32 MAINTAINING FISHES 



"tropicals," the small size of the characins adapts 

 them to aquarium conditions. However, the small size 

 is a disadvantage when one wishes to weigh the fish, 

 take a blood sample, or make injections. 



The goldfish ( Carassius auratus ) has been reared as 

 an ornamental fish for centuries, and is still raised in 

 great numbers, both as an ornamental and as a bait 

 species. It is widely available from commercial sources 

 in sizes from one to five inches. The species will 

 spawn at four to five inches in length. 



The goldfish has been selectively bred for variation 

 in finnage, color, and telescoping of eyes. Perhaps the 

 most satisfactory stock for experimental use is one as 

 near normal as possible in finnage, color and other 

 morphological features. The goldfish is easy to work 

 with. It tolerates handling, eats dried foods, and is a 

 convenient size for blood sampHng. As in the case of 

 the trout, a great deal is known about its physiology, 

 and standards for comparison are available for a num- 

 ber of its morphological and physiological character- 

 istics. 



The golden shiner (Notemigonus chrysoleucas) is 

 produced commercially as a bait species, and is 

 widely available in a selection of sizes. It feeds readily 

 upon dry foods and is fairly well adapted to aquarium 

 conditions. It is recommended here as suitable for 

 short term studies such as toxicity tests. 



The zebra fish (Brachydonii rerio), although not a 

 native of North America, is a favorite ornamental 

 variety and is widely available in pet shops. The 

 zebra grows and reproduces readily in captivity. It 

 has a short life cycle which is of particular value in 

 some studies. It can be maintained on dried foods and 



