OPERATING THE HATCHERY 



Neascus infection of fathead min- 

 nows in a pond at Leetown (W. 

 Va.). The encysted worms were 

 found in the abdominal cavity in 

 such numbers that the abdomen 

 was greatly distended. Mortality 

 was so high that a change to golden 

 shiners, a more resistant species, 

 was recommended. 



The only control for this para- 

 site is draining the pond long 

 enough to kill the snails and con- 

 trolling the kingfisher population. 

 Snails in ponds can be killed 

 rapidly by disinfection of the pond 

 with chlorine (see Disinfecting 

 Ponds and Equipment, p. 61). 



Tapeworm. — Ligula intestinalis 

 is a tapeworm whose last larval 

 stage is commonly found in the 

 body cavity of suckers and min- 

 nows, and rarely in perch, darters, 

 and bass. Infested fish are easily 

 recognized by their swollen bellies. 

 Worms 6 inches long have been 

 taken from minnows, and worms as 

 long as 12 inches have been taken 

 from suckers. The adult stage lives 

 in the intestines of water birds. 



Minnows and suckers reared in 

 ponds or taken from shallow waters 

 along lake shores may be infested. 

 The parasite is known to be of wide 

 occurrence in the Great Lakes and 

 adjoining areas. Because the para- 

 site's eggs are spread by water 

 birds, and early larval forms live 

 in the natural food organisms of 

 fish, tliere is little chance for perma- 

 nent control, although drying and 

 freezing of pond bottoms may re- 

 duce infestation. 



Other tapeworms can frexjuently 



be found in the intestinal tract of 

 warm- or cold-water fishes. Heav- 

 ily infested fish become sterile, 

 therefore, the removal of tape- 

 Avorms is important in the case of 

 brood stock. Several drugs given 

 orally may be effective. McKernan 

 (1940) found that the addition of 

 1 to 1.5 percent of kamala to their 

 food rids fish effectively of tape- 

 worm. One contributor to this pub- 

 lication (Snieszko and Powell, un- 

 published ) successfully cured adult 

 largemouth black bass by treating 

 the fish for 3 days with kamala in 

 capsules. Each adult bass received 

 daily one capsule containing 0.1 to 

 0.2 grams of kamala, dosage being 

 about 0.1 gram for each 3 pounds 

 of fish. The treated fish eliminated 

 great masses of tapeworms with the 

 feces. 



External animal parasites 



Here are included such proto- 

 zoans as Costia, Chilodon, Tricho- 

 diim^ Scyphidia, Epistylis^ Ichthy- 

 ophthinus, and external trematodes 

 such as Dactylogyrus and Gyrodac- 

 tylu^. All of these parasites except 

 Ichthyopkthirius live on the surface 

 of the fish's body and gills and are 

 readily removed by salting, dipping 

 in glacial acetic acid, or by using 

 prolonged treatments with forma- 

 lin. I chthyophthirius differs from 

 the other external parasites listed 

 here, since in its adult stage it buries 

 in the epidermis of the fish; there- 

 fore, these treatments are not effec- 

 tive against it unless they are re- 

 peated daily until the desired 

 results are attained. Where water 



60 



