Caution degraded reef: Custodial maintenance of Lake Huron’s natural and constructed reefs

Session: Great Lakes Reefs: Research, Monitoring, Creation, and Maintenance (2)

Alex Gatch, Purdue University, [email protected]
Jayson Beugly, Purdue University and IL-IN Sea Grant, [email protected]
Edward Roseman, USGS-Great Lakes Science Center, [email protected]
Tomas Hook, Purdue University, Dept. Forestry and Natural Resources, [email protected]

Abstract

Natural and constructed reefs in the Laurentian Great Lakes provide spawning and nursery habitat for native fish such as lake trout (Salvelinus namaycush), lake whitefish (Coregonus clupeaformis), and walleye (Sander vitreus). While many reefs are productive sites for fish reproduction, increases in anthropogenic sources of sedimentation and invasive biofouling can cause reefs to become less viable for spawning. To explore a novel approach for restoring reef habitat, we developed two reef-cleaning devices that use 1) propulsion and 2) water jets. Cleaning devices were used in Thunder Bay, Lake Huron and in Saginaw Bay, Lake Huron during fall of 2018. Relative hardness of each reef was measured before and after cleaning to determine magnitude of cleaning by each device. Fish usage of cleaned and uncleaned plots on each reef was determined by collecting deposited lake trout and whitefish eggs. Analysis suggests that egg deposition was significantly higher in plots cleaned by the propulsion device compared to the control in Saginaw Bay reefs. However, in Thunder Bay there was no significant difference between egg depositions on cleaned v. uncleaned plots. Further sampling will be carried out in spring 2019 to determine patterns in walleye egg deposition and overall performance of cleaning devices.