Testing habitat’s influence on Cisco reproductive success using egg translocation

Contributing Authors

Brian Weidel (USGS, bweidel@usgs.gov), Alex Gatch (USGS), Dimitry Gorsky (USFWS), Brian O'Malley (USGS), Josephine Johnson (USFWS), Gregg Mackey (USGS), Marc Chalupnicki (USGS), Ryan Walquist (USGS), Nicholas Sard (SUNY-Oswego)

Project Description

Great Lakes Restoration Initiative studies from the Coordinated Science and Monitoring Initiative, Native Fish Restoration, and DOI Steering Committee from fiscal years 2018 - 2022 have rapidly improved our understanding of how habitat influences coregonine spawning and incubation success. Studies of egg deposition found spawning was more habitat-specific than descriptions based on spawning adult fish observations, but preferred spawning habitat may be population specific. In Lake Ontario’s Chaumont Bay, multiple years of surveys show that spawning Cisco and Lake Whitefish target egg deposition on relatively shallow substrates with interstices (infilled rock, dreissenid mussels, mussel shell hash), and April larval emergence is greatest on those habitats. Since Lake Ontario substrate has been heavily infilled by sediment and dreissenid mussels, most of the eggs are displaced into deeper, fine substrates where survival appears minimal. In 2022, a substrate addition in Chaumont Bay found lower egg deposition on added substrate relative to control sites, however larval emergence was ten times greater on the clean substrate relative to the control sites, suggesting greater incubation success in substrates with interstitial spaces. These experiments will be expanded (2023) to include a treatment where substrate interstices are restored by removing infilled sedimented material to evaluate if this action alone can improve coregonine incubation success. This proposal seeks funding to continue evaluation of these two habitat experiments and expand our restoration toolkit by developing coregonine egg translocation (egg stocking) approaches. Translocating embryos to historically productive, but contemporarily degraded, sites can help determine the incubation potential of different substrates and if suitable incubation substrate exists, restore coregonine populations in regions where they have been lost. Lake Ontario’s unique history of habitat degradation and current coregonine spawning research combined with fisheries management’s interest in coregonine restoration make it well suited to evaluate the utility of coregonine egg translocation. Lake Ontario has experienced the greatest habitat degradation in the Great Lakes contributing to Cisco and Lake Whitefish populations declines over the past centuries. Lake-wide larval fish surveys in 2018 illustrated, that at a lake scale, successful Cisco and Lake Whitefish spawning only occurs in a small fraction of their historic ranges and suggested habitat quality was a key driver of coregonine recruitment. New sampling gears have been developed in Lake Ontario to quantify habitat-specific egg deposition, larval emergence, and variability in physical habitats and conditions where coregonines spawn. These methods have been successfully applied to other Lake Ontario regions of restoration interest (Sodus Bay) and other Great Lakes. December egg deposition surveys have consistently shown egg deposition is targeted on relatively shallow rock and dreissenid substrates. Interestingly, lower egg densities are observed on a broader range of depths and substrates since interstitial substrate on targeted deposition sites is limited causing eggs to be easily dispersed by lake currents. First-of-their-kind larval coregonine emergence traps illustrate incubation success is greatest on habitats where egg deposition is highest, while few or no larvae emerge deeper than 6 - 7 m, where finer silt substrates predominate. The Lake Ontario Committee’s Fish Community Objectives seek to increase coregonine populations and their Fish Habitat Priorities specifically call to improve coregonine spawning and nursery habitat. New York State Department of Environmental Conservation developed and permitted the Chaumont Bay substrate addition and substrate cleaning experiments. Managers are also intersted in experimentally evaluating if egg translocation, using the Chaumont Bay embryos, can determine if spawning substrate in other Lake Ontario regions is suitable for incubation. If egg translocation processes can be developed it could provide an additional to to restore Lake Ontario or other Cisco populations. The research team has 12 years of experience collecting gametes and rearing Cisco from the Chaumont Bay spawning stock. As a research tool, egg translocation has been successfully used to quantify impediments in Great Lakes Lake Trout and as conservation tool for coregonines in Europe. Lake Trout egg translocation experiments in Lakes Huron, Michigan, and Champlain illustrated the negative impacts of physical disturbance and egg predators on incubation success but other studies suggested the approach is not an effective tool for restoration. In Scotland, Coregonus lavaretus and Coregonus albula egg translocations have been used to develop refuge site populations that maintain phenotypic and genotypic diversity without requiring captive rearing efforts. Egg stocking (translocation) was suggested as a restoration tool for Cisco in Lake Erie but to our knowledge this approach has not been evaluated in Great Lakes coregonines.

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Restoration Framework Phase

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