945 resultados para catch and effort data
Resumo:
Humpback whales (Megaptera novaeangliae) undertake extensive seasonal migrations from summer feeding areas in high latitudes to winter mating and calving grounds in tropical waters (Clapham and Mead 1999, http://www.jstor.org/stable/3504352). In the Southern Hemisphere, seven populations are recognized by the International Whaling Commission (IWC). In this study, we report the movements of seven whales satellite-tagged in the Cook Islands, including the first documented migration to an antarctic feeding ground. In September 2006 and 2007 we attached Argos satellite-monitored tags to eight humpback whales of various sex and behavioral classes. All whales were tagged in the nearshore waters of Rarotonga (the largest island in the Cooks group).
Resumo:
Knowledge of the local and migratory movements of humpback whales (Megaptera novaeangliae) from New Caledonia is very limited. To investigate this topic, we attached satellite-monitored tags to 12 whales off southern New Caledonia. Tag longevity ranged from 1 to 52 days (X = 22.5 days). Tagged whales generally moved to the south or southeast, with several spending time in a previously unknown seamount habitat named Antigonia before resuming movement, generally toward Norfolk Island or New Zealand. However, 1 female with a calf traveled the entire length of the western coast of New Caledonia (~450 km) and then west in the direction of the Chesterfield Reefs, a 19th century American (''Yankee'') whaling ground. None of the New Caledonia whales traveled to or toward eastern Australia, which is broadly consistent with the low rate of interchange observed from photo-identification comparisons between these 2 areas. The connections between New Caledonia and New Zealand, together with the relatively low numbers of whales seen in these places generally, support the idea that whales from these 2 areas constitute a single population that remains small and unrecovered.
Resumo:
We present a suite of new high-resolution records (0-135 ka) representing pulses of aeolian, fluvial, and biogenic sedimentation along the Senegalese continental margin. A multiproxy approach based on rock magnetic, element, and color data was applied on three cores enclosing the present-day northern limit of the ITCZ. A strong episodic aeolian contribution driven by stronger winds and dry conditions and characterized by high hematite and goethite input was revealed north of 13°N. These millennial-scale dust fluxes are synchronous with North Atlantic Heinrich stadials. Fluvial clay input driven by the West African monsoon predominates at 12°N and varies at Dansgaard-Oeschger time scales while marine productivity is strongly enhanced during the African humid periods and marine isotope stage 5. From latitudinal signal variations, we deduce that the last glacial ITCZ summer position was located between core positions at 12°26' and 13°40'N. Furthermore, this work also shows that submillennial periods of aridity over northwest Africa occurred more frequently and farther south than previously thought.