This indicator is a continuous index of dolphin and whale density based on monthly density predictions for ten species of cetaceans and yearly density predictions for three rarer cetacean species. Note: This indicator is at a 200 m resolution, which is coarser than other indicators used in the 2020 Blueprint.
Reason for Selection
Marine mammals help identify key areas of ocean productivity and overall ocean health, are regularly monitored, and resonate with a variety of audiences. Marine mammals are often used as ocean health indicators due to their long life spans, feeding at a high trophic levels, and large blubber stores that can serve as repositories for anthropogenic chemicals and toxins (Bossart 2011).
–Input data for this indicator was provided by the Duke Marine Lab. These habitat-based density models cover the entire U.S. Atlantic. They use aggregated survey information, distance-sampling, and oceanographic variables to predict cetacean density throughout the region. Species with monthly models used in this indicator are: North Atlantic Right Whale, Sperm Whale, Sei Whale, Humpback Whale, Fin Whale, Bottlenose Dolphin, Short-Beaked Common Dolphin, Risso’s Dolphin, Harbor Porpoise, and Atlantic White-Sided Dolphin. Species with yearly models used in this indicator are: Pilot Whale, Beaked Whale, and Striped Dolphin. Additional species not included (e.g., minke whale) lacked sufficient data to produce detailed models for the entire South Atlantic area. For additional information, please visit the project page.
– Blueprint 2.1 ecosystem map (see Appendix A)
1) To identify high quality areas for each species during each month, we used the core area algorithm in Zonation. We included each monthly density layer for each species as a separate input and weighted them equally. We used the information gap uncertainty option on the coefficient of variation with an alpha of 1 ensure robustness to the spatial uncertainty in each model. To account for boundary effects, we ran all the models across the entire U.S. Atlantic.
2) We clipped the resulting raster to the “Marine” class in the Blueprint 2.1 ecosystem map.
Final indicator values
The final indicator is continuous, with values ranging from:
High: 100 (most important for seasonal density of marine mammal index species)
Low: 0 (least important for seasonal density of marine mammal index species)
– North Atlantic right whale models are underpredicting densities in the calving grounds, likely due to the limited amount of sighting data available at the time the models were run. An updated version of the right whale input data using far more sighting information is in production.
– While this layer has a 200 m resolution, the source data was coarser than that. We downsampled 10 km pixels to 200 m.
– Please note that this indicator is at a 200 m resolution, which is coarser than other indicators used in the 2020 Blueprint. This is an artifact of the approach used for the marine environment in Blueprint 2020.
Disclaimer: Comparing with Older Indicator Versions
There are numerous problems with using South Atlantic indicators for change analysis. Please consult Blueprint staff if you would like to do this (email email@example.com).
Roberts JJ, Best BD, Mannocci L, Fujioka E, Halpin PN, Palka DL, Garrison LP, Mullin KD, Cole TVN, Khan CB, McLellan WM, Pabst DA, Lockhart GG (2016) Habitat-based cetacean density models for the U.S. Atlantic and Gulf of Mexico. Scientific Reports 6: 22615. doi: 10.1038/srep22615.
Bossart, G. D. “Marine Mammals as Sentinel Species for Oceans and Human Health.” Veterinary Pathology Online 48, no. 3 (May 1, 2011): 676–90. doi:10.1177/0300985810388525.
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