334 



FISH HATCHERY MANAGEMENT 



ARGULUS 



Argulus spp. have been given the common name of fish lice because of their 

 ability to creep about over the surface of the fish. On first glance, they 

 look like a scale but, on closer examination, are seen to be saucer shaped 

 and flattened against the side of the fish. They have jointed legs and two 

 large sucking discs for attachment that may give them the appearance of 

 having large eyes (Figure 104). Argulids have an oral sting that pierces the 

 skin of the host fish. They then inject a cytolytic substance, and feed on 

 blood. If these organisms become abundant, even large fish may be killed. 

 Masoten (registered by the Food and Drug Administration) at 0.25 part per 

 million active is used for the treatment of Argulus in ponds. Complete dry- 

 ing of rearing units will kill eggs, larvae, and adults. 



LERNAEA 



Lernaea spp. are most commonly found on warmwater fish. However, one 

 species, L. elegans, lacks host specificity and even attacks frogs and 

 salamanders. Heavy infestations have caused massive mortality in carp and 

 goldfish populations. The parasite penetrates beneath scales and causes a 

 lesion at the point of attachment. The damage caused is associated with 

 loss of blood and exposure to secondary infections by fungi, bacteria, and 

 possibly viruses. 



Lernaea are long (5-22 millimeters) slender copepods which, when at- 

 tached, give the appearance of a soft sticks with two egg sacs attached at 

 the distal ends. Actually, the head end is buried in the flesh. This end has 

 large, horn- like appendages that aid in identification of the parasite (Figure 

 105). 



Figure 104. Argulus sp. 



Figure 105. Lernaea sp. 



