Spawning Habitat of Kootenai River White Sturgeon, Post-Libby Dam

Abstract

The Kootenai River white sturgeon Acipenser transmontanus has been isolated from other white sturgeon populations for over 10,000 years, Bonnington Falls in British Columbia, Canada, creating the isolation. Libby Dam, constructed in 1972, modified the flow and temperature regime of the river, which affected spawning and recruitment of white sturgeon. Kootenai River white sturgeon are only known to spawn in a reach near Bonners Ferry, Idaho, 100 km downstream from the dam. In 2 of 8 years of study, only 15 white sturgeon eggs were collected over gravel–cobble substrate. However, in the other 6 years, 1,193 eggs were collected over sand substrate; these areas usually exceeded 5 m in depth, were within the main channel, and had water velocities of 0.2–1.0 m/s and temperatures of 8.5–12°C. In general, these characteristics differed from optimum white sturgeon spawning habitat in the Columbia River, where velocities average 0.8 m/s, water temperatures are 12–17°C, and gravel–cobble substrate is available. Spawning over sand substrate might contradict survival strategies because white sturgeon have an adhesive egg to which sand adheres. Differences in spawning habitat may be an outcome of behavioral divergence or disruption to environmental cues but was probably caused by preferred habitat no longer being available. Recovery of Kootenai River white sturgeon will depend primarily on continuation of mitigated flows for spawning migrations, suitable spawning habitat, and ultimately survival of eggs and larvae. It is unknown at this time whether recent spawning alone will lead to sufficient recruitment to help recovery of the population, but if it does not recruit substantial year‐classes, we believe consideration must be given to measures that would provide coarser spawning substrates and warmer water temperatures.

Early Life Stage Mortality Rates of Lake Sturgeon in the Peshtigo River, Wisconsin

“…Eggs naturally deposited on substrate egg mats have been used to locate and describe spawning habitat for many sturgeon species (e.g., Fox et al 2000;Paragamian et al 2001;Duncan et al 2004); however, only a single study has produced estimates of total egg deposition using this sampling gear. Sulak and Clugston (1998) estimated that total deposition of Gulf sturgeon eggs in the Suwannee River, Florida, ranged between 404,600 and 711,000 eggs/spawning event.…”

The effect of substrate rearing on the growth, development, and survival of larval white sturgeon (Acipenser transmontanus) during early ontogeny.

“…Currently, there is no clear understanding of the cause of recruitment failure; however, there is consensus that river regulation is a significant contributing factor (McAdam et al 2005;Paragamian et al 2001Paragamian et al ,2009). …”

“…Several studies including McAdam et al (2005), McAdam (2011), and Paragamian et al (2001 have suggested that suitable spawning and larval incubation habitat used by sturgeon may be negatively impacted by river regulation, limiting survival, leading to recruitment failure.…”

Dam-lake Operation to Optimize Fish Habitat

“…It not only provides food and recreation for humans, but also maintains a healthy ecological balance in the flora and fauna of riparian habitats. Due to construction and operation of a dam, the natural fluctuations in the stream water are no longer available which reduces the required areas for fish to grow and reproduce, and even to hide from predators (King et al 2015;Waters et al 2015;National Fish Habitat Action Plan 2009;Null and Lund 2012;Piman et al 2013;Jager and Smith 2008;Paragamian et al 2001).…”

“…After the completion of Libby dam on the Kootenai River in 1972, the white sturgeon population became isolated and distinct in the Columbia River basin (McDonald et al 2010;Paragamian et al 2001;Setter and Brannon 1990). The white sturgeons in the Kootenai River became listed as an endangered species in 1994 (USFWS 1994).…”