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Title: EFFECT OF BUFFERED AND UNBUFFERED TRICAINE METHANESULFONATE (MS-222) AT DIFFERENT CONCENTRATIONS ON THE STRESS RESPONSES OF CHANNEL CATFISH (ICTALURUS PUNCTATUS RAFINESQUE)

Author
item Welker, Thomas
item Lim, Chhorn
item Aksoy, Mediha
item Klesius, Phillip

Submitted to: Journal of Applied Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2006
Publication Date: 9/20/2007
Citation: Welker, T.L., Lim, C.E., Aksoy, M., Klesius, P.H. 2007. Effect of buffered and unbuffered tricaine methanesulfonate (ms-222) at different concentrations on the stress responses of channel catfish (Ictalurus punctatus Rafinesque). Journal of Applied Aquaculture. 19(3)pgs. 1-18.

Interpretive Summary: Practices that require fish handling are a common source of stress in aquaculture operations and fisheries research. To address this problem, fish handlers have employed the use of anesthetics, added to water, to immobilize fish, reduce stress levels, and prevent mortality. Tricaine methanesulfonate (MS-222) is the only anesthetic approved by the Food and Drug Administration (FDA) for use with food fish in the United States. MS-222 produces acidic solutions and is known to cause acid-stress in fish by lowering the water pH. To overcome this problem, buffering or neutralizing the water acidity has been practiced. However, MS-222 is known to produce stress in fish even in buffered solutions. We evaluated the effects of MS-222 (buffered and unbuffered with sodium bicarbonate) on anesthetization efficacy and stress responses of juvenile channel catfish. Fish were sampled before, after 10 min exposure to one of four exposure concentrations of MS-222 (0, 90, 120, 180 mg/L), and after recovery in aquaria (30, 60, 120, 240, 480 min post-exposure) to measure blood stress parameters. With increasing MS-222 concentration, there was a significant decrease in pH in unbuffered but not buffered water. As expected, anesthesia induction time was reduced and recovery time was increased as MS-222 exposure concentration increased. Buffering of exposure water had no effect on anesthetization induction or recovery. MS-222 concentration but not buffering or pH had significant effects on the stress responses. Although anesthetization reduced the cortisol response to handling, plasma cortisol concentrations increased with increasing MS-222 concentration regardless of buffering, suggesting an anesthesia effect that was unrelated to MS-222 acidification of exposure water. We determined 90 mg/L MS-222 to be an effective dose for fingerling channel catfish, which provided a moderate rate of anesthesia without significantly exacerbating the stress response to handling.

Technical Abstract: The effects of four concentrations (0, 90, 120, and 180 mg/L) of the anesthetic tricaine methanesulfonate (MS-222) (buffered and unbuffered with sodium bicarbonate) were evaluated on anesthetization efficacy and stress responses of juvenile channel catfish (Ictalurus punctatus Rafinesque). Buffered MS-222 treatments were neutralized with sodium bicarbonate to bring the pH of exposure water to that of rearing water (pH ~7.0). Fish were exposed to MS-222 treatments for 10 min after reaching stage 3 anesthetization or for 10 min only for the control treatment (0 mg/L MS-222). Blood was sampled from fish at the end of the 10 min exposure period and after 30, 60, 120, 240, and 480 min recovery in aquaria to measure blood glucose and plasma cortisol and osmolality. With increasing MS-222 concentration, there were significant decreases in pH (7.0 to 5.7) and increases in osmolality (40 to 63 mOsm/kg) in unbuffered water, while osmolality (43 to 69 mOsm/kg) but not pH were significantly different among the treatments in buffered water. As expected, anesthesia induction time was reduced and recovery time was increased as MS-222 exposure concentration increased. Buffering of exposure water had no effect on anesthetization induction or recovery. Sampling time and MS-222 concentration, but not buffering or pH, had significant effects on the stress responses. Although anesthetization reduced the cortisol response to handling, plasma cortisol concentrations increased with increasing MS-222 concentration regardless of buffering, suggesting an anesthesia effect that was unrelated to MS-222 acidification of exposure water. The blood glucose response also increased with increasing MS-222 concentration; however, glucose concentrations, unlike cortisol, were lowest in handled, non-anesthetized fish, which suggests that stress-related hyperglycemia may not be solely under cortisol control. We determined 90 mg/L MS-222 to be an effective dose for fingerling channel catfish, which provided a moderate rate of anesthesia without significantly exacerbating the cortisol response to handling.