[MARMAM] Two papers on vessel/whale collisions

Greg Silber Greg.Silber at noaa.gov
Thu Oct 14 04:29:12 PDT 2010

We wish to note the availability of two recent publications concerning 
vessel collisions with large whales.  Abstracts appear below and the 
papers are available at:




Greg Silber
Office of Protected Resources
NOAA, Fisheries Service
Silver Spring, MD, USA

Silber, G.K., J. Slutsky, and S. Bettridge.  2010.  Hydrodynamics of a 
ship/whale collision. Journal of Experimental Marine Biology and Ecology 


            All endangered large whale species are vulnerable to 
collisions with large ships; and "ship strikes" are the greatest known 
threat to one of the world's rarest whales, the North Atlantic right 
whale (_Eubalaena_ _glacialis)_. The magnitude of this threat is likely 
to increase as maritime commerce expands. Factors influencing the 
incidence and severity of ship strikes are not well understood, although 
vessel speed appears to be a strong contributor. The purpose of this 
study was to characterize hydrodynamic forces at play near a moving hull 
that may cause a whale to be drawn to or repelled from the hull, and to 
assess the forces exerted on a whale at the time of impact particularly 
as it relates to vessel speed. Using scale models of a container ship 
and a right whale in experimental flow tanks, we measured accelerations 
experienced by a whale model in the presence of a moving vessel, and 
assessed hydrodynamic actions near the hull on the static, free floating 
whale model. Impact accelerations were measured while the whale was at 
the surface at various vessel speeds, orientations of the whale relative 
to the vessel path, and distances off the direct path of the vessel. We 
observed that accelerations experienced by the whale model in a 
collision: increased in magnitude with increasing ship speed; were not 
dependent on whale orientation to the vessel path; and decreased 
exponentially with increasing separation distances from the ship track. 
Subsequent experiments with the whale model submerged indicate a 
pronounced propeller suction effect, a drawing of the whale toward the 
hull at one to two times the ship's draft, and increased probability of 
propeller strikes resulting from this class of encounter. We present a 
heuristic map of the hydrodynamic field around a transiting hull likely 
involved in close whale/vessel encounters. These results may have 
bearing on policy decisions, particularly those involving vessel speed, 
aimed at protecting endangered large whales from ship strikes worldwide.

Silber, G.K., and S. Bettridge. 2010. Vessel operations in right whale 
protection areas in 2009. U.S. Dep. Commer., NOAA Tech. Memo. 
NMFS-OPR-44. 44 p.

Executive Summary

One of the greatest threats to the recovery of the highly depleted North 
Atlantic right whale (/Eubalaena glacialis/) is collisions with ships 
(or "ship strikes").  The U.S. National Oceanic and Atmospheric 
Administration's (NOAA) National Marine Fisheries Service (NMFS) has 
taken a number of steps to reduce the threat, including issuing a final 
rule (73 Federal Register 60173, October 2008) that requires vessels 
_>_65 feet in length to travel at 10 knots or less in certain times and 
locations (termed "Seasonal Management Areas", or SMA) of right whale 
occurrence.  NMFS also initiated a program whereby "Dynamic Management 
Areas" (DMA) are established in areas in which right whales are observed 
outside SMAs, whereby temporary zones are created and vessels are 
requested (but, not required) to either navigate around the zone or 
travel through it at 10 knots or less.  This process allows for 
management measures that are tied directly to the known, but perhaps 
transitory, presence of right whales, and provides a means to establish 
areas effecting vessel operations that are smaller (in area) and shorter 
(in duration) than seasonal management measures.  NMFS is monitoring the 
effectiveness of the restrictions by assessing compliance with the 
vessel speed limits as well as adherence to associated voluntary 
measures.  Automatic Identification System (AIS) technologies provide a 
precise and easily accessible means to do so.

        Originally conceived as a safety of navigation technology, the 
AIS uses Global Positioning System (GPS)-linked, very high frequency 
(VHF) radio signal that provides for ship-to-ship and ship-to-shore 
information transfer.  It transmits the ship's name, call sign, 
position, dimensions, speed, heading and other information multiple 
times each minute.  The AIS signal provides a suite of information, both 
dynamic (that is unique to a particular voyage) and static (that is 
consistent for a given vessel).  Dynamic information includes the 
vessel's position, speed over ground, course over ground, heading, rate 
of turn, and position accuracy (< or > 10 m) which are determined by 
continuous GPS-linked updates.  Static information includes the 
vessel's:  name, call sign, type, cargo, and its Maritime Mobile Service 
Identity (MMSI) number. Given the rate at which it provides this 
information, AIS is a precise means to remotely track vessel speeds and 
other vessel operations.

Our goal here is to provide (a) a characterization of vessel traffic 
volume, patterns, and speeds of vessels transiting SMAs, and (b) an 
initial assessment of vessel adherence to the vessel speed 
restrictions.  This summary is for the period of January 2009 (the rule 
was enacted December 2008) through December 2009.  We also provide an 
initial characterization of vessel use of DMAs in the same period.

We gathered information on vessel activity in 10 operational SMAs, and 
in 18 DMAs for the period January to December 2009.  As set forth in the 
rulemaking, the SMAs we analyzed were effective in: Cape Cod Bay (1 
January -- 15 May); an area Off Race Point, MA (1 March -- 30 April); an 
area in the Great South Channel (1 April -- 31 July); an area extending 
from mid-coastal Georgia to northern Florida (15 November -- 15 April); 
and (1 November -- 30 April for each of the following) Block Island 
Sound, port entrances of New York City and New Jersey, Philadelphia, PA, 
Norfolk VA, Wilmington, NC, and an area extending from Wilmington, NC to 
just south of Savannah, GA.

A total of 39,615 vessel transits were recorded in active SMAs in 2009.  
Of these, 10,982 were not applicable to conditions set forth in the Rule 
or were deemed inaccurate and were therefore removed from further 
analysis.  Thus, a total of 28,633 transits were analyzed to determine 
vessel types, vessel speeds, SMA use, and other characteristics of these 

The New York-New Jersey port entrance SMA had the greatest number of 
transits (n = 7,651) followed by the North Carolina-Georgia complex and 
the Norfolk SMAs (6,502 and 4,790 transits, respectively).  Cargo 
vessels constituted the majority of ship passages in all SMAs, 
comprising over 50.3 % of all vessel transits, (and excluding the 
"other" vessel type category) followed by tanker vessels (14.9%), and 
tug-type vessels (10.2%).  Cargo vessels were strongly represented in 
the New York-New Jersey, Norfolk and North Carolina-Georgia SMAs, with 
the North Carolina-Georgia complex having the highest number of cargo 
transits of all SMAs.  Considering all transits in all active SMAs the 
ratio of foreign flagged to domestic vessels was 1.6:1

The most common maximum speed represented was 11 knots; and the majority 
of all transits were between 11 and 16 knots.  A substantial number of 
transits were at maximum speeds in excess of 16 knots.  Aggregate 
maximum speeds in most SMAs exhibited a "bell-curve" with peaks between 
10 and 16 knots; while the most highly represented maximum speed in 
nearly all SMAs was 11 - 12 knots.  Generally, domestic vessels had 
lower aggregate vessel speeds than did foreign-flagged vessels; 
foreign-flagged vessels tended to travel at 12 knots or greater.  Cargo 
vessels exhibited the highest aggregate maximum speeds (with the most 
traveling in the 15-16 knot range), followed by tankers (with peaks in 
the 11-13 knot range), and aggregate speeds for passenger vessels had 
peaks around 12 knots.  Vessels in the "tug, tow, dredge", and "other" 
categories exhibited peak aggregate speeds around 10 knots. 

In 2009, 18 DMAs were "triggered" by right whale presence, all occurring 
in waters off New England.  A total of 1,406 vessel transits occurred in 
these active DMAs.  The majority were tankers (n = 521), nearly twice as 
many as any other vessel category.  Excluding the "other" category, 
cargo vessels were the second most common type.  The distribution of 
vessel speeds through DMAs is different than the distribution for vessel 
speeds utilized in SMAs (it was not a "bell-shape" as in the SMA speed 
distributions).  In DMAs, 11 knots was the most common maximum speed; 
and there appeared to be a higher proportion of vessels traveling 11 
knots or less than those vessels traversing SMAs.  A second peak 
occurred at 14 knots with a large portion traveling at 13 and 14 knots; 
probably reflecting the number of cargo ships and tankers traversing the 
zones.  Likely, many tug and barges and "big-tows" (vessels typically 
traveling at speeds under 12 knots) have limited options to route around 
such areas:  being largely coastal and having specific destinations that 
require routes through DMAs and therefore opt to travel through DMAs; 
whereas larger, ocean-going vessels on more lengthy routes may have the 
latitude to avoid a particular area.

        It is not clear why "compliance" (defined strictly here as 
maximum speed _<_10 knots) with vessel speed requirements was low.  
Contributing factors may be a lack of public recognition of the rule, 
disregard for it, or inadequate early enforcement.  There are almost 
certainly learning and acquisition phases to a requirement that 
substantially alters standard practices.  With regard to 
"foreign-flagged" vessels and their operators, particularly those making 
infrequent port calls, language barriers or simple lack of familiarity 
with domestic requirements may hamper acquisition of the significance 
and requirements of the rule.  Regarding knowledge of the rule, however, 
NOAA and a suite of partners made a concerted effort to notify the 
public and maritime community about the requirements both prior to their 
enactment and during the periods in which SMAs were in effect.  Perhaps 
one significant weakness in efforts to alert mariners is that of NOAA's 
printed nautical charts which currently do not depict SMAs.  There are 
lessons to be learned about the importance of an effective enforcement 
program, and about possible weaknesses in the distribution of various 
notification outlets, their capacity to reach the targeted audience, or 
the level of their impact in influencing the behavior of certain 
maritime operators.
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