The effects of very short pulse-exposures with the synthetic pyrethroid esfenvalerate on survival and growth of larval crimson-spotted rainbow fish (Melanotaenia fluviatilis) were investigated in two series of experiments. Larval rainbow fish [2, 7, or 14 days (d) old] were pulse-exposed to esfenvalerate (30-700 ng L-1) for 1 h and then transferred to growth chambers where survival and growth were monitored for periods of 7-28 d, depending on the experimental protocol. Mortality was found to be a more sensitive indicator of pesticide effects than growth. Effects on growth were only observed in treatments where there was significant pesticide-related mortality. In these treatments, rainbow fish larvae were larger than control larvae. However, as increase in growth was always associated with mortality, it was not possible to determine if this was a direct effect of the pesticide or an artefact of density-dependent interactions within test populations. There was some evidence to suggest that pulse-exposure with esfenvalerate at an early age may cause subtle long-term detrimental effects to growth of larval rainbow fish. Dry weight and condition (length/weight) were more sensitive indicators of treatment effect than total length. Esfenvalerate was extremely toxic to larval fish, with 1 h pulse-exposures as low as 60 ng L-1 causing significant mortality. Newly hatched larvae were more sensitive to esfenvalerate than animals that were 14 d old. The effects of esfenvalerate on 7-d-old larvae could not be determined because of high control mortality. Larvae of this age undergo transition from endogenous to exogenous feeding and may be more sensitive to handling stress. The lowest 1 h pulse-exposure esfenvalerate no observed effect concentration and lowest observed effect concentration were <60 and 60 ng L-1 respectively, based on 2-d-old larval mortality.
ASJC Scopus subject areas
- Health, Toxicology and Mutagenesis
- Water Science and Technology