Ceded Territory Sc enc Lake Gogebic A conservation success story Technical Summary A study from the Quantitative Fisheries Center at Michigan State University used long-term datasets from the Michigan Department of Natural Resources and Great Lakes Indian Fish & Wildlife Commision to 1) evaluate the status of wall- eye in Lake Gogebic and 2) determine if fish stocking or habitat enhancements influenced walleye stocks. The study revealedthat production and/or survival of age-0 walleye(typically 4–8 inches) has been cyclical since yearly surveys began in 1990 (Figure 1). Peaks in production and/or survival of age-0 walleye occur every 5–6 years, but these peaks have not always resulted in high catch rates of age-1 walleye (typically 8–12 inches) the following year. For example, approximately 200 age-0 walleye were captured per mile of shorelinein2001,butveryfewage-1walleye(15 inches) have been conducted in this lake 1–2 times per decade since 1975. The density of adult walleye in Lake Gogebic has been approximately equal to or above 2.5 fish/acre, the average for other large lakes in this region (Figure 2). Previous studies have indicatedthatanglerexploitationisbetween7.9%and9.3%oftheadultpopulation. Tribal harvest has consistently been around 3.3%, resulting in a collective upper exploitation rate of 12.6%. This is quite low relative to the maximum sustainable exploitation rates between 24% and 35% used by state and tribal management agencies in this region. Lastly, walleye were stocked in the 1970s–1980s and baitfish in the late 1980s and 1990s. Based on the assessmentsconducted,there was no impact on the abun- dance or growth of walleye in Lake Gogebic (Figure 1, Figure 2). Habitat enhancement projects (sinking of Christmas trees and wooden structures) also took place on this lake, but it is difficult to determine if this action had a positive impact on walleye production because of minimal to no monitoring efforts after the structures were deployed. Future habitat enhancement projects should also focus on maintaining water quality and rehabilitating shorelines (e.g., adding a riparian zone that mimics a natural shoreline). These projects could benefit fish and other aquatic organisms in Lake Gogebic as well as bring the community members together to protect this valuable natural resource. We value your feedback. Please send your comments/questions to biologist aaronshultz@glifwc.org. —Mark Luehring, Adam Ray, Joe Dan Rose, Ben Michaels and Aaron Shultz, GLIFWC Inland Fisheries Staff Summary Biologists often direct their efforts towards natural resources that are declining, yet rarely highlight when a fishery has been stable over time. Lake Gogebic, a large nutrient-poor (oligotrophic) lake in the1842 Ceded Territory, stands out as a stable walleye fishery relative to many walleye lakes (e.g., Lac Vieux Desert Lake, Mazina’gan Summer 2017, pg. 10) in this region. There have been boom and bust years for production and/or survival of young walleye (less than one year old) over time (a typical trend in most walleye lakes), but overall the number of young walleye in Lake Gogebic has been stable. This has translated into a relatively constant density (greater than 2.5 fish/acre) of adult walleye (greater than 15 inches) since the mid-1970s. A low combined state and tribal harvest rate of approximately 12.6% may be partially responsible for the success of this fishery. Future management actions should consider the success of managing this fishery with a relatively low exploitation rate as well as the needs of both tribal and state harvesters, with the ultimate goal of sustaining stable stocks of walleye in this lake for future generations. Map of Lake Gogebic. (D. Olson graphic) Figure 1. Number of walleye captured per mile of shoreline from 1990–2015. Recent 2016 surveys noted approximately 58 age-0 walleye per mile and 9 age-1 walleye per mile. Data were collected during fall electrofishing surveys conducted by GLIFWC. (Figure was reproduced from a stock assessment report from the Quantitative Fisheries Center at Michigan State University.) Figure 2. Abundance of walleye in large lakes (Lake Gogebic, Peavy Pond, Bond Falls Flowage, and Lake Michigamme) from 1975–2006. “Adult” means spawning age fish and “legal” means fish >15 inches. Density of fish was calculated from mark-recapture data collected by Michigan Department of Natural Resources. In 2017, the number of adult walleye was estimated to be 45‚453 ± 3‚245 or 3.5 adult walleye per acre. (Figure was reproduced from a stock assessment report from the Quantitative Fisheries Center at Michigan State University.) PAGE 17 MAZINA’IGAN WINTER 2017/2018 • CEDED TERRITORY SCIENCE •