Conditioning Channel Catfish Fingerlings Ictalurus punctatus to Acute Low-Water Stress and Comparison of Metomidate and MS-222 in Modulating the Short-Term Stress Response

The efficacy of the anesthetics Metomidate and MS-222 to modulate the cortisol response of channel catfish during a 10 min confinement stress was compared, in preparation for evaluating whether or not previous conditioning increases resistance to Edwardsiella ictaluri. Fingerlings anesthetized in Metomidate maintained baseline levels of cortisol concentrations throughout the study (P\u3c 0.05), whereas levels increased correspondingly in fish anesthetized in MS-222and controls. Metomidateis useful for long periods of anesthetization, but MS-222 suppressed cortisolsecretion for only the first 5 min of sedation. During the conditioning study, the cortisol response among disturbed fingerlings decreased over time, indicating conditioning occurred. However, cortisolconcentrations of conditioned fingerlings increasedwhen subjected to a disease challenge, although their responsewas significantly lower compared to unconditioned controls.This indicates a possibleadvantage in conditioningfish, although differential susceptibility to a disease challenge has not yetbeen demonstrated