The existence of different Fin Whale, Balaenoptera physalus, populations in South Atlantic waters. A preliminary study by means of morphological characters

The southern hemisphere has been divided into six Areas for baleen whale management purposes. It was assumed that of the different baleen whale species one population lives in each Area. However, evidence exists which suggests that different Fin Whale populations intermingle on the feeding grounds of an Area. This obviously would have implications with respect to Fin Whale management. Three different types of Fin Whales, distinguished by gunners and the second author of this paper, were visually observed in the South Atlantic catch of Fin Whales. It can be hypothesized that each type represents a different population. During the 1962/63 season on board the Dutch factory ship “Willem Barendsz”, data of mainly the following variables were collected from 53 female Fin Whales (total catch of female Fin Whales 460): the length of a whale, the width, the length of a baleen plate series, the length of the longest baleen plate and the degree of pigmentation. The type hypothesis could be tested by means of a multivariate analysis of variance on condition that, if the variables are age dependent, the age frequency distributions in the type subsamples must be similar. It turned out that most variables were age dependent and that the age frequency distributions were not similar. Only three variables were not correlated with the age of a whale, but no separation by type could be found with these remaining variables. It was concluded that presently the type hypothesis neither could be accepted nor rejected, and so has to be maintained. A preliminary analysis of the type distribution on the whaling grounds indicated a mixed distribution. Analyses of mark recoveries (Brown, 1977) and bloodtype frequencies (Fujino, 1964) suggest mixing of different populations on the feeding grounds of Area II (0-60°W) and Area III (0-70°E), respectively. At this moment the exploitation of the southern Fin Whale populations is prohibited, but when these populations will be recovered and a research catch will be allowed, the type hypothesis should be tested again. In this context the use of the isoenzyme frequency technique is recommended.