Assessing Walleye Movement among Reaches of a Large, Fragmented River

Abstract

Movement of Walleyes Sander vitreus among reaches in a large, fragmented river was assessed by employing a combination of tagging, telemetry, and genetic analyses. Our objective was to determine whether the existing dams in the Ottawa River, Canada, were impeding Walleye movement among river reaches. Movement was predicted to be greater among contiguous, unimpounded reaches in comparison with impounded reaches. In total, 1,586 Walleyes were tagged in five river reaches, and 35 Walleyes were tracked by radiotelemetry in three river reaches. Genetic analyses (linkage disequilibrium, genetic divergence and diversity, effective population size, genetic structuring, bottlenecks, and migration rates) were conducted on 221 Walleyes from seven river reaches by genotyping at six microsatellite loci. Based on both tag returns (return rate D 12.1%) and telemetry data, there was limited movement among river reaches whether impounded or unimpounded, and movement was predominately upstream. Genetic analyses identified population structuring, with three genetic groupings occurring within the river. There was also evidence of genetic isolation in an upper reach of the river, indicating potential residual effects of a bottleneck or genetic drift. Our results suggest that existing dams may not act as significant barriers to Walleye movement in the Ottawa River, but limited movements appear to maintain genetic diversity and minimize genetic drift. Consequently, maintaining the genetic attributes of Walleye stocks in segmented rivers may require some level of fish passage.

The Spatial Ecology and Biological Responses of Wild Fishes Relative to Hydropower Development on the Winnipeg River

“…I first examined the general habitat use of Lake Sturgeon and Walleye by quantifying residency across habitat types. Relatively limited information has been documented for Lake Sturgeon and Walleye within impoundments on the Winnipeg River system (Barth et al 2011) and across other areas of their range (Haxton et al 2015). In addition, the movement and space-use in regulated and impounded systems are not fully understood both for Lake Sturgeon (McDougall et al 2014) and Walleye (Bozek et al 2011).…”

“…Large river systems across the globe have been reshaped by anthropogenic developments, particularly due to hydropower facilities (Poff et al 1997;Rosenberg et al 1997). Hydropower dams can restrict the upstream and downstream migration of fish that can lead to genetic structuring due to the lack of gene flow between fragmented reaches (Haxton et al 2015), as well as limiting population growth and biodiversity loss due to the lack of available habitat (Beamesderfer 1998). Hydropower facilities regulate flow on a seasonal and diel basis, this can cause stranding events due to abrupt dewatering or drawdown (Nagrodski et al 2012).…”

“…Hydropower developments, which cause habitat alterations, and are thought to impact Lake Sturgeon (Barth et al 2011) and Walleye (Haxton et al 2015) populations that are confined within fragmented systems. The potential development of hydrokinetic turbine arrays in tailraces and forebays at existing hydropower stations to augment supply to the power grid (Khan et al 2009; Liu and Packey 2014) pose a possible additional threat.…”

“…Storage reservoirs and run-of-the-river systems are both common and lead to the creation of impoundments (Geen 1974;Baxter 1977) that can affect the natural flow regime of river systems (Poff et al 1997). In north temperate regions, Lake Sturgeon and Walleye are two fish species that are often found in larger storage reservoirs and smaller sized run-of-river reservoirs (McDougall et al 2014;Haxton 2011Haxton , 2015.…”

“…These species are migratory, often moving large distances between foraging/overwintering and spawning locations across the seasons (Caswell et al 2004;Haxton et al 2015). Fragmented river systems may hinder the wellbeing of Lake Sturgeon and Walleye populations by reducing habitat availability and cause genetic structuring (i.e., patterns in the genetic makeup; Gyllensten 1985) that may make them less capable of coping with environmental (e.g., drought, extreme flooding events) or anthropogenic stressors such as abrupt discharge reductions, habitat alterations, or recreational fishing and harvesting (Saunders et al 1991;Haxton et al 2015). In Canada, populations of Lake Sturgeon have been listed as a species of special concern, threatened or endangered across their range (COSEWIC 2006) (Bozek et al 2011).…”