Effects of naled, synergized, and non-synergized resmethrin on the swimming performance of young trout

The effects of 2 commercial formulations of naled and resmethrin insecticides (Dibrom and Scourge, respectively), commonly used in New York state, U.S.A., on the swimming performance of young brook trout (Salvelinus fontinalis) were investigated. Piperonyl butoxide -synergized and non-synergized formulations of resmethrin were used. Test concentrations for naled were 24 and 46 ug per litre during the first week and 91 ug per litre during the following week. Test concentrations for resmethrin were 1.6 and 3.2 ug per litre during week 1 and 6.3 ug per litre during week 2. Trout were exposed to the insecticides for 6 h and then swimming stamina was measured. In controls, there was a significant relationship between length and swimming performance. Resmethrin had a greater effect on trout stamina than naled. The synergist piperonyl butoxide greatly increased the effect of resmethrin. Swimming stamina of brook trout decreased significantly when exposed to synergized resmethrin at 3.2 ug per litre. Non-synergized resmethrin only reduced swimming stamina at concentrations of 6.3 ug per litre.