Spatial and temporal distributions of lake whitefish spawning stocks in Northern lakes Michigan and Huron, 2003–2008 Mark P. Ebener a, ⁎, Travis O. Brenden b , Greg M. Wright c , Michael L. Jones b , Mohamed Faisal d a Inter-Tribal Fisheries and Assessment Program, Chippewa Ottawa Resource Authority, 179 W. Three Mile Rd., Sault Ste. Marie, Michigan 49783, USA b Quantitative Fisheries Center, Department of Fisheries and Wildlife, Michigan State University, 153 Giltner Hall, East Lansing, Michigan 48824, USA c Nunns Creek Fishery Enhancement Facility, HC-47 Box 8100, Hessel, Michigan 49725, USA d Department of Pathobiology and Diagnostic Investigation, Michigan State University, East Lansing Michigan 48824, USA abstract article info Article history: Received 20 May 2009 Accepted 10 December 2009 Communicated by Trent M. Sutton Index words: Lake whitefish Tag recovery Spatial distributions Distance moved Percent movement Quantile regression tree Adult lake whitefish were tagged and released from the Big Bay de Noc (BBN) and Naubinway (NAB) stocks in northern Lake Michigan, and the Detour (DET) and Cheboygan (CHB) stocks in northern Lake Huron during 2003–2006 to describe their spatial and temporal distributions. The contemporary spatial distributions were compared with past distributions of the BBN and NAB stocks. Sixty-two percent of BBN tag recoveries occurred in Wisconsin waters during winter, spring and summer, but 83% of fall tag recoveries were made near the tagging site. Eighty-eight percent of the NAB tag recoveries were made in the management unit of tagging and 7% occurred into northern Lake Huron. Over 90% of the DET stock remained in the vicinity of the tagging sites regardless of the season, while 75% of the CHB tag recoveries were made in northwestern Lake Huron and 17% were made in Ontario. Based on regression tree analysis, there were strong stock, season, and year effects on movement distances, with weaker effects due to sex and length at tagging. Spatial distribution of the BBN stock changed from 1978–1982 to 2003–2008, but spatial distribution of the NAB stock did not. Substantial dif- ferences in movement and distribution existed among the four stocks, large seasonal differences in spatial distribution were found within some stocks, and lake whitefish exhibited strong spawning site fidelity. Present management unit boundaries are inappropriate for managing three of our four stocks, and agencies should consider developing single harvest limits for both northern Lake Huron and western Lake Michigan. © 2010 Elsevier B.V. All rights reserved. Introduction Fishery managers in the Laurentian Great Lakes of North America have long recognized that fostering recovery of depleted native spe- cies and protecting less productive populations requires managing at spatial scales smaller than individual political jurisdictions (Smith et al., 1961; Bails and Patriarche, 1974; Patriarche, 1976). The concept of managing at the stock level began to be implemented in the Great Lakes during the 1970s and 1980s to protect discrete spawning aggre- gations that behaved as cohesive units and that possessed different levels of productivity and life history characteristics (Spangler et al., 1981; MacLean and Evans, 1981). Management units were established with boundaries that were designed to encompass either the spatial distribution of individual stocks or the spatial distribution of a fishery that exploited a stock. Management of commercial fisheries for lake whitefish Coregonus clupeaformis in the Great Lakes has been focused on protecting individual naturally reproducing stocks (Rackozy, 1983; Ebener et al., 2005) because they have high economic and intrinsic values (Ebener et al., 2008). Both molecular and morphological studies have indicated that distinct genetic stocks of lake whitefish exist throughout the Great Lakes (Imhof et al., 1980; Casselman et al., 1981; VanDeHey et al., 2009; Stott et al., 2010). Mark–recapture studies conducted in the 1980s and early 1990s found that lake whitefish movement was generally restricted to areas proximal to the stocks' spawning loca- tions (Casselman et al., 1981; Ebener and Copes, 1985; Scheerer and Taylor, 1985; Walker et al., 1993). Since the early 1990s, however, there have been substantial increases in lake whitefish abundance in the Great Lakes (Wright and Ebener, 2007; DuBruyne et al., 2008); additionally, there have been significant system-level changes in the lakes due to the invasion of dreissenid mussels, including drastic reductions in Diporeia spp. abundance (Nalepa et al., 2007, 1998, 2009a). Together, these have resulted in changes in lake whitefish bathymetric distribution (Mohr and Ebener, 2005), food habits and growth (Pothoven et al., 2001; Schneeberger et al., 2005; Nalepa et al., 2009b), reproduction dynamics (Kratzer et al., 2007), and bioener- getics (Pothoven and Madenjian, 2008). Given the changes that have occurred, the distribution and movement of lake whitefish have likely Journal of Great Lakes Research 36 (2010) 38–51 ⁎ Corresponding author. E-mail addresses: mebener@lighthouse.net (M.P. Ebener), brenden@msu.edu (T.O. Brenden), gwright@sault.com (G.M. Wright), jonesm30@msu.edu (M.L. Jones), faisal@msu.edu (M. Faisal). 0380-1330/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jglr.2010.02.002 Contents lists available at ScienceDirect Journal of Great Lakes Research journal homepage: www.elsevier.com/locate/jglr