Quantitative estimates of the movement and distribution of North Atlantic right whales along the northeast coast of North America

Abstract

General movement patterns for North Atlantic right whales are known, but quantitative season-specific estimates of individual movements and the resultant distributions do not exist. We use a Brownian Bridge movement model to estimate individual movement patterns and spatial probability distributions using time- and location-specific photo-identified right whales from 1978 through 2007 to produce monthly estimates of movement and distribution patterns for the population in the NW Atlantic, from Cape Cod northward. For comparative purposes we also estimate right whale transition probabilities among ocean regions to estimate rates of emigration and immigration, likely destinations, and monthly regionally specific population estimates. Areas were identified that right whales may frequent and that are potential locations of the regularly unaccounted proportion of the population. These areas, requiring additional survey effort, include the Gulf of St. Lawrence, Scotian Shelf, Columbia Ledges and western Jordan Basin. Our results show that along the northeast Atlantic coasts of Canada and the USA, right whales annually migrate in a general counter-clockwise pattern; north and east along the continental shelf in the spring and summer, and south and west along the coast during autumn and winter. The results also provide quantitative spatio-temporal estimates of right whales for all regions, including those that are rarely or never surveyed. The spatial probability distributions that we provide can be used in the future to quantitatively evaluate risks to right whales from human activities, particularly vessel traffic and commercial fishing, and thereby increase our ability to manage the risks and improve right whale conservation.