Lake Michigan Wild Egg Collections Lead to the
Return of Deepwater Cisco in Lake Ontario!
BY DALE HANSON, GREEN BAY FWCO
For the fifth consecutive winter, U.S. Fish and Wildlife Service (Service) biologists collected bloater eggs (Coregonus hoyi), a species of deepwater cisco, from Lake Michigan to assist with efforts to restore this species into Lake Ontario. To date 24,000 bloater juveniles have been stocked into Lake Ontario that originated from the Service’s egg collections in 2010 – 2012, and another 67,000 are scheduled to be stocked this fall from 2013 egg collections. These stockings have returned bloater to Lake Ontario, where they disappeared in the 1950s from the combined effects of invasive species, poor water quality, and commercial exploitation. Their disappearance disrupted the historical foodweb structure in the lake as bloater were the primary link between deep water invertebrates and top predator species including lake trout. Lake Ontario managers hope to restore self-sustaining bloater populations through large-scale annual restocking efforts of 500 thousand bloater juveniles. This will increase the diversity among forage fish populations, reestablish the historical foodweb structure, and ultimately increase lake trout production. The USFWS Midwest Region Fisheries Program egg collection work is making a major contribution to the advancement of fish culture methods for bloater and is paving the way to achieve these large-scale stocking efforts needed for bloater restoration in Lake Ontario.
Accessing bloater eggs in the wild is extremely challenging as Lake Michigan bloater spawn at depths in excess of 300 feet in the heart of winter (January – March). Service crews, led by Dale Hanson from Green Bay Fish and Wildlife Conservation Office and Roger Gordon with Jordan River National Fish Hatchery, logged 24 trips in 2014 aboard two commercial bottom trawling vessels based out of Two Rivers, Wisconsin, located on the western shore of Lake Michigan. Despite one of the coldest winters on record, the boats broke through several miles of ice to reach the spawning grounds where bottom trawls caught roughly 25,000 bloater adults. Bloater spawn over a protracted period and only 394 “ripe” females contained fully developed eggs suitable for spawning. These ripe females yielded 500 thousand eggs that were fertilized and shipped via overnight delivery to the White Lake Fish Culture Station in Ontario, and the USGS Tunison Lab in New York. Half of these eggs (51%) successfully reached the eyed-egg stage and by mid-April these eggs will have hatched to produce over 180 thousand bloater fry to be reared in these hatcheries for the next 18 months. Managers anticipate the 2014 egg collections will produce 60,000 bloater juveniles that will be available for stocking into Lake Ontario in the fall of 2015.
Since their inception in 2010, the egg collection surveys have made substantial progress towards meeting the annual stocking targets of 500 thousand juveniles. Most notably, USFWS hatchery personnel have been on all surveys since 2012 to ensure only fully developed eggs are collected, and since 2013 surveys have employed bottom trawl gear, instead of gillnets, which has resulted in higher catches and markedly better fish condition. These changes have more than doubled the survival from egg to fry stages compared to that observed in 2010 – 2012. Despite these improvements we are still far short of meeting annual stocking target goals, but the future looks bright! Next year, collection methods will also include a captive broodstock program whereby pre-spawn wild caught bloater will be retained in a lab and spawned once the eggs become fully developed. Also, conventional bloater broodstock lines are beginning to mature.
Since 2011, a small proportion of bloater fry from each year-class, currently 15,000 in total, have been retained at the White Lake Fish Culture Station and raised as broodstock. The 2011 year-class of broodstock is just starting to mature and managers are hopeful that these broodstock fish will supplement the wild egg collections next year. With each year enthusiasm grows for bloater restoration and the growing success is a tribute to the hard work that the Service, Ontario Ministry of Natural Resources, New York Department of Environmental Conservation, Great Lakes Fishery Commission, and the USGS Tunison Laboratory have put forth to pave the way for deepwater cisco restoration.