Adjustable blade turbines

The present invention relates generally to hydroelectric turbine installations. More particularly, this invention pertains to hydroelectric installations utilizing propeller-type turbines in which the angular position of the runner blades relative to the hub of the turbine or propeller, i.e. the pitch of the blades, is adjustable. A turbine, adaptable to improve the survivability of fish present in water flowing therethrough, includes a hub and associated runner blades. Each blade comprises an inner edge and a distal outer edge, a leading edge and a trailing edge separated by a water directing surface. Each blade is rotatable relative to the hub about a blade rotational axis. The turbine is provided with a gap shielding device designed to shield a gap formed between the hub and the blade inner edge as the blade is rotated about its axis. The gap shielding device may comprise a plurality of independently biased pins, a plurality of fluid jets, a plurality of flexible members, a fluid-filled boot, and combinations thereof.