264 DISCOVERY REPORTS 



Standards and little affected by the condition of the light,^ by lateral standards, being exceedingly low. 

 For all we can tell, however, it may be that the passage of the ship and its resultant purely mechanical 

 thrust (p. 265) produces, and indeed might be expected to produce, in general far more lateral than 

 downward displacement of the krill, to the obvious advantage of the lateral net. For large oblique 

 catches of 10,000 and over, catches that might well represent the momentary sampling of the narrow 

 stratum (p. 149) of a sounding swarm, are exceedingly rare in our records, only seven out of the 

 1700 odd oblique nets we operated in the surface (loo-o m.) layer producing samples of this order of 

 magnitude of whale food of the staple class. 



It might, however, be objected that the dense concentrations of euphausians revealed by the boom 

 net are to some extent artificial since although already dense they might be rendered even denser 

 still, momentarily at least, by the effect of the wash, or actual pressing, of the hull upon them. This 

 objection, however, need not apply to every instance of sampling by the lateral method, it having 

 already been shown (p. 152) that in daylight it can be used to sample on the edge of a swarm not 

 previously disturbed by the hull. At night, although so far the lateral method has not been used at 

 night, sampling from the boom would be done at random and the chances are about equal that it 

 would be done either on the edge of an undisturbed swarm or fairly inside one that had previously 

 been disturbed. In any case it is manifest that for any future investigation of a discretely swarming 

 surface population such as this, lateral towing, whatever its limitations, might well and profitably be 

 adopted in preference to the long-established practice of towing from the stern. It is doubtful how- 

 ever whether it can be used except in a calm sea. 



Much of our oceanographical collecting gear, as Riedl (1958) has recently remarked, was recognised 

 as inefficient over half a century ago and it is becoming increasingly obvious that in our approach to 

 any specific ecological problem old methods must be cast aside, giving place to the revolutionary or 

 new. Only thus will the distribution and abundance of many marine animals, in time and space, 

 be revealed in its natural state. As Buzatti-Traverso (1958) has said, 'There undoubtedly is a need 

 for a fresh and original approach in the development of new tools and gears for the collection and study 

 of plankton and benthos at their various size ranges. Seven out of the fifteen suggested areas of 

 study from the oceanographic view point, do indeed stress such a need '.^ Perhaps in the end, as Piccard 

 (1956) suggests, it will be with the bathyscaphe, or some such contrivance, from which we can watch 

 as well as capture the animals we have for so long been blindly sampling, that we shall obtain a reliable 

 picture of their natural abundance, as well as of much else concerning them that at present remains 

 to us obscure. Laughton (1959) also calls attention to the rich future that opens up for the bathyscaphe 

 in the exploration of the deep-sea floor, and Romanovsky (1955) to the new approach to oceanography 

 provided by skin-diving, a technique becoming increasingly used to determine precisely how our 

 underwater gear is behaving. 



Scattering of swarms by the ship 

 If these swarming animals are in fact so densely crowded as one to the cubic inch (p. 151), jostling 

 or practically jostling one another, it seems obvious that a vessel ploughing into them must itself 

 mechanically split the swarm in two without postulating any particular evading action on the part of 



^ The low and obviously anomalous average night yield of the 16-20 mm. class is again to be noted here. It can again, 

 however, be attributed (p. 260, note i) to the fact that the night hauls involved, together in fact with the vast majority of the 

 day hauls, chanced to fall in places where euphausians of this size were not very abundant. Of the total oblique day catch of 

 this group 140,707, or 87%, were taken in four enormous hauls. If these be disregarded the average day yield is 66. 



^ From the author's summary of the proposals put forward at the recent symposium held at the Scripps Institution of 

 Oceanography in 1956. 



