Spawning lake sturgeon (Acipenser fulvescens Rafinesque, 1817) and their habitat characteristics in Rainy River, Ontario and Minnesota

Abstract

Summary Lake Sturgeon (Acipenser fulvescens) spawning habitat in the Rainy River was studied in light of the ongoing review of the rules governing water levels upstream that affect discharge rates through the International Falls dam. The objectives of this study were to assess the current status of spawning Lake Sturgeon below the dam by: (i) evaluating weight–length relationships, condition, age and growth; (ii) identifying spawning locations and characterizing its physical attributes; and, (iii) evaluating the effects of water surface elevation on the availability of spawning habitat. Spawning was confirmed with use of egg mats, and targeted sampling of spawning individuals was completed using gillnets and electrofishing. Physical attributes of spawning locations, including temperature, depth and water velocity were collected at a range of water levels using an Acoustic Doppler Current Profiler and representative sediment sampling. Biological characteristics and timing of spawning events were consistent with those previously reported for Lake Sturgeon. However, a wider range of depths (0.3–10.5 m) and velocities (0.01–1.9 m3/s) than reported in most single site studies was found here, with the ranges encompassing what is reported in the literature as a whole. Lake Sturgeon were found to prefer coarse spawning substrates dominated by bedrock, boulder or cobble. The availability of preferred spawning habitat varied significantly with the changing water levels observed during the study and was eventually limited at higher water levels by river channel form. Because of the implications for dewatering of nest sites, keeping flows constant during spawning is critical to Rainy River Lake Sturgeon spawning success.

Milt volume influences the probability of egg fertilization in lake sturgeon ( Acipenser fulvescens, Rafinesque, 1817)

“…Furthermore, the estimated interaction time of eggs and sperm in our simulations was approximately 3.32 s under high flow and 10.16 s under low flow within a laminar environment. Lake sturgeon actively spawn under considerably higher and turbulent river flow conditions than we were able to simulate experimentally (e.g., 1.90 m 3 /s; Smith et al, 2017). Thus, the hypothesized negative effect of water velocity on egg fertilization may not be realized until higher water velocities are experienced.…”

“…Water velocity is a key physical stream factor that has been important in spawning duration and spawning site selection (Auer 1996a, Forsythe et al, 2011; Forsythe et al, 2012; Smith, Smokorowski, & Power, 2017). However, the effects of water velocity on egg fertilization was minimal in this study.…”

“…At a minimum, we believe that operational sex ratios should be monitored and considered in modeling of recruitment in the context of egg fertilization rates, especially for small populations. Altering flow regimes that create mixed physical cues may disperse adults during optimal times of spawning that can potentially reduce reproductive success (Smith et al, 2017). Protecting habitats that congregate spawning activity, while maximizing adult abundance, should continue to be a focus of restoration effort and may indirectly elevate fertilization probabilities and thus overall population trajectories.…”

Assessment of lake sturgeon (Acipenser fulvescens) recruitment in a regulated spawning tributary of Rainy Lake, Ontario

“…Dams and dam operations can negatively affect lake sturgeon and their habitats (Houston, ; Auer, , ; Ferguson & Duckworth, ; Peterson, Vecsei, & Jennings, ; Randall, ; Haxton, Friday, Cano, & Hendry, ; Haxton, Friday, Cano, & Hendry, ; Pollock, Carr, Kreitals, & Phillips, ; Haxton & Cano, ; Jager et al, ). Dams are often constructed at or near lake sturgeon spawning areas, and as a result, many populations spawn immediately downstream of dams where operations can affect habitat quality and quantity (Randall, ; Dumont et al, ; Haxton et al, ; Kerr, Davison, & Funnell, ; Smith, Smokorowski, & Power, ). It is generally assumed that lake sturgeon hatch and recruitment success (defined herein as individuals surviving to age‐1) is improved downstream of dams if flow fluctuations are minimized during the spawning, egg incubation, and larval drift periods (Auer, ; Smith et al, ).…”

“…Dams are often constructed at or near lake sturgeon spawning areas, and as a result, many populations spawn immediately downstream of dams where operations can affect habitat quality and quantity (Randall, ; Dumont et al, ; Haxton et al, ; Kerr, Davison, & Funnell, ; Smith, Smokorowski, & Power, ). It is generally assumed that lake sturgeon hatch and recruitment success (defined herein as individuals surviving to age‐1) is improved downstream of dams if flow fluctuations are minimized during the spawning, egg incubation, and larval drift periods (Auer, ; Smith et al, ). Using data from 23 rivers in Ontario, Haxton et al () found that recruitment failure was more evident in regulated systems, particularly peaking systems.…”