Cetacean visual observations using line-transect survey methods onboard the NOAA Ship Gordon Gunter (GU) during the Atlantic Marine Assessment Program for Protected Species (AMAPPS) in the Western North Atlantic Ocean (survey GU2301) from 2023-02-04 to 2023-04-27 (NCEI Accession 0290563)

As part of the Atlantic Marine Assessment Program for Protected Species (AMAPPS), the Southeast Fisheries Science Center (SEFSC) conducted a shipboard survey of the U.S. waters of the Western North Atlantic (WNA) from approximately the 200m isobath out to the U.S. Exclusive Economic Zone (EEZ). The survey was conducted between February 4 and April 27, 2023 onboard the NOAA Ship Gordon Gunter, for a total of 44 days at sea split into three survey legs. Multiple days were lost due to mechanical problems with the ship (Jan 23 to Feb 2) and unfavorable weather conditions (April 8 to 10). February 3 and April 28 were departure (start survey) and arrival (end survey) days, respectively. The survey was designed for a two-team independent visual observer approach with distance sampling to estimate the detection probabilities for marine mammal sightings. A sighting constituted of a single or group of marine mammals (whales and dolphins) seen at the same location and time. This dataset includes marine mammal visual observation data and effort points with surveying conditions that can be used in abundance and density modeling per visual line-transect survey protocols. This dataset also includes opportunistic marine mammal photographs and non-marine mammal sightings such as sea turtles.