Population spatial structuring on the feeding grounds in North Atlantic humpback whales (Megaptera novaeangliae)

Abstract

Population spatial structuring among North Atlantic humpback whales Megaptera novaeangliae on the summer feeding grounds was investigated using movement patterns of identified individuals. We analysed the results from an intensive 2-year ocean-basin-scale investigation resulting in 1658 individuals identified by natural markings and 751 individuals by genetic markers supplemented with data from a long-term collaborative study with 3063 individuals identified by natural markings. Re-sighting distances ranged from o1 km to 42200 km. The frequencies (F) of resighting distances (D) observed in consecutive years were best modelled by an inverse allometric function (F=6631D À1.24 , r 2 = 0.984), reflecting high levels of site fidelity (median re-sighting distance o40 km) with occasional long-distance movement (5% of re-sightings 4550 km). The distribution of re-sighting distances differed east and west of 451W, with more long-distance movement in the east. This difference is consistent with regional patterns of prey distribution and predictability. Four feeding aggregations were identified: the Gulf of Maine, eastern Canada, West Greenland and the eastern North Atlantic. There was an exchange rate of 0.98% between the western feeding aggregations. The prevalence of long-distance movement in the east made delineation of possible additional feeding aggregations less clear. Limited exchange between sites separated by as little as tens of kilometres produced lower-level structuring within all feeding aggregations. Regional and temporal differences in movement patterns reflected similar foraging responses to varying patterns of prey availability and predictability. A negative relationship was shown between relative abundance of herring and sand lance in the Gulf of Maine and humpback whale movement from the Gulf of Maine to eastern Canada.

Geographic variation of persistent organic pollutant levels in humpback whale (Megaptera novaeangliae) feeding areas of the North Pacific and North Atlantic

“…In general, humpback whales appear to be good bioindicators, reflecting what is known about environmental levels of contaminants. This lends further support to studies of humpback whale population structure, which have shown strong site fidelity of whales to feeding areas [10][11][12][13]. For example, whales that feed off the coasts of California, Oregon, and Washington are thought to form a relatively distinct feeding aggregation [10].…”

“…Whales that overwinter in Central America were typically resighted in southern California feeding grounds, whereas those overwintering in mainland Mexico and Baja California were seen feeding primarily in northern California. Substructuring and fidelity of humpback whales to smaller areas within a feeding ground has also been observed in the North Atlantic [13]. Previous work examining PCB/DDE ratios in harbor porpoise (Phocoena phocoena) along the U.S. West Coast also found distinct regional patterns in contaminants [40].…”

“…During their migration and winter breeding season in the tropics, humpback whales fast and depend on energy reserves accumulated in their blubber. Additionally, genetic and photoidentification studies give evidence of strong site fidelity of humpback whales to their feeding areas in both the North Pacific and North Atlantic [10][11][12][13]. Seasonal feeding behavior and fidelity to feeding regions provide the basis for using humpback whales to better understand regional patterns of marine pollution.…”

A quarter of a world away: female humpback whale moves 10 000 km between breeding areas

“…Instances of extreme long-distance movement may represent exploration of a new habitat or a navigational miscue, and the observation presented here could be explained by either of these plausible explanations. Humpback whales may make large longitudinal movements while feeding at high latitudes, especially in changeable or unpredictable circumstances [31,32]. Such movement may occur through tracking prey, exploring potential foraging sites or in the Southern Ocean through drift with the Antarctic Circumpolar Current.…”

Abundance and exploitation of loggerhead turtles nesting in Boa Vista island, Cape Verde: the only substantial rookery in the eastern Atlantic

“…Estimating population trends for species that are widely dispersed, sometimes at the scales of whole ocean basins, is complicated and resource intensive (Forney, 2000;Taylor et al, 2007;Hammond, 2010), but can be facilitated when species exhibit predictable migrations to form seasonal breeding aggregations (Poncet et al, 2006;Stevick et al, 2006;Ramos et al, 2009;Foote et al, 2010). This is the case for marine turtles, where nonbreeding adults disperse at scales that range from regional to whole ocean basins .…”