Field work began in January 1992 with a large-scale study of humpbacks in their principal West Indies breeding range at Silver Bank, Navidad Bank and Samana Bay, Dominican Republic; and Mona Passage, Puerto Rico. During summer, sampling was conducted in all the known major North Atlantic feeding grounds: the Gulf of Maine, Gulf of St. Lawrence, Newfoundland, Labrador, southwestern Greenland, Iceland, and Norway. In 1993 the same schedule of field work was repeated. Purpose: The YoNAH project is a unique research program utilizing photo-identification techniques and molecular genetics to conduct an intensive survey of the population ecology of humpack whales throughout their known North Atlantic range. This internationally collaborative project involves scientists from seven nations. YoNAH's vast database supports a wide range of scientific investigations and also provides reliable, detailed information on which to base management policy. Archives of photographs, tissue samples and data will provide a valuable legacy for future research. Supplemental information: [2015-03-24] A sighting record at 1993-02-07 10:45:00 had a wrong animal count of zero. The value is replaced with a blank representing species presence only. The notes for this sighting mentions "NO GROUP SIZE ESTIMATE". A sighting record at 1992-08-04 15:00:00 had a wrong animal count of zero. The value is replaced with "1" that is an average of min and max counts, 0 and 2 respectively. Data collection and analyses were conducted by research groups familiar with the study sites and with a history in use of these techniques for the study of humpback whale ecology. Allied Whale is responsible for photographic analysis and for database management. All the 5,500 photographs have been compared to one another to identify re-sightings. The accompanying databases are receiving final corrections and revisions. There are five datasets from YoNAH, including this one. Behavior of whales were recorded in some surveys. Biopsy samples and photographs were taken if possible. Ships efforts and sightings of species other than humpback whales are recorded in the Effort dataset.