Dakin and LATARCHE^W?e Plankton of Lough Neagh. 73 

 1910. 



April Catches (time of max.). 

 3-0 11-5 6-0 



1-5 



August Catches 



1-5 11-5 



3-0 



September. 



0'5 0-9 



3-7 



7-5 



8-7 



1-5 



5-2 



5-7 



4-0 



1-8 1-5 



• 2-0 



8-2 



3-6 



0-9 



6-5 



4-2 



1-0 



1-7 



2-7 



8-5 



2-7 



2-5 



2-5 



5-8 



2-0 



3-0 etc. 









2-3 



3-8 



6-6 

 3-5 



1-3 

 0-8 

 1-3 



2-6 



The average Nansen catch in three tvmes the volume of u-ater in the Irish 

 Sea is about O'O cc, except in late April and May, when the spring maximum 

 occurs, and later on in September when another, but smaller, maximum 

 occurs. During these times the average catch is about 6'0 cc. We have 

 seen, however, this catch jump suddenly in volume to 40 cc. Every year 

 there is a most marked increase in volume in the spring. 



Now the volumes of the plankton caught in Lough Xeagh are remarkably 

 uniform. For example, in 1910 the bottora-to-surface hauls (only 40 feet) 

 gave : — 



Feb., 13 cc. ; March 5, 12-0 ; March 16, 90 ; April 13,12-5 ; 



April 7, 10-0; May 11, 12-0; May 25, 9-0; June 10, 17 ; 



July 13, 8-5; July 27, 4-0 ; August 18, 13-0; Sept. 8,3-5; 

 Sept. 29, 7-5. 



Thus there is no doubt that for the greater part of the year there is far 

 more plankton in the Lough ISTeagh water than there is in the Irish Sea. 

 Moreover, whilst the different organisms are appearing and disappearing in 

 Lough Neagh, and passing through then- maxima, the total volumes of the 

 plankton are not disturbed to any great extent. It is very doubtful if the 

 great spring maximum found usually in the Irish Sea is enough to bring 

 the marine figures near to the figures for the fresh-water plankton of Lough 

 Neagh. 



Now the appearance of the Lough Neagh plankton suggests, before any 

 microscopic observations are made, that the phytoplankton almost always far 

 exceeds the zooplankton in quantity. The zooplankton is most abundant at 

 the beginning of the summer and through the summer mouths. 



In our marine catches of plankton the catch might be predominantly 

 phytoplankton ; it might be entirely composed of zooplankton ; or it might 

 even be composed entirely of one species. On the whole, the number of 

 species, however, was much greater than in the fresh-water catches from 



