FISH HEALIU MANAGEMENT 



267 



Table 36. infectious diseases commonly considered io be stress-mediated 

 in pacific salmon, frol i'. caifish, common carp, and shad. 'schrce: 

 wedemeyer and wood 1974.) 



DISEASE 



STRES.S FACTORS 

 PREDISPOSING TO INFECTION 



Furunculosis 



Bacterial gill disease 



Columnaris (Flexibacter columnaris) 



Corynebacterial kidney disease 



Aeromonad and Pseudomonad 

 hemorrhagic septicemias 



Vibriosis (Vibrio anguillarum) 



Costia, Truhodina, Hexamita 



Spring viremia of carp 

 Fin and tail rot 



Infectious hematopoietic necrosis (IHN) 

 Cold water disease 



Channel catfish virus disease 



Low o,xygen; crowding; handling in the pres- 

 ence of Aeromonas salmunicida; handling a 

 month prior to an expected epizootic; 

 elevated water temperatures. 



Crowding; chronic low oxygen (4 ppm); 

 elevated ammonia (l ppm NH3-N); parti- 

 culate matter in water. 



Crowding or handling during warmwater 

 periods (59°F) if carrier fish are present in 

 the water supply; for salmonids, a tem- 

 perature increase to about rt8°F if the 

 pathogen is present, e\en if fish are not 

 crowded or handled. 



Low total water hardness (less than about 

 199 ppm as CaCO;^). 



Protozoan infections such as Costia, or Tri- 

 chodina, accumulation of organic materials 

 in water leading to increased bacterial load 

 in water; particulate matter in water; han- 

 dling; low oxygen; chronic sublethal expo- 

 sure to heavy metals, pesticides, or poyl- 

 chlorinated biphenyls (PCB'si; for com- 

 mon carp, handling after over- wintering. 



Handling; dissolved oxygen lower than 6 

 ppm, especially at water temperatures of 

 ,50-.59T; brackish water of lOl.Tppt. 



Overcrowding of fry and fingerlings; low 

 oxygen; excessive size variation among 

 fish in ponds. 



Handling after over-wintering at low tem- 

 peratures. 



Crowding; improper temperatures; excessive 

 levels of metabolities in the water; nutri- 

 tional imbalances; chronic sublethal expo- 

 sure to PCB's. 



Temperature decrease from .50°F to 4.5 5.i°F. 



Temperature decrease (from .50-,')9°F to 

 4,i-.iOT) if the pathogen is present; high 

 water flow during yolk absorption, e.g., 

 more than five gallons per minute in 

 Heath incubators. 



Temperature above 68°F; handling; low oxy- 

 gen: co-infection with Flexibacter, Aeromo- 

 nas, or Pseudomonas; crowding. 



