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Table 4. Summary of historic and ongoing  threats to white sturgeon and their habitats. Stressors are listed by type (abiotic or biotic), and the affected populations are indicated. To some extent these threats include natural limitations such as habitat or productivity. Definitions for the levels of relative risk are provided in Table 3 and include the following categories: negligible, low, moderate (mod), high, and unknown. These are not comparable across populations.
Potential Threat to Species or Habitat Level of Relative Risk
  Dam Affected System
Stressor Activity Lower Fraser Mid Fraser Upper Fraser Nechako Columbia Kootenay
Loss of habitat quality and quantity1 Habitat changes are associated with flow regulation (e.g. affecting geomorphology, depth, velocity, substrate), as well as gravel and sand extraction; upland, foreshore, floodplain and estuary use and development, including bank protection, dyking and infilling, and other in-channel works. high mod mod high high high
Habitat fragmentation Habitat fragmentation occurs where there are impassable dams and/or dykes (e.g., Kootenay River) and through inadequate flows or water level changes. low low low low high low-mod
Altered hydrograph components Altered hydrograph components may be related to flow regulation, flow diversion, and anthropogenic activities causing climate change. low low low high high high
Pollution Pollutant sources include industrial inputs (pulp mill effluents, various wastewater, and smelting effluents), municipal and domestic sanitary and storm sewage, non-point source urban runoff, point source agricultural discharges and chemical over-sprays, and non-point source agricultural runoff. mod mod low low mod low
Fishing and industrial effects (direct and indirect) Fishing effects are related to poaching (illegal retention), recreational catch-and-release fishery, scientific inquiry and monitoring, aboriginal and commercial net fisheries, and by-catch in the aboriginal and recreational fisheries. Industrial effects include interactions with industrial facilities or operations, including equipment at hydro-electric facilities (turbines, draft tubes, locks), high mod low mod mod low
Reduced turbidity Reduced turbidity may be related to flow regulation and stream channelization, which can influence water clarity low low low low mod low
Altered thermal regime Thermal regimes are affected by flow regulation and anthropogenic activities causing climate change. low low low low mod mod
Effects of small population size Anthropogenic factors causing recruitment failure. low mod high high low high
Hatchery and aquaculture effects on health and population These effects may occur from conservation aquaculture and commercial aquaculture. low mod mod mod low low
Reduced or altered food supply (including fishing of white sturgeon prey base) Food supply is affected by commercial, Aboriginal, and recreational fishing, upland, foreshore, floodplain and estuary development, dams (fragmentation and hydrograph changes) and anthropogenic activities causing climate change. mod high high high mod mod
Change in ecological community (predation/competition) Ecological community composition can be affected by flow regulation, species introductions and movements, fishing effects, habitat alteration, and anthropogenic activities causing climate change. mod low low low high low-mod
Disease Disease rates can be affected by aquaculture, thermal regime changes (e.g., anthropogenic activities causing climate change, river regulation), introduction of pathogens, and introduction of pollutant stressors. low low low low low low


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