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AUTHORS: Ryan Wehse, US Fish & Wildlife Service; Dale Hanson, US Fish & Wildlife Service; Ted Treska, US Fish & Wildlife Service; Mark Holey, US Fish & Wildlife Service; Roger Gordon, US Fish & Wildlife Service
ABSTRACT: Bloater (Coregonus hoyi), a form of deep water cisco, were once prevalent in Lake Ontario but excessive harvest, habitat degradation, and introduction of non-native planktivores led to their extirpation by the 1980s. Recent declines in non-native planktivore biomass now provide an opportunity to reintroduce bloater in Lake Ontario. Since 2011, the USFWS has collected gametes from spawning bloater in Lake Michigan with an objective of providing one million fertilized eggs to fish culture facilities in Ontario and New York to enable hatchery rearing studies, create hatchery broodstock lines, and provide an initial source of juveniles for Lake Ontario reintroductions. Prior to 2014, gill nets were used to catch spawning bloater, many of which were moribund and unspawnable, and we collected less than 500,000 eggs annually with egg survival rates between 1.5 - 45%. Beginning in 2014, use of bottom trawls greatly increased capture rates of spawnable females and resulted in an average of 1.1 million eggs collected with a mean egg survival rate of 67%. Aside from capture gear, we refined gamete harvest methods by adjusting the methods used to access the gametes and the egg transportation to the hatcheries. Though spawners are present between January and March, highest egg volumes were collected between late January and early February indicating the peak of the spawning occurs in a relatively short timeframe. Since 2011, staff has collected over 5.5 million eggs from over 5000 spawned females. These efforts will continue in 2018, but now that hatchery production is ramping up through broodstock sources, wild egg collection objectives are focused on collection of gametes throughout the spawning run to develop brood lines that better reflect characteristics of the wild population.
