Body mass, muscle, blubber and visceral fat content and their seasonal, spatial and temporal variability in North Atlantic common minke whales

Abstract

Total body mass and increase over the feeding season is important for estimating energy deposition used in ecological modelling. Weighing total whales is difficult, even in parts, while measurements of length, girth and blubber thickness can easily be obtained from catches at sea. The exponent for predicting total body mass from body length has been studied in many species and here data on common minke whales in the North Atlantic are added from both Icelandic and Norwegian research catches. The exponent was found to be not significantly different from 3 as is expected if there is little change in shape with growth. The exponent for how blubber mass increases with length was estimated to be significantly lower than 3. In addition, seasonal changes in body mass and in the parts of muscle, blubber and visceral fat are reported. In all cases a significant increase over the season was detected, in particular for the mature animals, and also in blubber thickness and girth measurements, particularly in girth at the posterior part of the body. Pregnant females had significantly more blubber than other whales. These results agree with studies on blubber thickness measurements and tissue energy content of the Icelandic whales and observed changes in the ecosystem around Iceland during the research period 2003 to 2007.