OF THE HABITS AND MIGRATIONS OF THE MACKEREL. 29 



observations taken by the Challenger between Bermuda and Halifax, 

 and New York and Bermuda, which are shown in two diagrams 

 in Brown Goode's paper on the "Menhaden Fishery,"* prove that 

 on the western side of the Atlantic extensive layers of water exist 

 in April and May below the Gulf Stream having temperatures similar 

 to those of the waters frequented by the mackerel when on the coast. 



For the parts of the Atlantic lying off the European coasts no obser- 

 vations giving the required information during the winter months 

 appear to have been made; but from the position of the isothermal for 

 50° F. for surface temperature in February, when such temperatures 

 are at a minimum, it is clear that water of the required warmth must 

 exist at no very great distance from the coasts frequented by the fish, 

 with the exception of the coasts of Norway and the North Sea. In the 

 latter case we have already seen that the fish probably retire in the 

 autumn by way of the English Channel. 



* Report of U.S. Fish. Com., 1877. 



