THE DISTRIBUTION OF CERATIAS HOLBOLLI 2 7 



depths and thus come within the range of the trawlers. Bertelsen, in fact, considers that C. holbolli is 

 limited to comparatively warm water. Against this is set the capture of the Antarctic specimen in 

 a water column which varies between limits of no more than 0-5 and 2 C. throughout its entire length. 

 Moreover, at stations where C. holbolli has been taken, the only available temperature record at the level 

 of a closing net haul, and therefore reliable in this context, is that for specimen 35, (Table 3, Fig. 6). This 

 specimen, ' Mancalias tentaculatus ' Norman, was caught between 650 and 700 m. when the temperature 

 recorded at 745 m. was 2-08° C. [Station List, 1929). According to Sverdrup et al. (1942, p. 658), the 

 deep water of the North Polar Sea has a uniform temperature of about —0-85° C. However, the most 

 northerly of the specimens from the coast banks came from west Greenland and were taken apparently 

 south of the submarine ridge across the Davis Strait. The bottom water in this area is nowhere less 

 than 1-7°, and the greater part of the column lies between 3-5 and 3-0° (Sverdrup et al. 1942, p. 663). 

 Therefore, by comparison with the southern specimens, it does not seem likely that the specimens 

 caught on the northern coast banks were there because they had been forced up by cold water. 



Bertelsen supports his argument by reference to Jensen (1942), who maintains that species of the 

 pelagic Sudiid fish, Paralepis, found in the same regions as the trawled specimens of Ceratias holbolli, 

 represent adults which have drifted northwards from lower latitudes until the water becomes so much 

 cooled that the Paralepis spp. are paralysed, ' becoming an easy victim to seals and fishes of prey, or 

 they float dying or dead up to the surface of the water, and thereupon may drift ashore'. Jensen's 

 evidence appears to be that post-larval Paralepis are found in warmer water than the adults, and that 

 these adults are rarely taken in nets in northern latitudes, but do occur in the stomachs of seals, tunnies, 

 coalfish and cod. The evidence that Paralepis drifts ashore dead seems to be confined to a missionary 

 report, a single floating specimen found by Jensen, and one specimen washed ashore at Jutland in 1865. 

 Contrary to Jensen's argument, it may be supposed that the presence of adult Paralepis in high 

 latitudes is a natural part of their migrational distribution, and that, possibly assisted by their attenuated 

 shape, they are able to avoid pelagic nets — but not predatory fishes. One may refer here to their 

 southern congener, Paralepis coatsi, which is of circumpolar distribution in the Antarctic within the 

 limits of the pack-ice (Norman, 1 937). I notice that here also adults of this species have not appeared in the 

 catches of oceanographical expeditions, whereas factory ship biologists, in their reports to the Discovery 

 Committee, have repeatedly noticed adult* Paralepis coatsi in the stomachs of Blue and Fin whales. 

 Their presence in the stomachs of these whales is undoubtedly fortuitous. Like the whales which 

 happened to engulf them, these fish had been feeding on the shoals of adult and yearling krill (Ettphaiisia 

 superba) which, as I am informed by Mr J. S. Marr, for the most part live right at the surface, between 

 o and 5 m. 



Jensen's survey of the occurrence of Paralepis is thus open to a different interpretation which does 

 not support Bertelsen 's argument regarding Ceratias. 



With so few specimens available, one can only speculate on what relation the known distribution of 

 C. holbolli does, in fact, bear to the great ocean currents, north and south. Dykgraaf (1934) has shown 

 that pelagic fish tend to drift or swim with the current, and not against it as formerly believed, so there 

 seems no doubt that the sluggish adults of C. holbolli are as much borne by the currents as the juveniles 

 are likely to be. If, as has been suggested, this fish in polar regions has a range from the middle depths 

 to within 100 m., or even less, of the surface, then, in the Antarctic, any vertical migration within the 

 upper part of this range would tend to keep it in a high southern latitude. It would move between the 

 shallow Antarctic surface water, 0-200 m. thick moving towards the north, and the Warm Deep Current 

 moving south (Mackintosh, 1937). During the low light intensity of the winter it might spend more 



* Thirty-seven individuals, removed from the stomachs of Blue and Fin whales in the Antarctic season 1947-8, had a mean 

 length (with caudal) of 297 cm., <r= +4-1. 



4-2 



