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AUTHORS: Mitchell Zischke, Department of Forestry and Natural Resources, Purdue University, Illinois-Indiana Sea Grant; Lee Henebry, Department of Forestry and Natural Resources, Purdue University; Andrew Ramirez, Department of Biological Sciences, Purdue University; Sara Andree, Department of Natural Resources and Environmental Sciences, University of Illinois; Tomas Höök, Department of Forestry and Natural Resources, Purdue University, Illinois-Indiana Sea Grant
ABSTRACT: Diel horizontal migration (DHM) has been less studied than diel vertical migration, but may be equally important in structuring food webs, particularly in systems that have productivity gradients from nearshore to offshore areas. One such system is Lake Michigan, which has relatively productive nearshore areas and less productive offshore areas. This gradient has been exacerbated by reduced nutrient loading and establishment of invasive dreissenid mussels. The objective of our study was to explore whether fishes use DHM to access productive nearshore areas in Lake Michigan. We collected fish at dawn, during the day, and at night using micromesh gillnets set parallel to the shore. We noted the direction that fish entered the gillnet assuming that this was indicative of their direction of travel. Mean catch rates of Alewife (Alosa pseudoharengus) and Yellow Perch (Perca flavescens) were highest at dawn and night, respectively; however, there was no difference between fish swimming inshore and offshore. As expected for visual feeding fishes, both Alewife and Yellow Perch had fuller stomachs during the day than at other times. Our preliminary data suggests possible DHM by some fish species in Lake Michigan and future research will investigate the timing of DHM and quantify associated food utilization.
