Likely Cause Found for Lakes Trout Reproduction Failure in the Great
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.
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."