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Effects of stocking density on stress response and susceptibility to infectious hematopoietic necrosis virus in rainbow trout

November 6, 2021
The goals of this study were to examine the effect of stocking density on the stress response and disease susceptibility in juvenile rainbow trout (Oncorhynchus mykiss). Fish were sorted into one of 2 stocking densities (high density "HD", 20-40 kg/m3) or (low density, "LD", 4-8 kg/m3) and 3 stress indices (cortisol levels in serum and water, and neutrophil: lymphocyte (N:L) ratios from blood smears) were measured at multiple time points over 21 d. Serum cortisol was significantly increased at 1 h in LD samples and at 14 d in HD samples. Water cortisol concentrations were significantly higher in LD tanks as compared with HD tanks on day 14. N:L ratios were significantly higher in HD tanks on day 14 as compared with LD tanks and with baseline. The effect of stocking density on mortality after exposure to infectious hematopoietic necrosis virus (IHNV) was compared between fish held in HD or LD conditions, with or without prior acclimation to the different density conditions. No significant differences in survival were found between HD and LD treatments or between acclimated and nonacclimated treatments. Cumulative results indicate that 1) 1 to 4 gram rainbow trout did not generally demonstrate significant differences in stress indices at the density conditions tested over a 21-d period, 2) independent differences were found in 3 stress indices at day 14 after sorting into LD and HD holding conditions; and 3) LD and HD stocking densities did not have a significant effect on mortality due to IHNV.

Citation Information

Publication Year 2021
Title Effects of stocking density on stress response and susceptibility to infectious hematopoietic necrosis virus in rainbow trout
DOI 10.30802/aalas-jaalas-21-000003
Authors Jenna J Klug, Piper M Treuting, George E. Sanders, James Winton, Gael Kurath
Publication Type Article
Publication Subtype Journal Article
Series Title Journal of the American Association for Laboratory Animal Science
Series Number
Index ID 70228744
Record Source USGS Publications Warehouse
USGS Organization Western Fisheries Research Center