SEA-FISHERIES LABORATORY. 



197 



Total Plankton throughout the Year. 



We give now, as the first summary statement from 

 our Forms, and in further illustration of the great 

 quantitative range shown by the gatherings taken on 

 different days, the following record of the k ' total 

 plankton," reduced to the average* per haul for each 

 individual dav : — 



Date. 



Jan. 

 Feb. 



Mar. 



April 



Average per Haul. 



1-2 c.c. 



1 



1-2 



2 



0-5 



1-6 



6 

 14-5 



9 

 17 

 31 

 42-5 

 31 

 30 

 34 

 235 

 15 

 17 

 21 

 25 

 13 

 11 

 51 

 14 

 17 

 13 

 22 

 16 



Date. 

 April 



May 



June 



July 



Aug. 



Average per Haul. 

 10 c.c. 



9 

 10 

 11 



5 



6 

 20 

 13-5 

 15 



4 



3-5 



4-5 

 11 



14-5 

 25 

 12-5 



4 

 18 

 18-5 

 12 

 13 

 12 

 12 



4-5 



6 



3 

 18 



5 



* We desire to point out that as the nets used were not all 

 comparable, the vertical nets catching as a rule less and the shear net 

 more than the open horizontal tow-nets, no conclusions are based 

 solely on the details of this record. Moreover, during the greater 

 part of the year, only open horizontal nets were used, while in spring 

 and autumn, while the yacht was at work, the vertical nets and the 

 shear net were used in addition. But as the number of observations 

 is large, and the non-comparable nets more or less neutralise one 

 another, the average per haul is probably a fair representation of the 

 plankton caught. The averages may be lowered unduly by the 

 vertical nets on some days, or raised too much by the shear net on 

 others, but must be substantially correct for the weeks and months, 

 and so the list serves to show the range in variation and the seasonal 

 change — and that is all we use it for. 



