My collaborators and I are pleased to announce the publication of our right whale density model. The paper and all results are open access, freely downloadable, and reusable under a CC-BY License. Download the paper: https://doi.org/10.3354/meps14547 Download the model: https://seamap.env.duke.edu/models/Duke/EC/ North Atlantic right whale density surface model for the US Atlantic evaluated with passive acoustic monitoring Jason J. Roberts, Tina M. Yack, Ei Fujioka, Patrick N. Halpin, Mark F. Baumgartner, Oliver Boisseau, Samuel Chavez-Rosales, Timothy V. N. Cole, Mark P. Cotter, Genevieve E. Davis, Robert A. DiGiovanni Jr., Laura C. Ganley, Lance P. Garrison, Caroline P. Good, Timothy A. Gowan, Katharine A. Jackson, Robert D. Kenney, Christin B. Khan, Amy R. Knowlton, Scott D. Kraus, Gwen G. Lockhart, Kate S. Lomac-MacNair, Charles A. Mayo, Brigid E. McKenna, William A. McLellan, Douglas P. Nowacek Orfhlaith O’Brien, D. Ann Pabst, Debra L. Palka, Eric M. Patterson, Daniel E. Pendleton, Ester Quintana-Rizzo, Nicholas R. Record, Jessica V. Redfern, Meghan E. Rickard, Melanie White, Amy D. Whitt, Ann M. Zoidis Abstract: The Critically Endangered North Atlantic right whale Eubalaena glacialis entered a population decline around 2011. To save this species without closing the ocean to human activities requires detailed information about its intra-annual density patterns that can be used to assess and mitigate human-caused risks. Using 2.9 million km of visual line-transect survey effort from the US Atlantic and Canadian Maritimes conducted in 2003-2020 by 11 institutions, we modeled the absolute density (ind. km-2) of the species using spatial, temporal, and environmental covariates at a monthly time step. We accounted for detectability differences between survey platforms, teams, and conditions, and corrected all data for perception and availability biases, accounting for platform differences, whale dive behavior, group composition, and group size. We produced maps of predicted density and evaluated our results using independently collected passive acoustic monitoring (PAM) data. Densities correlated positively (r = 0.46, ρ = 0.58, τ = 0.46) with acoustic detection rates obtained at 492 stationary PAM recorders deployed across the study area (mean recorder duration = 138 d). This is the first study to quantify the concurrence of visual and acoustic observations of the species in US waters. We summarized predictions into mean monthly density and uncertainty maps for the 2003-2009 and 2010-2020 eras, based on the significant changes in the species’ spatial distribution that began around 2010. The results quantify the striking distribution shifts and provide effort- and bias-corrected density surfaces to inform risk assessments, estimations of take, and marine spatial planning. For those of you already familiar with this model, the paper documents "version 12.2" of the model, which is the most recent version. Version 12 was first released for management use on 14 February 2022. On 27 May 2023, we released version 12.1, which included a supplementary report giving technical details of the model but did not change the model's density predictions. On 20 March 2024, we released 12.2 in conjunction with this publication, and again did not change the model's density predictions. If you downloaded version 12 or 12.1 and performed an analysis with it, your analysis does not need to be redone at this time, and it is OK to say your analysis was conducted against the latest right whale model (version 12.2) available at this time. This project builds upon the efforts of the hundreds of people involved in conducting line transect surveys in the eastern United States over the past 25 years. Thanks for the opportunity to analyze the data you helped collect. I hope you will find this project a worthy outcome of your efforts. All the best, Jason Roberts jason.roberts@duke.edu Duke Marine Geospatial Ecology Lab