THE WESTERN MACKEREL FISHERY. 



281 



speak for themselves in support of the theory that the quantity of 

 zooplankton occurring on the fislung grounds materially affects the 

 fishing ; the more food the more fish, and vice versa. 



Before leaving the consideration of the present matter, it is desirable 

 to draw attention to the relation of phytoplankton to zooplankton 

 during May, for the years 1903-7 inclusive. This can best be done 

 by an examination of a curve showing the flvictuation of phytoplank- 

 ton at the same stations and formed by the same method (Fig. 2). 



PLANKTON 



VALUES 



600 



500 



406 



300 



200 



100 



MACKEREL 



CWTS. 



'lOO.OOO 



350,000 



3oo,ooa 



250,000 



200,000 



/50,00a 



1903 



1904 



1905 



(906 



100,00a 



1907 



Fig. 2. — Curves showing, for the month of May, fluctuations in the quantities of mackerel 

 landed and of phytoplankton observed at Stations E. 5. and E. 6. 



PliytoplauUton : mean between Stations E. 5 and E. 6 for May — Dotted line. 

 Mackerel landed during May— Continuous line. 



In the present example, however, it was found necessary to take 

 every species of phytoplankton into consideration. In this it will be 

 seen there appears to be almost a direct inversion of the zooplankton 

 curve. There is an exception, however, in 1903, in which year 

 plankton generally is low. 



We have seen that there appears to exist a marked correlation 

 between fluctuation of zooplankton and that of the fishery. It will be 

 admitted that the fluctuation of zooplankton need not necessarily entail 



