I THE BROOK STICKLEBACK 



DR. E. EUGENE BARKER 



New York State College of Agriculture 



i 



In some of our shallow, weed-choked 

 pools and ditches there lives a most in- 

 teresting little fish — the brook or five- 

 spined stickleback (Eucalia inconstans 

 Kirtland.) He is so well accustomed 

 to living in stagnant water that he can 

 easily be transferred to an aquarium, 

 where he thrives well and is sure to prove 

 an interesting pet. He is diminutive in 

 size— the largest adults measuring barely 

 over one and one-half inch in length. 

 The males are bright in color, having a 

 veiling of black over an olive-green 

 ground color, which lightens to yellow on 

 the belly. The females are somewhat 

 lighter in color. They are extremely pug- 

 nacious little fishes, and show resentment 

 when another fish approaches, even one 

 of their own kind. The spines on the 

 back gristle up like hairs on a dog's back, 

 and with a vicious lunge, the tiny bit of 

 fury rushes, open-mouthed, at the inno- 

 cent intruder. Often the fish's emotion is 

 registered by a dark flush that sweeps 

 over his body for the time being. It is 

 interesting to note that, when these fishes 

 are transferred to a light or a dark bot- 

 tom, the color changes in accord with the 

 background. They are voracious feeders 

 and thrive on bits of angleworms, or of 

 fresh meat if it is cut into fine enough 

 pieces. 



Like other members of the stickleback 

 family, the brook stickleback is most in- 

 teresting, perhaps, in his family habits. 

 A true nest is built by the male, in which 

 the female deposits her eggs, and the 

 male remains on guard to protect it until 

 after the young have hatched. Some spe- 

 cies nest readily in the aquarium, but the 



brook stickleback has not been observed 

 to do so, at least as far as the writer's 

 experience and knowledge go. On one 

 occasion, however, a male fish was seen 

 guarding his nest in a pond. He was 

 captured and brought home and placed 

 in an aquarium, together with his nest 

 and its contents. As soon as all was set- 

 tled he assumed again his proprietary air, 

 and stood guard over the little home and 



Eucalia inconstans 



its precious contents. At one side of 

 the nest there is almost always a small 

 hole through which the eggs can be seen 

 inside it. This fish often approached the 

 opening, and if any of the eggs pro- 

 truded from it he took them into his 

 mouth, and, backing away a short dis- 

 tance, blew them back again securely into 

 the nest. He swam constantly around the 

 nest, from time to time coming close to it 

 and beating his pectoral fins rapidly, like 

 the wings of a hummingbird as it poises 

 before a flower; he would thus draw a 

 current of water through the nest and 

 aerate the eggs. If any other fish were 

 put into the aquarium, even a female of 

 his own species, he would bristle, flush 

 dark and dart viciously at the stranger 

 and chase it away from the vicinity of 

 his nest. 



In the wild state, nesting is begun 

 while the water is still at a low tempera- 

 ture, between 40 and 50 degrees Fahren- 



