Variation in lake sturgeon (Acipenser fulvescens) abundance and growth among river reaches in a large regulated river

Abstract

Lake sturgeon (Acipenser fulvescens) stocks are well below historical levels across their natural range. In this study, we examine why lake sturgeon have not substantially recovered to historical levels in a large regulated river (Ottawa River, Canada). Three primary anthropogenic stressors have been identified as potentially limiting lake sturgeon populations in the Ottawa River: (i) commercial harvest, (ii) contaminants, and (iii) water power management. Hypotheses i and iii were tested by comparing lake sturgeon abundance and examining growth among reaches differing in level of commercial harvest and water management regime; hypothesis ii was tested by assessing contaminant loads in lake sturgeon and examining effects on growth and condition. Relative abundance, growth, mortality, and mean size of lake sturgeon did not differ among river reaches with (n = 6) and without (n = 3) a commercial harvest. Mercury was the only contaminant that was elevated. Neither growth nor condition showed any detectable relationship with mercury body burden. Relative abundance of lake sturgeon was greater in unimpounded than impounded reaches; additionally, there is evidence of faster growth in the impounded versus unimpounded reaches, suggesting density-dependent compensation. Water power management appears to be the primary factor affecting lake sturgeon in this river.

A global perspective of fragmentation on a declining taxon—the sturgeon (Acipenseriformes)

“…Dams act as barriers to upstream move ment to historic spawning areas (Bir stein 1993, DeVore et al 1995, Wei et al 1997, congregating migrating sturgeon and exposing them to harvest and the perils of poaching (Cohen 1997, Fernández-Pasquier 1999, and altering flows, affecting the success of natural sturgeon recruitment within rivers (Khoroshko 1972, Ivanov et al 1999, Jager et al 2002, Goto et al 2015, Haxton et al 2015. Moreover, variation in sturgeon abundance across the landscape has been attributed to the presence of hydroelectric generating stations (DeVore et al 1995, Haxton & Findlay 2008, Haxton et al 2014, demonstrating that dams can play a significant role in limiting the recovery processes for sturgeon.…”

Predicted effects of future climate warming on thermal habitat suitability for Lake Sturgeon (Acipenser fulvescens, Rafinesque, 1817) in rivers in Wisconsin, USA

“…Current abundance has been much reduced from historical levels, and the species is considered imperiled in many areas and vulnerable overall (Jelks et al, 2008). Population declines have been caused primarily by overfishing, pollution, and dams that modified habitats and blocked migrations (Scott and Crossman, 1973;Becker, 1983;Ferguson and Duckworth, 1997;Haxton and Findlay, 2008). Over the past 50 years there have been major efforts to restore Lake Sturgeon populations, involving strict fishery regulations and closures, stocking of juveniles, pollution abatement, habitat restoration, modification of hydroelectric dam operation, and provision of fish passage through barrier dams (Auer, 1996a;Schram et al, 1999;Lyons et al, 2000;Johnson et al, 2006;Drauch and Rhodes, 2007).…”

Genetic assessment of lake sturgeon (Acipenser fulvescens) population structure in the Ottawa River

“…Fragmentation of rivers by hydroelectric and water control dams is a major contemporary obstacle inhibiting lake sturgeon recovery (Haxton 2006;Hay-Chmielewski and Whelan 1997;Haxton and Findlay 2008). Despite restrictive harvest controls since the early 1900s, improvements in water quality, and pollution control, sturgeon populations have not recovered significantly across their range (COSEWIC 2007).…”