| Summary: | The growth and survival of larval fish are influenced by a suite of biotic and abiotic factors. Because aquatic systems are characterized by strong heterogeneity in biotic and abiotic conditions along a vertical gradient, the vertical distribution of larval fish can profoundly affect their growth and survival. In large systems such as the Great Lakes, vertical distribution patterns can also influence dispersal and ultimately settlement events. Despite its importance during early life stages, little is known about vertical distribution patterns of larval fish in Lake Michigan. My objective was to describe the vertical distribution of the larval fish community in pelagic waters of Lake Michigan and determine which biotic and abiotic factors most strongly influence their vertical distribution. Additionally with controlled laboratory experiments I sought to determine how two of these factors (light intensity and prey density) influence the foraging success of a fish species with a pelagic larval stage, yellow perch (Perca flavescens). To determine vertical distribution, the upper 27 meters of the water column was divided into six discrete depth bins where larval fish and zooplankton were collected, in addition to recording light intensity, and temperature. Larval fish from 5 species were collected during the study: alewife (Alosa pseudoharengus), bloater (Coregonus hoyi), burbot (Lota lota), deepwater sculpin (Myoxocephalus thompsonii), and yellow perch (Perca flavecens). Among the five species, I observed three general patterns of larval distribution. Alewife and yellow perch larvae were restricted to the epilimnion, deepwater sculpin were restricted to the hypolimnion, and bloater and burbot were collected throughout the upper 27 m of the water column, and exhibited diel differences in distribution patterns. My analysis elucidates the importance of abiotic over biotic factors in the structuring of larval fish vertical distribution in Lake Michigan, as temperature was shown to influence the distribution of most ...
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