WWW.WA S .ORG • WORLD AQUACULTURE • JUNE 2022 55 ( C O N T I N U E D O N P A G E 5 6 ) Prior facility research has demonstrated walleye growth potential in indoor systems, reaching an average of around 0.5 kg in 12 months (Fig. 5) from egg to market size utilizing RAS at commercial density levels of 60-90 kg/m3. Not only is there demand for this marketsize walleye, but also an additional market exists for pellet-fed and intensively-reared fingerlings that are biosecure and can be utilized for stocking into other RAS or aquaponics facilities for grow-out. Bottlenecks for commercial walleye production remain, with one of the most important being a domesticated in-house broodstock reared in RAS that is capable of supplying high-quality eggs and fry for out-of-season commercial production. Building on past and ongoing research projects related to commercial walleye production funded byWisconsin Sea Grant (WISG) and the North Central Regional Aquaculture Council (NCRAC), the facility is very close to achieving the goal of a commercial, land based, regional walleye industry. The most recent walleye project funded byWISG—“Commercial application of out-of-season spawning of walleye (Sander vitreus)”— is succeeding in completing the full life cycle of walleye reproduction under intensive conditions and is providing the methodology for supplying suitable eggs and fingerlings to a growing commercial walleye industry. Efficient technology and information transfer of research findings to industry is crucial for species adoption and commercial success. Therefore, the facility shares research outcomes, best management practices and techniques to farmers through on-site demonstration, publications, workshops, presentations at industry events and technical videos such as the UWSP NADFWalleye VideoManual (www.uwsp. edu/cols-ap/nadf/Pages/Walleye-and-Hybrid-Video-Manual.aspx). Development of theLakeHerring IntensiveCulture Manual forRestoration Historically, lake herring or cisco Coregonus artedi was the most prolific prey fish in the Great Lakes basin and supported the largest commercial freshwater fishery in North America. The cisco was a vital link in lake trout food webs, the collapse of which altered predatorprey dynamics and commercial fisheries on the Great Lakes. Cisco populations have rebounded in Lake Superior (Bronte et al. 2003) and are increasing in Lake Huron (Mohr and Ebener 2005). However, they remain restricted in the remaining Great Lakes. With funding from the US Fish andWildlife Service through the Great Lakes Fish andWildlife Restoration Act, UWSP NADF scientists and staff worked to answer important questions related to culture and rearing for future reintroduction of lake herring into the lower Great Lakes. Working collaboratively with US Geological Survey Upper Midwest Environmental Sciences Center and US Fish andWildlife Service Lacrosse Fish Health Center, the facility investigated research questions regarding lake herring that involved iodophor egg treatment, incubation temperatures, larval feeds and overall rearing of lake herring for intensive production. The research has been organized by the facility into a Lake Herring Intensive Culture Manual (Fischer et al. n.d.). The manual is a template for lake herring production applied at a commercial level utilizing the latest aquaculture technology advancements, feeds, designs and practices to provide critical information and assistance in the propagation and handling of cisco for conservation restoration projects. GroundbreakingResearchonSeaLampreyParasitismonLakeTrout Lake trout Salvelinus namaycush have been an important species in the Great Lakes for commercial, subsistence and sport fisheries, and are a top predator in Lake Superior. Although many non-native species have entered the Great Lakes over the years, the parasitic sea lamprey Petromyzon marinus has been one of the most harmful, especially for lake trout populations. At their parasitic stage, the sea lamprey attaches to a fish host (Fig. 6), extracting blood and tissue fluids with their specialized mouth parts. Around 45-75 percent of lake FIGURE 6. Sea lamprey attached to lake trout as part of a project to assess the effects of sub-lethal sea lamprey parasitism on two different lake trout morphotypes. FIGURE 7. Utilizing ultrasound on broodstock Atlantic salmon (top left), spawning Cascade strain Atlantic salmon (top right), Atlantic salmon broodstock RAS (middle left), interactive, hands-on tours at the facility for all ages (middle right), intensively and pellet-reared walleye fry (bottom left) and 0.7 kg, 10-month post hatch walleye hybrid raised in intensive RAS (bottom right).
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