Deep-water cisco captive broodstock developed from wild-caught juveniles: proof of concept with Lake Michigan bloater

Dale Hanson (USFWS, dale_hanson@fws.gov), Ted Treska (USFWS), Charles Bronte (USFWS), Roger Gordon (USFWS), Doug Aloisi (USFWS), Carey Edwards (USFWS), Kevin Keeler (USGS), Dimitry Gorski (USFWS), John Coll (USFWS), Amanda Ackiss (USGS), Dave Warner (USGS), Ben Turschak (MIDNR), Dan Yule (USGS), Jason Smith (Sault Ste Marie Tribe of Chippewa Indians), Matthew Herbert (TNC), Kevin Donner (Little Traverse Bay Band of Odawa Indians), Mike Sneider (USFWS), Ken Phillips (USFWS)

Hatchery broodstocks (Coregonus artedi and C. hoyi) created via fertilizing eggs with sperm from wild spawning populations or captive brood stock fuel current restoration efforts for ciscoes in the Great Lakes. But, creating these broodstock involves hazards to access off-shore winter spawning aggregations. Serious logistical challenges exist: locating spawning aggregations, attaining high capture efficiencies as only a fraction of spawners have ‘ripe’ gametes, yet gamete quality must be preserved by ensuring spawners are freshlive at capture (Holey et al. 2021). Further, it is likely that the genetic diversity of broodstocks created in this manner does not match the entire potential donor population. Genetic diversity may be reduced, or changed, due to temporally limited gamete collections (e.g. no gametes from early/late season spawners), unequal parental contributions (e.g. differential egg/larval survival among spawn-pair families), and misclassification of spawners that result in hybrid crossings. For these reasons, developing cisco broodstock in hatcheries is difficult and probably unattainable for most forms of deep-water ciscoes, especially with most large source populations found in Lake Superior, and the disappearance of commercial fishers to assist in collection efforts. After a decade of executing such methods for C. hoyi, there may be safer, efficient, and more widely applicable methods, such as captive broodstock sourced from the capture of wild juvenile life-stages in situ. Broodstock originating from summer-caught juvenile coregonines alleviates most of the barriers previously identified for traditional methods. For starters, wild juvenile collections avoid the loss or altering of genetic diversity associated with the artificial spawn-pairing process in traditional methods. With juvenile life-stage collection, broodstock genetic diversity is more representative of overall donor populations and represents the product of successful spawning and post-hatch survival, likely increasing broodstock fitness over artificial pairing methods. The logistics of locating/capturing coregonine juveniles are straight-forward, and in fact knowledge of juvenile densities, specific locations, and fishing depths can often be known apriori as annual summer hydroacoustic/midwater trawl surveys are conducted throughout the Great Lakes. These assessment surveys routinely capture juvenile coregonines in midwater trawls fished in the epilimnion (Rosinski et al. 2020), thereby reducing the physiological stress placed on fish during capture. But it is unknown whether juvenile coregonines will survive capture and transport to hatchery facilities. As a proof-of-concept, we intend to capture wild juvenile coregonines (bloater, kiyi, and lake herring) during summer months and rear them for two months in hatchery facilities to demonstrate the approach is feasible for hatchery broodstock applications. This project addresses a ‘Restore’ action within the science-based approach to restoring Great Lakes coregonines whereby we seek to evaluate an alternative broodstock development method enabling reintroduction programs for species of cisco that are not currently possible (e.g. C. kiyi).