NO. 7 PROTECTIVE ADAPTATIONS McATEE II9 



of fishes that ahnost everything " picks on," such as the minnows 

 (Cyprinidae), was represented in the stomachs of 44 species of birds. 

 Numbers up to 50 of these Httle fishes were found in stomachs of the 

 belted kingfisher and the hooded merganser, and in the case of young 

 of the common carp a high count of 106 was made from the stomach 

 contents of a glossy ibis. Thirty-nine species of birds are known to 

 prey upon the common killifishes and their allies ; and numbers were 

 taken from many stomachs, the maximum being 526 from a little 

 blue heron. 



Other enemies. — Fishes have no more destructive enemies than the 

 predacious element among their own kind. Among the highly preda- 

 tory marine forms may be mentioned the dogfishes and other sharks, 

 swordfish, bluefish, squeateague, conger eel, and the angler, and among 

 fresh-water fishes, the gars, sculpins, trout, amia, pikes, and bass. 

 In a study of the fisheries of Buzzard's Bay, Mass.. Field estimated 

 that two species of sharks destroy more than 500,000 fishes annually 

 in that body of water. Pearse found fishes to compose 12.3 per cent 

 of the food of ^2 species of their class in Wisconsin lakes. Forbes 

 notes that the principal piscivorous fishes of Illinois, those which 

 obtain three-fourths or more of their total subsistence from their 

 fellow fin-bearers, are Lota, Stizostedion, Eso.v, Micvopterus, Icta- 

 lurus, Leptops, and Lepidosteiis. Six other species are listed as taking 

 from 25 per cent to 65 per cent of fish food. 



Predators devour fishes in all stages, and there are numerous 

 special enemies of fish spawn ; worst among these are other fishes 

 such as the suckers, sculpins, minnows, sticklebacks, killifishes, top 

 minnows, and trout. 



Not many enemies of fishes are numbered among our batrachians 

 and reptiles, those worthy of note including only the bullfrog, Nec- 

 turus and CryptobraiieJiiis of amphibians ; the king, garter, and water 

 snakes, copperhead, rattlesnake, and cottonmouth moccasin among 

 snakes ; and the painted terrapin, and snapping and soft-shelled 

 turtles. 



Some mammals are important enemies of fishes but the number is 

 not large ; we may mention the raccoon, mink, otter, seals, sea-lions, 

 porpoises, and whales. 



The young of fishes especially fall a prey to a variety of insects, as 

 the larvae of aquatic beetles and of dragonflies, and to several kinds 

 of water bugs and to hydras. Insects also, and crawfishes and leeches 

 prey upon the eggs of fishes, and squids are said to be among the most 

 destructive foes of adult fishes. Parasites of fishes abound and are 

 recruited from the ranks of such diverse groups as bacteria, proto- 



