Plastic Responses to Altered Selection Regimes in Larval Lake sturgeon

Human disturbances have altered natural environments and disrupted selection regimes across all biological scales. Organisms likely respond to anthropogenic changes through modifications in genotypic composition and through phenotypic and/or behavioral plasticity. We tested the hypothesis that plasticity in larval behavior (timing and distance of larval dispersal), phenotype (body size, shape) and physiology (yolk sac utilization) would vary among families for a fish species within an anthropogenically-modified habitat. Additionally, we predicted this developmental plasticity would be mediated by the environmental conditions experienced during each ontogenetic stage. The experiment was conducted using a well-studied population of lake sturgeon (Acipenser fulvescens), a long-lived exploited species of conservation concern in the Black River drainage of Michigan. Experiments were conducted within the stream where fertilized eggs from several families were allowed to incubate in multiple thermal and flow regimes at varying spawning locations downstream of the Kleber Dam. Upon hatch, individuals were photographed to quantify phenotype and time to hatch was compared between families across the various sites. To mimic dam-mediated flow conditions experienced during embryogenesis, fertilized eggs from multiple families were exposed to one of three flow treatments (high, low, and variable) within our stream-side facility. Upon hatch, individuals were photographed to quantify phenotype and placed in individual chambers within raceways to quantify growth and the timing of transition between ontogenetic stages. The implication of results quantifying variability among families and across ontogenetic stages is discussed relative to potential long-term consequences of anthropogenically modified environments altering population phenotypic distributions, recruitment, and genetic composition.