Southern Hemisphere humpback whales Megaptera novaeangliae migrate from wintering grounds in tropical latitudes to feeding areas in the Antarctic Ocean. It has been hypothesized that the population wintering off eastern South America migrates to feeding grounds near the Antarctic Peninsula (ca. 65°S, 60°W) and/or South Georgia (54°20' S, 36°40' W), but direct evidence to support this has never been presented. Between 19 and 28 October 2003, 11 humpback whales (7 females and 4 males) were instrumented with satellite transmitters off Brazil (ca. 18°30' S, 39°30' W) to investigate their movements and migratory destinations. Mean tracking time for the whales was 39.6 d (range = 5 to 205 d) and mean distance travelled was 1673 km per whale (range = 60 to 7258 km). Movements on the wintering ground showed marked individual variation. Departure dates from the Brazilian coast ranged from late October to late December. Whales migrated south through oceanic waters at an average heading of 170°and travelled a relatively direct, linear path from wintering to feeding grounds. Two whales were tracked to feeding grounds in offshore areas near South Georgia and in the South Sandwich Islands (58°S, 26°W) after a 40 to 60 d long migration. Historical catches and current sighting information support these migratory routes and destinations. This study is the first to describe the movements of humpback whales in the western South Atlantic Ocean.

ABSTRACT. Recent analyses have revealed trends over the past 20-30 years of decreasing sea ice extent in the Arctic Ocean coincident with warming trends. Such trends may be indicative of the polar amplification of warming predicted for the next several decades in response to increasing atmospheric CO 2 . We have summarized these predictions and nonuniform patterns of arctic climate change in order to address their potential effects on marine mammals. Since recent trends in sea ice extent are nonuniform, the direct and indirect effects on marine mammals are expected to vary geographically. Changes in the extent and concentration of sea ice may alter the seasonal distributions, geographic ranges, patterns of migration, nutritional status, reproductive success, and ultimately the abundance and stock structure of some species. Ice-associated seals, which rely on suitable ice substrate for resting, pupping, and molting, may be especially vulnerable to such changes. As recent decreases in ice coverage have been more extensive in the Siberian Arctic (60˚E-180˚E) than in the Beaufort Sea and western sectors, we speculate that marine mammal populations in the Siberian Arctic may be among the first to experience climate-induced geographic shifts or altered reproductive capacity due to persistent changes in ice extent. Alteration in the extent and productivity of ice-edge systems may affect the density and distribution of important ice-associated prey of marine mammals, such as arctic cod Boreogadus saida and sympagic ("with ice") amphipods. Present climate models, however, are insufficient to predict regional ice dynamics, winds, mesoscale features, and mechanisms of nutrient resupply, which must be known to predict productivity and trophic response. Therefore, it is critical that mesoscale process-oriented studies identify the biophysical coupling required to maintain suitable prey availability and ice-associated habitat for marine mammals on regional arctic scales. Only an integrated ecosystems approach can address the complexity of factors determining productivity and cascading trophic dynamics in a warmer Arctic. This approach, integrated with monitoring of key indicator species (e.g., bowhead whale, ringed seal, and beluga), should be a high priority.Key words: Arctic Ocean, climate change, sea ice extent, global warming, marginal ice edge zone, bowhead whale, Balaena mysticetus, ice-associated seals, ringed seal, Phoca hispida, beluga, Delphinapterus leucas RÉSUMÉ. Des analyses récentes ont fait apparaître des tendances, au cours des 20 à 30 dernières années, à la diminution de l'étendue des glaces de mer dans l'océan Arctique qui coïncident avec des tendances au réchauffement. Ces tendances pourraient être symptomatiques de l'amplification polaire du réchauffement prédit pour les prochaines décennies suite à la hausse de CO 2 dans l'atmosphère. Cet article offre un résumé de ces prédictions et des schémas non uniformes de changement climatique dans l'Arctique, en vue d'examiner leurs retombées potentielles sur les ...

The “stock” is the fundamental population unit of legally mandated conservation efforts, yet its formal definition in the scientific literature and in two U.S. conservation acts is varied and so general that attempts to apply it in practice are arbitrary. Because choice of stocks deserving management protection is sometimes politically contentious, improvement of the working definition is important. A key element should be the degree to which a population can be considered an evolutionarily significant unit. We propose that a hierarchial classification scheme be applied to stock designations. Category I populations, having the highest probability of being evolutionarily significant units, are characterized by a discontinuous genetic divergence pattern where locally adapted and closely related genome assemblages are separated from others geographically and by significant genetic distances. Category II populations are similarly characterized by significant genetic diversity, but with weak geographic partitioning. Category III populations are the converse of II, having little genetic differentiation between assemblages that are clearly separate and likely to be reproductively isolated. Category IV assemblages have the lowest probability of being evolutionarily significant units and are characterized by extensive gene flow and no subdivision by extrinsic barriers. In addition to phylogeographic designation, the following information is used in the classification, as indicated by single‐letter abbreviations: distribution (a), population response (b), phenotypic (c), and genotypic (d) information. Included are evidence both for and against designating population as a separate stock. In the designation “Type II a/bc,” for example, information to the right of the solidus would be evidence for “lumping,” to the left would be for “splitting.” Missing letter abbreviations would signify lack of reliable data. Note that phylogeographic designation depends on the results of selection operating to produce a locally adapted genome (indicated by differences in demographic, phenotypic, and genotypic measures) and on gene flow (indicated by differences in distribution or by movement data). Hierarchial stock categorization allows resource managers to direct limited resources to the populations most deserving of protection, that is, the populations that are most likely to be evolutionarily significant units. Using this comprehensive classification of stock allows preliminary, conservative splitting of assemblages where data are lacking without the danger that these divisions will become entrenched as biological dogma.

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