Larval Yellow Perch Capitalize on a Finite Resource: Potential Negative Effects for Early-Hatched Bluegill Larvae

Our objective was to determine if larval yellow perch abundance was related to Daphnia spp. abundance.  If larval yellow perch abundance was related to Daphnia spp. densities, we then wanted to determine if this reduced prey availability and would limit growth of earlier hatched bluegill (e.g., first weekly cohort to emerge).  We measured chlorophyll-a, Daphnia spp., and larval yellow perch and bluegill densities during 2004-2009 in Pelican Lake, Nebraska.  Larval bluegill daily growth rates were determined by aging saggital otoliths.  Daphnia spp. densities often declined within 2-3 weeks of peak larval yellow perch abundance and remained low throughout summer months in all years except during 2005, which corresponded with the lowest larval yellow perch abundance observed during all years examined.  In 2004, yellow perch positively selected Daphnia spp.  During 2005, Daphnia spp. was available to early hatched bluegill larvae and was positively selected in the diets, which also corresponded to the highest growth rates for early hatched bluegill in all years examined.  These results suggest that larval yellow perch may influence Daphnia spp. densities through predation, thereby indirectly reducing prey availability and daily growth rates of early hatched bluegill, which could ultimately affect bluegill recruitment.