Importance of seasonal ice zone for blue and fin whales in the Southern Ocean feeding ground

• Main Authors: Cédric Cotté, Laurent Dubroca, Christophe Guinet
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Indian; Southern Ocean; Fin whale; Sea ice
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.513.5490; http://www.iwcoffice.co.uk/_documents/sci_com/SC58docs/SC-58-SH1.pdf

Blue and fin whales were major krill predators in the Southern Ocean but intensive whaling industry dramatically reduced the populations by 99 % and 95 % respectively. We have used whaling dataset in a new analysis on circumpolar abundance of these whales relatively to environmental (sea surface temperature (SST), seasonal ice zone (SIZ)) and trophic parameters (summer oceanic primary production (SOCC) and krill densities). Most of whale catches was located in the Atlantic- West Indian sector. SIZ encompassed most of these whale catches and fin whale distribution corresponds to a wider SST range than blue whale’s. This global circumpolar analysis shows that historical abundances of whales were highly correlated to SIZ extent and only marginally related to the available densities of their krill prey. No relationship is found with the SOCC. Although circumpolar assessment of krill biomasses remain uncertain possibly leading to an unreliable relationship between whales and krill abundance, sea ice acts as a major feature for krill-eating whales in the Southern Ocean. Large SIZ provides favourable feeding ground throughout summer sought by blue and fin whales migrating in these high latitudes due to their large energy requirements.