Rapid uptake of [5-3H]MAB1a by bluegill was observed
under flow-through aqueous conditions,
attaining steady-state concentration by about 21 and 10 days,
respectively, in whole fish and viscera.
Uptake by fillet was, by comparison, much lower, and steady state
was not attained by 28 days.
Residue levels on the final exposure day (i.e., day 28) were 90,
40, and 128 μg/kg, respectively, in
whole fish, fillet, and viscera. Following 14 days of depuration,
these residue levels all declined by
about 90%. The steady-state bioconcentration factors for whole
fish, fillet, and viscera were 80, 30,
and 116, respectively, indicating that emamectin benzoate will neither
bioconcentrate in individual
aquatic organisms nor biomagnify in the food chain. Analysis of
28-day-exposed fish by HPLC
showed that the only significant metabolite was the N-demethylated
derivative, comprising about
14% and 9%, respectively, of total residues in fillet and viscera,
while parent emamectin benzoate
was about 63% and 49%, respectively.
Keywords: Avermectin; bioaccumulation; bioconcentration; HPLC;
biomagnification; bluegill
sunfish; emamectin benzoate; metabolism