Elimination of malachite green residues from meat of rainbow trout and carp after water-born exposure

Uptake, accumulation and depuration of malachite green (MG) in muscle and skin of rainbow trout and carp were studied. The concentrations of MG and its mayor metabolite leuchomalachite green (LMG) were determined with liquid chromatography coupled with an absorbance and a fluorescence detector. Rainbow trout were exposed to 1 mg l− 1 of MG for 1 and 3 h and to a slightly increased concentration 1.5 mg l− 1 for 1 h. Changing the dose of MG in the bath did not significantly affect the residue levels in rainbow trout, but the duration of the exposure had a major influence. One day after exposure, the rainbow trout that were exposed three times longer contained 3 times more LMG and 4.5 times more MG than the trout in the one-hour bath. The level of MG in rainbow trout quickly fell below the decision limit (CCα) of 0.6 μg kg− 1, while the level of LMG was still greater than 0.5 μg kg− 1 (CCα) at the end of the experiment (289 days after exposure). Carp were exposed to higher concentrations of MG, 2 mg l− 1 for 1 and 3 h, and 4 mg l− 1 for 1 h. Nevertheless, they accumulated less MG than rainbow trout and the elimination of LMG was slower. Because of the low water temperature (11 °C–15 °C), the carp metabolism, and therefore also LMG elimination, were slowed.

► Rainbow trout and carp were exposed to malachite green.
► Exposure time significantly affects the residue levels in meat.
► Small change in dose does not affect the residue levels in meat.
► 289 days after treatment we still detected the residues of LMG in trout.
► Carp exposed to higher dose than trout accumulate less MG and eliminate it slowly.