Walleye (Sander vitreus) egg deposition and spawning habitat suitability in the Maumee River, OH (2014-2015)

Tributaries support spawning habitats for three of the four major sub-stocks of Lake Erie walleye (Sander vitreus). Despite a history of anthropogenic degradation and the extirpation of other potamodromous species, the Maumee River, OH continues to support one of the largest fish migrations in the Laurentian Great Lakes. To determine if spawning habitat availability and quality could limit production of Maumee River walleye, a habitat suitability model based on river bottom substrates and water depth was created for the lower 51 km of the Maumee River, and the distribution and relative abundance of walleye eggs deposited in a 25-km stretch of river were assessed. Walleye eggs were collected using a diaphragm pump at 7-10 sites two to three times per week from 1 April?7 May 2014 and from 24 March?5 May 2015, beginning shortly after ice out and continuing until early May when spawning ceased. To quantify spawning habitat within the Maumee River, a side-scan sonar unit and a bow-mounted transducer were used to identify river bottom substrate types. Substrate composition was visually delineated by drawing polygons around substrate patches and assigning the dominant substrate classification to each polygon in GIS software. Visual substrate surveys were conducted throughout the study area during June and September 2014?2016 and were used to inform the substrate classifications made by the side-scan sonar. Water depth and water velocity were modeled in the hydraulic modeling program HEC-RAS based on topographic data and water level gage data. Known walleye spawning habitat preferences from peer-reviewed literature were used to assign habitat suitability index (HSI) values from two different HSI models to substrate, modeled water depth, and modeled water velocity for spawning adult walleye, and habitat suitability maps were generated.