Energy reserves mobilization in the yellow eel as herbicide exposure effect

Thiobencarb and propanil are two of the most extensive used herbicides worldwide in rice cultivation. Especially scanty is the available information regarding the effect of herbicides on fish energy resources. In the present study, the effect of sublethal exposure to these herbicides on the energy reserves of juvenile eel Anguilla anguilla was compared. Eels were exposed to 72 h to the herbicide thiobencarb (0.22 mg L−1) or Propanil (0.63 mg L−1), and allowed to recover in clean water (144 h). Caloric content was determined in liver and skeletal muscle. Fish exposed to thiobencarb rapidly mobilized energy. Reserves from liver were depleted (21%) compared to control values (2.50 kcal g−1) at 2 h, whereas in muscle diminished between 12 and 72 h (35%) (control value 0.89 kcal g−1). Energy reserves from liver normalized after 144 h in water while in the skeletal muscle were still depleted (24%). Major harmful effects were induced by propanil. Caloric content in liver diminished from the first hours (depletion of 70% at 48 h exposure) and in skeletal muscle a 60% (72 h). At the end of the recovery period, energy reserves in pre-exposed eels represented less than 50% compared to control animals. The study indicated that thiobencarb and propanil would constitute a great risk to animals inhabiting freshwater bodies nearby fields of application. Judging from the results, herbicides resulted toxic enough to mobilize fish energy stores. On the other hand, a period of six days in herbicide-free water was not enough time to allow fish to restore energy budgets.