THE SEI WHALE, BALAENOPTERA 



BORE A LIS 



By L. Harrison Matthews, m.a. 

 (Plates XVIII, XIX; Text-figs. 1-113) 



INTRODUCTION 



Two hundred and twenty Sei whales have been examined during the course of the 

 Discovery investigations ; sixty-five males and one hundred and fifty-five females. 

 This report analyses and discusses the data obtained from them. 



The Sei whale is a species of whale that is not of great economic importance on most 

 of the whaling grounds of the world, though it is taken in some numbers in a few places. 

 In the areas where the work has been done it forms only a small fraction of the total 

 catch, so that data have been slow in accumulating. The information here considered 

 was collected during the course of six whaling seasons. 



The information recorded during examination of the whales at the whaling stations 

 consisted of the routine system of measurements of various parts of the body that has 

 been adhered to throughout the investigations, notes on the external characters, baleen, 

 food, internal and external parasites, condition of the genitalia and degree of physical 

 maturity. Frequently, however, the set of observations has not been complete on any 

 one whale. The information collected is discussed under the appropriate headings below, 

 together with certain information derived from other sources. 



Once again it is a pleasure to record my thanks to those friends to whom I am 

 indebted for assistance and criticism in compiling this report, and especially to Dr S. 

 Kemp, Dr A. S. Parkes, Mr Martin A. C. Hinton and Dr Francis C. Fraser. 



MATERIAL 



Particulars of the date and place of capture of the Sei whales in the present series 

 are given in Table I. Table II shows similar information about the fifty-six foetuses 

 examined. Statistics in the British Museum (Natural History) recording the catches of 

 Sei whales, and information about foetuses, have also been used in this report: they 

 are referred to in the appropriate sections below. 



The material, though not very extensive, appears to be sufficient to provide a good 

 foundation for an outline of the biology of this species of whale. 



SEX RATIO 

 The sex ratio of the adult whales shown in Table I is 29-5 per cent of males. This 

 figure, however, does not represent the true sex ratio in nature, for consideration of 

 the figures and their origin shows that it is unUkely that the sample is representative. 



