Evidence for the importance of invasive Dreissena veligers as a novel prey item for larval fish in Lake Huron

The establishment of invasive dreissenid mussels Dreissena polymorpha and Dreissena rostriformis bugensis in the Laurentian Great Lakes has affected multiple aspects of the ecosystem. However, the effects of their larvae (veligers) on lower trophic levels are relatively unknown. Previous research has documented that some larval fishes consume veligers, but it is unclear if they select for veligers. To assess the role of veligers in larval fish diets in Lake Huron, we examined the diets of larval burbot Lota lota, rainbow smelt Osmerus mordax, and Coregonus spp., mainly bloater Coregonus hoyi, sampled in July of 2017. Preference for available zooplankton prey was evaluated using Vanderploeg and Scavia’s E*. Results indicated that veligers were on average avoided by large larval burbot, rainbow smelt, and coregonines but were sometimes preferred by small (< 7 mm) and medium-sized (7–10 mm) larval burbot. A mixed model analyzing factors contributing to veliger preference by larval burbot indicated that greater environmental zooplankton prey size is associated with more positive preference for veligers. Thus, veligers may be important for gape-limited larval fish. We also found that, on average, larval burbot and coregonines consumed larger veligers than those sampled in the environment. Overall, consideration of larval fishes’ ability to exploit veligers could help managers to understand the role of dreissenid mussels in Great Lakes food webs.