ARS | Publication request: Effects of condtioning channel catfish Ictalurus punctatus to acute low water stress

Submitted to: Catfish Farmers of America Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: November 6, 2011
Publication Date: N/A

Technical Abstract: Physiological stress and injury are the primary reasons for increased outbreak of diseases in catfish. Since stress cannot be eliminated from culture practices entirely, researchers are investigating ways to decrease the stress response in order to increase survival to diseases. Booth and Peterson (2009) reported that “conditioning” channel catfish fry to the physical stress of regular “exercise” increased their growth rate following transfer to ponds. Booth and Peterson (2009) also noted fry reared in areas of a hatchery subjected to frequent human activity had significantly lower mortality in an experimental disease challenge with Edwardsiella ictaluri than did fish reared in areas with less disturbances. These observations suggest that conditioning fish to stress may modulate their stress response and thus reduce their susceptibility to disease. I hypothesized that one: conditioning catfish fingerlings would reduce their cortisol stress response and two: that conditioned fingerlings challenged with E. ictaluri would have lower mortality than non-conditioned fish. Three groups of channel catfish fingerlings from pooled spawns of USDA industry strains were disturbed at different times by lowering the water level to two inches for fifteen minutes every other day- for either 3 or 6 weeks. A fourth group of fingerlings were not disturbed and served as a control. On sampling days, fish were either stressed or undisturbed and then anesthetized immediately prior to collection of blood for cortisol determination. Treatment variables are indicated in Figure 1, with arrows indicating when samples are taken. The cortisol response in experimental fish sampled two weeks after the conditioning trials were dampened in the conditioned fish, with cortisol levels similar to undisturbed control fish (Figure 2), which supports the hypothesis that conditioning channel catfish fingerlings would reduce their cortisol stress response. Due to virulence difficulties when growing E. ictaluri, the disease challenge failed in Fall 2010 (only 0.1% of fish died overall). However, methodology was corrected and the conditioning experiment is being repeated with the disease challenge to follow. Results of these experiments will be reported