A simple two-dimensional model of ship encounter risk for right whales in Cape Cod Bay:

Final results and management implications

Owen C. Nichols1, Hauke L. Kite-Powell2, Robert D. Kenney3, Moira W. Brown4

     1) Center for Coastal Studies, PO Box 1036, Provincetown, MA 02657, USA2) Marine Policy Center, Woods Hole Oceanographic Institution, MS 41, Woods Hole, MA 02543, USA

3) Graduate School of Oceanography, University of Rhode Island, Bay Campus Box 41, Narragansett, RI 02882, USA4) New England Aquarium, Central Wharf, Boston, MA 02110, USA

Objectives:

Provide a baseline estimate of risk to right whales fromcollisions with shipping traffic in Cape Cod Bay

Evaluate potential management measures designed to reduce collision risk

Aerial Surveys 1998-2002

Sightings Per Unit Effort (SPUE)

• The sampling season was defined as December through mid-May and divided into twelve two-week periods (1 December – 17 May)

• Study area partitioned into 117 3-minute quadrats (23 km2)

• 14 quadrats completely over land; thus 103 quadrats sampled

• Standardized aerial survey effort: visibility 2 nm, sea state ≤ 3, altitude < 325 m (1066 ft), observers on watch

• Only sightings and effort meeting the above criteria used in analysis

Sightings Per Unit Effort (SPUE)

• Total effort and total sightings within each quadrat summed by year and separated into two-week periods

SPUE = right whales sighted/1000 km survey effort

/• Kriging interpolation algorithm* used to estimate SPUE at twice the geographic resolution (1.5 minute quadrats)

* GLOBEC Kriging Software Package, Dezhang Chu, WHOI

• Number of whales sighted divided by effort to generate SPUE index

Density Estimates

SPUE converted to density estimate (whales/km2) for each 1.5 min quadrat over 2-week periods - assuming 3 km effective survey swath

Average Daily Transits by Route to/from CCCanal

0

1

2

3

4

5

6

7

8

9

1Dec-14Dec

15Dec-28Dec

29Dec-11Jan

12Jan-25Jan

26Jan-8Feb

9Feb-22Feb

23Feb-8Mar

9Mar-22Mar

23Mar-5Apr

6Apr-19Apr

20Apr-3May

4May-17May

Cape Cod Bay

mid-Cape

Plymouth

Provincetown

Gulf of Maine

Boston

• Data provided by USACE Cape Cod Canal Field Office• 6 routes based on origin/destination in USACE dataset• ~ 7 vessel movements/day: 4 - Boston, 2 - Gulf of Maine• 75% of the traffic is tug-barge combinations

Vessel Transits

Route Traffic to/from… Course (true) from Cape Cod Canal

Boston Greater Boston area 45○ to longitude 70.38○W,then 340○

Gulf of Maine north of Cape Ann 25○

Plymouth Plymouth/Duxbury and vicinity

355○ to latitude 41.92○N, then 330○ to latitude 42.00○N

Provincetown Provincetown and anchorages

45○ to latitude 42.03○N

mid-Cape inner “elbow” region of CCBay

85○ to longitude 70.05○W

Cape Cod Bay

unspecified locations in CCBay

45○ to latitude 41.92○N

Routes(based on origin/destination in USACE dataset)

?

Calculation of Expected Ship/Whale Encounters

For each route and 2-week period, the expected number of ship/whale encounters was calculated based on the passage of a knownnumber of vessels through quadrats of estimated right whale density

• Effective beam (width of path “swept” by vessels) estimated based on vessel type: tug = 10m; tug-barge, dry cargo, passenger = 15 m; tanker = 20m

• Routes divided into 1 km segments – right whale density is assumed based on the 1.5 min quadrat over which most of the segment lies

• Assumptions: whales always at surface and neither whales nor vessels attempt to avoid collision

# of ship/whale encounters = area of path “swept” by vessel (beam x 1 km) x density (whales/km2)

Expected Ship/Whale Encounters

• Results of model = 1.5 ship/whale encounters/year• Boston traffic contributes ~ 46% of expected encounters, while Gulf of Maine traffic contributes ~ 35% - the latter poses high risk despite relatively low volume - transects areas of high whale density

Expected Vessel-Whale Encounters per 2-Week Period, by Route

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

1Dec-14Dec

15Dec-28Dec

29Dec-11Jan

12Jan-25Jan

26Jan-8Feb

9Feb-22Feb

23Feb-8Mar

9Mar-22Mar

23Mar-5Apr

6Apr-19Apr

20Apr-3May

4May-17May

Cape Cod Bay

mid-Cape

Plymouth

Provincetown

Gulf of Maine

Boston

• Two proposals incorporated into model

Proposal A: Simple demonstration exercise

Effects of Rerouting

Proposal B: Draft routing option presented at ANPR meetings

• Both proposals involved shifting Boston, Gulf of Maine, and Provincetown traffic to the west

• Expected ship-whale encounters reduced by about 60% on the Gulf of Maine route and by about 40% on the Provincetown and Boston routes

Effects of Rerouting

route expected ship-whale encounters/year

  present Proposal A Proposal B

Boston 0.71 0.44 0.38

Gulf of Maine 0.54 0.25 0.19

Provincetown 0.02 0.01 0.01

Cape Cod Bay 0.26 0.26 0.26

Plymouth/mid-Cape 0.02 0.02 0.02

total 1.55 0.98 0.86

• Across all routes, reduction of 37% (Proposal A) to 45% (Proposal B) in the overall ship-whale encounter risk for Canal traffic in Cape Cod Bay (from ~ 1.5 encounters/year to ~ 0.9)

• Model results allow identification and comparison of areas of risk to right whales – baseline estimate that can be used to inform management decisions

• Expected encounters calculated based on several assumptions – Model can be refined with additional data as it becomes available: detection probability for density estimates, surface/dive and avoidance behavior, addition of subsequent years of right whale and traffic data

Summary

• Routing existing vessel traffic away from known concentrations of right whales will cause a quantifiable reduction of the potential number of ship/whale encounters

Acknowledgements• Funding provided by the NOAA Fisheries North Atlantic Right Whale Competitive Grant Program

• Aerial surveys supported by the Massachusetts Division of Marine Fisheries as part of the Commonwealth of Massachusetts Right Whale Conservation Plan – funding sources include National Fish and Wildlife Foundation, NOAA Fisheries, Massachusetts Environmental Trust, and the Northeast Consortium – Special thanks to Dan McKiernan

• Vessel traffic data provided by the US Army Corps of Engineers Cape Cod Canal Field Office – Scott Barr, Bill Norman and Fran Donovan - Guidance and advice on routes: Pat Gerrior, Bruce Russell