Resolving Some of the Complexity of a Mixed‐Origin Walleye Population in the East Basin of Lake Erie Using a Mark–Recapture Study

Abstract

At least two genetically distinct populations of walleye Sander vitreus reproduce in Lake Erie: one west-basinorigin population and one east-basin-origin population. Each year, some west-basin-origin walleyes migrate to the east basin and create a mixed-origin walleye population. Uncertainties associated with this migratory behavior make it difficult to describe the dynamics of the east-basin-origin population. We used mark-recapture analysis to estimate the dynamics of the east-basin-origin walleye population and to measure the contribution of west-basin-origin walleyes to the total walleye harvest in the east basin. Compared with the west-basin-origin walleyes, the east-basin-origin walleyes experienced lower fishing pressure, lower natural mortality, and a higher survival rate. On average, the west-basin-origin walleye migrants comprised about 90% of the annual harvest in the east basin. The number of the west-basin-origin walleyes migrating to the east basin was linearly related to their abundance. Walleyes showed a strong fidelity to their spawning sites. This study provided an approach to the assessment of population dynamics and the management of walleye fisheries in the east basin of Lake Erie.Lake Erie is the southernmost, warmest, and most productive of the five Laurentian Great Lakes (Hartman 1972). The lake consists of three distinct basins varying in depth, thermal regime, and productivity. The three basins are the shallow and warm west basin, the intermediate-depth and cool central basin, and the deep and cold east basin (Figure 1). The three basins are also distinguishable by their trophic states and local fish communities. Identification of these differences directly helped

Accuracy and precision of fishery and demographic estimates from a spatial tag-recovery model when inter-regional movements are treated as fixed

“…Using a spatial tag-recovery model and recoveries from a long-term jawtagging study, Vandergoot and Brenden (2014) found that Lake Erie walleyes exhibited age and spatial variability with respect to movement and mortality components. In particular, walleyes in the Lake Erie's western basin were more likely to move to other regions of the lake than eastern basin fish, which was consistent with previous movement studies (Wang et al, 2007;Zhao et al, 2011). Natural mortalities of age-5 and older walleyes were estimated to be lower than those of younger fish in both the lake's western and eastern basins (Vandergoot and Brenden, 2014).…”

“…Spatial structuring in the Lake Erie walleye population has been attributed to several factors, including metapopulation dynamics and regional differences in water quality, trophic structure, and incidence of invasive species (Wang et al, 2007;Berger et al, 2012). In addition to functioning as an apex predator (Ryan et al, 2003), walleye support important commercial and recreational fisheries throughout Lake Erie, with fishing activity mostly concentrated in the western and central basins (Roseman et al, 2011;Zhao et al, 2011). Harvest quotas are set annually to promote sustainability of this economically and ecologically important fishery (Roseman et al, 2011).…”

“…Harvest quotas are set annually to promote sustainability of this economically and ecologically important fishery (Roseman et al, 2011). Under the current harvest policy, quotas fluctuate with population abundance, which are estimated using SCAA models (Vandergoot et al, 2010;Zhao et al, 2011).…”

Improving fishery-independent indices of abundance for a migratory walleye population

“…The primary spawning grounds for Lake Erie walleye are in rivers and on mid-lake reef complexes affiliated with the west basin (Busch et al, 1975;Regier et al, 1969). There is evidence of emigration from the west and central basins to the eastern basin (Zhao et al, 2011) and through the Detroit River corridor (Wang et al, 2007).…”

“…For highly mobile species, for example, survey indices of abundance may remain inaccurate because of seasonal or local changes in distribution within and among management units used in population assessments (Gerber et al, 2003;Schwarz and Seber, 1999). Although the knowledge base is growing (e.g., Wang et al, 2007;Zhao et al, 2011), a comprehensive treatment of walleye movement and migratory patterns in Lake Erie and the ensuing impact it has on rational management remains a critical goal. Such information could provide insight into specific factors that affect the timing, extent, and duration of walleye migratory patterns and how they influence abundance indices used in stock assessment.…”