Stomach content of blue catfish (Ictalurus furcatus). Stomach samples of blue catfish

Understanding diet helps researchers more accurately assess the health, survivorship, growth, and stability of an invasive species, as well as their effect on native populations. With fish, it is important to develop techniques capable of identifying multiple prey species from fish stomach contents. We used a multi-locus metabarcoding approach to identify fish and invertebrate prey in stomach samples of blue catfish (Ictalurus furcatus) from two sites in Maryland. The mitochondrial 12S (mt12S) and mitochondrial 16S (mt16S) gene regions were sequenced and compared. First, a mock sample for each gene region was created with pooled PCR product of known fish species and quantities were used to determine efficacy of the amplicon. Results varied between gene regions analyzed. Then, when using the mt12S primers, next-generation sequencing determined that nine fish species were found at levels >1% of the diet of blue catfish. The most common species included both yellow perch (Perca flavescens) and common carp (Cyprinus carpio). Our mt16S gene region analyses found 10 fish species >1% of the diet, which primarily included spinycheek crayfish (Orconectes limosus), alewife (Alosa pseudoharengus) and yellow perch. Partially digested eggs were identified via next-generation sequencing as yellow perch in two of the stomach samples, and a TaqMan® qPCR assay was developed to more economically identify egg species in the future. The yellow perch-specific TaqMan® qPCR assay was tested using primers that were developed to detect a 154-bp amplicon in the mitochondrial control region. Consumption of yellow perch eggs indicates that blue catfish could potentially negatively impact young-of-year recruitment of this native sportfish. Analyses of two gene regions helped confirm major prey of the fish sampled and allowed identification of fish species that weren’t available in the database for both gene regions. We conclude the mitochondrial ribosomal marker-based next-generation sequencing method is useful in determining the prey of fish species.