Intergenerational Contingent Structure in White Perch (Morone americana) within the Hudson River Estuary

Partial migration, the presence of multiple migratory groups (contingents) within the same population, is likely common in marine and estuarine fishes. We evaluated the occurrence, potential causes and carryover effects of partial migration in white perch (Morone americana) within the Hudson River Estuary. Juvenile white perch were collected by seine in fall 2013, and adults were sampled via gillnet during the spring of 2014. Fish were assigned to resident or migratory contingents based on strontium:calcium profiles within the first annulus of the otolith, while a subsample of adults was further examined to test whether juvenile migratory behaviors persisted into adulthood. Within the juvenile sample, analyses of otolith microstructure and length back-calculations revealed differences in hatch dates, larval size-at-age and late-juvenile growth rates between contingents. For the adult sample, von Bertalanffy growth models were constructed for each contingent to examine carryover effects of partial migration on population dynamics. Finally, contingent proportions for each year class were related to corresponding temperature and freshwater flow data from the winter and spring to assess the potential influence of environmental variables on contingent structure.