Modeling the Effects of Turbidity on Age-0 Yellow Perch (Perca Flavescens) in the Western Basin of Lake Erie PDF Download

Author: Nathan F. Manning
Publisher:
ISBN:
Category : Algal blooms
Languages : en
Pages : 121

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Book Description
Understanding the effects of turbidity on visually foraging fish species can be difficult due to the dynamic nature of sediment plumes and algal blooms in productive aquatic systems. In this dissertation, I examined the effects of turbidity type, timing and intensity on age-0 yellow perch (Perca flavescens). To accomplish this, I used ArcGIS and generalized additive models (GAMs), individual based models (IBMs) and the Soil and Water Assessment Tool (SWAT). The initial study utilized ArcGIS and GAMs to determine the relationship between turbidity and size and abundance in August of age-0 yellow perch. The GAMs presented in this dissertation show that water clarity (in this case used as a surrogate for turbidity) is an important environmental factor in determining the length and abundances of age-0 yellow perch in western Lake Erie. The results suggest that the influence of water clarity produces a distinct separation of areas of higher growth potential and areas of higher abundances in the western basin. While this division may be attributable to a number of mechanisms, including size dependent predation risk, foraging ability, and density dependent growth, the effects of water clarity, and in particular the negative effects of algal blooms, on foraging ability are of particular interest in Lake Erie. For the second step in this research I used laboratory derived feeding rates in a range of turbidity types and intensities to inform IBMs that varied the timing, type and intensity of turbidity to determine the effects of changes to a systems turbidity regime on growth and starvation mortality. The results of the model suggest that the timing and persistence of sediment plumes and algal blooms can drastically alter the growth potential and starvation mortality of a yellow perch cohort. The timing of sediment plumes in particular can have significant consequences to the growth, and ultimate success of a yellow perch population. High sediment turbidity early in the season, prior to the ontogenetic shift, can be potentially beneficial to fish growth. However, if high sediment turbidity conditions persist, they can slow growth and increase the starvation mortality of juvenile fish. In contrast, algal blooms, no matter when during the season they occur. In the final study, I used SWAT and IBM models to link watershed level changes in land use and climate to potential changes in age-0 yellow perch growth in the Maumee Bay, Lake Erie. Changes in land-use, either through increased urbanization, or changing agricultural practices, primarily affect fish growth through the alteration in the timing and intensity of sediment plumes. However, it may be that, at least in the Maumee River watershed, the negative effects have reach a plateau of sorts, with significant reductions in fish growth requiring changes to the watershed that are unlikely in the near future due to economic and infrastructure restrictions. Climate change, on the other hand, could potentially compound the effects of current land use practices through the promotion of algal blooms due to increased water temperatures, thus further reducing fish growth. The results of these three studies show that the effects of turbidty on age-0 yellow perch are dynamic, and can vary significantly depending on a number of different factors. The results of this research help to illuminate these complex interactions, and provide a warning about potential consequences due to anthropogenic alterations of an aquatic system's turbidity regime.