Increased taxonomic resolution of Laurentian Great Lakes ichthyoplankton through DNA barcoding: A case study comparison against visual identification of larval fishes from Stokes Bay, Lake Huron

Ichthyoplankton can be difficult to identify due to a lack of morphological differences among closely-related species. Traditional visual identification of ichthyoplankton requires special knowledge to employ morphological keys. Accurate species-level identification is often required to support monitoring programs for those taxa that are considered valued ecosystem components in environmental assessments. DNA-based methods are gaining in popularity as an alternative to visual identification techniques, but direct comparisons of methodological performance between identification techniques are lacking. The goal of this study was to evaluate and explore the consistency between visual and DNA barcoding species-level identification methods, using a case study of larval fish caught in plankton tows at Stokes Bay, Lake Huron during the spring of 2011. Four participants served as Identifiers (3 Novice, 1 Expert) for visual identification of this multi-species set of larval fishes; including Lake Whitefish, Lake Herring, Yellow Perch, Iowa Darter, Ghost Shiner, and Rainbow Smelt. Barcoding successfully identified 51/55 (92.7%) of the larval fishes, while visual identification using a dichotomous key showed substantial variation between observers, and across family/species. There was a 93.7% consistency between visual and barcoding identification at the family level, and a 71.5% consistency level between visual and barcoding at the species level. Potential sources of error are discussed for both identification methods, leading to a recommendation for the coordinated use of both visual and barcoding identification methods to improve species-level assessments for wild ichthyoplankton samples.