has been specially exam-
ined to ensure so far as possible that it is free of dangers and along
which vessels are advised to navigate.
Regulated Navigation Area: an area for which specific regula-
tions for vessels navigating within the area have been established.
Roundabout: a routing measure comprising a separation point
or circular separation zone and a circular traffic lane. Traffic
within the roundabout is separated by moving in a counter-
clockwise direction around the separation point or zone.
Separation Zone or separation line: a zone or line separating
the traffic lanes in which vessels are proceeding in opposite or
nearly opposite directions; or from the adjacent sea area; or
separating traffic lanes designated for particular classes of vessels
proceeding in the same direction.
Traffic lane: an area in which one-way traffic is established.
Natural obstacles, including those forming separation zones, may
constitute a boundary.
Traffic Separation Scheme (TSS): a routing measure aimed at
the separation of opposing streams of traffic by appropriate
means and by the establishment of traffic lanes. The traffic-lanes
(or clearways) indicate the direction of the ships in that zone;
ships navigating within a TSS all sail in the same direction or they
cross the lane in an angle as close to 90 degrees as possible. TSS’s
are used to regulate the traffic at busy, confined waterways
or around capes, and usually consist of at least one traffic-lane
in each main-direction, turning-points, deep-water lanes and
separation zones between the main traffic lanes.
Two-way route: a route in which two-way traffic is estab-
lished, aimed at providing safe passage of ships through waters
where navigation is difficult or dangerous.
Vessel routing system: any system of one or more routes or
routing measures aimed at reducing the risk of casualties;
it includes traffic separation schemes, two-way routes, recom-
mended tracks, areas to be avoided, no anchoring areas, inshore
G.K. Silber et al. / Marine Policy 36 (2012) 1221–1233 1231

traffic zones, roundabouts, precautionary areas, and deep-water
routes.
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