Barcoding PCR primers detect larval lake sturgeon ( Acipenser fulvescens ) in diets of piscine predators

Population levels of recruitment are often affected by high rates of mortality during early life stages. Lake sturgeon ( Acipenser fulvescens ), a regionally threatened species, experiences high rates of mortality during the larval stage, partially due to predation. The objective of this study was to quantify and compare relative rates of larval sturgeon predation by piscine predators in the upper Black River (Cheboygan County, MI, USA). A molecular barcoding assay was developed using lake sturgeon-specific primers that amplify a region of mitochondrial DNA cytochrome oxidase I as an alternative to morphological analysis of gastrointestinal (GI) contents to quantify the presence or absence of larval fish collected from potential fish predators (353 specimens, 17 potential predator species). The assay was verified to be sturgeon-specific and sufficiently sensitive to amplify the low quantities of degraded DNA in GI samples. Lake sturgeon DNA was identified in 26 of 353 predator diet samples (7.34%) in 9 of 17 potential predator fish species present. There was a significant positive correlation between the numbers of predators that had consumed larval lake sturgeon and the number of samples from a predator species analyzed. No relationship between predation level and habitat type (sand or gravel substrate) was observed, though predator community composition varied between habitats. Genetic assays as described here can be used to investigate predator–prey dynamics affecting species of conservation interest during important life stages that may otherwise be under-represented in diet studies that rely solely on morphological analysis.