SEA-FISHERIES LABORATORY. 



351 



average catch for the otter net is 353 c.c, and for the 

 stern net 4*30 c.c. Out of the 44 double hauls, the amount 

 of the catch in the two nets does not differ by more than 

 0'5 c.c. in 19 cases, in 8 of which it differs by not more 

 than 0'2 c.c. In 16 cases the catches differ by 1 c.c. or 

 over. The average difference is 0*76 c.c. 



In 27 cases out of the 44 the stern net caught more 

 than the otter net, in 13 the reverse was the case, and in 

 4 pairs of hauls the catches made by the two nets were 

 equal. As examples of cases where two very different hauls 

 were made (just as was sometimes the case with two nets 

 at the stern), the stern net caught 8*5 c.c. and the otter 

 only 22 c.c. ; and again, the stern net caught 9'4 c.c. and 

 the otter 4*5 c.c. In fact, it is obvious that the otter net 

 gave the same kind of catch as it would have done if it 

 had been placed beside its fellow at the stern. 



As a further test, however, we propose this coming 

 season to use two otter-nets, one on each side of the ship, 

 for comparison both with the stern nets and with one 

 another. If any difference shown between the two otter- 

 nets is as ffreat as the difference between the stern nets it 

 is clear that the variations are real and not due to any 

 supposed action of the propeller or other influence of the 

 ship. 



As to the organisms present, in five cases the catches 

 are remarkably similar. As an example, take April 22nd, 

 Stat. III:-- 



Total Catch. Diatoms. Dinofl. Copepoda. 



Otter 



Stein 



7-2 c.c. 



6-8 



513,650 

 515,050 



9,500 

 3,400 



61 



70 



Weight 



7 



568,200 



1,500 



105 







Echin. 

 larvae. 



Copep. 

 Nanpl. 



Oikopleura. 



Otter 



Stern 



i 



J 00 

 100 



900 

 800 



400 

 400 



Weight 





100 



500 



910 



