Influence of Total Phosphorus Variability on the Fishery Resources in the Bay of Quinte

The Bay of Quinte, an Area of Concern (AOC) in Lake Ontario, Canada, was listed due to eutrophication. Since 1978, phosphorus abatement efforts have increased water clarity and decreased total phosphorus (TP) concentrations. Recent global environmental changes and species invasion (i.e., dreissenid) have further changed the ecosystem, which can influence the available energy for fishes and affect fishery restoration targets in the Bay. With these altered ecological conditions, it is important to understand how further reductions under a phosphorus management program will influence the maintenance of healthy fish populations. We assessed how fish biomass varies along TP gradients paired with zooplankton, surface water temperature and dreissenid invasion in the Bay of Quinte over 41 years (1972-2013). Positive rates of change in fish biomass with TP gradients were characterized during the initial years, but switched to weakly negative after the late 1980s. With respect to timing of events, the biomass of piscivores, percids, walleye and freshwater drum decreased during the pre-TP control period, increased post-TP control followed by a drop after the dreissenid invasion. In general, we found a negative response to dreissenid invasion by fish communities except sunfishes. Our analysis also shows how proposed TP reduction may affect fish biomass.