Years of the North Atlantic Humpbacks (YoNAH)

The Years of the North Atlantic Humpback (YoNAH) project is an international collaboration to study North Atlantic humpback whales across most of their known range. It was conceived to address large-scale issues, such as the size and structure of the population, vital rates, migratory movement and the structure of the mating system.

The project involved two intensive years of field research. During the summers of 1992 and 1993, intensive photographic and genetic sampling was performed concurrently in five high-latitude feeding grounds: the Gulf of Maine (U.S.), Canada, Greenland, Iceland and Norway. During the winter months, field work was performed in the West Indies, a shared, low-latitude breeding ground. Sampling techniques were standardized within and between areas to ensure data comparability and to minimize sampling bias. A central archive was established for all photographs, tissue samples and data to facilitate analysis and to provide a valuable legacy for future investigators. See Smith et al. 1999 for a detailed description of the project.

The YoNAH Research Team

The Center for Coastal Studies is primarily responsible for work performed in two areas: the Gulf of Maine feeding ground and the West Indies breeding ground. The following is a full list of primary YoNAH participants (in alphabetical order):

Selected YoNAH Findings

1) Population size and trend

The YoNAH project produced the first estimate of the size of the entire North Atlantic population--approximately 11,570 animals in 1993 (see Stevick et al. 2003). It also estimated the size of the West Indies breeding population (a major subset of the North Atlantic) to be 10,752 animals. Finally, the West Indies population was found to be growing at a rate of 3% at that time. Population estimates are important to the management and conservation of endangered species like the humpback whale. The YoNAH estimate will serve as a baseline against which to evaluate whether the population is increasing or decreasing over time. A subsequent project, known as MONAH, was undertaken in 2003-2005 to help to answer this question. Analyses of those results are still underway in 2010.

2) Population Structure

YoNAH also provided detailed information on exchange between high-latitude feeding grounds and low latitude breeding grounds (see image, right). For example, it was once assumed that whales from Norway mated and gave birth in the eastern North Atlantic (the Cape Verde Islands). We now know that at least some of these whales mingle with whales from the western North Atlantic on the Caribbean breeding grounds. Individuals have been tracked between Norway and the Caribbean both by photographs of natural marks (see Stevick et al. 1998) and "genetic tags" (see Palsbøll et al. 1997). 

Nevertheless, there are important diffences in migratory timing among feeding areas, resulting in differences in how they overlap on the West Indies ground (see Stevick et al. 2003). As a result, whales from western North Atlantic may still have a lower likelihood of mating with the whales that do migrate there from eastern North Atlantic. The distribution and resightings of individuals across the North Atlantic suggest essentially four feeding aggregations: the Gulf of Maine, eastern Canada, West Greenland and the eastern North Atlantic (see Stevick et al. 2006). This is based on evidence of higher site fidelity and smaller movements in the western North Atlantic as compared to off Iceland and Norway.

Detailed YONAH findings can be found in articles on our publication page.