Towers J.R.,Marine Education and Research Society |
Towers J.R.,Canadian Department of Fisheries and Oceans |
McMillan C.J.,Marine Education and Research Society |
Malleson M.,2768 Satellite Street |
And 3 more authors.
Journal of Cetacean Research and Management | Year: 2013
In the eastern North Pacific Ocean, common Minke whales (Balaenoptera acutorostrata) arc widespread but encountered relatively infrequently. It is generally believed that they make annual migrations between higher latitudes in the summer and lower latitudes in the winter; however, in some temperate coastal regions where common Minke whales have been sighted year-round they have been referred to as resident. To determine movement patterns of common minke whales found in coastal waters of British Columbia and Washington we examined photo-identification data that were collected opportunistically from 2005-12. These data were from four non-overlapping areas between 48°N and 53°N. Despite year-round search efforts, common Minke whales were only encountered between April and October. Most of the 44 unique individuals identified in 405 encounters displayed fidelity to areas both within and among years. Five of these whales made relatively large-scale intra-annual movements between areas on six occasions. They were documented to move up to 424km in a northerly direction in spring and up to 398km in a southerly direction in autumn. The seasonal patterns of these movements provide new insights into the foraging ranges and migrations of the individuals. Ecological markers provide evidence that the common Minke whales photographed undertake annual long distance migrations. Scars believed to be from cookiecutter shark (Isistms brasiliensis) bites were observed on 43 individuals and the majority of whales documented with good quality images each year had acquired new scars since the previous year. Furthermore, the commensal barnacle Xenobalanus globiapitis was observed on three individuals. Since these sharks and barnacles are from relatively warm waters, it can be inferred that they interacted with the common Minke whales at lower latitudes These findings may have important implications for the definition and management of common Minke whale stocks and/or populations in the eastern North Pacific.
Pitman R.L.,National Oceanic and Atmospheric Administration |
Durban J.W.,National Oceanic and Atmospheric Administration |
Greenfelder M.,14940 Elton St. SW |
Guinet C.,French National Center for Scientific Research |
And 5 more authors.
Polar Biology | Year: 2011
Studies have shown that killer whale (Orcinus orca) communities in high latitudes regularly comprise assemblages of sympatric 'ecotypes'-forms that differ in morphology, behavior, and prey preferences. Although they can appear superficially similar, recent genetic evidence suggests that breeding is assortative among ecotypes within individual communities, and species-level divergences are inferred in some cases. Here, we provide information on a recently recognized 'type D' killer whale based on photographs of a 1955 mass stranding in New Zealand and our own six at-sea sightings since 2004. It is the most distinctive-looking form of killer whale that we know of, immediately recognizable by its extremely small white eye patch. Its geographic range appears to be circumglobal in subantarctic waters between latitudes 40°S and 60°S. School sizes are relatively large (mean 17.6; range 9-35; n = 7), and although nothing is known about the type D diet, it is suspected to include fish because groups have been photographed around longline vessels where they reportedly depredate Patagonian toothfish (Dissostichus eleginoides). © 2010 US Government.