58 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 
in nearly the same latitude as the mouths of the rivers in which they 
were born, and return to them at the proper season. The young remain 
in the fresh water for a time, the period varying with the species, after 
which they also follow their parents in their return to the sea. 
The movements of what we had previously designated as inshore and 
pelagic fish are also largely connected with the same reproductive in- 
stinct, and even the fishes of the Banks illustrate it to a greater or less 
degree. 
SEARCH FOR FOOD.—Next, perhaps, to the influence of reproduction ~ 
comes the search for food as influencing the migration and movements 
of fishes, certain species of fishes following up particular forms of other 
fishes, the attempts of which to escape fall under the same category; 
or of the lower animals, as they are carried almost unresistingly by 
winds and currents in various directions. A notable illustration of this 
is seen in the herring. 
Professor Mobius, in investigating the food of the herring in the Ger- 
man seas, found that a certain copepod shrimp, one of the Entomostraca 
(Temora longicornis), was more eagerly sought after than anything else; 
this being so minute, however, that 18,000 were taken from the stomach 
of one herring and 60,000 from that of another.* 
Professor Mobius shiriles that the comb-like fringes attached to the 
gills of the herring serve as tangles in capturing these shrimps, pre- 
cisely as do the similar apparatus of the basking shark and the whale- 
bone of the whale. These specimens were obtained in February of 
1872, when both the shrimp and the herring were in exceptional abund- 
ance; and he subsequently observes that the same relations were found 
continually, the abundance of the herring being in strict proportion to 
that of the shrimp. t 
The chain of connection does not cease in the relation between the 
Temora or shrimp and the herring. A great variety of sea birds, gulls, 
gannets, &c., follow up the herring, as also numerous mackerel, tunnies, 
blackfish, swordfish, and even whales and porpoises, which devour the 
herring in countless numbers. The movements of the capelin in the 
North Atlantic influence very largely those of the cod and other species, 
as when the former come into the shores of Newfoundland and else- 
where in immense numbers to deposit their eggs on the beach, the cod, 
&c., follow, and are then captured within a very short distance of the 
shore. 
DRIVEN BY ENEMIES.—A notable instance of these relationships is 
seen in the menhaden and thé bluefish. The menhaden, in its move- 
ments along the coast, is very frequently accompanied by vast schools 
of bluefish, which, as already explained in a previous report, probably 
destroy more menhaden in a day than are taken by man in a whole sea- 
* Circulare des Deutschen Fischerei-Vereins, 1873, p. 112. 
tCirculare des Deutschen Fischerei-Vereins, 1874, p. 90. 

