POPULATION ESTIMATION OF SPERM WHALES (PHYSETER MACROCEPHALUS) FROM BLEIK CANYON, NORWAY

• Main Author: Rødland, Elisabeth
• Other Authors: Stein Fredriksen og Arne Bjørge
• Format: Master Thesis
• Language: English
• Published: 2011
• Subjects: VDP::480; Bleik; Norway; Norwegian Sea; Northern Norway; Physeter macrocephalus; Sperm whale
• Online Access: http://hdl.handle.net/10852/11613; http://urn.nb.no/URN:NBN:no-29689

The focus of this thesis is the population of adult male sperm whales in Bleik Canyon off the coast of northern Norway. Previous studies have shown this population to be an open population with a few individuals present for many years and a large group of exchanging males, mainly younger individuals. My study aims to update the current abundance estimate with data from 1987 to 2010, investigate individuals that are long-time present in the area and highlight some of the concern of using both photo-ID and commercial whalesafaris as platforms for scientific studies. The study supports the results from previous studies and confirms the presence of both transient and resident male sperm whales in Bleik Canyon as a loose feeding aggregation. The number of sighted whales fluctuated between years, and no trend was found. The number of sampling trips only explained about half of the varying number of sightings, and presence of killer whales, pilot whales and a variable food distribution was proposed as other influencing factors. The estimated abundance also fluctuated between years without any trend. An open model with multiple seasonal sightings is suggested to be the most realistic model for the abundance estimates. The presence of male sperm whales in Bleik Canyon is not unique for the Norwegian Sea, as several matches have been found between Bleik Canyon and Malangsdjupet. However, it is unique to have such a high abundance of sperm whales so close to land, which is of great importance for the tourism of this area. Further investigations is needed to reveal the whereabouts of these male sperm whales during winter and whether or not the individuals sighted in Bleik Canyon also has been sighted at other important sperm whale locations, such as the mating grounds of the Azores.