Survival of cool and warm freshwater fish following chloramine-T exposure

Chloramine-T is presently available in the USA to control mortalities associated with bacterial gill disease or external columnaris only through an Investigational New Animal Drug Permit authorized by the US Food and Drug Administration (FDA). Its US approval hinges on FDA's acceptance of several key data, including those describing animal safety. Chloramine-T is presently applied in US aquaculture, by permit only, once daily on consecutive or alternate days for 1??h at 10 to 20??mg/L to control mortalities associated with bacterial gill disease or external columnaris. Our objective was to determine the safety of chloramine-T bath exposures at multiples of the proposed maximum treatment concentration (i.e., 0, 20, 60, 100, and 200??mg/L) administered on four consecutive days at 20????C to lake sturgeon Acipenser fulvescens, northern pike Esox lucius, and walleye Sander vitreum, or at 27????C to channel catfish Ictalurus punctatus, and largemouth bass Micropterus salmoides. All fish were tested as five to eight week old fry except for walleye and channel catfish which were tested as both fry and fingerling (fingerlings were at least four weeks older than the fry tested). Walleye and channel catfish were selected to evaluate the effects of life stage (fry vs. fingerling), temperature (walleye - 15, 20, or 25????C; channel catfish - 22, 27, or 32????C), exposure duration (60 vs. 180??min), and water chemistry (walleye only - reconstituted soft water vs. well water). Except for channel catfish fry, survival was significantly reduced only when fish were treated at 100 or 200??mg/L. Channel catfish fry survival was significantly reduced when exposed at 60??mg/L for 180??min at 27????C. Based on our mortality data, chloramine-T administered once daily for 60??min on four consecutive days at concentrations of up to 20??mg/L is not likely to adversely affect survival of cool or warmwater fish cultured in freshwater. Crown Copyright ?? 2007.