Lake Ontario and its tributaries are no longer the ecosystems they were when native Atlantic salmon were abundant; they are not even the ecosystems they were when Atlantic salmon were finally eliminated from the lake. Over two hundred years of settlement has had continual major impacts on all aspects of the lake and tributaries’ environment and ecology. Other native fish species, particularly lake trout, lake herring, and lake sturgeon, have declined, and naturalized Pacific salmon are now at the top of the aquatic food web, and invasive alewife and rainbow smelt are the common fish prey base. Sea lamprey have invaded the lake but are controlled through barriers and lampricide applications; recently round gobies have exploded into Lake Ontario, but their effects are still under investigation. Generally their impact on the ecosystem is expected to be negative. Zebra and quagga mussels have also established themselves in the lake, and have had profound impacts on the food web. More information on these and other invasive species can be found at the Invading Species Awareness Program’s web site.
The tributaries have also undergone extensive physical changes since European settlement in the Great Lakes basin. The initial environmental changes that resulted from clearing the land for agriculture and building mills and dams on the streams were among the primary causes of the extirpation of Atlantic salmon in Lake Ontario. Since then much of the region’s land use has changed to industry and housing, which of themselves have not improved stream quality, and have added further channelization, erosion, and point source pollution of both heat and chemicals. However, in the latter half of the 20th century stream stewardship gained momentum, and many tributaries of Lake Ontario are on the way to recovery thanks to the efforts of local landowners and conservationists. The recovery of Lake Ontario’s tributaries prompted both New York and Ontario to reconsider the potential return of Atlantic salmon in the 1980’s.
The New York State Department of Environmental Conservation (NYSDEC) began a small Atlantic salmon recovery program in 1983 to restore a self-sustaining population in Lake Ontario. The specific goals were modest, and while growth rates were excellent and a small recreational fishery developed, natural reproduction in the returning adults consistently failed. By 1990 the course of the program changed from a small recovery program to a larger scale put-grow-take trophy sport fishery. However, recently New York has again expressed interest in restoring self-sustaining populations to their side of Lake Ontario.
In 1987, the Ministry of Natural Resources and Forestry (MNRF) began its own small stocking program to research the feasibility of restoring Atlantic salmon to Lake Ontario, with hoped-for side benefits of establishing a self-sustaining population in at least one tributary on the Canadian side of Lake Ontario, and to provide a sport fishery based on stocking and a naturally reproducing population. When initial returns were lower than expected, MNRF developed the first formal Recovery Strategy in 1995 to research stocking Atlantic salmon in Lake Ontario. The research program would use experimental stockings of approximately 150,000 to 200,000 fry (young fish) per year to study the factors believed to be most important for developing self-sustaining populations. Research areas included embryo survival and rearing success, juvenile survival, and adult salmon habitat selection and movement behaviour. Benchmarks were set for a 5-20 year timeline, and a review in 2003 considered the initial research phase to have successfully met the short-term benchmarks. With this knowledge in hand, it is now time to begin full-scale recovery efforts.