Cetacean Density and Distribution Mapping Working Group
In 2011, the U.S. National Oceanic and Atmospheric Administration (NOAA) convened a working group to map cetacean density and distribution within U.S. waters. The specific objective of the Cetacean Density and Distribution Mapping Working Group (CetMap) was to create comprehensive and easily accessible regional cetacean density and distribution maps that are time- and species-specific, ideally using survey data and models, that estimate density using predictive environmental factors. In order to depict the best comprehensive cetacean density and distribution maps, the CetMap:
- Identified a hierarchy of preferred density and distribution model or information types;
- Conducted a cetacean data availability assessment that included making previously less accessible data available through this effort;
- Modeled or re-modeled density using first-tier habitat-based density models in some critical areas, based upon updated methods and/or new data;
- Created standardized GIS files from the new modeling results and other existing modeling results, and;
- Developed a NOAA website interface that: organizes these datasets and maps to highlight the best available information type; makes them searchable by region, species, and month; and provides many of the GIS files for download.
The Tier 1 species-specific CetMap products presented (i.e., the habitat-based density models) are predominantly at a spatial resolution of 10 km2, with a few at 25 km2, based on the manner in which the data were initially collected or modeled. Products are organized by month, but depicted in a manner that reflects when model results are predicting only seasonal resolution. The Cetmap products can be viewed and downloaded, with accompanying metadata, here.
Separately, to augment the more quantitative density and distribution mapping described above and provide additional context for marine mammal impact analyses, the CetMap also identified (through literature search, current science compilation, and expert consultation) known areas of importance for cetaceans, such as reproductive areas, feeding areas, migratory corridors, and areas in which small or resident populations are concentrated. A more detailed description of this research effort can be viewed here.
The sections below describe the CetMap efforts outlined above and provide links to the products or other information, where appropriate.
The CetMap identified and broadly evaluated the information-types and modeling methods available for estimating marine mammal density and distribution and ranked them in Tiers based on their expected ability to accurately predict presence, distribution, or density in a spatially and temporally explicit manner. Following are ranked Tiers:>
- Habitat-based density models, which allow fine-scale predictions of density (individuals per throughout a survey region using regression-based models that relate habitat variables to species encounter rates and group sizes;
- Stratified density models, which assume uniform animal density within each stratum (area), for which boundaries are determined based on survey coverage, the number of sightings, and prior knowledge of cetacean distribution and habitats;
- Probability of occurrence models, which indicate areas where a species is likely to occur based on statistical models that relate habitat variables to the presence/absence of a species, but do not provide absolute density estimates;
- Records of presence, which include visual observations, acoustic detections, or satellite tagging indicators;
- Expert knowledge, reflects a lack of spatio-temporally explicit data for a species, but indicates if a species is believed to be present or likely absent by regional experts.
A more detailed description of the information tiers, as well as the factors considered in evaluating them and deciding which data should be included in any given model may be viewed here.
Cetacean Data Availability Assessment
- Identified and compiled existing cetacean density models, some of which were not previously available to the public
- Identified and compiled existing indicators of cetacean presence, including visual observations, acoustic detections, and satellite tagging data, some of which were not previously available to the public, and several of which expand the known range of certain species.
- Organized the available modeling results and data in a manner that allows the user to quickly identify what type of data is available for a species/region/month and where data gaps exist.
The Cetacean Data Availability page shows the available information for each species/region/month, and also serves as the link to the downloadable products.
Following the development of the Information Heirarchy and an early assessment of Cetacean Data Availability, the CetMap identified and undertook two key modeling efforts to meaningfully improve the understanding of cetacean density and distribution in the U.S. EEZ:
- Beaufort and Chukchi Seas – The CetMap is using two long-term survey datasets and preferred modeling methods to produce comprehensive habitat-based density models for the species commonly found in the Beaufort and Chukchi Seas. Habitat-based density models were not previously available for this region.
- Atlantic Coast and Gulf of Mexico – Using newer survey data provided by NOAA’s Fisheries Science Center staff from both the Northeast and the Southeast, as well as habitat-based density modeling methods reflecting those utilized by the Southwest Fisheries Science Center, the CetMap is creating new comprehensive regional density estimates for all of the Atlantic Coast and Gulf of Mexico species.
In addition, the CetMap is working with NOAA’s Southwest Regional Office to showcase an effort that uses shore-based visual sighting data for grey whales along the U.S. West Coast, combined with their swim speed, to model the estimated location and density of the majority of migrating gray whales on any date within the migration period. A summary of this West Coast gray whale model and the associated products can be viewed here.
Mapping and Product Accessibility
Finally, CetMap members with Duke University’s Marine Geospatial Ecology Lab were responsible for creating standardized GIS files for the new modeling results produced by the CetMap, as well as for several existing model results compiled for this effort, but for which GIS maps had not previously been generated.
Further, CetMap worked with NOAA’s Office of Science and Technology to develop this dedicated website through which to access both the CetMap GIS products as well as the Underwater Sound-field Working Group products.
We welcome your feedback in prioritizing next steps for development of these tools. Feedback can be submitted using this form.
We are grateful for financial support for this effort provided by U.S. NOAA, U.S. Navy and U.S. Bureau of Ocean Energy Management to the Marine Geospatial Ecology Lab at Duke University. Additionally, the working group chairs (Sofie Van Parijs and Megan Ferguson) thank all of the participants for their time, dedication, and enthusiasm.