Feeding Ecology of Pelagic Larval Burbot in Northern Lake Huron, Michigan

Abstract

Burbot Lota lota are a key demersal piscivore across the Laurentian Great Lakes whose populations have declined by about 90% in recent decades. Larval Burbot typically hatch in the early spring and rely on abundant crustacean zooplankton prey. We examined the stomach contents of larval Burbot from inshore (≤15 m) and offshore sites (37 and 91 m) in northern Lake Huron, Michigan. Concurrent zooplankton vertical tows at the same sites showed that the prey community was dominated by calanoid copepods, dreissenid mussel veligers, and rotifers. Burbot consumed mostly cyclopoid copepods, followed by copepod nauplii and calanoid copepods. Chesson's index of selectivity was calculated and compared among sites and months for individual Burbot. According to this index, larval Burbot exhibited positive selection for cyclopoid copepods and copepod nauplii and negative selection for calanoid copepods, cladocerans, rotifers, and dreissenid veligers. This selectivity was consistent across sites and throughout the sampling period. Burbot displayed little variation in their prey preferences during the larval stage, which suggests that the recent shifts in zooplankton abundance due to the invasion of the predatory zooplankter Bythotrephes longimanus and competition from invasive Rainbow Smelt Osmerus mordax could negatively impact larval Burbot populations.

Received September 7, 2012; accepted March 14, 2013

ACKNOWLEDGMENTS

Bryon Daley, Erick Larson, Erik McDonald, Phil “Phlipp” Pepper, and Edward O. Roseman assisted with field collections and laboratory processing. Jeffrey S. Schaeffer provided statistical assistance. Patricia Thompson and Jenny Sutherland assisted with editing and formatting. This project was funded by the U.S. Environmental Protection Agency Project DW-14-94816701-0 and the U.S. Geological Survey, Great Lakes Science Center. This is contribution number 1733 of the Great Lakes Science Center.