104 FRESH-WATER FISHES OF NEW JERSEY. 
Habits of fresh-water fish. We have never met with any 
elaborate treatise upon this subject; and have been surprised 
that it should be so little referred to by those who have so 
carefully described the fish themselves, unless it is that 
the describer has not generally been the collector. "Clear 
water,” “muddy streams,” “rapid creeks,” “sluggish brooks,” 
and such phrases cover the whole ground, frequently, of the 
habits of the species, unless like the stickle-backs they do 
something so marked that it cannot well be overlooked. The 
introduction of aquaria has not done much to elucidate the 
subject, in consequence of the meagre dimensions of the 
tanks and carelessness to imitate nature. To what we pro- 
pose to réfer now, more particularly, is that the habits of 
the same fish vary much in accordance with their surround- 
ings, and that the various species are not as confined to 
certain kinds of streams as is usually supposed. 
We make these two statements after a careful résumé 
of our many notes, giving them as the result of eleven 
years study of the habits of the forty-nine species, that 
are found in the Delaware River or its tributaries, within 
five miles of Trenton, in one direction or another. Take 
the ten percoids as an example. We have found them in 
every variety of water the neighborhood produced, even to 
the little rivulets, where young Pomotes and Brytti hovered 
behind rocks, in the stiller water, but dashed up stream on 
being disturbed. Now these “sun-fish” as a class, are deni- 
zens of still water; but the exceptions are not so few, as to 
be put under the head of “merely accidental.” In sluggish, 
gloomy water, we have found many a school of White-perch 
(Morone Americana), that had but to swim a thousand yards 
to join their fellows in the swift waters of the river and like 
them prey upon the cyprinoids there abundant, but scarce 
in the muddy, quiet ereek we mentioned. Often when fish- 
ing for pout and the larger Pike (sox reticulatus), we have 
found these schools of White-perch, occasionally having the 
Rock-fish (Roccus lineatus) associated with them. 
