Contents 5 REMARKS ON THE DISTRIBUTION AND MIGRATION OF WHALES with regard to the determination of the species than those of other observers. His data have been collected in a special table (table 5). Grateful acknowledgment is also made to Dr. S. G. BROWN (N.I.O.-Wormley-England) who was extremely helpful in reading the manuscript and suggesting a number of corrections based on a very thorough knowledge of the subject. 2. DETERMINATION OF SPECIES In the instructions given to our collaborators on board of the ships, it was asked to record sightings of all big whales, i.e. all Baleen Whales and the Sperm Whale. In the forms date, hour, position of the ship, visibility, wind and other factors influencing the reliability of the observations could be filled in, as well as the number of animals, the presence or absence of calves and the presumptive species. It was asked to record as many characteristics as possible that could be of some use to the determinationof the species, as for example the estimated length, colour, height and shape of the blast, absence or presence of the dorsal fin, visibility of flukes and flippers etc. It was also asked to record some particulars about respiration, speed of swimming and behaviour of the animals. These particulars were used by collaborators of the Whale Research Group in determining the species of the animals involved. It turned out that this was possible with a high degree of reliability in Right Whales (Eubalaena glacialis Bonnat.; Eubalaena australis Desm.), Humpback Whales (Megaptera novaeangliae (Borowski)) and Sperm Whales (Physeter macrocephalus L.). There was such a small number of sightings of Right Whales, Grey Whales and Little Piked Whales, that by charting the records on monthly maps, it was not possible to draw the same sort of conclusion about their distribution or migration as with regard to the other species. They are dealt with in separate chapters. It was quite evident that unexperienced observers would not be able to distinguish with any reliability between Blue Whales (Balaenoptera musculus (L.)), Fin Whales (Balaenoptera physalus (L)), Sei Whales (Balaenoptera borealis (Lesson)) and Bryde Whales (Balaenoptera brydei (Olsen)). Just as it was done by BROWN (1957, 1958) we collected the sightings of these four species under one single heading: rorquals. And just as BROWN, we distinguished also a category "whales" for all those cases in which it was not even possible to distinguish 8 E. J. SLIJPER, W. L. VAN UTRECHT AND C. NAAKTGEBOREN says that in April Blue Whales are observed at the Faroes coming from the Southwest on their northward run. It is also in accordance with the statements that Blue Whales migrate northward along the west coast of Ireland and the Hebrides in May and June (KELLOGG, 1929) and that Fin Whales pass these coasts in a north east direction in May (HINTON, 1925). From the charts it is quite evident that there are large concentrations of rorquals in some special regions of the Atlantic Ocean, especially in certain coastal waters. These are...

Data and material are collected from 106 Harbour Porpoises (P. phocoena) from the southern part of the North Sea. All animals are accidentally caught or found stranded. The greatest length for males in the sample is 151 cm, for females 186 cm. For detailed analysis of body measurements, 30 males and 37 females are selected, while from 20 males and 34 females teeth are used for age analysis. The analysis of the body measurements shows sexual dimorphism in the anterior and posterior part of the back, in the flukes and flippers and in the position of the genital slit. The maximum number of dentinal layers found in the teeth is 12. Males attain sexual maturity after the deposition of 5 dentinal layers, females when 6 layers are formed, at a body length of about 135 cm and 150 cm, respectively. Some evidence is found that the population of P. phocoena from the North Sea has a lower growth rate than the population from Canadian waters. The gestation period is estimated to be eleven months, the peak of the birth period being in June. The animals are born at a length varying between 67 cm to 80 cm. Growth of the visceral organs is isogonic. The mean weight of the organs is greater in females than in males.

L'examen d'un petit nombre de Marsouins (Phocaena phocaena) pris en mer du Nord par des pecheurs hollandais a permis de mettre en evidence des cicatrices comparables a celles rencontrees chez les Baleines. Ces cicatrices, qui n'apparaissent que chez les adultes, en relation, semble-t-il, avec les migrations annuelles des Marsouins, sont provoquees par les Lamproies.Brought to you by |

Eel larvae caught in the mid North Atlantic and along the continental slope off the Portuguese coast are studied together with samples of glass eels caught just before entering fresh water along the Dutch and French coasts.