Walleye in the Grand River, Ontario: an Overview of Rehabilitation Efforts, Their Effectiveness, and Implications for Eastern Lake Erie Fisheries

Portfolio theory as a management tool to guide conservation and restoration of multi‐stock fish populations

“…Past and current habitat restoration efforts on the Maumee River include a dam removal impact assessment (Mueller 2008) and characterization of habitat quality and extent below the first barriers (B. Schmidt, C. M. Mayer, and E. F. Roseman, personal communication). Although the results of these efforts remain uncertain, facilitated barrier passage on other Lake Erie tributaries, such as the Grand River, Ontario, have led to increased stock-specific recruitment and spawner abundance (MacDougall et al 2007), providing optimism for the riverine stocks discussed herein. Additionally, recognition of stock dynamics and management at ecologically relevant scales (e.g., individual stocks) could help reduce the potential for stockspecific overharvest and loss of stock diversity (Stephenson 1999, Crozier et al 2004, Hutchinson 2008.…”

Microsatellite and mitochondrial DNA markers show no evidence of population structure in walleye (Sander vitreus) in Lake Winnipeg

“…For example, Billington et al (1991) and Gatt et al (2000) resolved three major mitochondrial lineages thought to reflect the postglacial colonization of walleye within the Great Lakes area from three glacial refugia (Atlantic, Mississippian and Missourian), and Stepien and Faber (1998) found significant structure at three broad scales (lake basins, lakes and putative glacial refugia) as well as among some spawning sites (i.e., on a finer scale). Microsatellite markers, which generally are able to resolve finer-scale genetic differences among populations (Selkoe and Toonen, 2006), have been successful in detecting walleye population structure between reef and river spawning sites in Lake Erie Stepien, 2007), detecting lineages (MacDougall et al, 2007;Wilson et al, 2007), determining the success of hatchery stocking (Eldridge et al, 2002;MacDougall et al, 2007), determining relationships between physical lake parameters and genetic diversity (Cena et al, 2006), and detecting genetic differences within nine pools in the Ohio River (White et al, 2005). However, some studies have found no genetic variation between walleye spawning sites using microsatellites (e.g., walleye from the Bay of Quinte and the New York waters of Lake Ontario or among spawning aggregations along the southern shore of western and central Lake Erie; Mathers, 2002, andStepien et al, 2010, respectively), indicating that not all spawning sites are genetically different.…”

Spawning by walleye (Sander vitreus) and white sucker (Catostomus commersoni) in the Detroit River: Implications for spawning habitat enhancement

“…4) was in the low end of the range of white sucker egg density measured with a Surber sampler in an Ontario stream (0.5-710 eggs/m 2 ; Corbett and Powles, 1986). An explanation for the relatively low density of deposited walleye eggs on the Belle Isle spawning ground in our study Our estimated size of the walleye spawning ground at the head of Belle Ile (20 ha) falls near the low end of the size range of fluvial walleye spawning grounds reported in the literature (6-240 ha; Cheng et al, 2006;MacDougall et al, 2007). Extrapolating from our average cumulative density of 346 walleye eggs/m 2 measured in 2005 within the 6-m contour area that we sampled on the Belle Isle spawning ground (202,378 m 2 ), we estimate that 70,022,788 total eggs were deposited on this 20-ha spawning ground in 2005.…”

“…Walleye that spawn in tributaries smaller than this connecting channel contribute to mixed-stock walleye populations elsewhere in the Great Lakes. For example, Gatt et al (2003) and MacDougall et al (2007) showed that fluvial spawning stocks of walleye contribute to the mixed-stock walleye population in eastern Lake Erie, and walleye that spawned in the Black Sturgeon River were genetically related to walleye that were historically harvested in Black Bay, Lake Superior .…”

“…If we assume that the average fecundity of a walleye spawning on this ground at Belle Isle was equal to that of walleye from western Lake Erie in 1990-91 (228,875 eggs/female; Muth and Ickes, 1993), we estimate that 306 females spawned at Belle Isle in 2005. Using an estimated spawning substrate requirement of 20 m 2 /female (Furlong et al, 2006in MacDougall et al, 2007, the Belle Isle spawning ground could theoretically accommodate 10,119 females, if optimal spawning substrates were available. Because walleye spawn on shoals in Lake Erie at water depths of 10 m (Roseman et al, 1996), and by design we restricted our egg sampling to water depths of 2-6 m, we may have missed egg deposition by walleye around this shoal at depths greater than 6 m and underestimated the size of this spawning ground at Belle Isle.…”