334 THE SEAS 



or four years' time there would be a very flourishing 

 fishery. The prophecy was fully borne out. It is clear 

 that such prediction must prove of value to the fishing 

 industry as it will obviate an unnecessary glut on the market 

 in the event of a coming good year, or direct attention to 

 some more profitable fish before the lean year comes. 



After making detailed observations of the temperature 

 and saltness of the waters of the Danish coasts throughout 

 a period of many years, the Danish Fishery investigators 

 have discovered that there is a connection between the 

 hydrographical conditions of the water and the mackerel 

 fishery. As soon as the observations of the saltness of the 

 water are known for March and April it becomes possible 

 to predict whether the mackerel fishery taking place two 

 months ahead will be good or bad. The presence of 

 mackerel in this case is probably determined by the 

 strength of certain currents flowing into the Baltic. 



It is unlikely that, as yet, such a method will be possible 

 in such waters as those of the English Channel. Conditions 

 in the Danish waters are somewhat special owing to the 

 admixture of fresh water from the Baltic Sea and Salter 

 water from the North Sea. Differences in the hydro- 

 graphical conditions of the various water layers are 

 there much more marked than we should expect to find 

 in more open water such as the English Channel, where 

 connections between these conditions and the movements 

 of fishes are harder to find. This is not to say that they 

 may not be found some day when our observations are more 

 complete and the methods of making them more perfected. 



Now a fisherman is essentially a gatherer of a harvest 

 he has not sown. He goes out and catches fish from the 

 sea but does nothing to increase the supply contained 

 therein. What has happened in other cases where man has 

 hunted without thought for the future ? Whole seal popula- 



