SEAFWA 2017

AUTHORS: Nagaraj G. Chatakondi, Brian C. Peterson - USDA ARS Warm water Aquaculture Research Unit

ABSTRACT: Stress is unavoidable in aquaculture and hence strains of fish that are resilient and adaptable to stress need to be developed. In teleosts, cortisol is considered the primary stress hormone and an increase in its concentration corresponds to its response to stress. The objective of the study was to assess if cortisol responsiveness to stress in channel catfish, (Ictalurus punctatus) influences susceptibility to (Edwardsiella ictaluri) under controlled conditions. Six month old channel catfish fingerlings were subjected to standardized hypoxia stress (1.8 ppm of dissolved oxygen) to classify them as either ‘low responders (LR)’ or ‘high responders (HR)’ based on their plasma cortisol concentration. HR and LR fish were held either in individual or co-cultured in 80 L aquaria and were challenged with virulent E. ictaluri by an in situ bath immersion to evaluate their susceptibility to the pathogen. At the end of the 21 day challenge, mean percent mortality of LR fish was lower than the mean percent mortality of the HR fish. An increase in susceptibility of HR fish to E. ictaluri may be the result of their higher responsiveness to standardized stress. Hence, the results of the present study suggest LR fish may be resilient and adaptable to stressful conditions.