CHAPTER XII 



HYDROGRAPHICAL INVESTIGATIONS 



BY far the greater portion of the literature of 

 fisheries science deals with the biological investiga- 

 tion of the natural conditions of the fishes and 

 other animals sought by the fisherman. Anyone 

 making a somewhat cursory survey of this literature 

 may well conclude that only such investigations 

 as the life-histories of marine economic animals, 

 their habits, food, abundance, migrations, and the 

 like, are likely to prove of practical value. But 

 a more attentive study will show that another 

 line of research, which we may call the hydro- 

 graphical investigation of the sea, is just as essential 

 for a proper understanding of sea-fisheries questions. 

 Such investigations deal with the depths of the sea, 

 the nature of the deposits forming its floor, the 

 movements of water caused by tides, winds, and 

 ocean currents, the chemical composition of sea- 

 water, its varying temperature, salinity, and specific 

 gravity. The exact nature of the connections 

 between all these phenomena (and meteorological 



