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The decline of lake trout in the Great Lakes prior to 1960 had large regional economic impacts. It was thought to have been caused by overfishing and the introduction of an exotic species, the lamprey. For 3 decades since the fisheries collapsed, Great Lakes fisheries agencies have sought to re-establish successful lake trout breeding populations. The lamprey was brought under control and all commercial fishing other than tribal was halted. The re-establishment effort failed nonetheless in 4 of the 5 lakes. New Results reported by Dr. Richard Peterson now show that the re-establishment failures were due to dioxin poisoning: lake trout fry experience 100% mortality at 100 parts per trillion dioxin, and that mortality is evident at concentrations as low as 30 ppt. According to Peterson: "Our data suggest that dioxins and related chemicals may have contributed to the extinction of lake trout in Lake Ontario prior to 1960 and to the recruitment failure of stocked lake trout since then. But the good news is that declining levels of these contaminants and signs of general ecosystem recovery suggest that significant recruitment of lake trout through natural reproduction may start occurring in Lake Ontario and the other Great Lakes in the near future." |
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