Effect of fish density and
number of infectious fish on the survival of rainbow trout fry, Oncorhynchus
mykiss (Walbaum), during epidemics of infectious pancreatic necrosis
J. Bebak-Williams, P.E. McAllister, G. Smith, R.
Boston-2002
Journal of Fish
Diseases, 25(12): 715-722
Abstract:
Two laboratory studies compared the effect of fish
density and number of infectious fish on characteristics of survival of
rainbow trout fry during controlled epidemics of infectious pancreatic
necrosis (IPN). Analyses of hazard functions and survivor functions were
used to determine whether peak death rate, time at which the peak death rate
occurred and probability of survival to the end of the experiment were
associated with fish density and number of infectious fish added (i.e.
pathogen concentration). When number of infectious fish was low and fish
density increased, the peak death rate increased, time of the peak death
rate decreased and the probability of survival to the end of the experiment
decreased. When number of infectious fish was high, the effect of density
diminished. Loglogistic regression of survival data revealed that fish
density, number of infectious fish and interaction between these two
variables significantly affected time to death from IPN (P < 0.01).
(Freshwater Institute, P.O. Box 1889, Shepherdstown,
WV 25443, USA, e-mail: j.bebak@freshwaterinstitute.org)