FISHES 103 



Family Gasterosteidae. — Sticklebacks. Body elliptical, rather 

 slender, compressed; caudal peduncle slender; tail fin small; no true 

 scales present, but body either naked or protected laterally by vertically 

 elongate bony plates; 2 to 15 free spines in front of the dorsal fin; a 

 patch of naked skin between the pectoral fin and the opercle on each 

 side; ventral fins consist of i spine and i or 2 rays and subabdominal in 

 position; middle and sides of belly protected by the pubic bones: 

 5 genera and about 12 species in America and Europe, 6 in the United 

 States; small fishes living in fresh waters and arms of the sea, most of 

 which build elaborate nests in which the eggs are deposited and where 

 they and the young are protected by the male; they are savage little 

 fish and very destructive to the eggs and young of larger fishes. 



Key to the Fresh Water Genera of Gasterosteidae in the United States 



ai Free dorsal spines 3 to 5. 



bi Sides protected by bony plates. 



ci Ventral spine serrate i. Gasierosieus. 



C2 Vertral spine not serrate 2. Glandiunculus. 



bo Sides naked. 



Ci Free dorsal spines 5 3. Eucalia. 



C2 Free dorsal spines 3 5. Apeltes. 



32 Free dorsal spines 7 to 1 1 4. Pungitius. 



1. Gasterosteus L. Sides of body usually protected by vertically 

 elongated plates; 3 or 4 free dorsal spines; pubic bones broad and little 

 divergent, joined on the belly, forming a median ventral plate behind 

 and between the ventral fins; gill membranes not joined across the 

 isthmus: several species in America and Europe, i in fresh water in 

 America. 



G. aculeatus L. Common stickleback. Length 60 mm. to 100 mm. ; 

 head 3.5; depth 4.5 to 5; dorsal fin II-I, 13; anal fin I, 9; ventral fin I, i; 

 color olivaceous, more or less mottled above; lateral plates and also the 

 dorsal spines variable, depending in some degree on the salinity of the 

 water: arctic and subarctic, on both coasts, in shallow bays and ascend- 

 ing the rivers; southwards to New Jersey and Lower California. 



2. Glandiunculus Jordan and Evermann. '^irmldi.i to Gasterosteus; 

 ventral fin rays I, 2; ventral spine not serrate: i species. 



G. wheatlandi (Putnam). Length 100 mm.; head 3.5; depth 4.5; 

 color dark greenish above; sides silvery or yellow; ventral membrane 

 often red; dorsal spines long and slender; rays of dorsal fin II, 10 or 11 ; 

 anal I, 8; ventral fin I, 2; caudal peduncle very slender: Atlantic coast 

 from New Jersey to Labrador, ascending the streams. 



