Age determination and reproduction of female Fin Whales Balaenoptera physalus (Linnaeus, 1758), with special regard to baleen plates and ovaries

• Main Author: Utrecht-Cock, C.N. van
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 1965
• Subjects: Antarctic; Ruud; The Antarctic; Antarc*; Balaenoptera physalus
• Online Access: http://www.repository.naturalis.nl/record/504146; http://www.repository.naturalis.nl/document/547795

1. From Antarctic female Fin Whales, Balaenoptera physalus, a collection, consisting of baleen plates and the parts of these plates embedded in the gum, ovaries, and a number of earplugs was examined, in order to determine the age of these animals and to get a better insight in some characteristics of their reproduction. Data concerning pregnancy and lactation were also recorded. The material was sampled from animals worked up on board the f.f. “Willem Barendsz” during the Antarctic seasons 1953/1954 to 1959/1960 inclusive. The possibilities and values of age determination for this species were considered, based on the results of the analyses of the above material. 2. In most seasons the length distribution of the female Fin Whales, from which the material for the age determination was sampled (“examined animals”), did not differ significantly from that of the total catch of females of the “Willem Barendsz” in the same seasons. Neither was there any significant difference in length distribution between the total number of females from which the material was sampled and that of the females in the catch of the “Willem Barendsz” in all seasons. However, the length distribution of the catch of the “Willem Barendsz” differed significantly from the total Antarctic pelagic catch. 3. Baleen records were made according to the method described by RUUD (1940). In contrast with his age determinations with the aid of the part of the baleen plate protruding from the gum also the part of the plate hidden in the gum was used. A method of reading this part was developed. The advantage of this method is that the total length of baleen plate examined is much longer, and that the part hidden in the gum is not yet worn. In addition, the use of the part hidden in the gum has the undeniable advantage that the end of the cortical layer at the base of the “root” of the baleen plate represents the only exact date: the date at which the animal was killed. 4. Apart from the large waves of the cortical layer of the baleen plate the ...