The Institute of Cetacean Research
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Marine ecosystem
This research section conducts investigation of feeding ecology of large whales, investigation of body condition of whales and examination of the relationship of whale distribution and oceanographic conditions. Overall, this section investigates the role and status of whales in the ecosystem.
Studies based on sample collected by lethal means include stomach content analyses and body condition. The stomach content analysis aims to investigate food consumption by whales from qualitative and quantitative point of views. The analyses follow the following sequence: i) stomach content weight in relation to whale body weight; ii) daily prey consumption by whale reproductive category; iii) seasonal prey consumption of the population based on available abundance estimates; iv) estimation of the percentage of prey consumed in relation to the abundance of the prey in the research area.
For the study of body condition, blubber thickness, girth and stomach content weight are used as indices, and the temporal trends are investigated through several statistical procedures. In addition, several statistical approaches are used to understand the temporal and geographical pattern of distribution of whales in relation to prey species and several abiotic parameters.
This section also engages in research of non-lethal techniques for the attainment of some data required for investigating qualitatively the feeding ecology of whales. For example, stable isotopes analysis of biopsy samples is being conducted to investigate the kind of prey consumed by whales. Available stomach content data obtained by lethal approaches from the same samples in the isotope analyses are used for calibration purposes.
In collaboration with the abundance estimation section, this section also engages in the development of a novel approach of investigating the ecosystem through the microbiota living on the surface of whales. Microbiota living on the surface of the animals is compared with the microbiota in the surrounding sea water. Also, microbiota in whales from different localities can be compared and therefore the information derived from this approach can complement the studies on population structure conducted by the genetic ecology section.