# Presentation: 730650

## 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, USA
- 2) 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, USA
- 4) New England Aquarium, Central Wharf, Boston, MA 02110, USA

## Objectives:

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

- Evaluate potential management measures designed to reduce
- collision risk

## Aerial Surveys 1998-2002

**Notes:**
During period of right whale presence (Dec/Jan – mid-May)
Spatiotemporal consistency of effort

## 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

## /

-  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

**Notes:**
Quadrats with effort < 2km/period removed

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## 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

**Notes:**
3 km falls between swath width from CeTAP and SCOPEX

## Vessel Transits

-  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

**Notes:**
Data set includes vessels at or over 65’ LOA of the following types: tanker, dry cargo or passenger, tug, tank barge, or dry cargo barge.  Each entry includes the date, vessel type, origin, and destination.  First attempt to characterize ship traffic in CCB.

## Routes

- (based on origin/destination in USACE dataset)

**Notes:**
Rationale for choosing routes, straight line/shortest distance b/w 2 points, comp w/NEMP, CCS data

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## 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 known
- number 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)

**Notes:**
MATLAB, segments summed, x # transits by type, types summed, routes summed

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## 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

**Notes:**
Periods summed to provide annual value.

## Effects of Rerouting

- Proposal A: Simple demonstration exercise

- Proposal B: Draft routing option presented at ANPR meetings

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

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## Effects of Rerouting

-   Gulf of Maine route and by about 40% on the Provincetown and
-   Boston routes

-  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)

## Summary

-   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

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

**Notes:**
It is important to note that there are numerous factors that must be taken into account by managers considering rerouting vessel traffic, including but not limited to: navigational safety, conflicts with other human activities such as fixed-gear fishing, and the potential economic effect of the greater distance traveled by vessels that are rerouted around whale concentrations.  The above factors are beyond the scope of this report and consequently were not considered when rerouting options were selected for analysis.

## 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