In November 2003, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) downgraded the ranking of the white sturgeon from a species of special concern to endangered. On August 24, 2006, the white sturgeon populations of the Nechako, Upper Fraser, Kootenay and Columbia were officially designated as endangered under the Federal Species at Risk Act. A survivor from before the time of the dinosaurs and a species relatively unchanged for 175 million years, this fish has, in the last 50 years, come to the brink of extinction.
The reasons for this dramatic decline are currently being studied. Contributing factors may include over-fishing prior to the 1994 ban on angling, incidental catches and poaching since then, pollution and changes to the river landscape by human construction. Changes to the level and times of water flows in the Nechako River, resulting from the construction of the Kenney Dam, may also have had a substantial effect on the sturgeon.
There are many flow-related factors that are thought to have impacted the successful survival and growth of young white sturgeon. The factors listed below may contribute to unsuccessful spawning conditions and/or juveniles failing to reach maturity. Each of these factors relates in some way or other to another factor, and therefore cannot be considered independently of each other. In addition, more research is needed to determine the role each factor plays, and how it affects the success of the white sturgeon.
Water Flow: The Nechako River was dammed for power generation in 1952 and there have been dramatic changes in the amount of water and the timing of flows in the river ever since. It is believed white sturgeon require specific conditions for spawning, and flow-related issues such as water temperature and sediment may be important factors in the frequency and success of spawning.
Temperature: The amount of water in the river affects the temperature of the water. We need to better understand how changes in temperature affect white sturgeon spawning success, development of their eggs and their early life stages, as well as juvenile survival and growth.
Predators: It is possible that changes to the river, including sediment load and water clarity, have increased the numbers of predators that feed on white sturgeon eggs and other vulnerable life stages.
Food Resources: Another factor may be that there is less of the food preferred by juvenile sturgeon available today then there was historically. Changes to water flow and temperature, reduction in abundance of salmon, as well as shoreline development may have affected the food resources available to young white sturgeon.
Turbidity and Sedimentation: Muddy or cloudy water with high levels of sediment is the preferred habitat for white sturgeon. Less water in the river means less sediment mixing in the water, which increases the water clarity. This directly relates to the success of predators who rely on sight to find white sturgeon eggs, larvae, fry and juveniles.
Channel Structure: Changes in the amount of water and the speed at which it travels have redistributed bottom sediments in the river. Research is needed to see how such changes have restructured the flood plain habitat required for white sturgeon spawning locations and juvenile rearing habitats.
Rooted Aquatic Plants: Reductions in the speed of the river’s current, along with municipal nutrient loads have greatly increased the numbers of rooted aquatic plants in the Nechako River, especially between Vanderhoof and the confluence of the Stuart River. This increase in plant life can suppress oxygen levels, change water chemistry, and increase sedimentation, all factors that can influence white sturgeon spawning and survival rates.
For more information about the factors affecting the Nechako white sturgeon and the plan for their recovery, please see the Recovery Plan for Nechako White Sturgeon.
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