No one factor is responsible for the current state of lake sturgeon in the Moose River Basin. Major influences include:
Over-fishing: Lake sturgeon populations cannot sustain more than a five per cent adult mortality rate (about 0.30 kilogram per hectare) from fishing. This means for a spawning run of 100 adult fish, no more than five fish should be removed if the sturgeon population is to be sustained. This estimate only applies to populations where there has been no prior fishing. For a fished (harvested) population, the sustainable yield is lower.
With the recent collapse of the sturgeon fishery in the Caspian Sea and ongoing demand for caviar (sturgeon eggs), fishing pressure has shifted to other sturgeon populations including those in Ontario. The harvest and illegal sale of sturgeon has increased to unsustainable levels in some parts of the province.
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| Figure 6. Island Falls generating Station, Abitibi River. |
Physical barriers: Lake sturgeon’s migratory needs are not compatible with many forms of waterpower development. Dams (Figure 6) typically block the upstream movement of lake sturgeon, and fish migrating downstream can be killed when they are drawn into the spillway or turbine intakes of these facilities. Dams also fragment rivers and isolate populations of fish. Once separated from broader populations, smaller subpopulations become more vulnerable to over-fishing. In addition, these sub-populations have a lower genetic diversity. Lower genetic diversity is associated with a reduced ability to adapt to environmental change and an increased risk of elimination from a particular area. Fish ladders have been successfully used to pass some fish species around barriers such as dams. However, the value of this technology for lake sturgeon is still unproven.
The best locations for dams are sometimes the same locations where lake sturgeon reproduce. The operation of some hydroelectric facilities can flood or reduce water levels in important habitats, as well as alter the timing of water flow in a river. These changes can affect the availability of suitable habitat for sturgeon, alter water temperatures, influence sturgeon behaviour, and ultimately affect their population size.
Industrial wastes and other contaminants: Historically, pulp and paper and lumber mills released woody debris and chemicals into river systems. Ongoing advances in waste treatment technology and new environmental regulations have reduced the amount of woody fibre that mills release. Sturgeon populations are showing signs of improvement in some of these locations. Communities and mines adjacent to rivers are also linked to the discharge of pollutants and contaminants. Legislation and monitoring help ensure provincial water quality standards are maintained.
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