170 SEA FISHERIES 



makes an irruption into the Skagerack by way of the 

 Jutland banks (shoal water) ; it pushes the Baltic water 

 back to the shores, and expels even the oceanic water, 

 which by the winter can only be found at the bottom 

 of the deepest depressions. Now, the Scandinavian 

 hydrographers have believed this movement of the 

 waters to coincide with the approach of the herring 

 to land ; they even state that the herring hug the land 

 closer as the invasion of the shoal water is more ener- 

 getic ; and that even in its changes and oscillations the 

 herring obey the successive impulses of the new current. 

 It would be rash to seek, as some have done, the part 

 played by the elementary factors in these movements 

 of the herring ; the temperature and salinity of the water, 

 and the dynamic action of the current may perhaps play 

 only an indirect part in these movements ; nevertheless 

 these conditions must greatly affect the multiplication 

 of the infinitesimal creatures on which the herring feed. 

 In any case, there remains one crude fact : the coinci- 

 dence of the movement of the waters with the arrival 

 of the herring ; and the conclusion that the herring has 

 adapted itself to these annual changes. For this reason 

 it is legitimate to connect any notable change in the 

 habits of the herring with a change in the cycle of the 

 currents." 



Mr. Walter Garstang has published some curious 

 observations relating to the mackerel of the Channel. 

 There was a scarcity of this fish in the February and 

 the March of 1896 and 1898, but in 1897 ^ was abundant. 

 The cause resided in the fact that in 1897 tne winds 

 of February and March had blown from the south- 

 west, so that the warmer waters of the Atlantic caused 

 a rise of temperature in the Channel ; during the other 

 two seasons the winds had blown from the opposite 



