64 REPORT OF COMMISSIONER OF FISH AND FISHERIES, 
sent by no means an insignificant factor in the casualties of the class. 
Every fish-culturist is painfully aware of the destruction of his trout, 
carp, or other fresh-water species by herons and kingfishers. The fish- 
hawks take their toll in the rivers and lakes, perhaps more rarely in the 
sea; but it is among aquatic birds, especially the gulls, the Pelecanide 
(including cormorants, pelicans, gannets, &c.), the Alcide, or auks, and 
some of the ducks that we find the most active oceanic enemies of the 
finny tribe. In many parts of the ocean the number of birds belong- 
ing to these groups is enormous, and even supposing that each bird de- 
vours daily only half, or even a quarter, of its weight (a by no means 
difficult feat), the amount of destructiveness is something quite appall- 
ing. It has been estimated that the gannets alone, on the coast of 
Scotland, devour more herring than are taken by man, their voracity, 
like that of the cormorant; being very marked. The gulls are less de- 
structive, as they must confine themselves more particularly to the 
smaller fish which come to the surface, either spontaneously or as driven 
by predaceous fishes. 
The reptiles probably contribute but little to the mortality among 
fishes in the open sea; but in lagoons and along the shores of islands, 
especially in brackish water, as well as in fresh, they play their part in 
the economy of nature. It is especially among the crocodiles, alligators, 
and caymans that this destructiveness is seen. The sea-snakes of the 
tropics and sub-tropics. in all probability consume large numbers of 
fishes of such size as can be readily swallowed entirely. In fresh waters 
the various species of water-snakes also consume a considerable number. 
Some species of turtle are very destructive to fish, although it is more 
particularly in fresh water where such forms as the snapping-turtle of 
North America play well theinpart. The sea-turtles are said to be veg- 
etable feeders rather than animal, seeking the eel-grass, algae, and other 
plants. Probably, however, they do not disdain an occasional fish. 
Frogs are also very destructive to fish in fresh water, and require a 
careful looking after by the fish-culturist. The salamanders are too di- 
minutive to devour large fish, but probably consume eggs and young 
on a large scale. The Menobranchus, or large salamander, in the Great 
Lakes, is said to commit great havoc on the whitefish spawning-grounds, 
gorging itself on the eggs, and by the aggregate of their numbers largely 
reducing the crop of young fish. 
The destruction of fish in the sea, as might naturally be expected, 
is greatest from fellow-fishes, the smallest being consumed by those a 
little larger, these again falling victims to the still more powerful, and 
so on until we reach such forms as the swordfish, the tunny, the largest 
sharks, &¢., which apparently at least, when fully grown, are free from 
danger from their own kind. Here, however, there come in as antag- 
onists and destroyers the larger cetaceans; possibly the giant cuttle- 
fish, and man; although such insidious enemies as the lamprey, the 
myxine, or hag, the pug-nosed eel, and other parasitic fish may even 
cause the very largest to succumb. 

