The matter of how these types of facilities would affect and be affected by fish and [FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]marine mammals is the overriding environmental issue to be resolved.[/FONT]
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[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]As noted at the outset, there is also a dearth of actual experience based information on the subject. Examination of the most favourable sites, Table 1 and Table 2 indicate that two thirds are located in the area of Johnstone Strait/Discovery Channel. This is also a major migration route for salmon and is home to resident marine mammals notably killer whales.[/FONT]
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[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]It is uncertain if salmon, which will generally seek out advantageous currents during their migration, would “see”, react and avoid large rotating turbine blades. There is not any particular elevation in the water column which the fish favour over others and which could be used to locate turbines to avoid collisions. The blades themselves rotate quite slowly relative to hydroelectric and wind turbines, namely a few revolutions per minute depending on current speed, blade curvature and size but always to maintain a blade tip speed of less than 7m/s (when cavitation is likely to occur).[/FONT]
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[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]Those configurations which either use a ducted turbine or a venturi and which could be fitted with a screen to keep fish from entering the machine would be advantageous. It may also be worth testing other, behavioural means of keeping fish and mammals away, e.g., tickle voltages, strobe lights.[/FONT]
[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]As noted this is a major issue for tidal current power facilities. It is doubtful that it can be fully resolved prior to installing a demonstration unit. However, such a demonstration unit would provide a much-needed opportunity to assess this technology and its environmental effects especially those related to fish and marine mammal impacts.[/FONT]