Spatiotemporal Variation in Size-At-Age of Juvenile Yellow Perch and Effects of Size-Selective Mortality on Year- Class Strength in Lake Michigan

Current estimates of yellow perch recruitment in Lake Michigan are based on the premise that year-class strength is determined prior to the end of the first growing season. However, spatiotemporal variation in size at the end of the first growing season coupled with size-selective mortality throughout the juvenile stage may have a significant influence on recruitment at sexual maturity. Temporal variation in size-at-age and cumulative size-selective mortality were investigated using juvenile yellow perch collected from 2006-2010 in Illinois waters of Lake Michigan, whereas spatial comparison of size-at-age was made using yellow perch collected near Muskegon, MI and Waukegan, IL in 2010. Sagittal otoliths were removed and fish total length was recorded. Otolith microstructure analysis was used to determine age and back-calculate size-at-age. First year overwinter mortality was examined by comparing pre and post winter lengthfrequency distributions. Cumulative mortality was assessed by comparing length distributions and mean length-at-age at initial capture to back-calculated lengths of the same age at a later capture date. This study provides insights into juvenile yellow perch life history and determines that mortality during this life stage has the potential to shape year-class strength.