Utilizing DNA metabarcoding to characterize the diet of marine-phase Arctic lamprey (Lethenteron camtschaticum) in the eastern Bering Sea

To understand the marine feeding ecology of Arctic lamprey (Lethenteron camtschaticum) in the eastern Bering Sea, visual observations and DNA metabarcoding of gut contents (N = 250) were used to characterize Arctic lamprey diet composition in 2014 and 2015. Differences among individual diets were evaluated by collection year, capture site, and fish size. Hard structures and tissues were observed during visual examinations of gut contents, and 10 ray-finned fish taxa were identified by DNA metabarcoding. The most frequently observed taxa included capelin (Mallotus villosus), Pacific herring (Clupea pallasii), Pacific sand lance (Ammodytes hexapterus), and gadids. Six taxa were reported for the first time as prey for Arctic lamprey. Individual diets differed between collection years, among capture sites, and among size classes; however, both collection year and size class explained only a small portion of diet variability (R-2 = 0.01 and 0.04, respectively) relative to capture site (R-2 = 0.49). These study results indicate that Arctic lamprey is a flesh-feeding species and highlight the value of DNA metabarcoding to characterize the diet of a poorly understood lamprey species.