Author
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Small, Brian |
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Submitted to: Book of Abstracts World Aquaculture Society
Publication Type: Abstract Only Publication Acceptance Date: 11/25/2003 Publication Date: 3/1/2004 Citation: Small, B.C. 2004. Effect of aqui-s sedation on the stress response of channel catfish exposed to three environmental stressors. Aquaculture 2004, Honolulu, HI. p. 549. Interpretive Summary: Technical Abstract: Anesthetics are commonly used in aquacultural management procedures to ease handling and reduce fish stress. In addition to preventing physical injury, certain anesthetics reduce or block activation of the hypothalamo-pituitary-interrenal (HPI) axis associated with handling stressors. Failure to suppress activation of the HPI axis results in a release of cortisol which in turn causes various physiological responses, including affecting energy balance. Response to environmental stressors during harvesting has been shown to have detrimental effects on fish health and fillet quality. A relatively new fish anesthetic, AQUI-S has foodfish approval in Australia, Chile and New Zealand with a no withholding period, and has been used for rested (low stress) harvesting of salmonids. Catfish harvesting and transport cause elevated levels of circulating cortisol and glucose as a result of handling and poor water quality. Sedatives with no withdrawal time, such as AQUI-S, may prove to be useful tools for managing fish stress during handling and transportation. We examined the effect of AQUI-S sedation (5 ppm) during crowding, low dissolved oxygen, and ammonia stress on channel catfish stress indices. Plasma cortisol, glucose, and lactate concentrations were used to determine the effect of AQUI-S sedation when compared to two controls. The positive control (PC) for each treatment was no sedation, and the negative control (NC) was sedation with metomidate hydrochloride (1.5 ppm). Metomidate has been shown to effectively block cortisol synthesis and release in catfish. Fish were acclimated to rearing tanks 1-wk prior to starting the experiment, and were not moved during treatment. During sampling, fish were rapidly and simultaneously bled without further anesthetic. AQUI-S sedated catfish had 65% lower (P<0.05) cortisol levels than PC fish following a 15-min crowding stress. Glucose and lactate increased due to crowding, and were not suppressed by either AQUI-S or metomidate (NC). Fish exposed to high ammonia for 24-h, had elevated (P<0.05) cortisol levels in PC and AQUI-S treatment groups. Ammonia did not affect plasma glucose or lactate levels. The highest stress response for all three indices was obtained following a 30-min low oxygen exposure. Glucose levels increased in all three treatments; however, sedation with AQUI-S significantly suppressed the cortisol and lactate response by 75 and 25%, respectively, compared to PC fish. As expected, cortisol levels in NC fish were below detection limits for all stress treatments. As a sedative, AQUI-S has suppressive effects on catfish cortisol levels in circulation during crowding and low oxygen conditions, and reduces the lactate response to low oxygen conditions. These results suggest AQUI-S could be a useful tool during catfish harvesting and transport, potentially improving fish health and fillet quality. |
