Stress response of bonytail, roundtail chub, and razorback sucker to handling and confinement

Authors: Teresa A. Hunt, David L. Ward, Alice C. Gibb

Year: 2009 (xli)

Abstract

We measure plasma cortisol levels for bonytail (Gila elegans), roundtail chub (Gila robusta), and razorback suckers (Xyrauchen texanus) to determine physiological stress responses before and after exposure to capture and handling. We captured fish held in 1.8 m circular tanks and extracted blood with in an average of 13:55 minutes. Each fish was then confined in a covered bucket for 1 hour after which blood was again extracted. Plasma cortisol concentrations were analyzed to determine cortisol levels before and after confinement. These experiments were conducted with all three species of fish held in 1.8 m, circular tanks; as well as razorback suckers captured from a 0.25 hectare hatchery grow-out pond. Bonytail, roundtail chub and razorback suckers have baseline cortisol levels that exceed values reported for most other fish species tested under similar conditions. Roundtail chub exhibited the highest levels of baseline cortisol (207.8 ± 36.4 ng/mL) which was over twice as high as the cortisol levels for bonytail (89.2 ± 34.6) and razorback suckers (102.9 ± 38.7). Razorback suckers held in a pond environment exhibited much lower cortisol levels then razorback suckers held in circular tanks. This indicates there is likely some degree of chronic stress associated with fish in 1.8 m circular fiberglass tanks. Chronic stress may lead to increased illness and reduced reproductive capability.