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Otoliths as elemental tracers of walleye environmental history: insights for interjurisdictional fisheries management
Journal or Book Title: Lake and Reservoir Management
Year Published: 2016
Understanding fish natal origins and movement is important for managing interjurisdictional fisheries. We used otolith microchemistry to assess walleye (Sander vitreus) provenance, movement, and natal homing in Lake Oahe, an interjurisdictional reservoir fishery in North Dakota and South Dakota, USA. Historical (1983–1989) water chemistry varied among six tributaries for strontium:calcium (Sr:Ca; μmol/mol) and barium:calcium (Ba:Ca) and between two main-stem sites for Ba:Ca. Current (2012) water chemistry was spatially heterogeneous for Sr:Ca and Ba:Ca. Both ratios were consistent between the historical and current periods in tributaries and main-stem sites. Natal otolith Sr:Ca and Ba:Ca of age-0 walleye varied in proportion to water chemistry, resulting in high reclassification accuracies to habitat types (87%) and individual sites (78%). For adult walleye, contributions of South Dakota natal sites to the North Dakota population (48%, n = 30) and North Dakota natal sites to the South Dakota population (48%, n =29) were highest for tributaries and embayments (e.g., Moreau and Cannonball rivers, Beaver bay). Annual downstream movement was more prevalent than upstream movement, particularly during a flood in 2011. An average of 36% of North Dakota walleye and 33% of South Dakota walleye exhibited natal homing each year from 2009–2013. Otolith element:Ca ratios are effective natural tracers for evaluating walleye natal origins, movement within and between states, and natal homing. Otolith microchemistry is a tool for interjurisdictional walleye management in reservoirs, providing a methodology for assessing natal origins and movement and designing spatially informed habitat conservation programs and harvest regulations.