Improving The Accuracy Of Red Snapper, Lutjanus Campechanus, Diets With The Addition Of DNA Barcoding

It is important to understand energy flow in marine food webs, and one way to do this is through the diet analyses. For most fish diet analyses are difficult, because a large portion (many times > 50%) of stomach contents are unidentified due to advanced states of digestion. Identifying these prey to genus or species could help answer long-standing questions about many important fishery species. We examined the diets of red snapper (Lutjanus campechanus) with traditional stomach content analyses coupled with DNA identification (barcoding) of unidentified fish prey. Fish were collected via hook-and-line or fish trap from randomly selected sites in the Gulf of Mexico. Stomachs were removed and stored in ethanol. Prey items were identified to the lowest possible taxon using morphology. Prey that could not be identified to family with traditional methods, were examined with DNA analyses of the barcode gene, cytochrome oxidase subunit I (COI). DNA was extracted, amplified, and sequenced from unknown tissue samples (n=142) and known prey fish controls (n=45). Obtained sequences were compared to published sequences, and identified 93% of the control prey fish and 60% of the unknown prey fish. This represents a 32% increase in identified prey items in red snapper diets.  These new DNA based identifications of prey fish are applicable for many other species, and may greatly improve our understanding of predator – prey dynamics