6i6 



DEPTHS OF THE OCEAN 



in the waters examined by the " Michael Sars," viz. the North 

 Atlantic and the Norwegian Sea. 



To commence with, it will be advisable to consider the details 

 of our fishing methods. The method of simultaneously towing 

 many appliances at different depths cannot be supposed to give 

 such exact results as hauls with closing nets, because the tow- 

 nets function not only while being towed along, but are also 

 liable to do so while being lowered and raised. To counteract 

 the errors arising in this way we generally towed our nets all 

 night long, or for lengthened periods sometimes extending to 

 twelve hours. The distance thus covered in towing the nets 

 was infinitely greater than the distance traversed by the nets 

 in being lowered and raised, and the sources of error were 

 presumably proportionally diminished. 



In order to judge of the results obtained in this way we 

 may examine the catches of individuals belonging to a definite 

 species at all depths and at all stations. Of the well-known 

 species Argyropelecus kcmigyinmis we took during our cruise a 

 total of 286 individuals, at the various depths indicated in the 

 following table : — 



Vertical Surface 



distribution of At a depth of 50 metres 



Argyropelecus. ^^ 100 



150 

 300 



500 



750 

 1000 

 1250 

 1500 

 2000 



The bulk occurred at depths between 150 and 500 metres; 

 no individuals were caught above 150 metres, and only about 

 7 per cent were taken at depths lower than 500 metres. If we 

 assume, then, that these 7 per cent were captured during the 

 process of hauling in the appliances, and that none of them 

 live at depths below 500 metres, we will have an idea of the 

 accuracy of our method. 



We see, further, that by far the greater number were caught 

 at a depth of 300 metres, where we generally had out a |-metre 

 silk net, whereas at 150 metres and at 500 metres the appliance 

 used was, as a rule, a young-fish trawl, that would have had a far 

 greater capacity for catching these fishes. It seems, accordingly, 

 that a preponderating majority of the individuals of this species 



