Interactions Between Age-0 Yellow Perch and Bluegill and Elucidating Factors Influencing Their Subserquent Recruitment in Nebraska Sandhill Lakes

A knowledge gap limits our ability to predict recruitment patterns for bluegill (Lepomis macrochirus) and yellow perch (Perca flavescens) despite extensive study. Recruitment patterns in yellow perch and bluegill populations are typically divergent (yellow perch = less consistent; bluegill = more consistent) and recruitment processes could also vary (i.e., abiotic = yellow perch vs. biotic = bluegill). My objective was to test these hypotheses in multiple Nebraska Sandhill lakes, with extensive focus on one lake during 9 years, by sampling multiple early life stages to examine recruitment patterns and processes involved. Overall, biotic factors more prominently affected growth and survival of bluegill and yellow perch during early life stages. Substantial inter- and intraspecific interaction between and within bluegill and yellow perch populations influenced growth and survival of both species, often switching direction and magnitude across life stages. Age-0 yellow perch negatively influenced growth and potentially survival of early-hatched larval bluegill by outcompeting bluegill for zooplankton resources. In contrast, age-0 bluegill negatively affected age-0 yellow perch growth rates later in the growing season by outcompeting yellow perch for macroinvertebrate resources. Larval bluegill growth was also related to increased water transparency (early-and-late-hatched) and temperature (early-hatched). Early-hatched (May-June) bluegill survival was positively related to age-0 bluegill relative abundance; late-hatched (July- August) bluegill survival was positively related to preferred available zooplankton biomass. Late-hatched larval bluegill consistently recruited to the fall population, but few early-hatched larval bluegill survived to fall each year. Larval yellow perch growth and mortality were largely regulated by hatching date, temperature, and zooplankton availability. Young (5-14 d old) larval yellow perch growth was positively related to temperature and hatch date; old (15-24 d old) larval yellow perch growth was positively related to water temperature and age-0 yellow perch densities, but negatively related to available preferred zooplankton. Mortality was inversely related to total zooplankton biomass and positively related to water temperature. Study results indicated the potential for substantial intra- and interspecific interactions for prey resources; in addition to predation, competition for food availability in these lakes may help explain recruitment variability for bluegill and yellow perch populations that was otherwise obscured. Long-term, in-depth analyses provided information otherwise difficult to obtain for disentangling such complex processes as fish recruitment