Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 Page 10 Page 11 Page 12 Page 13 Page 14 Page 15 Page 16 Page 17 Page 18 Page 19 Page 20 Page 21 Page 22 Page 23 Page 24• INLAND FISHERIES/AQUATIC INVASIVE SPECIES • Walleye diet, forage at center of GLIFWC study Interns dig into fishery menu at Lac Vieux Desert By Aaron Shultz, PhD GLIFWC Climate Change Inland Fisheries Biologist On the hunt for aquatic invasive species Resource Specialist Sam Quagon lowers an Ekman dredge into Lake Lac Vieux Desert’s Misery Bay, part of a multi-lake GLIFWC effort to detect the aquatic invasive species, spiny water fleas. The spring-loaded dredge collects a 6x6” sample of silt, which is being analyzed by laboratory technicians. (COR) MAZINA’IGAN PAGE 6 FALL 2016 In recent years, walleye stocks in many Ceded Territory inland lakes have declined, although the reasons for these declines remain unknown. GLIFWC researchers have noted that fewer and fewer juvenile and adult walleye are pres- ent in fall and spring surveys respectively. In an effort to explain these declines, GLIFWC is exploring the role of forage fish availability, or a change in diet over seasons or years. This past summer the inland fisheries team ramped up data collection on Lake Lac Vieux Desert (LVD) to gain a better understanding of potential underlying mechanisms that may be depressing walleye stocks. The team, led by veteran staff Butch Mieloszyk and Edward White, myself, and inland fisheries interns—Andre Gastric lavage, or stomach pumping, on perch (pictured) and walleye help biologists pinpoint what young fish are eating. (COR photo) INSET: Stomach contents are examined under microscope at the GLIFWC laboratory. Research biologist Aaron Shultz awaits the catch nearshore as inland fisheries interns pull a small seine net to collect forage fish in Lake Lac Vieux Desert’s Misery Bay. (COR photo) Gilles and Nick Quagon—identified available forage/bait fish for both adult and juvenile walleye. To do this, the team seined sandy beaches at several locations throughout the lake. Forage fish like yellow perch were counted and measured prior to release. Taken together, this study will indicate how prey fish for both juvenile and adult walleye may change over seasons and years. “We’re learning that many variables such as predation, available prey and harvest pressure could be affecting walleye stocks on Lake LVD,” said Gilles, a Bad River member. “It’s exciting for me to learn how to quantify available prey and potentially answer why walleye stocks seem to be declining.” Juvenilewalleye,especiallyyoungoftheyear,oftenfeedoninvertebratesand consume fish once they reach a large enough size. Prey availability and encounter rates will also determine which prey items walleye consume. Diets composed of mostly invertebrates may result in walleye that have poor condition relative to walleye that consume fish, a higher quality food item. The research team piloted a technique called gastric lavage on fish in LVD, which allowed us to count and identify prey (invertebrates and fish) and release the fish alive after sampling. Unfortunately, we did not capture juvenile walleye in LVD, but we did sample perch stomachs. Surprisingly, perch consumed only invertebrates in June, with the majority of their diets composed of scuds and midges. Future work will focus on sampling several age classes of walleye across seasons and years to determine how their diets may be changing. For GLIFWC inland fisheries interns, the work is a meaningful gateway into managing treaty natural resources. “My mind is set on working in the field,” said intern Quagon, a Lac Courte Oreilles member and nephew of longtime GLIFWC technician Sam Quagon. “The research we are conducting has been an invaluable experience for me, and has given me great hands-on skills.” Between field study and laboratory work at GLIFWC’s central office, the research is scheduled to continue through 2017. For more information contact me at aaronshultz@glifwc.org or (715) 682-6619 ext. 2170. Andre Gilles (left) and Nick Quagon record total length of captured forage fish. (COR photo)