RUDOLPHI'S RORQUAL. 241 



up to as many as fifty individuals. Their association, however, is somewhat irregular and 

 not as with fish that go in compact masses. Probably it is partly the presence of plankton 

 in favorable currents that brings them into association. 



At the Finmark stations, Collett observed large foetuses in whales of this species taken 

 during the summer. Although there was much variation in the size of foetuses taken at approxi- 

 mately the same dates, none the less it seemed to be generally true that those of spring or early 

 summer were smaller than those found later in the season. Thus in July most of those seen 

 were from three to four feet long, while in August some were seen up to eight, ten, or twelve 

 feet in length. This indicates a rapid growth, and leads to the supposition that copulation 

 takes place in winter and that the young are born in the fall or winter following. As in whales 

 generally, a single young one is normally produced at a birth. Collett records one instance, 

 however, in which two young, each six feet seven inches long, were taken from a female 43 feet 

 long on the Finmark coast at Varangerfjord, July 27th. 



Food. 



The Pollack Whale is believed to be almost altogether a plankton feeder, and so far as 

 known subsists chiefly on the minute copepod Calanus finmarchicus and the schizopod Thy- 

 sanoessa inermis. The former is probably taken largely at the surface, where it often appears 

 in such dense masses as to redden the sea, yet it is but four or five millimeters in length. It 

 is suggested by Collett that the very fine wool-like bristles of the whalebone in this whale are 

 an adaptation for sieving out this minute prey. The schizopod is perhaps taken at greater 

 depths or on the surface at night, since it is sensitive to bright light and is less commonly near 

 the surface by day. Andrews (1916) has lately published his observations on this species in 

 Japanese waters, where he found that small fish were sometimes taken. 



Commercial Value. 



The yield of oil in this whale is comparatively small, averaging, according to Collett, 17 

 to 23 hectoliters or 14 to 20 barrels, but may be as much as 25 or 30 barrels from large fat in- 

 dividuals. In 1886 this oil was valued at from $135 to $165 per whale. It is of good quality 

 and contains less stearine than that of the other species of Balaenoptera. The baleen, though 

 short, is considered the best of that produced by any of the Rorquals on account of its finer 

 grain. In Finmark the flesh of this species is canned for human consumption. It is con- 

 sidered to be superior to that of the other species taken, and alone is preserved. Guldberg 

 (1885) describes it as in color about the same as beef, whereas that of the other Balaenopteridae 

 is much darker. 



