Midwest Fish & Wildlife Conference 2016

AUTHORS: Brian A. Schmidt*, University of Toledo; Christine M. Mayer, University of Toledo; Edward F. Roseman, U.S.G.S. Great Lakes Science Center; Wendylee Stott, U.S.G.S. Great Lakes Science Center; Jeremy J. Pritt, Ohio Department of Natural Resources: Division of Wildlife

ABSTRACT: Three Western Basin rivers support diverse spawning habitats for three of the four major sub-stocks of Lake Erie walleye Sander vitreus. Despite a long history of anthropogenic degradation and the extirpation of other potadromous species, the Maumee River continues to support one of the largest fish migrations in the Great Lakes. Habitat degradation and an impassable low head dam at river kilometer (rk) 55 are some of the likely reasons for the decline of several species. To determine if spawning habitat availability and quality could limit production of Maumee River walleye, we assessed the longitudinal distribution and relative abundance of walleye eggs deposited in a 31 km river stretch between the dam, (first known upstream barrier to potadromous fish migration, rk 55) and the head of the Maumee River estuary (rk 24), the downstream end of preferred walleye spawning substrate. Sampling was focused on areas identified as preferred walleye spawning habitat based upon substrate, depth, and water velocity. Eggs were collected using a diaphragm pump at ten sites in 2014 and eight sites in 2015 from mid-March to early May. In both years, eggs from downstream spawning sites were present in a higher proportion of samples and had greater relative abundances than upstream sites. We saw a sharp decline in relative abundance at river kilometer 33, apparently indicating a previously unrecognized longitudinal barrier. This section of river, known as Jerome Rapids, is characterized by a shallow, narrow limestone shelf and high water velocities. Due to this barrier, walleye spawning in the Maumee River appears to be longitudinally restricted to the lower 10 km reach of the study segment, despite large areas of available habitat suitable for spawning in the upper reaches. Our results suggest that spawning habitat connectivity in the Maumee River is lower than previously thought.