| Summary: | Historical aerial applications of the insecticide Matacil 1.8D provide an opportunity to look for potential effects of the endocrine disrupting compound 4-nonyiphel (4-NP) on Atlantic salmon (Sdlmo slar) populations. Matacil 1.8D contained the carbamate insecticide aminocarb, with 4-NP as primary solvent Between 1975 and 1985 Matacil 1.8D was applied to forests in Atlantic Canada to control damage from the spruce budworm (Cboristonerafumiferana). After spraying, estimated concentrations of 4-NP in water fell within a range in which estrogenic effects might be anticipated. The spraying coincided with final stages of smolt development in salmon. Salmon catch data were evaluated considering effects on survival of the smolt stage. There wa siificant negative. r ionship between the returns of salmo and the proportion of tributaries sprayed within. the Restigoudhe River drainage basin in 1977. There was also a broader event of unusually heavy salmon smolt mortality in 1977, which contains a significant relationship indicating that where Matacil 1.8D spraying occurred, the smolt mortality increased. For 16 rivers exposed to spraying between 1973 and 1990, a significant proportion (0.005) of the lowest salmon catches coincided with Matacil 1.8D spraying. A decline coinciding with the use of Matacil 1.8D1 was also apparent in: blueback herring (Alsa aestiva) catches
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