How have changes to coregonine spawning habitat influenced reproductive success?

Contributing Authors

Brian Weidel (USGS,, Brian Lantry (USGS), Alexander Gatch (USFWS), Michael Connerton (NYSDEC), Brian O’Malley (USGS), Peter Esselman (USGS), James McKenna (USGS), Zy Biesinger (USFWS)

Project Description

Coregonines once dominated Great Lakes fish communities and fisheries, however populations have declined or been extirpated, making conservation and restoration an increasing priority. Restoration will depend on regulation, reintroduction/supplementation, and habitat restoration. Spawning habitat restoration, which has proven critical in other fish restorations, is relatively untested for coregonines. This is due to our poor empirical and conceptual understanding of habitat’s role in coregonine reproductive success. Recent GLRI research in Lake Ontario and across the basin found depth and substrate were strong determinants of Lake Whitefish and Cisco egg deposition and pilot data suggests they also influence incubation success. Given the intense alterations of Great Lakes habitats, and desires to restore coregonines, it seems useful to determine how alterations to spawning habitat influence reproductive success. Lake Ontario is well suited to experimentally test how habitat changes have influenced coregonine reproduction. Surplus reef materials from an adjacent river habitat restoration will create clean substrate spawning reefs in Chaumont Bay in 2021. Post-construction assessment funding was not available, but the fortuitous creation of spawning habitat provides a unique opportunity to evaluate reef creation as a tool for coregonine conservation. In Lake Ontario, evidence suggests coregonine egg incubation habitat has been narrowed by the infilling of interstitial substrates and by the loss of consistent ice cover which protects nearshore spawning habitats during the five-month incubation. Lake wide surveys illustrate larval Cisco and Lake Whitefish are found only nearshore and primarily in northern embayments where ice duration is longest. In those areas, egg deposition peaks on the deepest-available hard substrates with interstices. Sediment and dreissenid mussels have drastically altered substrates such that embayment substrates with interstices only occur at depths less than 4 m where they are susceptible to physical disturbance before ice forms. When eggs settle on substrates that have been infilled, the near neutral eggs are displaced into deeper, sand and slit substrates. Eggs that settle without interstices are easily predated while those settling on silt experience low survival. Eggs are most vulnerable for the first month after fertilization. If ice forms early in that period, physical disturbance in shallow habitats is minimized increasing egg survival. In years with late or no ice, waves continually disturb eggs and resuspended sediment. This is likely why Lake Ontario coregonine year-class strength is positively related to early ice formation and why the most successful Lake Ontario coregonine spawning occurs in the north, where the ever-declining ice cover is most consistent. We hypothesize that within a site, larval coregonine production will increase if we experimentally increase interstitial substrates at water depths sufficient to minimize the impact of waves or lack of ice cover. Year one, of a three-year project, requested by NYSDEC to GLRI, is establishing baseline conditions for how habitat influences coregonine reproduction (deposition to emergence) at experimental Lake Ontario sites. That funded project is also studying Lake Superior coregonine spawning ecology, to provide context for how habitat may influence coregonine reproduction in a less anthropogenically-impacted system. This proposal seeks two years of funding (2022-2024), to determine if Lake Ontario egg deposition or larval production can be increased in restored, relative to unaltered, habitats. The current project provides the before data, in a before-after-control-impact experimental design. Lake Ontario managers want to know if spawning habitat modification is a tool to help achieve coregonine restoration objectives.

Funded In

Funding Agency


Restoration Framework Phase

Project Impact



Project Subjects