THE SEA FISHERIES OF EASTERN NORTH AMERICA. 49 



The regular migrations of fishes are for the most part dependent, 1st, 

 on the instinct of reproduction which causes them to seek grounds and 

 regions more suitable to the purpose, especially so far as relates to a 

 safe abode for the young during the earlier months of their life ; 2d, 

 the search for food; 3d, the influence of temperature, a most potent 

 factor. A fourth agency is the pursuit of predaceous fishes, although 

 this is generally much more restricted in its operations than the others 

 The pursuit of fish by man has doubtless some effect, but this is exhib- 

 ited more in a reduction of numbers by actual destruction of parent 

 fish or their eggs and young than by causing a definite change of place. 



I have already grouped the marine fishes provisionally according to 

 their relations to the shores and sea-bottom. Their migrations involve 

 a temporary change in their relations, offshore fish coming in to the 

 coast or even ascending rivers. We may, however, arrange fish by the 

 migrations and movements into the following groups : 



(1) Anadromous fish. — Species passing most of their time in the ocean, 

 and when mature entering and ascending fresh-water rivers and lakes 

 for the purpose of depositing their eggs ; the young fish remaining for 

 more or less time, and then descending to the ocean and there attaining 

 their full growth, probably not going very far from the mouth of the 

 river which they thus descend. The more important species in this 

 connection are as follows : 



The Sturgeon (in part). The Tailor Shad. 



The Salmon. The Gizzard Shad (■?). 



The Smelt. The Striped Bass (in part). 



The Shad. Various species of Cyprinidse. 



The iUewife. The Lamprey Eel. 



A. somewhat similar condition occurs entirely in fresh-water, where 

 certain species which spend most of their time in larger or smaller lakes 

 pass at the breeding season into the streams empying therein, to lay 

 their eggs on the gravelly ripples. This is the case with nearly all the 

 Coregoni or whitefish, the landlocked salmon, and smelt, the Salmo 

 oquassa, or Eangeley trout, the brook trout, &c. Whether the fish ever 

 descend into an outlet is an interesting problem. 



Among the fish of this group we find species of great economical 

 value, embracing as it does some of the finest table-fish, and sometimes 

 in overwhelming abundance. They appear with great regularity in the 

 mouths of rivers, ascending them to their very source, or at least until 

 stopped by some impassable obstruction. They present a great advan- 

 tage over the sea fishes so far as man is concerned, in the greater facil- 

 ity of capture. This pursuit is prosecuted with little comparative risk 

 and exposure, while any one with a line, or a net of simplest construc- 

 tion, and a small boat, or even from the shore, can secure an abundant 

 supply of food. 



Si Mis. 90— —4 



