Use of individual based models to explore the effects of turbidity on early life history traits of yellow perch

Turbidity is an environmental factor that can affect the foraging and hence growth and survival of age-0 yellow perch. Western Lake Erie is a turbid system, where recruitment is positively related to Maumee River discharge, a major source of suspended solids and nutrients. Laboratory experiments showed reduced larval feeding rates with increasing phytoplankton-derived turbidity and a significantly lower juvenile feeding rate with phytoplankton-derived and sediment -derived turbidity. Previous modeling exercises suggest that turbidity may be the most important environmental factor in determining length and abundances in August of age-0 yellow perch.  We modified published Individual Based Models (IBM) (Letcher et al. 1996, Fulford et al. 2006) to create a model system that explicitly accounts for turbidity intensity and type, and allows for the examination of its effects on growth, predator avoidance, and the timing of the ontogenic shift from pelagic to demersal habitats. We show that changes in turbidity type and intensity alter feeding and predator avoidance ability at multiple life stages, for example: increased sediment turbidity in the encounter sub-models significantly reduced the mass increase per day/ per juvenile but had very little effect on larvae, and increased turbidity significantly decreased predator mortality rates in both groups.