ON - Representatives from the five fisheries agencies on Lake Erie don't want changes to phosphorus target levels in Lake Erie until a more thorough scientific review of the situation can be undertaken. Fisheries managers noted that the significant reductions in phosphorus have benefited Lake Erie but warned that further reductions could have a serious negative impact on the fish stocks in the lake. They also stated that it would be irresponsible to advocate a position of adding phosphorus to the lake to increase fish production until there is clear scientific evidence that this would be an appropriate strategy. The Committee strongly encouraged all relevant agencies to commit resources and to work together to undertake a scientific review of phosphorus management on Lake Erie. Phosphorus is the principle nutrient controlling primary productivity in freshwater ecosystems.
Primary productivity has a direct and major influence on fish production.
Too much phosphorus can lead to excessive amounts of algae while too little phosphorus can reduce the capability of a lake to support large amounts of fish. In 1972, Canada and the United States agreed to work together under the terms of the Great Lakes Water Quality Agreement to reduce phosphorus loadings in Lake Erie. The recent invasion of zebra and quagga mussels into Lake Erie have also caused a pronounced change in the lake's food web. The mussels filter phytoplankton and zooplankton from the water and are reducing the food supply for planktivorous fish and juvenile fish. Quagga mussels are linked to a decline in a key food organism for fish in the deep waters of the eastern basin, while in nearshore areas of the lake quagga and zebra mussels have been associated with greater productivity of bottom-living organisms which are potential food for some species of fish.