HISTORY OF THE AMERICAN MENHADEN. 51 



the shores of the coutiueut, or by chaiigiug to waters of less or greater 

 depth. The former may be called equatorial, the latter bathic migration. 



Bathic migration is the most common. The cod family, the halibut, 

 and flounders, the scuppaug, tautog, sea bass, and sculpins, are well known 

 examples. The cod prefers a temperature of from 35° to 42° F. and 

 this it secures in a temperate climate, such as that of Southern Xew 

 England by remaining on the off-shore banks in 15 to 30 fathoms of 

 water, coming near the shore in winter. On the coasts of Labrador, New- 

 foundland, Xova Scotia and Eastern Maine they are near the shore in 

 summer and in deep water in winter. In Norway the fish are caught 

 to some extent in the fiords in the summer season, though more in winter. 

 In summer they still remain on the off-shore banks. The halibut moves 

 up and down on the sides of the great oceanic banks and the continental 

 slopes, with the seasonal changes of temperature. In summer they are 

 abundant in the shallows of South Greenland, while in winter they are 

 in deep water. On the coast of Massachusetts they come near the shores 

 only in the dead of winter, though abundant in summer on the edges of 

 the outside banks in 80 to 300 fathoms of water. The sand dabs {Ilippo- 

 glossoides dentatus) are abundant in July in water of 60 and 80 fathoms 

 ten miles off Cape Ann ; in the middle of winter they swarm upon the 

 sand flats in two or three fathoms depth. 



The Spanish mackerel, the bonito, and the tunnies are good examples 

 of nomadic species. In summer they throng our northern waters^ in 

 winter thej' are under the tropics. 



Others, like the sea-herring, appear to migrate in two ways. Their 

 movements are, approximately, both parallel with and vertical to the 

 coast line ; that is to say, they secure changes of temperature both by 

 leaving the upper strata of the ocean and by moving toward and from the 

 equator. The researches of Boeck in Norway, show that the schools ap- 

 proach the coast by gullies or submarine valleys from the oceanic depths. 

 Such is doubtless the case on our own coast, in their earliest approaches, 

 though having reached the shallows near the shore, the schools range 

 along great stretches of coast line. Since fishes have no restrictions 

 upon their movements except those of food and temperature, all active 

 si)ecies must traverse areas of many hundreds of miles during the year. 



The tendency of all the researches made during the past few years 

 has been to confirm the views advanced by Professor Baird in an un- 

 luiblished letter written in 1873 to the Hon. Hamilton Fish, Secretary 

 of State. 



" The question in regard to the migration of fishes is one that has 

 attracted the attention of both fishermen and naturalists for many years 

 past, and a great deal of eloquence has been expended by Pennant and 

 other writers, in their history of the movement of herring and other 

 species. 



" For many years it was considered beyond question that the sea 

 herring, having their homes in the northern seas, were in the habit of 



