46 FISHES OF ILLINOIS 



and tapering forward, 3.7 to 4.3 in length; width of head 1.9 to 2.2 in its 

 length; interorbital greater than eye, 3.6 to 4.3 in head; eye 3.4 to 4.8 in 

 head; nose shorter than eye, 4.9 to 6.1 in head; mouth small, more or less 

 inferior, extending Httle back of front of eye; maxillary 3.4 to 4.2 in head; 

 lower jaw shorter than upper. Dorsal fin about midway between muzzle 

 and base of caudal, slightly behind ventrals, of 12 rays; last dorsal ray greatly 

 elongated, extending past middle of anal; anal rays 30 or 31; pectorals 1.2 

 to 1.5 in head; ventrals half way to front of anal in adults. Scales 56 to 

 57, transverse series 23; no lateral line; ventral scutes 19 (before ventrals), 

 12 or 13 (behind ventrals). 



This immensely abundant species, although little esteemed 

 as a food fish, is one of the most useful in our waters because of 

 the almost exhaustless food supply which it offers to all the 

 game fishes of our larger streams and lowland lakes. Living 

 itself mainly upon food derived from the muddy bottoms of our 

 very muddy rivers and lakes, it serves as a means of converting 

 this mere waste of nature into the flesh of our most highly 

 valued fishes. 



For this service it is especially adapted by the possession of 

 a very effective straining apparatus in its gills, by means of 

 which it separates the finest particles of silt from objects large 

 enough to serve it as food, and bj^ the extraordinary develop- 

 ment of its digestive surface in a long and convoluted small 

 intestine, thickly beset with finger-like villi within, and with 

 tubular caeca without, each of which is closed at its outer end 

 and pours into the intestine through its inner opening the diges- 

 tive juices which it is the function of these organs to secrete. 

 The thick-walled muscular stomach, resembling the gizzard of 

 a bird — whence its name of gizzard-shad — is another adaptation 

 to a kind of food not available to most other fishes. 



It occurs throughout the Mississippi Valley, in brackish 

 waters along the Atlantic and the Gulf as far as Mexico, and in 

 the streams and lakes of the Mississippi Valley. In Illinois 

 the gizzard-shad inhabits all our larger rivers, together with 

 the lakes connected with them, sometimes ascending smaller 

 tributaries during the season of the spawning migration, and it 

 has also made its way, by means of canals, into lakes Erie and 

 Michigan. In summer it is a rather active fish, sometimes 

 darting rapidly about in all directions and often leaping out of 

 the water. When surrounded by the seine, it is likely to escape 

 in schools by skipping lightly over the cork line. In winter it 

 withdraws largely to the deeper waters, where it hibernates in 

 a benumbed condition. 



