Interactive Monthly DMA Analyses

An Analysis of Dynamic Management Areas, January 2010- August 2019,
in Support of the U.S. Take Reduction Team

April 2019
Updated September 2019
Tim Cole and Leah Crowe

Introduction

We used the Dynamic Management Area (DMA) dataset housed at the NOAA NEFSC to generate maps that are roughly analogous to analyses used to create Seasonal Area Management zones (SAMs) for fisheries management (Merrick et al. 2001) and Seasonal Management Areas (SMAs) for vessel speed restrictions (Merrick 2005) to protect right whales. These seasonal areas were drawn to contain areas where sightings of three of more right whales occurred over multiple years. In Merrick et al. (2001), only NOAA aerial survey sightings 1999-2001 were used, and SAMs were drawn around areas where sightings of three of more right whales occurred seasonally over at least two years. In Merrick (2005), survey sightings from the North Atlantic Right Whale database (NARW) 1999-2003 were used, and SMAs were drawn around areas where sightings of three of more right whales occurred seasonally over at least three years. This analysis provides the most recent 9+ years of verified sightings of three of more right whales for Take Reduction Team (TRT) members. An interactive interface is provided for members to facilitate their review of right whale distribution and potential persistence relative to fisheries.

Dynamic Management Areas (DMAs)

DMAs are a component of the 2008 NOAA Ship Strike Rule to minimize lethal ship strikes of North Atlantic right whales. DMAs are temporary protection zones that are triggered when three or more whales are sighted within 2-3 miles of each other outside of active Seasonal Management Areas (SMAs). The size of a DMA is larger if more whales are present. A DMA is a rectangular area centered over whale sighting locations and encompasses a 15-nautical mile buffer surrounding the sightings’ core area to accommodate the whales’ movements over the DMA’s 15-day lifespan. The DMA lifespan is extended if three or more whales are sighted within 2-3 miles of each other within its bounds during the second week the DMA is active. Only verified sightings are used to trigger or extend DMAs. The trigger of three or more whales is taken from a NOAA NEFSC analysis of sightings data from Cape Cod Bay and Stellwagen Bank from 1980 to 1996 (Clapham & Pace 2001). This analysis found that an initial sighting of three or more right whales was a reasonably good indicator that whales would persist in the area, and the average duration of the whale’s presence based on these sightings data was two weeks.

Analysis

DMAs issued since January 2010 that occurred north of 36° North were used in this analysis. For the winter seasonal analysis, November and December 2009 were additionally included. An overall analysis was done that included all DMAs to show density within 1nm^2 grid cells of management areas issued similar to methods in Asaro (2012). Additionally, maps were compiled grouped by months as well as by seasons and included iterative, consecutive 3-year periods to compare to the methods of Merrick et al. (2001) and Merrick (2005). Within each year, one layer was created so that overlapping DMAs within a year were flattened so that each zone was only represented once. Shading indicates the number of consecutive years an area had overlapping DMAs by month or season.

The trigger date, defined here as the date of observed right whale sightings that triggered a DMA or DMA extension, was used for monthly/seasonal binning. Please note that instances where a DMA’s 15-day lifespan went into the following month are not reflected in these maps, e.g., a DMA that is triggered by sightings on 17 February and expires on 05 March will only be included in the February map. A DMA would be reflected the following month if the extension was made in the following month, e.g., sightings on 03 March would extend the DMA example above through March 17 and would be reflected in maps within the month of March. We decided to use the trigger date, rather than the span of the DMA, because the trigger month is reflective of whale sightings, and this analysis did not aim to quantify the effectiveness of the DMA process.

For the seasonal analysis, seasons were divided in three 4-month groups as follows:

The spring season grouping was chosen to coincide with the spring bloom (generally Feb/Mar south of the islands, April on George’s and the GOM), and the summer period ending in October to coincide with fall turnover (generally October in the Mid-Atlantic).

Proposed Area Closures

The following proposed area closures were included with the DMA analysis:

Caveats

This analysis used DMAs rather than sighting locations as in Merrick et al. (2001), and therefore the results are analogous but not directly comparable. More importantly, however, DMAs are not triggered if a right whale aggregation is sighted within an active SMA. Therefore, this analysis does not assess the recurrence of right whales in the existing SMAs. The boundaries of SMAs are shown on the maps as blue polygons, and any grey shading indicates DMAs that were triggered either outside an SMA or were triggered during periods when an SMA was not active (see SMA regulations).

Interpretive Value

Perhaps the most important result of this analysis is the apparent changes as well as consistency in the distribution of DMAs over the years. There are areas where right whales have been consistently sighted that are outside of SMAs, but there has also been an increase in the persistence of right whale occupancy south of the Cape and Islands.

References

Asaro, M.J. 2012. Geospatial analysis of management areas implemented for protection of the North Atlantic right whale along the northern Atlantic coast of the United States. Marine Policy. 36: 915-921.

Clapham, P.J.; Pace, R.M., III. 2001. Defining triggers for temporary area closures to protect right whales from entanglements: issues and options. Northeast Fish. Sci. Cent. Ref. Doc. 01-06; 28 p.

Merrick, R.L.; Clapham, P.J.; Cole, T.V.N.; Gerrior, P.; Pace, R.M., III. 2001. Identification of seasonal area management zones for North Atlantic right whale conservation. Northeast Fish. Sci. Cent. Ref. Doc. 01-14; 18 p.

Merrick, R.L. 2005. Seasonal management areas to reduce ship strikes of northern right whales in the Gulf of Maine. U.S. Dep. Commer., Northeast Fish. Sci. Cent. Ref. Doc. 05-19; 18 p. Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026.


Acoustic Indicators of Right Whale Occurrence

April 2019
Danielle Cholewiak, Genevieve Davis, Josh Hatch

Purpose

An indicator of the spatial and temporal occurrence of North Atlantic right whales is presented based on passive acoustic monitoring conducted along the US eastern seaboard from 2010-2018.  These results are intended to complement the DMA analyses and additional analyses in support of the ALWTRT.

Indicator of Occurrence based on Passive Acoustics

Passive acoustic data collected by the NEFSC and multiple collaborators along the U.S. eastern seaboard from 2010-2018 were used to acoustically assess right whale presence on a monthly basis (i.e. Davis et al. 2017).  Acoustic receivers were deployed at varying times and locations depending on project-specific goals. Acoustic data were analyzed using the Low-Frequency Detection Classification System (LFDCS, Baumgartner & Mussoline 2011), and detections of right whale up-calls were verified by an experienced analyst.  Right whales were considered “present” at a site on any given day if at least three verified up-calls were detected that day. For more information, see Davis et al. 2017.

An indicator of right whale occurrence was developed using the percentage of days within a month in which right whales were present on any given acoustic receiver. The number of days with right whale detections, as well as the number of recording days, were aggregated by month across years for each acoustic receiver to provide the percentage of days within a month that had right whale detections.  The acoustic indicator of occurrence was then calculated as,

where i denotes the acoustic receiver, j denotes the month, and k denotes the year.  The acoustic indicator was then divided into three categories to reflect levels of occurrence:

Category % Days/month with Acoustic Detections
Low < 10%
Medium 10 - <50%
High >= 50%

Caveats

Passive acoustic monitoring can only detect vocally-active animals; silent animals are not detectable.  Additionally, automated detectors may miss some calls, leading to an underestimation of vocal activity. Therefore, these results represent a minimum number of days in which right whales were present, but there may be additional days in which animals were present but not detected. 

Acknowledgments and Funding

The passive acoustic data summarized here are the result of contributions from many collaborators and funding streams.  The compilation of these data and subsequent analyses were conducted under the direction of Dr. Sofie Van Parijs, NEFSC. For data from 2010-2014, please see Davis et al. 2017 for a complete list of collaborators and acknowledgements.  For data from 2015-2018, data collection and analyses by the NEFSC Passive Acoustics Group were supported by NOAA Fisheries, BOEM and the US Navy, and were conducted in collaboration with Cornell University and Scripps Institution of Oceanography Whale Acoustics Lab. We thank Alyssa Scott and Sarah Weiss for analysis assistance.

References

Baumgartner, M.F. and Mussoline, S.E., 2011. A generalized baleen whale call detection and classification system. The Journal of the Acoustical Society of America, 129(5), pp.2889-2902.

Davis, G.E., Baumgartner, M.F., Bonnell, J.M., Bell, J., Berchok, C., Thornton, J.B., Brault, S., Buchanan, G., Charif, R.A., Cholewiak, D. and Clark, C.W., 2017. Long-term passive acoustic recordings track the changing distribution of North Atlantic right whales (Eubalaena glacialis) from 2004 to 2014. Scientific reports, 7(1), p.13460.