Accumulation and clearance of the anaesthetics clove oil and AQUI-S™ from the edible tissue of silver perch (Bidyanus bidyanus)

The accumulation and clearance of the main component of the fish anaesthetic clove oil (eugenol), from the edible tissue of silver perch (Bidyanus bidyanus) were examined. Fish were sampled from a commercial silver perch farm to determine the efficiency of commonly employed purging practices in clearing fish treated with this product. After initial exposure to clove oil at harvest, fish were purged for 48 h. This proved sufficient to clear eugenol to below detectable levels. However, following an additional application of clove oil for transport and subsequent purging for I week, fish had a mean of 0.32 mg kg(-1) of eugenol in their tissues. This indicates that repeated doses of clove oil may lead to fish having a decreased capacity to completely clear their tissue of residue. The effect of temperature and treatment upon the accumulation and clearance of eugenol (or isoeugenol) was also examined. Fish were exposed to 50 mg L-1 clove oil, 15 mg L-1 clove oil, 15 mg l(-1) AQUI-S-TM, or to no anaesthetic, in water that was either heated or at ambient temperature. At the high dose of clove oil, more eugenol was accumulated in heated water but at the low dose, temperature did not influence the amount of eugenol accumulated. Fish treated with AQUI-S-TM accumulated more iso-eugenol at ambient temperature than they did in the heated water. Silver perch were generally able to clear their flesh of residue more rapidly at the higher temperature, although regardless of treatment, residue was cleared to below detectable levels in all fish after 48 h. (C) 2004 Elsevier B.V. All rights reserved.